User’s

Manual WT310/WT310HC/WT332/WT333
Digital Power Meter
Getting Started Guide

IM WT310-02EN
2nd Edition
 Product Registration
Thank you for purchasing YOKOGAWA products.

YOKOGAWA provides registered users with a variety of information and

services.
Please allow us to serve you best by completing the product registration
form accessible from our homepage.

http://tmi.yokogawa.com/

PIM 103-03E
 Thank you for purchasing the WT310, WT310HC, WT332, or WT333 Digital Power Meter (hereinafter,
“WT300 series” will refer to all of these products). The WT300 series is a power measurement
instrument that can measure parameters such as voltage, current, and power.
This getting started guide primarily explains the handling precautions and basic operations of the
WT300 series. To ensure correct use, please read this manual thoroughly before beginning operation.
Keep this manual in a safe place for quick reference in the event that a question arises.
This manual is one of three WT300 series manuals. Please read all manuals.
Manual Title Manual No. Description
WT310/WT310HC/WT332/WT333 IM WT310-01EN The manual explains all the WT300 series features,
Digital Power Meter User’s Manual except for the communication interface features, and
how to use them.
WT310/WT310HC/WT332/WT333 IM WT310-02EN This guide. Provided as a printed manual. The manual
Digital Power Meter Getting Started explains the handling precautions and basic operations
Guide of the WT300 series and provides an overview of its
features.
WT310/WT310HC/WT332/WT333 IM WT310-17EN This manual explains the WT300 series communication
Digital Power Meter Communication interface features and how to use them.
Interface User’s Manual
PDF files of all the manuals above are included in the accompanying CD.

Notes
• The contents of this manual are subject to change without prior notice as a result of continuing
improvements to the instrument’s performance and functionality. The figures given in this manual
may differ from those that actually appear on your screen.
• Every effort has been made in the preparation of this manual to ensure the accuracy of its
contents. However, should you have any questions or find any errors, please contact your nearest
YOKOGAWA dealer.
• Copying or reproducing all or any part of the contents of this manual without the permission of
YOKOGAWA is strictly prohibited.
• The TCP/IP software of this product and the documents concerning it have been developed/created
by YOKOGAWA based on the BSD Networking Software, Release 1 that has been licensed from
the Regents of the University of California.

Trademarks
• Microsoft, Internet Explorer, MS-DOS, Windows, Windows NT, Windows XP, Windows Vista, and
Windows 7 are either registered trademarks or trademarks of Microsoft Corporation in the United
States and/or other countries.
• Adobe and Acrobat are either registered trademarks or trademarks of Adobe Systems Incorporated.
• In this manual, the TM and ® symbols do not accompany their respective registered trademark or
trademark names.
• Other company and product names are registered trademarks or trademarks of their respective
holders.

Revisions
• January 2013 1st Edition
• June 2013 2nd Edition

2nd Edition: June 2013 (YMI)

All Rights Reserved, Copyright © 2013 Yokogawa Meters & Instruments Corporation
IM WT310-02EN 
 Checking the Contents of the Package
Unpack the box and check the contents before operating the instrument. If the wrong items have been
delivered, if items are missing, or if there is a problem with the appearance of the items, contact your
nearest YOKOGAWA dealer.

WT310/WT310HC/WT332/WT333 (WT300 series)

Check that the product that you received is what you ordered by referring to the model name and suffix
code given on the name plate on the left side panel.
The WT300 series includes the WT310, WT310HC, WT332 and WT333.
The WT330 series includes the WT332 and WT333.

WT310/WT310HC WT332/WT333 (WT330 series)

Model Suffix Code Description

WT310 WT310 Digital Power Meter
One input element model
WT310HC WT310 Digital Power Meter
One input element/large current model
WT332 WT330 Digital Power Meter
Two input element model
WT333 WT330 Digital Power Meter
Three input element model
Power cord1 -D UL/CSA Standard power cord (Part No.: A1006WD)
Maximum rated voltage: 125 V
-F VDE Standard power cord (Part No.: A1009WD)
Maximum rated voltage: 250 V
-Q BS Standard power cord (Part No.: A1054WD)
Maximum rated voltage: 250 V
-R AS Standard power cord (Part No.: A1024WD)
Maximum rated voltage: 250 V
-H GB Standard power cord (Part No.: A1064WD)
Maximum rated voltage: 250 V
-N NBR Standard power cord (Part No.: A1088WD)
Maximum rated voltage: 250 V
Communication interface -C1 GP-IB interface
(The instrument is equipped -C2 RS-232 interface
with one of these.)
Options /C7 Ethernet Communication
/EX12 2.5 V/5 V/10 V external input
/EX22 50 mV/100 mV/200 mV/500 mV/1 V/2 V external input
/G5 Harmonic measurement
/DA4 DA output (4CH); for the WT310 or WT310HC
/DA12 DA output (12CH); for the WT332 or WT333
1 Make sure that the attached power cord meets the designated standards of the country and area
that you are using it in.
2 A single instrument cannot have both the /EX1 and /EX2 options.

ii IM WT310-02EN
 Checking the Contents of the Package

No. (Instrument number)

When contacting the dealer from which you purchased the instrument, please give them the instrument
number.

Standard Accessories
The instrument is shipped with the following accessories. Make sure that all accessories are present
and undamaged.

Power cord (one cord that matches the suffix code is included)1

UL/CSA Standard VDE Standard BS Standard AS Standard GB Standard NBR Standard

A1006WD A1009WD A1054WD A1024WD A1064WD A1088WD

D F Q R H N

Safety terminal adapter set2 D/A cable3 Rubber feet

758931 B9879SX A9088ZM

Current input protection Current input protection One set of manuals6

cover4 cover5
B8212BX B8212FX

1 Make sure that the attached power cord meets the designated standards of the country and area
that you are using it in.
2 Same number of sets as the number of installed input elements
WT310: One set with one hexagonal socket wrench
WT310HC: One set with one hexagonal socket wrench
WT332: Two sets with one hexagonal socket wrench
WT333: Three sets with one hexagonal socket wrench
3 Included with models that have D/A output and remote control (/DA4 or /DA12)
4 For the WT310/WT310HC
5 For the WT332/WT333
6 For information on the types of printed manuals and manuals on the CD that are provided, see
page i.

IM WT310-02EN iii
Checking the Contents of the Package

CD-R
The CD-R contains the data listed below. To view the PDF user’s manuals, you need Adobe Reader 5.0
or later.

PDFs of the WT300 Series User’s Manuals

These manuals are in the Manuals folder.
English
• WT310/WT310HC/WT332/WT333 Digital Power Meter User’s Manual
IM WT310-01EN
• WT310/WT310HC/WT332/WT333 Digital Power Meter Getting Started Guide
IM WT310-02EN
• WT310/WT310HC/WT332/WT333 Digital Power Meter Communication Interface User’s Manual
IM WT310-17EN

Japanese
The PDFs of the Japanese user’s manuals are also included on the CD-ROM.

Installer for the WTViewerFreePlus Application Software (For the

WT300 Series)
• WTViewerFreePlus_Installer.exe
• WTViewerFreePlus (folder)
• YKMUSB (folder)

PDF of the Manual for the WTViewerFreePlus Application Software

These manuals are in the Manuals folder.
English
• Application Software WTViewerFreePlus for WT310/WT310HC/WT332/WT333 User’s Manual
IM 760121-02E

Japanese
The PDFs of the Japanese user’s manuals are also included on the CD-ROM.

WARNING
Never play this CD-R on an audio CD player. Doing so may cause loss of hearing or speaker
damage due to the large sounds that may be produced.

iv IM WT310-02EN
 Checking the Contents of the Package

Optional Accessories (Sold separately)

The following optional accessories are available for purchase separately.
For information about ordering accessories, contact your nearest YOKOGAWA dealer.

Item Model/ Min. Q’ty Note

Part No.
External sensor cable B9284LK 1 For connecting to the WT300 series’s external
current sensor input connector.
Length: 0.5 m.
Measurement lead 758917 1 Two leads in one set. Used with the 758922 or
758929 adapter (sold separately). Length: 0.75 m.
Rated voltage: 1000 V.*
Safety terminal adapter set 758923 1 Two pieces in one set. Rated voltage 600 V.*
758931 1 Two pieces in one set. Rated voltage 1000 V.*
Alligator clip adapter set 758922 1 Two pieces in one set. For use with measurement
lead 758917.
Rated voltage 300 V.*
758929 1 Two pieces in one set. For use with measurement
lead 758917.
Rated voltage 1000 V.*
Fork terminal adapter set 758921 1 Two pieces in one set. For use with measurement
lead 758917.
Rated voltage 1000 V.* Rated current: 25 A.
Conversion adapter 758924 1 BNC-4 mm socket adapter. Rated voltage: 500 V.*

* The actual voltage that can be used is the lowest voltage of the WT300 series and cable
specifications.

External sensor Measurement Safety terminal Safety terminal

cable lead adapter set adapter set
B9284LK 758917 758923 758931

Alligator clip Alligator clip Fork terminal Conversion adapter

adapter set adapter set adapter set 758924
758922 758929 758921

IM WT310-02EN 
 Safety Precautions
This instrument is an IEC safety class I instrument (provided with a terminal for protective earth
grounding).
The general safety precautions described herein must be observed during all phases of operation.
If the instrument is used in a manner not specified in this manual, the protection provided by the
instrument may be impaired. YOKOGAWA assumes no liability for the customer’s failure to comply
with these requirements.

The WT300 series is a power measurement instrument that can measure parameters such as voltage,
current, and power. Do not use this instrument for anything other than its intended purpose.

The following symbols are used on this instrument.

Warning: handle with care. Refer to the user’s manual or service manual. This symbol appears
on dangerous locations on the instrument which require special instructions for proper handling
or use. The same symbol appears in the corresponding place in the manual to identify those
instructions.

Electric shock, danger

Ground (earth) or functional ground terminal (do not use this terminal as a protective ground

terminal.)

Alternating current

Both direct and alternating current

ON (power)

OFF (power)

Power-on state

Power-off state

vi IM WT310-02EN
 Safety Precautions

Failure to comply with the precautions below could lead to injury

or death.

WARNING
Use the Instrument Only for Its Intended Purpose
The WT300 series is a power measurement instrument that can measure parameters such
as voltage, current, and power. Do not use this instrument for anything other than as a power
measurement instrument.

Check the Physical Appearance

Do not use the instrument if there is a problem with its physical appearance.

Use the Correct Power Supply

Make sure that the power supply voltage matches the instrument’s rated supply voltage and
that it does not exceed the maximum voltage range specified for the power cord.

Use the Correct Power Cord and Plug

To prevent the possibility of electric shock or fire, be sure to use the power cord supplied by
YOKOGAWA. The main power plug must be plugged into an outlet with a protective earth
terminal. Do not invalidate this protection by using an extension cord without protective earth
grounding.
Additionally, do not use the power cord supplied with this instrument with another instrument.

Connect the Protective Grounding Terminal

Make sure to connect the protective earth to prevent electric shock before turning on the
power. The power cord that comes with the instrument is a three-prong type power cord.
Connect the power cord to a properly grounded three-prong outlet.

Do Not Impair the Protective Grounding

Never cut off the internal or external protective earth wire or disconnect the wiring of the
protective earth terminal. Doing so may result in electric shock or damage to the instrument.

Do Not Operate with Defective Protective Grounding or Fuses

Do not operate the instrument if the protective earth or fuse might be defective. Check the
grounding and the fuse before operating the instrument.

Do Not Operate in an Explosive Atmosphere

Do not operate the instrument in the presence of flammable gasses or vapors. Doing so is
extremely dangerous.

Do Not Remove Covers

Only qualified YOKOGAWA personnel should remove the instrument’s covers. The inside of
the instrument is dangerous because parts of it have high voltages.

Ground the Instrument before Making External Connections

Securely connect the protective grounding before connecting to the item under measurement
or to an external control unit. Before touching a circuit, turn off its power and check that it has
no voltage.

Measurement Category
This instrument is a measurement category II product. Do not use it for measurement category
III or IV measurements.

Install or Use the Instrument in Appropriate Locations

• Do not install or use the instrument outdoors or in locations subject to rain or water.
• Install the instrument so that you can immediately remove the power cord if an abnormal or
dangerous condition occurs.
IM WT310-02EN vii
Safety Precautions

Connect Cables Correctly

Power meters can measure large voltages and currents directly. If you use a voltage
transformer or a current transformer together with this power meter, you can measure even
larger voltages or currents. When you are measuring a large voltage or current, the power
capacity of the item under measurement becomes large. If you do not connect the cables
correctly, an overvoltage or overcurrent may be generated in the circuit under measurement.
This may lead to not only damage to the power meter and the item under measurement, but
electric shock and fire as well. Be careful when you connect the cables, and be sure to check
the following points.

Before you begin measuring (before you turn the item under measurement on), check that:
• Cables have been connected to the power meter’s input terminals correctly.
Check that there are no voltage measurement cables that have been connected to the
current input terminals.
Check that there are no current measurement cables that have been connected to the
voltage input terminals.
If you are measuring multiphase power, check that there are no mistakes in the phase
wiring.
• Cables have been connected to the power supply and the item under measurement
correctly.
Check that there are no short circuits between terminals or between connected cables.
• The cables are connected firmly to the current input terminals.
• There are no problems with the current input terminals and the crimping terminals, such as
the presence of foreign substances.

During measurement (never touch the terminals and the connected cables when the item
under measurement is on), check that:
• There no problems with the input terminals and the crimping terminals, such as the
presence of foreign substances.
• The input terminals are not abnormally hot.
• The cables are connected firmly to the input terminals.
The terminal connections may become loose over time. If this happens, heat may be
generated due to changes in contact resistance. If you are going to take measurements
using the same setup for a long time, periodically check that the cables are firmly
connected to the terminals. (Be sure to turn both the power meter and the item under
measurement off before you check the connections.)

After measuring (immediately after you turn the item under measurement off):
After you measure a large voltage or current, power may remain for some time in the item
under measurement even after you turn it off. This remaining power may lead to electric
shock, so do not touch the input terminals immediately after you turn the item under
measurement off. The amount of time that power remains in the item under measurement
varies depending on the item.

See below for operating environment limitations.

CAUTION
This is a class A instrument designed for an industrial environment. Operation of this product
in a residential area may cause radio interference in which case the user will be required to
correct the interference.

viii IM WT310-02EN
 Waste Electrical and Electronic Equipment

Waste Electrical and Electronic Equipment (WEEE), DIRECTIVE 2002/96/EC

(This directive is valid only in the EU.)
This product complies with the WEEE Directive (2002/96/EC) marking requirement. This
marking indicates that you must not discard this electrical/electronic product in domestic
household waste.

Product Category
With reference to the equipment types in the WEEE directive Annex I, this product is classified
as a “Monitoring and control instruments” product.

Do not dispose in domestic household waste. When disposing products in the EU, contact your
local Yokogawa Europe B. V. office.

New EU Battery Directive

New EU Battery Directive, DIRECTIVE 2006/66/EC

(This directive is valid only in the EU.)
Batteries are included in this product. This marking indicates they shall be sorted out and
collected as ordained in ANNEX II in DIRECTIVE 2006/66/EC.

Battery type: Lithium battery

You cannot replace batteries by yourself. When you need to replace batteries, contact your
local Yokogawa Europe B.V.office.

IM WT310-02EN ix
 Conventions Used in This Manual

Units
k: Denotes 1000. Example: 100 kS/s (sample rate)
K: Denotes 1024. Example: 720 KB (file size)

Notes
The notes and cautions in this manual are categorized using the following symbols.

Improper handling or use can lead to injury to the user or damage to the
instrument. This symbol appears on the instrument to indicate that the user must
refer to the user’s manual for special instructions. The same symbol appears in
the corresponding place in the user’s manual to identify those instructions. In the
user’s manual, the symbol is used in conjunction with the word “WARNING” or
“CAUTION.”

WARNING Calls attention to actions or conditions that could cause serious or fatal injury to
the user, and precautions that can be taken to prevent such occurrences.

CAUTION Calls attention to actions or conditions that could cause light injury to the user
or cause damage to the instrument or user’s data, and precautions that can be
taken to prevent such occurrences.

Note Calls attention to information that is important for the proper operation of the
software.

Characters That Appear on the 7-Segment LED

Because this instrument uses a 7-segment LED display, numbers, letters, and mathematical symbols
are displayed using special characters. For details, see section 1.3, “Digital Numbers and Characters.”

 IM WT310-02EN
 Conventions Used in This Manual

Symbols and Conventions Used in Procedural Explanations

The contents of the procedural explanations are indicated using the following symbols.

This mark appears on the right side of the page to indicate features and settings that can be
operated and configured using the WTViewerFreePlus application software, which comes with the
instrument.

Procedure Operations are explained using flowcharts. See the example below for an
explanation of how various operations are indicated. All procedures are written
under the assumption that you are starting operation at the beginning of the
procedure, so you may not need to carry out all the steps in a procedure when
you are changing the settings.

Example: Operations for turning the storage feature on and off

Configure the storage feature.
1. (Display B)

2.

3. (Display C) 5. 6.

4.
Confirm Close menu.
the setting.

The above flow chart indicates the following operations.

You can configure items that are blinking.
1. Press the SHIFT key so that it illuminates, and then press SETUP (UTILITY).
A menu appears in display B.
2. Use ▲ or ▼ to select StorE.
Pressing either key cycles through 9 menu items.
3. Press SET to confirm the selection of StorE.
The StorE function menu that you selected in step 2 appears in display C.
4. Use ▲ or ▼ to select oFF or on.
Pressing either key cycles through 3 menu items.
5. Press SET to confirm the selection of oFF.
The selected or set item is confirmed when you press SET.
A menu appears in display B.
6. Press HOLD (ESC) to return the menu display to the measurement data display.

• When you are making a number positive (no sign) or negative (–) or setting a number, when the
digit in the display that the input will be added to is blank, an underscore flashes at the position of
the digit.
• While you are performing menu operations, to leave the menu display, press HOLD (ESC). All
setting changes that you have confirmed by pressing the SET key will be reflected in the settings.

Explanation This section describes the setup items and the limitations regarding the
procedures. It may not give a detailed explanation of the feature. For a detailed
explanation of the feature, see chapter 1 in the User’s Manual, IM WT310-01EN.

IM WT310-02EN xi
 Workflow
The figure below is provided to familiarize the first-time user with the workflow of WT300 series
operation. For a description of an item, see the relevant section or chapter. In addition to the sections
and chapters that are referenced in the figure below, this manual also contains safety precautions for
handling and wiring the instrument. Be sure to observe the precautions.

Installation and Circuit Wiring

Getting Started Guide
Install the WT300 series. Section 2.2
Connect the power supply, and turn the power on. Sections 2.3 and 2.4
Select the measurement method. Section 2.8
Wire the circuit under measurement. Sections 2.9 to 2.11
Read the precautions in sections 2.5 and 2.7 thoroughly before connecting the wires.
Also, if necessary, assemble the input terminal adapter that connects to the voltage
input terminal (see section 2.6) before connecting the wires.

Common Operations
Getting Started Guide
Perform key operations. Sections 3.1 and 3.2
Initialize settings. Section 3.3

Set the Measurement Conditions

User’s Manual
Measurement conditions Chapter 2

Display Measured/Computed Results

User’s Manual
Voltage, current, and active power Section 4.1
Apparent power, reactive power, and power factor Section 4.2
Phase angle and frequency Section 4.3
Peak value Section 4.4
Crest factor, etc. Section 4.5
Integrated power (watt hour) Chapter 5
Harmonic measurement Chapter 6

Acquire Data
User’s Manual
Store data to internal memory. Chapter 7
Transmit data using D/A output (option). Section 8.4 and chapter 5 of the
Getting Started Guide
Transmit data through the USB, GP-IB, Communication Interface
RS-232, or Ethernet interface. User’s Manual

xii IM WT310-02EN
 Contents 1

Checking the Contents of the Package............................................................................................. ii

Safety Precautions............................................................................................................................ vi 2
Waste Electrical and Electronic Equipment...................................................................................... ix
New EU Battery Directive................................................................................................................. ix
Conventions Used in This Manual.....................................................................................................x
Workflow.......................................................................................................................................... xii 3

Chapter 1 Component Names and Functions

1.1 Front Panel, Rear Panel, and Top Panel........................................................................... 1-1 4
1.2 Displayed Items................................................................................................................. 1-5
1.3 Digital Numbers and Characters....................................................................................... 1-7
1.4 Keys.................................................................................................................................. 1-8
1.5 Auto Range, Overrange, and Error Indications During Measurement............................. 1-12 5
1.6 System Configuration...................................................................................................... 1-14

Chapter 2 Making Preparations for Measurements

2.1 Handling Precautions........................................................................................................ 2-1
6
2.2 Installing the Instrument.................................................................................................... 2-3
2.3 Connecting the Power Supply........................................................................................... 2-6
2.4 Turning the Power Switch On and Off............................................................................... 2-7 7
2.5 Precautions When Wiring the Circuit under Measurement............................................... 2-9
2.6 Assembling the Adapters for the Voltage Input Terminals............................................... 2-12
2.7 Wiring for Accurately Measuring a Single-phase Device................................................. 2-14
2.8 Guide for Selecting the Method Used to Measure the Power......................................... 2-15 App
2.9 Wiring the Circuit under Measurement for Direct Input................................................... 2-16
2.10 Wiring the Circuit under Measurement When Using Current Sensors............................ 2-31
2.11 Wiring the Circuit under Measurement When Using a Voltage or Current Transformer.. 2-38
2.12 Connecting to a PC via USB (Installing WTViewerFreePlus).......................................... 2-44 Index

Chapter 3 Common Operations

3.1 Key Operation and Functions............................................................................................ 3-1
3.2 Entering Values................................................................................................................. 3-3
3.3 Initializing the Settings....................................................................................................... 3-4

Chapter 4 Operating the WT300 series

4.1 Setting the Measurement Ranges..................................................................................... 4-1
4.2 Configuring the Wiring System Settings (Only on the WT332/WT333)............................. 4-4
4.3 Displaying the Voltage, Current, and Active Power on the WT310/WT310HC.................. 4-5
4.4 Displaying Voltages, Currents, and Active Powers on the WT332/WT333....................... 4-6

Chapter 5 External I/0 (Option)

5.1 External I/O Connector Pin Arrangement and Pinout........................................................ 5-1
5.2 Controlling the WT300 series Remotely............................................................................ 5-3
5.3 Producing D/A Output........................................................................................................ 5-4

IM WT310-02EN xiii
Contents
Chapter 6 Troubleshooting, Maintenance, and Inspection
6.1 Troubleshooting................................................................................................................. 6-1
6.2 Error Code Descriptions and Corrective Actions............................................................... 6-2
6.3 Recommended Part Replacement.................................................................................... 6-3
6.4 Calibration and Adjustment............................................................................................... 6-4

Chapter 7 Specifications
7.1 Input.................................................................................................................................. 7-1
7.2 Measurement Items........................................................................................................... 7-4
7.3 Accuracy............................................................................................................................ 7-5
7.4 Functions........................................................................................................................... 7-9
7.5 External Current Sensor Input (/EX1 and /EX2 options)................................................. 7-14
7.6 D/A Output (/DA4, /DA12 Options).................................................................................. 7-14
7.7 Remote Control Input/Output Signal (/DA4, /DA12 Options)........................................... 7-15
7.8 GP-IB Interface (Standard on -C1).................................................................................. 7-15
7.9 Serial (RS-232) Interface (Standard on -C2)................................................................... 7-15
7.10 USB PC Interface............................................................................................................ 7-15
7.11 Ethernet Interface(/C7 Option)........................................................................................ 7-16
7.12 Safety Terminal Adapter.................................................................................................. 7-16
7.13 General Specifications.................................................................................................... 7-17
7.14 External Dimensions....................................................................................................... 7-19

Appendix
Appendix 1 How to Make Accurate Measurements............................................................... App-1

xiv IM WT310-02EN
Chapter 1 Component Names and Functions

1.1 Front Panel, Rear Panel, and Top Panel 1

Component Names and Functions

WT310/WT310HC 2
Front Panel
Function and unit indicators
7-segment LED
display
→ section 1.2
3
Keys
→ section 1.2 → section 1.4

Handle
Used to carry the WT310/WT310HC 4
→ section 2.1

Power switch
6
→ section 2.4

Rear Panel 7
Current input terminal
For connecting current measurement
cables → sections 2.8, 2.9, and 2.11
External current sensor input connector App
For connecting cables from an external current sensor
→ section 2.10

Voltage input terminals

For connecting voltage measurement cables
→ sections 2.8 to 2.11 Index
USB port for PCs
Used to connect the WT300 series
to a PC that has a USB port
→ Communication Interface User’s Manual

Power inlet
Power connection → section 2.3

GP-IB or RS-232 connector

Used to communicate with the WT300 series through the
GP-IB or RS-232 interface
→ Communication Interface User’s Manual

Ethernet port
Used to connect the WT300 series to a network
→ Communication Interface User’s Manual
External I/O connector
For connecting D/A output and remote control cables
→ chapter 5

IM WT310-02EN 1-1
1.1 Front Panel, Rear Panel, and Top Panel

Top Panel
Inlet holes → section 2.2
(There are also inlet holes on the bottom panel.)

Vent holes → section 2.2

1-2 IM WT310-02EN
 1.1 Front Panel, Rear Panel, and Top Panel

WT332/WT333 (WT330 series) 1

Front Panel

Component Names and Functions

Function, unit, and element indicators
7-segment LED → section 1.2 2
display Keys
→ section 1.2 → section 1.4

Power switch 6
→ section 2.4
Handle
Used to carry the WT332/WT333
→ section 2.1
7
Rear Panel
Current input terminal
For connecting current measurement cables App
→ sections 2.8, 2.9, and 2.11

External current sensor input GP-IB or RS-232 connector

Used to communicate with the WT300 series through the GP-IB
connector
For connecting cables from an
or RS-232 interface Index
→ Communication Interface User’s Manual
external current sensor
→ section 2.10
Ethernet port
Voltage input terminals Used to connect the WT300 series to a network
For connecting voltage measurement cables → Communication Interface User’s Manual
→ sections 2.8 to 2.11

External I/O connector

For connecting D/A output and remote
control cables
→ chapter 5

Power inlet
Power connection → section 2.3

USB port for PCs

Used to connect the WT300 series to a PC that has a
USB port
→ Communication Interface User’s Manual

IM WT310-02EN 1-3
1.1 Front Panel, Rear Panel, and Top Panel

Top Panel
Inlet holes → section 2.2
(There are also inlet holes on the bottom panel.)

Vent holes → section 2.2

1-4 IM WT310-02EN
 1.2 Displayed Items 1

Component Names and Functions

WT310/WT310HC 2
Data update indicator (UPDATE)
Blinks when measurement data is being updated.
Auto range monitor (CHECK RANGE) 3
Lights when an input signal meets the conditions for auto range switching
Measurement mode indicator (MODE)
Indicates the voltage and current measurement modes
MAX HOLD indicator (MAX HOLD) 4
Lights when MAX HOLD is enabled

7-segment LED display

Displays the measured data for the function that you select using the function key 5
and displays menus when you are using menus to configure the settings

Function and unit indicators

Indicates the type of function and unit that are being shown on the
7-segment LED display 6

App

Index
Scaling indicator (SCALING)
Lights when scaling is enabled
Averaging indicator (AVG)
Lights when averaging is enabled
Line filter indicator (FILTER-LINE)
Lights when the line filter is enabled
Frequency filter indicator (FILTER-FREQ)
Lights when the frequency filter is enabled
Harmonic measurement display indicator (HARMONICS)
Lights when the harmonic measurement display is on
Storage indicator (STORE)
When you start storage, this indicator blinks at the pace at which storage is taking place.
Key protection indicator (KEY PROTECT)
Lights when the keys are locked
Remote indicator (REMOTE)
Lights when the WT310/WT310HC is in remote mode

IM WT310-02EN 1-5
1.2 Displayed Items

WT332/WT333 (WT330 series)

Data update indicator (UPDATE)
Blinks when measurement data is being updated.
Auto range monitor (CHECK RANGE)
Lights when an input signal meets the conditions for auto range switching
Measurement mode indicator (MODE)
Indicates the voltage and current measurement modes
MAX HOLD indicator (MAX HOLD)
Lights when MAX HOLD is enabled

7-segment LED display

Displays the measured data for the function that you select using the function key and
displays menus when you are using menus to configure the settings

Function and unit indicators

Indicates the type of function and unit that are being shown on the
7-segment LED display

Wiring method indicator

Indicates the wiring method

Scaling indicator (SCALING)

Lights when scaling is enabled
Averaging indicator (AVG)
Lights when averaging is enabled
Line filter indicator (FILTER-LINE)
Lights when the line filter is enabled
Frequency filter indicator (FILTER-FREQ)
Lights when the frequency filter is enabled
Harmonic measurement display indicator (HARMONICS)
Lights when the harmonic measurement display is on
Storage indicator (STORE)
When you start storage, this indicator blinks at the pace at which storage is taking place.
Key protection indicator (KEY PROTECT)
Lights when the keys are locked
Remote indicator (REMOTE)
Lights when the WT332/WT333 is in remote mode

1-6 IM WT310-02EN
 1.3 Digital Numbers and Characters 1

Component Names and Functions

Because this instrument uses a 7-segment LED display, numbers, letters, and mathematical symbols 2
are displayed using special characters in the manner shown below. Some of the characters shown
below are not used by this instrument.

0 A K U ^ (exponentiation)
1 B L V
3
2 C Lowercase c M W
3 D N X
4 E O Y
5 F P Z 4
6 G Q +
7 H Lowercase h R –
8 I S ×
9 J T ÷ 5

App

Index

IM WT310-02EN 1-7
 1.4 Keys

Switching the Display

FUNCTION Key
Choose which function to display.

ELEMENT Key (Only on the WT332/WT333)

Choose which input element to display. The indicator of the selected element lights.

WT310/WT310HC WT332/WT333

Measurement Range and Mode

VOLTAGE Key
Displays the voltage range setting menu. The AUTO indicator lights when the range is set to AUTO.

CURRENT Key
Displays the current range setting menu. The AUTO indicator lights when the range is set to AUTO.

SHIFT+VOLTAGE (MODE) Key

Switches the measurement mode.

Wiring System
WIRING Key (Only on the WT332/WT333)
Select the wiring system that corresponds to the wiring system you are using to connect to the voltage
and current terminals on the rear panel.

1-8 IM WT310-02EN
 1.4 Keys

Display Hold/MAX Hold 1

SHIFT+CURRENT (MAX HOLD) Key

Component Names and Functions

Turns the MAX hold feature on and off. When the MAX hold feature is on, the MAX HOLD indicator
lights. 2
HOLD Key
Switches from updating the display after each data update interval to stopping the series of display
operations and holding the display of the numeric data. The HOLD key lights. If you press HOLD
again, the data starts getting updated again, and the HOLD key light turns off.
3
SHIFT + HOLD Key
While the numeric data is held, press SINGLE to measure data only once at the set data update
interval and then update and hold the displayed values. 4

5
General-Purpose Keys
▲ and ▼ Keys
Select features and set values. 6
SHIFT+▼ (►) Key
Moves the digit that is being set in a value to the right (or from the farthest right position back to the
farthest left position)
7
SHIFT+▲ (.) Key
Moves the decimal point to the right (or from the farthest right position back to the farthest left position)

SET Key App

Confirms the specified range, feature, or value

Index
Zero-Level Compensation
SHIFT+SET Key (CAL)
Executes zero-level compensation. When zero-level compensation is executed, the WT300 series
creates a zero input condition in its internal circuitry and sets the zero level to the level at that point.

IM WT310-02EN 1-9
1.4 Keys

Integrated Power (Watt hour)

START Key
Starts integration

STOP Key
Stops integration

SHIFT+START (INTEG SET) Key

Displays a menu for setting the integration mode, timer, and rated integration time

SHIFT+STOP Key (RESET)

Resets the integrated value and the elapsed integration time.

Communication Interface
INTERFACE Key
Displays the communication interface setting menu and connection information

Key Lock
SHIFT+INTERFACE (KEY PROTECT) Key
Turns key protection on and off.
The key protection indicator lights, and the front panel keys are locked. Press this key combination
again to unlock the keys.

1-10 IM WT310-02EN
 1.4 Keys

Other Features 1
SETUP Key

Component Names and Functions

Set the measurement synchronization source, input filter, scaling, external sensor input, averaging,
computation, data update interval, etc. 2
SAVE/LOAD Key
Save or load setup data.

SHIFT+SETUP (UTILITY) Key 3

Displays a menu for displaying system information (model information, suffix code, instrument number,
and firmware version), initializing settings, setting the number of displayed digits, performing self-tests,
and configuring crest factor, storage, network, and D/A output settings.
4
SHIFT+SAVE/LOAD (HARMONICS) Key
Displays a setting menu for turning the harmonic measurement display on and off, setting the PLL
source, etc.

SHIFT Key 5
When you press the SHIFT key once, an indicator illuminates, and you can access the features that
are written in purple below each key. Pressing the key again disables the shifted state. Holding the key
for at least two seconds enables SHIFT lock.
6
SHIFT (LOCAL) Key
Press this key to switch from remote mode (in which the REMOTE indicator is illuminated) to local
mode (in which front panel key operations are valid). This key is disabled when the WT300 series is in
local lockout mode. 7

App
ESC Key
Pressing this key when a setup menu is showing returns the screen to the waveform data display.
Index

IM WT310-02EN 1-11
 1.5 Auto Range, Overrange, and Error Indications
During Measurement
Overrange Indication
The measured voltage and rated current values are determined to be overrange when they exceed
140% of their rated range.* When auto range is enabled, the range is automatically increased, but
if a values exceeds 140% of its maximum range, it is determined to be overrange, and the following
indication appears.

* On the WT310HC, the current is determined to be overrange when it exceeds 110% of the
maximum current range (40 A range).

Computation Overflow Indication

If a computed value cannot be displayed using the specified decimal place or unit, the following
indication appears.

Auto Range Monitor Indications

When an input signal meets the conditions for auto range switching, an indicator lights.

WT310/WT310HC WT332/WT333

Colors and Meanings of Auto Range Monitor Indicators

Color Description
Red Peak overrange
Magenta Greater than 140% of the rated range (overrange)1
Yellow Greater than 130% of the rated range and not more than 140% (condition for raising the auto range)2
Cyan 30% or less of the rated range (condition for reducing the auto range)
If the range is already at the minimum measurement range, this indicator will not light even when
values are 30% or less of the rated range.
1 On the WT310HC, the current is determined to be overrange when it exceeds 110% of the maximum current
range (40 A range).
2 On the WT310HC, the current is determined to be overrange when it exceeds 100% of the maximum current
range (40 A range).

Indications When the Measured Value Is Too Small

When the measured voltage or current is 0.5% or less of the rated range (1% or less when the
crest factor is set to 6), the following indications appear. These indications only appear when the
measurement mode is RMS or VOTLAGE MEAN.
Function Indication
Voltage, current, apparent power, or reactive power A zero appears.
Power factor or phase angle

Measurement Suspension/No Data Indication (Dashes)

When the measurement range, function, or element is switched and the displayed contents change or
when there is no data to display, the following dashes are displayed temporarily.

1-12 IM WT310-02EN
 1.5 Auto Range, Overrange, and Error Indications During Measurement

Error 1
Displayed in cases such as when a measured value is outside of its determined range.

Component Names and Functions

2

App

Index

IM WT310-02EN 1-13
 1.6 System Configuration

Load

Power
Supply
Current sensor
VT CT (optional)

Voltage Current
(Apply one of them.) (Apply one of them.)

Remote control signal WT300 series

(optional)
Integration start Internal memory
Integration stop Numeric data storage
Hold/
single

USB interface/
GP-IB interface*/
RS-232 interface*/ D/A output (option)
Ethernet interface (optional) Measured values
Setup parameters Numeric data are transmitted
as DC voltages.

PC Recorder

Printer

* The WT300 series is standard-equipped with a GP-IB or RS-232 interface (whichever you choose).

1-14 IM WT310-02EN
Chapter 2 Making Preparations for Measurements

2.1 Handling Precautions 1

Safety Precautions 2
If you are using this instrument for the first time, make sure to read “Safety Precautions” on pages vi to

Making Preparations for Measurements

viii.

3
Do Not Remove the Case
Do not remove the case from the instrument. Some parts of the instrument use high voltages and
are extremely dangerous. For internal inspection and adjustment, contact your nearest YOKOGAWA
dealer. 4

Unplug If Abnormal Behavior Occurs

If you notice smoke or unusual odors coming from the instrument, immediately turn off the power and 5
unplug the power cord. Also, turn off the power to any circuits under measurement that are connected
to the input terminals. Then, contact your nearest YOKOGAWA dealer.

Do Not Damage the Power Cord 6

Nothing should be placed on top of the power cord. The power cord should also be kept away from
any heat sources. When removing the plug from the power outlet, do not pull on the cord. Pull from the
plug. If the power cord is damaged, purchase a replacement with the same part number as the one
7
indicated on page iii.

General Handling Precautions

App
Do Not Place Objects on Top of the Instrument
Never stack the instrument or place other instruments or any objects containing water on top of it.
Doing so may damage the instrument.
Index
Keep Electrically Charged Objects Away from the Instrument
Keep electrically charged objects away from the input terminals. They may damage the internal
circuitry.

Unplug during Extended Non-Use

Turn off the power to the circuit under measurement and the instrument and remove the power cord
from the outlet.

IM WT310-02EN 2-1
2.1 Handling Precautions

When Carrying the Instrument

First, turn off the circuit under measurement and remove the measurement cables. Then, turn off the
instrument and remove the power cord and any attached cables. When carrying the instrument, use
the handle as shown in the following figure, or use both hands to hold the instrument firmly.

WT310/WT310HC WT332/WT333

When Cleaning the Instrument

When cleaning the case or the operation panel, turn off the circuit under measurement and the
instrument and remove the instrument’s power cord from the outlet. Then, wipe the instrument
lightly with a clean dry cloth. Do not use chemicals such as benzene or thinner. Doing so may cause
discoloring and deformation.

2-2 IM WT310-02EN
 2.2 Installing the Instrument 1

Installation Conditions 2
WARNING

Making Preparations for Measurements

• Do not install the instrument outdoors or in locations subject to rain or water. 3
• Install the instrument so that you can immediately remove the power cord if an abnormal or
dangerous condition occurs.

Install the instrument in an indoors environment that meets the following conditions.
4

Flat, Even Surface

Use the instrument on a stable surface that is level in all directions. If you use the instrument on an
5
unstable or tilted surface, the accuracy of its measurements may be impeded.

Well-Ventilated Location
Inlet and vent holes are located on the top and bottom of the instrument. To prevent internal 6
overheating, allow at least 20 mm of space around the inlet and vent holes.

When connecting measurement wires and other various cables, allow extra space for operation.

7
CAUTION
If you block the inlet or outlet holes on the instrument, it will become hot and may break down.
App

Ambient Temperature and Humidity

Ambient temperature: 5 to 40°C
Ambient humidity: 20 to 80% RH Index
(No condensation)

Do Not Install the Instrument in the Following Places

• In direct sunlight or near heat sources
• In an environment with excessive amounts of soot, steam, dust, or corrosive gas
• Near strong magnetic field sources
• Near high-voltage equipment or power lines
• In an environment that is subject to large levels of mechanical vibration
• On an unstable surface
• Outdoors or in locations subject to rain or water

Note
• For the most accurate measurements, use the instrument in the following kind of environment.
Ambient temperature: 23°C ± 5°C Ambient humidity: 30% RH to 75% RH (no condensation)
When using the instrument in a place where the ambient temperature is 5°C to 18°C or 28°C to 40°C, add the
temperature coefficient to the accuracy as specified in chapter 7.
• When installing the instrument in a place where the ambient humidity is 30% or less, take measures to
prevent static electricity such as using an anti-static mat.
• Condensation may occur if the instrument is moved to another place where the ambient temperature or
humidity is higher, or if the temperature changes rapidly. In these kinds of circumstances, wait for at least an
hour before using the instrument, to acclimate it to the surrounding temperature.

IM WT310-02EN 2-3
2.2 Installing the Instrument

Storage Location
Do not store the instrument:
• Where the relative humidity is greater than 80% • Where the level of mechanical vibration is high
• In direct sunlight • Where there are corrosive or explosive gasses
• Where the temperature is 60°C or higher • Where an excessive amount of soot, dust, salt,
or iron is present
• Near a strong source of heat or moisture • Where water, oil, or chemicals may splash onto
the instrument
We recommend that the instrument be stored in an environment where the temperature is between 5°C
and 40°C and the relative humidity is between 20% RH and 80% RH.

Installation Position
Desktop
Place the instrument in a horizontal position or tilt it on its handle or movable legs. Place the instrument
on a flat, level surface as shown in the figure below.
• WT310/WT310HC
To use the handle as a stand to tilt the instrument, first check that the handle is fixed in place,
and then position the instrument. To rotate the handle, first pull the handle’s rotary axis out
approximately 2 mm to 3 mm on both the left and right sides of the instrument, and then rotate it
slowly to one of its stop positions.
Handle stop positions (We recommend that you use positions 1, 3, 5, and 8. Do not place a heavy load
on the WT310/WT310HC when the handle is in stop position 2 or 4.)
Rotating base
7 8 Pull this out approximately 2 mm
6 to 3 mm, and rotate the handle.

5
1
4
3 2

3 1

• WT332/WT333

Movable legs

WARNING
• When adjusting the WT310/WT310HC handle, be careful not to injure your hand with the
edges of the handle.
• When you put away the handle or movable legs, be careful not to get your hand caught
between the handle or movable legs and the instrument.
• Handling the movable legs or handle without firmly supporting the instrument can be
dangerous. Please take the following precautions.
• Only handle the movable legs or handle when the instrument is on a stable surface.
• Do not handle the movable legs or handle when the instrument is tilted.
• Do not place the instrument in any position other than those shown in the above figures.

Rubber Feet
If the instrument is installed so that it is flat as shown in the above figure, rubber stoppers can be
attached to the feet to prevent the instrument from sliding. One set of rubber stoppers (two stoppers)
are included in the package.

2-4 IM WT310-02EN
 2.2 Installing the Instrument

Rack Mounting 1
To mount the instrument on a rack, use a rack mount kit (sold separately).
• For the WT310/WT310HC
Item Model Note
Rack mount kit 751533-E2 For EIA single mount 2
Rack mount kit 751533-J2 For JIS single mount

Making Preparations for Measurements

Rack mount kit 751534-E2 For EIA dual mount
Rack mount kit 751534-J2 For JIS dual mount

• For the WT332/WT333

3
Item Model Note
Rack mount kit 751533-E3 For EIA single mount
Rack mount kit 751533-J3 For JIS single mount
Rack mount kit 751534-E3 For EIA dual mount 4
Rack mount kit 751534-J3 For JIS dual mount

A summary of the procedure for mounting the instrument on a rack is given below. For detailed
instructions, see the manual that is included with the rack mount kit.
5
1. Remove the handle from the instrument.
• WT310/WT310HC
Rotate the handle to position 8 (see the figure on the previous page), and then pull out the rotating base 6
of the handle by approximately 10 mm on both sides.

• WT332/WT333
Remove the handle attachment section cover, and remove the handle attachment screws.

WT310/WT310HC WT332/WT333
7
To remove the handle, rotate
the handle to position 8, and
then pull out the rotating base
Rotating base
of the handle by approximately
App
10 mm on both sides. Cover

Handle
Cover Index
For detailed instructions for the procedures below, see the manual that is included with the rack mount kit.

2. Remove the feet from the bottom of the instrument.

3. Peel off the seals over the rack mount attachment holes on both side panels of the instrument,
and pull out the rubber rivets.
4. Place seals over the feet and handle attachment holes.
5. Attach the rack mount kit to the instrument.
6. Mount the instrument on a rack.

Note
• When rack-mounting the instrument, allow at least 20 mm of space around the inlet and exhaust holes to
prevent internal heating.
• Make sure to provide adequate support from the bottom of the instrument. The support should not block the
inlet and vent holes.

IM WT310-02EN 2-5
 2.3 Connecting the Power Supply

Before Connecting the Power Supply

To prevent electric shock and damage to the instrument, follow the warnings below.

WARNING
• Make sure that the power supply voltage matches the instrument’s rated supply voltage
and that it does not exceed the maximum voltage range specified for the power cord.
• Connect the power cord after checking that the power switch of the instrument is turned
OFF.
• To prevent fire and electric shock, only use a power cord supplied by YOKOGAWA.
• To avoid electric shock, be sure to ground the instrument. Connect the power cord to a
three-prong power outlet with a protective earth terminal.
• Do not use an ungrounded extension cord. If you do, the instrument will not be grounded.
• Use an AC outlet that complies with the power cord provided and securely connect the
protective grounding. If such an AC outlet is unavailable and protective grounding cannot
be furnished, do not use the instrument.

Connecting the Power Cord

1. Check that the instrument’s power switch is off.
2. Connect the power cord plug to the power inlet on the rear panel of the instrument.
3. Connect the other end of the cord to an outlet that meets the following conditions. Use a
grounded three-prong outlet.
Item Specification
Rated supply voltage 100 VAC to 120 VAC, 200 VAC to 240 VAC
Permitted supply voltage range 90 VAC to 132 VAC, 180 VAC to 264 VAC
Rated power supply frequency 50/60 Hz
Permitted supply frequency range 48 Hz to 63 Hz
Maximum power consumption WT310/WT310HC: 50 VA, WT332/WT333: 70 VA
* This instrument can use a 100 V or a 200 V power supply. The maximum rated voltage differs according
to the type of power cord. Before you use the instrument, check that the voltage supplied to it is less
than or equal to the maximum rated voltage of the power cord provided with it (see page v for the
maximum voltage rating).

WT310/WT310HC WT332/WT333
Three-prong outlet

2-6 IM WT310-02EN
 2.4 Turning the Power Switch On and Off 1

Before Turning On the Power, Check That: 2

• The instrument is installed properly. → section 2.2, “Installing the Instrument”
• The power cord is connected properly. → section 2.3, “Connecting the Power Supply”

Making Preparations for Measurements

Power Switch Location 3
The power switch is located in the lower left of the front panel.

Turning the Power Switch On and Off 4

The power switch is a push button. Press the button once to turn the instrument on and press it again
to turn the instrument off.

WT310/WT310HC WT332/WT333 5
OFF ON

6
PO
WE
R

App
Operations Performed When the Power Is Turned On
When the power switch is turned on, a self-test starts automatically. When the self-test completes
successfully, the screen that was displayed immediately before the power was turned off appears.
Index
Note
• After turning the power off, wait at least 10 seconds before you turn it on again.

When the Power-on Operation Does Not Finish Normally

• If the instrument does not operate as described above when the power switch is turned on, turn the power
switch off, and then:
• Check that the power cord is securely connected.
• Check that the correct voltage is coming to the power outlet. → section 2.3, “Connecting the Power
Supply”
• After checking the above, try turning on the power while holding down SET to initialize the settings (reset
them to their factory defaults). For details about initializing the settings, see section 3.3, “Initializing
Settings.”
• If the instrument still does not work properly, contact your nearest YOKOGAWA dealer for repairs.
• If an error code is displayed, see section 6.2, “Error Code Descriptions and Corrective Actions,” and take
the appropriate actions.
• It may take a few seconds for the startup message to appear.

To Make Accurate Measurements

• Allow the instrument to warm up for at least 30 minutes after turning on the power switch.
• After the instrument warms up, execute zero-level compensation. → section 8.3 of the User’s
Manual, IM WT310-01EN

IM WT310-02EN 2-7
2.4 Turning the Power Switch On and Off

Operations Performed When the Power Is Turned Off

After the power is turned off, the instrument stores the setup parameters in its memory before shutting
down. The same is true when the power cord is disconnected from the outlet. The next time the power
is turned on, the instrument powers up using the stored setup parameters.

Note
The instrument stores the settings using an internal lithium battery. When the lithium battery voltage falls
below a specified value, you will no longer be able to store setup parameters, and error code 901 will
appear on the screen when you turn on the power (see section 6.2, “Error Code Descriptions and Corrective
Actions”). If this message appears frequently, you need to replace the battery soon. Do not try to replace the
battery yourself. Contact your nearest YOKOGAWA dealer to have the battery replaced.

Power-on Messages
Power on

2 All the LEDs light.

3
Model: WT310, WT310HC, WT332, or WT333

Firmware version

Measurement data display

2-8 IM WT310-02EN
 2.5 Precautions When Wiring the Circuit under 1
Measurement
To prevent electric shock and damage to the instrument, follow the warnings below.
2
WARNING

Making Preparations for Measurements

• Ground the instrument before connecting measurement cables. The power cord that comes 3
with the instrument is a three-prong cord. Insert the power cord into a grounded three-
prong outlet.
• Turn the circuit under measurement off before connecting and disconnecting cables to it.
Connecting or removing measurement cables while the power is on is dangerous. 4
• Do not wire a current circuit to the voltage input terminal or a voltage circuit to the current
input terminal.
• Strip the insulation covers of measurement cables so that when they are wired to the input
terminals, the conductive parts (bare wires) do not protrude from the terminals. Also, make
5
sure to fasten the input terminal screws securely so that cables do not come loose.
• When connecting measurement cables to the voltage input terminals, only connect
measurement cables that have safety terminals that cover their conductive parts. Using
a terminal with bare conductive parts (such as a banana plug) can be dangerous if the
6
terminal comes loose.
• When connecting cables to the external current sensor input terminals, only connect cables
that have safety terminals that cover their conductive parts. Using a connector with bare
conductive parts can be dangerous if the terminal comes loose.
7
• When you apply current directly to the current input terminals to measure it, the voltage of
the item under measurement appears at the external sensor input connector. To prevent
electric shock, remove the cable connected to the external sensor.
• When the voltage of the circuit under measurement is being applied to the current input
App
terminals, do not touch the external current sensor input terminals. Doing so is dangerous
because the terminals are electrically connected inside the instrument.
• When connecting a measurement cable from an external current sensor to an external
current sensor input connector, remove the cables connected to the current input terminals.
Index
Also, when the voltage of the circuit under measurement is being applied to the external
current sensor input terminals, do not touch the current input terminals. Doing so is
dangerous because the terminals are electrically connected inside the instrument.
• When using an external voltage transformer (VT) or current transformer (CT), make sure
that it has enough dielectric strength for the voltage (U) being measured (2U + 1000 V
recommended). Also, make sure that the secondary side of the CT does not become an
open circuit while the power is being applied. If this happens, high voltage will appear at
the secondary side of the CT, making it extremely dangerous.
• When using an external current sensor, make sure to use a sensor that comes in a case.
The conductive parts and case should be insulated, and the sensor should have enough
dielectric strength for the voltage of the circuit under measurement. Using a bare sensor is
dangerous, because there is a high probability that you might accidentally touch it.
• When using a shunt-type current sensor as an external current sensor, turn off the circuit
under measurement before you connect the sensor. Connecting or removing the sensor
while the power is on is dangerous.
• When using a clamp-type current sensor as an external current sensor, make sure that
you understand the voltage of the circuit under measurement and the specifications and
handling of the clamp-type sensor, and then confirm that there are no dangers, such as
shock hazards.
• For safety reasons, when using the instrument after mounting it on a rack, furnish a switch
for turning off the circuit under measurement from the front side of the rack.
• For safety reasons, after you connect the measurement cables, use the included screws to
attach the current input protection cover (screw tightening torque: 0.6 N•m). Make sure that
the conductive parts do not protrude from the protection cover.

IM WT310-02EN 2-9
2.5 Precautions When Wiring the Circuit under Measurement

• To make the protective features effective, before applying the voltage or current from the
circuit under measurement, check that:
• The power cord provided with the instrument is being used to connect to the power
supply and that the instrument is grounded.
• The instrument is turned on.
• The current input protection cover provided with the instrument is attached.
• When the instrument is turned on, do not apply a signal that exceeds the following values
to the voltage or current input terminals. When the instrument is turned off, turn the circuit
under measurement off. For information about other input terminals, see the specifications
in chapter 6.
Instantaneous maximum allowable input (within 20 ms)

Voltage input
Peak value of 2.8 kV or rms value of 2 kV, whichever is less.

Current input
Direct input
• WT310 and WT332/WT333
When the crest factor is 3: 0.5 A to 20 A
When the crest factor is 6: 0.25 A to 10 A
Peak value of 450 A or rms value of 300 A, whichever is less.
• WT310
When the crest factor is 3: 5 mA to 200 mA
When the crest factor is 6: 2.5 mA to 100 mA
Peak value of 150 A or rms value of 100 A, whichever is less.
• WT310HC
When the crest factor is 3: 1 A to 40 A
When the crest factor is 6: 0.5 A to 20 A
Peak value of 450 A or rms value of 300 A, whichever is less.
External sensor input
Peak value less than or equal to 10 times the range.

Instantaneous maximum allowable input (1 s or less)

Voltage input
Peak value of 2 kV or rms value of 1.5 kV, whichever is less.

Current input
Direct input
• WT310 and WT332/WT333
When the crest factor is 3: 0.5 A to 20 A
When the crest factor is 6: 0.25 A to 10 A
Peak value of 150 A or rms value of 40 A, whichever is less.
• WT310
When the crest factor is 3: 5 mA to 200 mA
When the crest factor is 6: 2.5 mA to 100 mA
Peak value of 30 A or rms value of 20 A, whichever is less.
• WT310HC
When the crest factor is 3: 1 A to 40 A
When the crest factor is 6: 0.5 A to 20 A
Peak value of 150 A or rms value of 44 A, whichever is less.
External sensor input
Peak value less than or equal to 10 times the range.

2-10 IM WT310-02EN
 2.5 Precautions When Wiring the Circuit under Measurement

Continuous maximum allowable input 1

Voltage input
Peak value of 1.5 kV or rms value of 1.0 kV, whichever is less.

Current input
2
Direct input

Making Preparations for Measurements

• WT310 and WT332/WT333
When the crest factor is 3: 0.5 A to 20 A 3
When the crest factor is 6: 0.25 A to 10 A
Peak value of 100 A or rms value of 30 A, whichever is less.
• WT310
When the crest factor is 3: 5 mA to 200 mA 4
When the crest factor is 6: 2.5 mA to 100 mA
Peak value of 30 A or rms value of 20 A, whichever is less.
• WT310HC
When the crest factor is 3: 1 A to 40 A 5
When the crest factor is 6: 0.5 A to 20 A
Peak value of 100 A or rms value of 44 A, whichever is less.
External sensor input
Peak value less than or equal to 5 times the range. 6

7
CAUTION
Use measurement cables with dielectric strengths and current capacities that are appropriate
for the voltage or current being measured. App
Example: When making measurements on a current of 20 A, use copper wires that have a
conductive cross-sectional area of 4 mm2 or greater.
Attaching a measurement cable to this product may cause radio interference in which case
the user will be required to correct the interference. Index

Note
• If you are measuring large currents or voltages or currents that contain high frequency components, take
special care in dealing with mutual interference and noise when you wire the cables.
• Keep measurement cables as short as possible to minimize the loss between the circuit under
measurement and the instrument.
• The thick lines on the wiring diagrams shown in sections 2.9 to 2.11 are the parts where the current flows.
Use wires that are suitable for the current levels.
• To make accurate measurements of the voltage of the circuit under measurement, connect the
measurement cable that is connected to the voltage input terminal to the circuit as closely as possible.
• To make accurate measurements, separate the measurement cables as far away from the ground wires
and the instrument’s case as possible to minimize static capacitance to the ground.
• To measure the apparent power and power factor more accurately on an unbalanced three-phase circuit,
we recommend that you use the three-voltage, three-current method (3V3A).

IM WT310-02EN 2-11
 2.6 Assembling the Adapters for the Voltage Input
Terminals
When connecting a measurement cable to a WT300 series voltage input terminal, use the included
758931 Safety Terminal Adapter or the 758923 Safety Terminal Adapter (sold separately).

758931 Safety Terminal Adapter

Cover
Internal insulator
Plug

When using the 758931 Safety Terminal Adapter, assemble it according to the following procedure.

Assembling the Safety Terminal Adapter

1. Remove approximately 10 mm of the covering from the end of the cable and pass the cable
through the internal insulator.

Internal insulator
Attachable cable
10 mm Covering: max. diameter 3.9 mm
Cable
Core wire: max. diameter 1.8 mm

2. Insert the tip of the cable into the plug. Fasten the cable in place using the hexagonal wrench.
Hexagonal
wrench Plug

Cable tip
Insert the hexagonal wrench into the plug and tighten.

3. Insert the plug into the internal insulator.

4. Attach the external cover. Make sure that the cover does not come off.

Cover

Note
Once you attach the cover, it is difficult to disassemble the safety terminal adapter. Use care when attaching
the cover.

Below is an illustration of the adapter after it has been assembled.

2-12 IM WT310-02EN
 2.6 Assembling the Adapters for the Voltage Input Terminals

Explanation 1
Wire the adapters that come with the WT300 series or the adapters and various sensors that are sold
separately as shown below:

Wiring to a Voltage Input Terminal 2

Making Preparations for Measurements

Voltage under
measurement
758921 3
758917 WT310/WT310HC
Voltage input terminals
4
758922

5
758923
758929 WT332/WT333
Voltage input terminals

6
758931

Wiring to a Current Input Terminal

Use the clamp-on probes (sold separately) as shown below. App

Current under
measurement
When you are connecting to the 96030, 96031, Index
96030 or 758924, remove the terminal sleeves.
96031
96001 Sleeves
(voltage output type)
758924 WT310/WT310HC
EXT input
terminal

Current input
terminals
96001 terminal

751552 WT332/WT333
(current output type)
758917 758921
EXT input terminal

Current input
terminals
* The current input terminal and EXT input terminal cannot be wired (used) simultaneously.

Connecting a clamp-on probe

IM WT310-02EN 2-13
 2.7 Wiring for Accurately Measuring a Single-
phase Device
When you are wiring a single-phase device, there are the four patterns of terminal wiring positions
shown in the following figures for wiring the voltage input and current input terminals. Depending on
the terminal wiring positions, the effects of stray capacitance and the effects of the measured voltage
and current amplitudes may become large. To make accurate measurements, refer to the items below
when wiring the voltage input and current input terminals.

Effects of Stray Capacitance

When you are measuring the power of a single-phase device, you can minimize the effects of stray
capacitance on measurement accuracy by connecting the instrument’s current input terminal to the
side that is closest to the earth potential of the power supply (SOURCE).

• Easily affected • Not easily affected

C ±
I
V V
SOURCE U LOAD SOURCE U LOAD
± ±
± C
I

C ±
I
V V
SOURCE U LOAD SOURCE U LOAD
± ±
± C
I

Effects of the Measured Voltage and Current Amplitudes

• When the measured current is • When the measured current is
relatively large relatively small
Connect the voltage input terminal Connect the current input terminal
between the current input terminal between the voltage input terminal
and the load. and the load.

C ± C ±
I I
V V
SOURCE U LOAD SOURCE U LOAD
± ±

V V
SOURCE U LOAD SOURCE U LOAD
± ±
± C ± C
I I

Explanation
For details on the effects of stray capacitance and the effects of the measured voltage and current
amplitudes, see appendix 1, “How to Make Accurate Measurements.”

2-14 IM WT310-02EN
 2.8 Guide for Selecting the Method Used to 1
Measure the Power
Select the measurement method from the table below according to the amplitude of the measured
voltage or current. For details about a wiring method, see the section indicated in the table. 2

Making Preparations for Measurements

Voltage Measurement Methods
When the Voltage When the Voltage
3
Is 600 V or Less Exceeds 600 V

Voltage Direct input → section 2.9 Direct input is not possible.

wiring Voltage transformer (VT) → section 2.11 4
Current Measurement Methods
When the Voltage Is 600 V or Less 5
When the Current When the Current
WT310/WT332/WT333 When the Voltage
Product Is 20 A or Less Exceeds 20 A
Exceeds 600 V
name When the Current When the Current
WT310HC
Is 40 A or Less Exceeds 40 A 6
Direct input → section 2.9 Direct input is not possible.
Shunt-type current
Shunt-type current sensor → section 2.10 sensors cannot be used.
Current Clamp-type current sensor
7
wiring → section 2.10
(voltage output type)
Clamp-type current sensor
→ section 2.11
(current output type)
Current transformer (CT) → section 2.11 App

Index

IM WT310-02EN 2-15
 2.9 Wiring the Circuit under Measurement for
Direct Input
This section explains how to wire the measurement cable directly from the circuit under measurement
to the voltage or current input terminal. To prevent electric shock and damage to the instrument, follow
the warnings given in section 2.5, “Precautions When Wiring the Circuit under Measurement.”

Connecting to the Input Terminals

Voltage Input Terminals
The terminals are safety banana jacks (female) that are 4 mm in diameter.
Only insert a safety terminal whose conductive parts are not exposed into a voltage input terminal.
If you are using the included 758931 Safety Terminal Adapter, see section 2.6.

Voltage input terminals

758931

WT310/WT310HC WT332/WT333

Current Input Terminals

The terminals are binding posts, and the screws are M6. Either wind a wire around a screw or pass a
crimped terminal through the screw axis, and then tighten firmly with the terminal knob.

3.1 2.1 Unit: mm Current input terminals

Current input terminals

7

WT310/WT310HC WT332/WT333

WARNING
• When the voltage of the circuit under measurement is being applied to the current input
terminals, do not touch the external current sensor input terminal. Doing so is dangerous
because the terminals are electrically connected inside the instrument.
• When connecting a measurement cable from an external current sensor to an external
current sensor input connector, remove the cables connected to the current input terminals.
Also, when the voltage of the circuit under measurement is being applied to the external
current sensor input terminals, do not touch the current input terminals. Doing so is
dangerous because the terminals are electrically connected inside the instrument.

CAUTION
Confirm that no foreign materials are caught between the current input terminal and the
crimped terminal. Periodically confirm that the current input terminal is not loose and that there
are no foreign materials caught between the current input terminal and the crimped terminal.

2-16 IM WT310-02EN
 2.9 Wiring the Circuit under Measurement for Direct Input

Connecting to a Round Crimped Terminal 1

To connect a cable with a round crimped terminal to a current input terminal, follow the procedure
below.

1. Turn the current input terminal knob to loosen it. If the knob becomes difficult to turn, apply 2
more force to turn it further. Inside the terminal base, the stopper for the knob will disconnect

Making Preparations for Measurements

from the screw portion of the knob, and the knob will become easier to turn.
The stopper for the knob will fall out of the hole in the terminal base. Be careful not to lose the stopper.
Terminal base Knob 3

4
Current input terminal
Stopper

2. Insert the screw of the knob into the crimped terminal, and attach the knob to the terminal base.
Tighten the knob until the tip of the knob screw is slightly visible from the hole in the terminal 5
base.

6

Crimped terminal

7
3. Use one of the following methods to insert the stopper into the terminal base and hold it in
place.
• Hold the stopper with tweezers and insert it into the terminal base.
App
• Wrap adhesive tape around a flathead screwdriver so that the adhesive side of the tape faces
outward, then attach the stopper to the adhesive tape.
Tweezers Flathead screwdriver
Stopper shaft Center hole
Index

Adhesive tape

4. Align the shaft of the stopper with the hole in the center of the knob screw. Twist the knob until
the shaft of the stopper enters all the way into the center of the screw.
If the shaft of the stopper doesn’t enter all the way into the screw even after you tighten the knob, insert the
shaft of a screwdriver into the hole in the terminal base, and twist the knob.

Flathead screwdriver shaft

Note
When using a crimped terminal with a measurement cable, be sure to use a crimped terminal that matches
the size of the cable and to crimp the terminal to the cable using the appropriate crimping tool for the
terminal. For precautions about using crimped terminals and crimping tools, see the manuals for the crimped
terminal and the crimping tool that you are using.

IM WT310-02EN 2-17
2.9 Wiring the Circuit under Measurement for Direct Input

Connecting to the WT310/WT310HC

In the wiring examples that follow, the WT310/WT310HC input elements, voltage input terminals, and
current input terminals are simplified as shown in the following figure.

Input element
Current input Voltage input
WT310/WT310HC terminals terminals

V: VOLTAGE terminal ± C V
C: CURRENT terminal ±

V The voltage input terminals

U and current input terminals
± C ±
I are labeled as U and I,
respectively.

CAUTION
The thick lines on the wiring diagrams are the parts where the current flows. Use wires that are suitable for
the current levels.

Wiring Patterns
When you are wiring a single-phase device, there are the four patterns of terminal wiring positions
shown in the following figures for wiring the voltage input and current input terminals. To select which
pattern to use, see section 2.7.

SOURCE LOAD SOURCE LOAD

± C V ± C V
± ±

V V
SOURCE U LOAD SOURCE U LOAD
± ±
± C ± C
I I

SOURCE LOAD SOURCE LOAD

± C V ± C V
± ±

C ± C ±
I I
V V
SOURCE U LOAD SOURCE U LOAD
± ±

2-18 IM WT310-02EN
 2.9 Wiring the Circuit under Measurement for Direct Input

Example Wiring Procedure 1

This example will explain the procedure that you should use to configure the wiring when using the
WT310 to measure the power of a single-phase, two-wire DUT. The procedure is the same when
measuring using the WT310HC.
2
Power supply

Making Preparations for Measurements

DUT 3
Power cables

This example shows how to configure the wiring pattern shown in the upper left of the figure on the
4
previous page.

SOURCE LOAD
V 5
SOURCE U LOAD
± C V ±
± ± C
I
6
Order of Connection
Generally, it is easier to follow the wiring diagram if you wire to the current input terminals first and
then to the voltage input terminals. In this example as well, we will wire to the WT310 current input
terminals first and then to the voltage input terminals.
7

Wiring to the Current Input Terminals

Connect the current input terminals in series with the DUT along one of the power cables between App
the DUT and the power source.

1 Cut one power cable at the position that you want to insert the power meter into.
Cutting the low-voltage cable and inserting the power meter reduces the effects of noise during power Index
measurement.

LH
High-voltage cable

Low-voltage cable
WT310

IM WT310-02EN 2-19
2.9 Wiring the Circuit under Measurement for Direct Input

2 Strip the insulation of the power cable that you cut, and attach round crimped terminals if
necessary. Connect the power cable to the WT310 in the following ways.
• Power-source-side cable: Connect to the ± current input terminal.
• DUT side cable: Connect to the CURRENT current input terminal.
Pay attention to the terminal polarities so that you don’t attach the cables to terminals (C and ±) with the
wrong polarities.
Power supply

DUT

Round crimped terminal

± C

Current input terminals

(C: CURRENT terminal)

The wiring for current measurement is complete.

SOURCE LOAD

± C
I

Wiring to the Voltage Input Terminals

Connect the voltage input terminals in parallel with the DUT.
3 Connect the voltage measurement cables to the power supply terminals of the DUT.
Use cables that meet the following conditions.
• Sufficient dielectric strength for the voltage of the circuit under measurement
• Of a size to which the 758931 Safety Terminal Adapter can be attached
• Covering: max. diameter 3.9 mm
• Core wire: max. diameter 1.8 mm

Voltage measurement cables

2-20 IM WT310-02EN
 2.9 Wiring the Circuit under Measurement for Direct Input

4 Attach 758931 Safety Terminal Adapters to the voltage measurement cables. 1

For details on how to assemble and attach the safety terminal adapters, see section 2.5.
You can avoid wiring mistakes by connecting a red adapter to the high-voltage cable and a black adapter to
the low-voltage cable.
2

Making Preparations for Measurements

3

Red 4
Black
Safety terminal adapter
5
5 Connect the safety terminal adapters to the WT310 voltage input terminals.
• Red adapter: Connect to the VOLTAGE voltage input terminal.
• Black adapter: Connect to the ± voltage input terminal. 6
Pay attention to the terminal polarities so that you don’t attach the cables to terminals (V and ±) with the
wrong polarities.

App

Voltage input terminals
(V: VOLTAGE terminal)

V Index
±

The wiring for voltage measurement is complete. The wiring for measuring the power of a single-
phase, two-wire DUT is complete.

Power supply

DUT

WT310

V
SOURCE U LOAD
±
± C
I

IM WT310-02EN 2-21
2.9 Wiring the Circuit under Measurement for Direct Input

You can also connect to the circuit under measurement by placing a terminal block near the WT310
and connecting the power cables and voltage measurement cables to the terminal block.

Terminal block

2-22 IM WT310-02EN
 2.9 Wiring the Circuit under Measurement for Direct Input

Connecting to the WT332/WT333 1

In the wiring examples that follow, the WT332/WT333 input elements, voltage input terminals, and
current input terminals are simplified as shown in the following figure.

V: VOLTAGE terminal 2
Voltage input
± VOLTAGE
C: CURRENT terminal
WT332/WT333
terminals

Making Preparations for Measurements

V The voltage input terminals
U1 and current input terminals of
± V
3
CURRENT

±
EXT
input element 1 are labeled
as U1 and I1, respectively.
Current input C
terminals C
± ±
I1
± 4
Input element

Note 5
The thick lines on the wiring diagrams are the parts where the current flows. Use wires that are suitable for
the current levels.

Wiring Examples of Single-Phase, Two-Wire Systems (1P2W)

6
The following wiring example shows how to configure the wiring to connect to input element 1. To
configure the wiring for other input elements, substitute the numbers in the figures with the appropriate
element numbers. 7

SOURCE LOAD SOURCE LOAD

App
± V ± V

C C Index
± ±
Input element 1 Input element 1

V V
SOURCE U1 LOAD SOURCE U1 LOAD
± ±
± C ± C
I1 I1

SOURCE LOAD SOURCE LOAD

± V ± V

C C
± ±
Input element 1 Input element 1
C ± C ±
I1 I1
V V
SOURCE U1 LOAD SOURCE U1 LOAD
± ±

IM WT310-02EN 2-23
2.9 Wiring the Circuit under Measurement for Direct Input

Wiring Example of a Single-Phase, Three-Wire System (1P3W)

The wiring is connected to input elements 1 and 3.

SOURCE LOAD
N C ±
I1
V
± V ± V U1
N ±
SOURCE LOAD
±
C C
U3
± ± V
I3
C ±
Element 1 Element 3
(V1, A1) (V3, A3)

Wiring Example of a Three-Phase, Three-Wire System (3P3W)

The wiring is connected to input elements 1 and 3.
Measure the line voltage using S-phase power as the reference.

SOURCE LOAD C ±
R I1
V
S
T R U1
SOURCE ±
LOAD
± V ± V T S

C C ±
U3
± ± V
I3
C ±
Element 1 Element 3
(V1, A1) (V3, A3)

Wiring Example of a Three-Phase, Four-Wire System (3P4W)

Applies to the WT333.
The wiring is connected to input elements 1, 2, and 3.

SOURCE LOAD C ±
R I1
V
S
T R U1
N SOURCE N ±
LOAD
T S ±
± V ± V ± V U2
C ± V
I2 ±
C C C U3
± ± ± V
I3
C ±
Element 1 Element 2 Element 3
(V1, A1) (V2, A2) (V3, A3)

2-24 IM WT310-02EN
 2.9 Wiring the Circuit under Measurement for Direct Input

Wiring Example with the Three-Voltage, Three-Current Method 1

(3V3A)
Applies to the WT333.
The wiring is connected to input elements 1, 2, and 3.
2
SOURCE LOAD C ±
R I1
V

Making Preparations for Measurements

S
R U1
T
SOURCE N ±
V LOAD 3
± ± ± T S U2
V V V
±
C ±
I2 ±
C C C U3
V
4
± ± ± I3
C ±
Element 1 Element 2 Element 3
(V1, A1) (V2, A2) (V3, A3)
5
Note
For details about the relationship between the wiring system and how measured and computed values are
determined, see appendix 1, “Symbols and Determination of Measurement Functions.”
6

App

Index

IM WT310-02EN 2-25
2.9 Wiring the Circuit under Measurement for Direct Input

Wiring Procedure Example for a Three-Phase, Three-Wire System

(3P3W)
This example will explain the procedure that you should use to configure the wiring when using the
WT332/WT333 to measure the power of a three-phase, three-wire DUT.

Power supply DUT

TSR Power cables RST

This section will explain how to configure the wiring as shown below.

SOURCE LOAD C ±
R I1
V
S
T R U1
SOURCE ±
LOAD
± V ± V T S

C C ±
U3
± ± V
I3
C ±
Element 1 Element 3
(V1, A1) (V3, A3)

Note
The wiring procedure for a single-phase, two-wire DUT on page 2-19 is a useful reference for thinking about
the voltage of each phase and the current wiring.

Order of Connection
Generally, it is easier to follow the wiring diagram if you wire to the current input terminals first
and then to the voltage input terminals. In this example as well, we will wire to the WT332/WT333
current input terminals first and then to the voltage input terminals.

Wiring to the Current Input Terminals

Connect the current input terminals between the R phase and T phase of the power cable.

1 Cut the power cables at the positions where you want to insert the power meter.

TSR RST

WT332/WT333

2-26 IM WT310-02EN
 2.9 Wiring the Circuit under Measurement for Direct Input

2 Strip the insulation of the power cables that you cut, and attach round crimped terminals if 1
necessary. Connect the power cables to the WT332/WT333 in the following ways.
• R-phase cable: Connect to element 1.
• Power-source-side cable: Connect to the ± current input terminal of element 1.
• DUT side cable: Connect to the CURRENT current input terminal of element 1. 2
• T-phase cable: Connect to element 3.
• Power-source-side cable: Connect to the ± current input terminal of element 3.

Making Preparations for Measurements

• DUT side cable: Connect to the CURRENT current input terminal of element 3.
Pay attention to the terminal polarities so that you don’t attach the cables to terminals (C and ±) with the
wrong polarities.
3

Power supply DUT

4
TSR RST
R

T
5

C
Current input terminals
(C: CURRENT terminal) ±
6
1 3

The wiring for current measurement is complete. 7

App
TSR RST

Index

C ±
I1
1 3
R
SOURCE
LOAD
T S

I3
C ±

Note
Why You Do Not Have to Connect the WT332/WT333 Current Input Terminals to the S-Phase Cable
In a three-phase, three-wire wiring system, there is no neutral line. This means that either the R, S, or T
phase is treated as a virtual neutral line when power is measured. In this example, the S-phase cable is
treated as the virtual neutral line. Therefore, in the voltage terminal connection described later, phase S is
used as the reference to measure the line voltage between phase R and phase S and between phase T and
phase S. This type of power measurement method is referred to as the two-wattmeter method.

IM WT310-02EN 2-27
2.9 Wiring the Circuit under Measurement for Direct Input

Wiring to the Voltage Input Terminals

Connect the voltage input terminals in parallel with the DUT.
Using phase S as the reference, measure the line voltage between phase R and phase S and
between phase T and phase S.

3 Connect the voltage measurement cables to the power supply terminals of the DUT. Connect
two cables to the S-phase terminal.
Use cables that meet the following conditions.
• Sufficient dielectric strength for the voltage of the circuit under measurement
• Of a size to which the 758931 Safety Terminal Adapter can be attached
• Covering: max. diameter 3.9 mm
• Core wire: max. diameter 1.8 mm

TSR RST

Voltage measurement
cables

1 3

4 Attach 758931 Safety Terminal Adapters to the voltage measurement cables.

For details on how to assemble and attach the safety terminal adapters, see section 2.5.
You can avoid wiring mistakes by connecting red adapters to the R- and T-phase cables and black adapters
to the S-phase cables.

TSR RST

Red
Black
Black
Red
Safety terminal adapter

1 3

2-28 IM WT310-02EN
 2.9 Wiring the Circuit under Measurement for Direct Input

5 Connect the safety terminal adapters to the WT332/WT333 voltage input terminals. 1
• Red R-phase adapter: Connect to the VOLTAGE voltage input terminal of element 1.
• Red T-phase adapter: Connect to the VOLTAGE voltage input terminal of element 3.
• Black S-phase adapters: Connect to the ± voltage input terminals of elements 1 and 3.
Pay attention to the terminal polarities so that you don’t attach the cables to terminals (VOLTAGE and ±) 2
with the wrong polarities.

Making Preparations for Measurements

3
TSR RST

4
S S
R T

5
± V
Voltage input terminals
(V: VOLTAGE terminal)

1 3 6

The wiring for voltage measurement is complete. The wiring for measuring the power of a three-
phase, three-wire DUT is complete. 7
Power supply DUT

App
TSR RST
R

Index

S R S T
WT332/WT333

1 3 C ±
I1
V
R U1
SOURCE ±
LOAD
T S

±
U3
V
I3
C ±

IM WT310-02EN 2-29
2.9 Wiring the Circuit under Measurement for Direct Input

You can also connect to the circuit under measurement by placing a terminal block near the WT332/
WT333 and connecting the power cables and voltage measurement cables to the terminal block.

TSR Terminal block RST

R
S
T

Wiring Procedure with the Three-Voltage, Three-Current Method

(3V3A)
You can configure the wiring for the three-voltage, three-current method (3V3A) by adding the following
wiring to the wiring for a three-phase, three-wire system.

Wiring to the Current Input Terminals

In the aforementioned steps 1 and 2, connect the current input terminals of element 2 to the
S-phase power cable.

Wiring to the Voltage Input Terminals

In the aforementioned steps 3 to 5, connect the voltage input terminals of element 2 so as to
measure the line voltage between phase R and phase T.

The result of wiring the three-phase, three-wire system shown in the figure above is for the three-
voltage, three-current method (3V3A) is shown below.

TSR Terminal block RST

R
S
T

C ±
I1
V
R U1
S R T R S T
SOURCE N ±
± V ± V ± V V LOAD
T S U2
±
C ±
I2 ±
U3
V
I3
C ±

2-30 IM WT310-02EN
 2.10 Wiring the Circuit under Measurement When 1
Using Current Sensors
To prevent electric shock and damage to the instrument, follow the warnings given in section 2.5,
2
“Precautions When Wiring the Circuit under Measurement.”

Making Preparations for Measurements

If the maximum current of the circuit under measurement exceeds the maximum range of the input
elements, you can measure the current of the circuit under measurement by connecting an external 3
current sensor to the external current sensor input connector.
• WT310 and WT332/WT333
When the maximum current exceeds 20 Arms
• WT310HC 4
When the maximum current exceeds 40 Arms

Current Sensor Output Type 5

Voltage Output
Refer to the wiring examples in this section when using a shunt-type current sensor or a clamp-type
current sensor that outputs voltage.
6
Current Output
If you are using a clamp-type current sensor that outputs current, see section 2.11.

Connecting to the Input Terminals 7

Voltage Input Terminals
The terminals are safety banana jacks (female) that are 4 mm in diameter.
Only insert a safety terminal whose conductive parts are not exposed into a voltage input terminal.
If you are using the included 758931 Safety Terminal Adapter, see section 2.6. App

External Current Sensor Input Terminal

The terminal is an isolated BNC connector.
Connect an external current sensor cable with an isolated BNC connector (B9284LK, sold separately)
Index
to an external current sensor input connector.

Shunt-type current sensor External current sensor input connector

B9284LK
OUT H
I

±
OUT L

WT310/WT310HC WT332/WT333

Remove the measurement cable connected to the current input terminal. Because the external current
sensor input terminal and the current input terminal are connected internally, connecting both terminals
simultaneously not only results in measurement errors but may also cause damage to the instrument.
Also, when the voltage of the circuit under measurement is being applied to the external current sensor
input terminals, do not touch the current input terminals. Doing so is dangerous because the terminals
are electrically connected inside the instrument.

IM WT310-02EN 2-31
2.10 Wiring the Circuit under Measurement When Using Current Sensors

CAUTION
The thick lines on the wiring diagrams are the parts where the current flows. Use wires that
are suitable for the current levels.

Note
• Make sure that you have the polarities correct when you make connections. If the polarity is reversed,
the polarity of the measurement current will be reversed, and you will not be able to make correct
measurements. Be especially careful when connecting clamp-type current sensors to the circuit under
measurement, because it is easy to reverse the connection.
• Note that the frequency and phase characteristics of the current sensor affect the measured data.
• To measure the apparent power and power factor more accurately on an unbalanced three-phase circuit,
we recommend that you use the three-voltage, three-current method (3V3A).

Notes about Using Shunt-type Current Sensors and Clamp-on

Probes
Connecting an External Current Sensor Cable
To minimize error when using shunt-type current sensors, follow the guidelines below when
connecting the external current sensor cable.
• Connect the shielded wire of the external current sensor cable to the L side of the shunt output
terminal (OUT).
• Minimize the area of the space between the wires connecting the current sensor to the external
current sensor cable. This reduces the effects of the lines of magnetic force (which are caused
by the measurement current) and the external noise that enter the space.

Shunt-type current sensor

Space between the connection wires
OUT H
I B9284LK
WT300 series
± Shielded wire
OUT L

Position on the (Grounded) Circuit under Measurement That You Should Connect
the Shunt-type Current Sensor To
Connect the shunt-type current sensor to the power earth ground as shown in the figure below. If
you have to connect the sensor to the non-earth side, use a wire that is thicker than AWG18 (with
a conductive cross-sectional area of approximately 1 mm2) between the sensor and the instrument
to reduce the effects of common mode voltage. Take safety and error reduction into consideration
when constructing external current sensor cables.

WT300 series
V
Voltage input terminals
± LOAD

External current sensor
input connector

Shunt-type current sensor

2-32 IM WT310-02EN
 2.10 Wiring the Circuit under Measurement When Using Current Sensors

Ungrounded Measurement Circuits 1

When the circuit under measurement is not grounded and the signal is high in frequency or large
in power, the effects of the inductance of the shunt-type current sensor cable become large. In this
case, use an isolation sensor (CT, DC-CT, or clamp) to perform measurements.
2
Clamp-type current sensor

Making Preparations for Measurements

WT300 series

V
Voltage input terminals 3
± LOAD
External current sensor
input connector
4
Connecting the 96001 Clamp-on Probe
When using the Yokogawa 96001 Clamp-on Probe, use the 758924 Conversion Adapter (optional
accessory). 5
96001 (voltage output type)
758924 WT310/WT310HC
EXT input terminal
6

7
WT332/WT333

EXT input terminal App

Index

IM WT310-02EN 2-33
2.10 Wiring the Circuit under Measurement When Using Current Sensors

Connecting to the WT310/WT310HC

In the wiring examples that follow, the WT310/WT310HC input elements, voltage input terminals, and
current input terminals are simplified as shown in the following figure.

Voltage input
WT310/WT310HC terminals

External current sensor ± C V

input connector
±
(EXT)
EXT

Wiring Example
The following figures show how to connect to the WT310/WT310HC.

When You Are Using a Shunt-Type When You Are Using a Clamp-type
Current Sensor Current Sensor That Outputs Voltage

SOURCE LOAD SOURCE LOAD

Clamp-type current sensor
Shunt-type current sensor that outputs voltage

Earth side Earth side

OUT L OUT H

± C V ± C V
± ±
EXT EXT

When you use a shunt-type current sensor in the wiring configuration shown at the bottom of page
2-21, the configuration changes as shown in the figure below.

Shunt-type current sensor

B9284LK

2-34 IM WT310-02EN
 2.10 Wiring the Circuit under Measurement When Using Current Sensors

Connecting to the WT332/WT333 1

In the wiring examples that follow, the WT332/WT333 input elements, voltage input terminals, and
current input terminals are simplified as shown in the following figure.
± VOLTAGE
2
WT332/WT333 Voltage input
terminals

Making Preparations for Measurements

CURRENT

±
EXT
V
EXT 3
Current input C
terminals ±
±

4
Input element

Also, the wiring example is for when a shunt-type current sensor is connected. When connecting
a clamp-type current sensor that outputs voltage, substitute the shunt-type current sensor with the 5
clamp-type current sensor.

Shunt-type current sensor Clamp-type current sensor

that outputs voltage
I ± 6
OUT H OUT L

± V ± V 7
EXT EXT
C C
± ±
App
Input element Input element

Wiring Example of a Single-Phase, Two-Wire System (1P2W) with

Index
a Shunt-Type Current Sensor
The following wiring example shows how to configure the wiring to connect to input element 1. To
configure the wiring for other input elements, substitute the numbers in the figures with the appropriate
element numbers.

SOURCE LOAD

Shunt-type current sensor

Earth side
OUT L OUT H

± V
EXT
C
±

Element 1

IM WT310-02EN 2-35
2.10 Wiring the Circuit under Measurement When Using Current Sensors

Wiring Example of a Single-Phase, Three-Wire System (1P3W)

with Shunt-Type Current Sensors
The wiring is connected to input elements 1 and 3.

SOURCE LOAD
OUT H OUT L
N

OUT H OUT L

± V ± V
EXT EXT
C C
± ±

Element 1 Element 3

Wiring Example of a Three-Phase, Three-Wire System (3P3W) with

Shunt-Type Current Sensors
The wiring is connected to input elements 1 and 3. Measure the line voltage using S-phase power as
the reference.

SOURCE LOAD
R
OUT H OUT L
S

T
OUT H OUT L

± V ± V
EXT EXT
C C
± ±

Element 1 Element 3

Wiring Example of a Three-Phase, Four-Wire System (3P4W) with

Shunt-Type Current Sensors
Model: Applies to the WT333.
The wiring is connected to input elements 1, 2, and 3.

SOURCE LOAD
R
OUT H OUT L
S
OUT H OUT L
T
OUT H OUT L
N

± V ± V ± V
EXT EXT EXT
C C C
± ± ±

Element 1 Element 2 Element 3

2-36 IM WT310-02EN
 2.10 Wiring the Circuit under Measurement When Using Current Sensors

Wiring Example with the Three-Voltage, Three-Current Method 1

(3V3A) and Shunt-Type Current Sensors
Model: Applies to the WT333.
The wiring is connected to input elements 1, 2, and 3.
2
SOURCE LOAD
R

Making Preparations for Measurements

OUT H OUT L
S

T
OUT H OUT L 3
OUT H OUT L

± V ± V ± V 4
EXT EXT EXT
C C C
± ± ±
5
Element 1 Element 2 Element 3

Note
For details about the relationship between the wiring system and how measured and computed values are 6
determined, see appendix 1, “Symbols and Determination of Measurement Functions.”

App

Index

IM WT310-02EN 2-37
 2.11 Wiring the Circuit under Measurement When
Using a Voltage or Current Transformer
This section explains how to wire measurement cables from external voltage transformers1 or current
transformers2 to the voltage or current input terminals of input elements. Also refer to this section when
wiring clamp-type current sensors that output current.
*1 VT (voltage transformer)
*2 CT (current transformer)

To prevent electric shock and damage to the instrument, follow the warnings given in section 2.5,
“Precautions When Wiring the Circuit under Measurement.”

Voltage Measurement
When the maximum voltage of the circuit under measurement exceeds 600 Vrms, you can perform
measurements by connecting an external VT to the voltage input terminal.

Current Measurement
If the maximum current of the circuit under measurement exceeds the maximum measurement range,
you can measure the current of the circuit under measurement by connecting an external CT or a
clamp-type sensor that outputs current to the current input terminal.
• WT310 and WT332/WT333
When the maximum current exceeds 20 Arms
• WT310HC
When the maximum current exceeds 40 Arms

Connecting to the Input Terminals

Voltage Input Terminals
The terminals are safety banana jacks (female) that are 4 mm in diameter.
Only insert a safety terminal whose conductive parts are not exposed into a voltage input terminal.
If you are using the included 758931 Safety Terminal Adapter, see section 2.6.

Current Input Terminals

• The terminals are binding posts, and the screws are M6. Either wind a wire around a screw or pass
a crimped terminal through the screw axis, and then tighten firmly with the terminal knob.
• For the dimensions of the terminal parts, see section 2.9.
• When the voltage of the circuit under measurement is being applied to the current input terminals,
do not touch the external current sensor input terminals. Doing so is dangerous because the
terminals are electrically connected inside the instrument.
• When connecting a measurement cable from an external current sensor to an external current
sensor input connector, remove the cables connected to the current input terminals. Also, when
the voltage of the circuit under measurement is being applied to the external current sensor input
terminals, do not touch the current input terminals. Doing so is dangerous because the terminals
are electrically connected inside the instrument.
• For the precautions to follow when you connect the current input terminal and the crimping terminal
and after you connect these terminals, see section 2.9.

General VT and CT Handling Precautions

• Do not short the secondary side of a VT. Doing so may damage it.
• Do not short the secondary side of a CT. Doing so may damage it.
Also, follow the VT or CT handling precautions in the manual for the VT or CT that you are using.
2-38 IM WT310-02EN
 2.11 Wiring the Circuit under Measurement When Using a Voltage or Current Transformer

1
CAUTION
The thick lines on the wiring diagrams are the parts where the current flows. Use wires that
are suitable for the current levels. 2

Making Preparations for Measurements

Note
• Make sure that you have the polarities correct when you make connections. If the polarity is reversed, 3
the polarity of the measurement current will be reversed, and you will not be able to make correct
measurements. Be especially careful when connecting clamp-type current sensors to the circuit under
measurement, because it is easy to reverse the connection.
• Note that the frequency and phase characteristics of the VT or CT affect the measured data. 4
• For safety reasons, the common terminals (+/–) of the secondary side of the VT and CT are grounded in
the wiring diagrams in this section. However, the necessity of grounding and the grounding location (ground
near the VT or CT or ground near the power meter) vary depending on the item under measurement.
• To measure the apparent power and power factor more accurately on an unbalanced three-phase circuit, 5
we recommend that you use the three-voltage, three-current method (3V3A).

When using the Yokogawa 751552 Clamp-on Probe, use the 758917 Measurement Lead and the 6
758921 Fork Terminal Adapter Set (optional accessory).

751552
758917 758921 WT310/WT310HC
7
Current input
terminals
App
WT332/WT333

Index
Current input
terminals

IM WT310-02EN 2-39
2.11 Wiring the Circuit under Measurement When Using a Voltage or Current Transformer

Connecting to the WT310/WT310HC

In the wiring examples that follow, the WT310/WT310HC input elements, voltage input terminals, and
current input terminals are simplified as shown in the following figure.

Input element
Current input Voltage input
WT310/WT310HC terminals terminals

± C V
±

Wiring Example
The following figures show how to connect to the WT310/WT310HC.

VT and CT VT and pass-through CT

SOURCE LOAD SOURCE LOAD

Pass-through CT

L CT V VT V VT

v v

± C V ± C V
± ±

VT and Clamp-type Current Sensor

That Outputs Current
SOURCE LOAD
Clamp-type current
sensor that outputs
current

V VT

± C V
±

Note
Some CTs (including through types) require load resistance and power supplies. Check your CT’s manual.

2-40 IM WT310-02EN
 2.11 Wiring the Circuit under Measurement When Using a Voltage or Current Transformer

Connecting to the WT332/WT333 1

In the wiring examples that follow, the WT332/WT333 input elements, voltage input terminals, and
current input terminals are simplified as shown in the following figure.
± VOLTAGE
2
WT332/WT333 Voltage input
terminals

Making Preparations for Measurements

± V
CURRENT
EXT

3
Current input C
terminals ± ±

4
Input element

Also, the wiring examples are for when a CT is connected. When connecting a pass-through CT or a
clamp-type current sensor that outputs current, substitute the CT with the pass-through CT or clamp- 5
type current sensor.

Pass-through CT Clamp-type current

6
L CT
sensor that outputs
current

7
± V ± V ± V

C C C
± ± ± App
Input element Input element Input element

Index

IM WT310-02EN 2-41
2.11 Wiring the Circuit under Measurement When Using a Voltage or Current Transformer

Wiring Example of Single-Phase, Two-Wire Systems (1P2W) with a

VT and CT
The following wiring example shows how to configure the wiring to connect to input element 1. To
configure the wiring for other input elements, substitute the numbers in the figures with the appropriate
element numbers.

SOURCE LOAD SOURCE LOAD

L CT V VT L CT V VT

v v

± V ± V

C C
± ±

Element 1 Element 1

Wiring Example of a Single-Phase, Three-Wire System (1P3W)

with VTs and CTs
The wiring is connected to input elements 1 and 3.

SOURCE LOAD

L CT V VT L CT V VT

v v

± V ± V

C C
± ±

Element 1 Element 3

Wiring Example of a Three-Phase, Three-Wire System (3P3W) with

VTs and CTs
The wiring is connected to input elements 1 and 3. Measure the line voltage using S-phase power as
the reference.

SOURCE LOAD
R
S
T
L CT V VT L CT V VT

v v

± V ± V

C C
± ±

Element 1 Element 3

2-42 IM WT310-02EN
 2.11 Wiring the Circuit under Measurement When Using a Voltage or Current Transformer

Wiring Example of a Three-Phase, Four-Wire System (3P4W) with 1

VTs and CTs
Model: Applies to the WT333.
The wiring is connected to input elements 1, 2, and 3.
2
SOURCE LOAD
R

Making Preparations for Measurements

S
T
N 3
L CT V VT L CT V VT L CT V VT

v v v
4
± V ± V ± V

C C C
± ± ± 5
Element 1 Element 2 Element 3

Wiring Example With the Three-Voltage, Three-Current Method 6

(3V3A) and VTs and CTs
Model: Applies to the WT333.
The wiring is connected to input elements 1, 2, and 3.
7
SOURCE LOAD
R
S
T
App
L CT V VT L CT V VT L CT V VT

v v v

± ± ±
Index
V V V

C C C
± ± ±

Element 1 Element 2 Element 3

Note
For details about the relationship between the wiring system and how measured and computed values are
determined, see appendix 1, “Symbols and Determination of Measurement Functions.”

IM WT310-02EN 2-43
 2.12 Connecting to a PC via USB (Installing
WTViewerFreePlus)
When you connect the WT300 series to a PC, you can save measured data to the PC and change the
WT300 series settings from the PC. In addition, you can use WTViewerFreePlus, which is a software
application supplied with the WT300 series, to save measured data to the PC and change the WT300
series settings, without having to create original communication control programs.

PC monitor

WT332/WT333
WT310/WT310HC

Saved data
Setting changes

The WT300 series can be connected to a PC using the following communication interfaces.
• USB
• GP-IB
• RS-232
• Ethernet

This section explains how to connect the WT300 series to a PC via USB. To connect to a PC via
a different communication interface, see chapter 4 in the WTViewerFreePlus User’s Manual, IM
760121-02E.

Connecting the WT300 series to a PC via USB

Use a USB cable to connect the USB port for PCs (type B connector) on the rear panel of the WT300
series to the PC.

PC
WT332/WT333

WT310/WT310HC

USB port
USB port

USB cable

2-44 IM WT310-02EN
 2.12 Connecting to a PC via USB (Installing WTViewerFreePlus)

Installing WTViewerFreePlus 1
1 1 2
Supported operating systems: Microsoft Windows XP, Windows Vista, and Windows 7
*1 32-bit versions are supported.
*2 Both 32-bit versions and 64-bit versions are supported.
2
Have the CD-R that contains the software ready.

Making Preparations for Measurements

If an older version of WTViewerFreePlus has already been installed, uninstall it.
There is a PDF of the manual for the software on the CD-R in the Manuals folder. To view the manual,
you need to have Adobe Acrobat Reader 5.0 or later installed. 3
Before you install the software, make sure that your PC meets the system requirements.
The following procedure explains how to install the software on Windows 7.
1. Turn on the PC and start Windows. Log on as an administrator. 4
2. Insert the installation disk that contains this software into the CD drive.
3. On the PC, select the CD drive.
4. Double-click WTViewerFreePlus_Installer.exe. The InstallShield wizard will start. 5

6
5. Follow the instructions on the screen to install the software.
The following two items will be installed, one after the other.
• WTViewerFreePlus
• YKMUSB (USB driver)
7
6. On Windows Vista or Windows 7, the “User Account Control” window will appear during the
installation. Click Allow or Yes to continue the installation.
App
7. After the installation finishes, a new WTViewerFreePlus folder is added to the Start menu in
Windows. You can open the folder by clicking the Start button, All Programs, YOKOGAWA, and
then WTViewerFreePlus.
Index
Starting WTViewerFreePlus
1. Before you start WTViewerFreePlus, turn on the WT300 series.
2. To start WTViewerFreePlus, click the Start button, All Programs, YOKOGAWA,
WTViewerFreePlus, and then WTViewerFreePlus. After you start WTViewerFreePlus, it will
automatically identify the WT300 series devices that you can connect to and will display them in
the upper left of the screen.

Note
The WT300 series will not be automatically detected if you turn it on after starting WTViewerFreePlus.

3. Select the WT300 series that you want to connect to.

IM WT310-02EN 2-45
2.12 Connecting to a PC via USB (Installing WTViewerFreePlus)

For information on how to display measured data and change the WT300 series settings from
WTViewerFreePlus, see chapters 5 and 6 in the WTViewerFreePlus User’s Manual, IM 760121-02E.

Example of a Window for Configuring the WT300 series

You can change the WT300 series settings from a PC.

Example of a Window Showing the Measured Data of the WT300

series
You can display multiple measured data items at the same time and save measured data to files.

2-46 IM WT310-02EN
Chapter 3 Common Operations

3.1 Key Operation and Functions 1

Key Operations 2
Selecting Which Function to Display
Press FUNCTION to select which function to display.
Each time you press FUNCTION, the displayed function changes in the order shown below. 3
Display
A V A W VA var

Common Operations
TIME

4
B V A W PF
°
C V A W Vpk(+) Vpk(-) Apk(+) Apk(-) Wpk(+) 5
Wpk(-)
MATH Ah±(-) Ah±(+) Ah Wh±(-) Wh±(+) Wh
6
D V A W PF VHz AHz THD V% THD A%

• Vpk, Apk, Wpk, Wh±, and Ah± are all displayed twice. The first time is for the positive measurements and
the second time is for the negative measurements. 7
• MATH and THD are displayed on the left side of the 7-segment LED display.
• Press SHIFT before pressing FUNCTION to change the displayed function in reverse order.

Selecting Which Element to Display (Only on the WT332/WT333) App

Press ELEMENT to select which element to display.
Each time you press ELEMENT, the input element changes in the order shown below.
The WT310 and WT310HC only have one input element, so there is no input element selection.
Index
WT332 1 3 Σ
(two input element model)

WT333 1 2 3 Σ
(three input element model)

IM WT310-02EN 3-1
3.1 Key Operation and Functions

Setup and Execution Keys

How to Use the Setup Menus That Appear When Setup Keys Are Pressed
1. Press a setup key to display the setup menu that corresponds to that key.
2. Use ▲ or ▼ to select an item.
3. Press SET to confirm the item that you selected or set. If there are more items to set, those
items will appear. If you have finished configuring the settings and there are no more items to
set, you will return to the previous menu level or to the measurement data display.

How to Display the Setup Menus That Are Written in Purple below the Keys
In the explanations in this manual, “SHIFT+key name (written in purple)” is used to indicate the
following operation.
1. Press SHIFT. The SHIFT key illuminates to indicate that the keys are shifted.
Now you can select the setup menus and functions written in purple below the keys.
2. Press the desired setup or execution key.

Using the ▲ and ▼ Keys

The operation varies as indicated below depending on what you are setting.
• When you are setting a value, you can use the keys to increase and decrease the value.
• When you are selecting a setting to configure, you can use the keys to change the selected
setting.

SET Key Operation

Press SET to confirm the selected item.

ESC Key Operation

Press HOLD (ESC) while a setup menu is displayed to close the setup menu and return to the
measurement data display. All setting changes that you have confirmed by pressing the SET key
will be reflected in the settings.

Execution Key Operations

Press the HOLD, START, or STOP key to execute the specified feature.

3-2 IM WT310-02EN
 3.2 Entering Values 1

Selecting a Value 2
The digit that is blinking is the one that is currently being set.
Use ▲ or ▼ to select a number.

3
Moving the Digit That Is Being Set
Press SHIFT+▼ (►) to move the digit that is being set to the right.

Common Operations
If you press SHIFT+▼ (►) when the digit that is being set is the digit that is furthest to the right, the
digit that is being set will switch to the leftmost digit that can be set. 4

Moving the Decimal Point

Press SHIFT+▲ (.) to move the decimal point to the right.
5
If you press SHIFT+▲ (.) when the decimal point is as far to the right as it can be, the decimal point
will move to the leftmost possible position.

Increases the number

6

7
+ Moves the decimal point to the right
Reduces the number
+ Moves the digit that is being set to the right
App

Index

IM WT310-02EN 3-3
 3.3 Initializing the Settings

This section explains how to reset the WT300 series settings to their factory default values. This
feature is useful when you want to cancel all of the settings that you have entered or when you want to
redo measurement from scratch.

Procedure
Follow the procedure indicated by the thick lines in the following menu.

Select initialization. Confirm that you want to

1. (Display B) initialize the settings.
3. (Display C) 5.
2.
4.
End the operation, and
if YES is selected,
initialize the settings.

Explanation
For details on initialization, see section 8.2 in the User’s Manual, IM WT310-01E.

3-4 IM WT310-02EN
Chapter 4 Operating the WT300 series

4.1 Setting the Measurement Ranges 1

For details, see section 2.3 in the User’s Manual, IMWT310-01EN.

2
To make accurate measurements, you need to set the measurement ranges (the voltage and current
ranges) appropriately.

3
Setting the Voltage Range
AUTO indicator for the voltage range

4
VOLT

Operating the WT300 series

RANGE
5
300

6
For information about the other digital numbers and characters that are displayed in the
7-segment LED displays, see section 1.3.
An illustration of the WT310/WT310HC is used in this explanation, but this operation can be
performed using the same keys on the WT332/WT333.
7
1. Press .
The voltage range setup menu appears.
The selected voltage range blinks in display C.
If you previously set the voltage range to (the AUTO indicator for the voltage range is lit), the
App
voltage range that has been automatically selected on the basis of the measured voltage blinks.
2. Press or to display the voltage range that you want to select in display C.
3. Press . Index
The voltage range is confirmed, and each of the displays returns to showing measured values.

The figures below show steps 1 to 3 in flowcharts. The User’s Manual, IM WT310-01EN, uses these types
of flowcharts to explain procedures.

When the Crest Factor Is Set to 3 When the Crest Factor Is Set to 6

1. (Display C) 3. 1. (Display C) 3.

2. 2.
Confirm the Confirm the
setting. setting.

Note
In addition to the above operation, you can also change the voltage range without displaying the voltage
range setup menu. For details, see section 2.3 in the User’s Manual, IM WT310-01EN.

IM WT310-02EN 4-1
4.1 Setting the Measurement Ranges

Setting the Current Range

AUTO indicator for the current range

CURR

RANGE

For information about the other digital numbers and characters that are displayed in the
7-segment LED displays, see section 1.3.
An illustration of the WT310/WT310HC is used in this explanation, but this operation can be
performed using the same keys on the WT332/WT333.

1. Press .
The current range setup menu appears.
The selected current range blinks in display C.
If you previously set the current range to (the AUTO indicator for the current range is lit), the current
range that has been automatically selected on the basis of the measured current blinks.
2. Press or to display the current range that you want to select in display C.
3. Press .
The current range is confirmed, and each of the displays returns to showing measured values.

The figures below show steps 1 to 3 in flowcharts. The User’s Manual, IM WT310-01EN, uses these types
of flowcharts to explain procedures.

WT310 Current Ranges

When the Crest Factor Is Set to 3 When the Crest Factor Is Set to 6

1. (Display C) 3. 1. (Display C) 3.

2. 2.
Confirm the Confirm the
setting. setting.

The unit is A. The unit is A.

The unit is mA. The unit is mA.

There are more ranges to choose from on models with the /EX1 or /EX2 option. For details, see section 2.4
in the User’s Manual, IM WT310-01EN.

4-2 IM WT310-02EN
 4.1 Setting the Measurement Ranges

WT310HC Current Ranges 1

When the Crest Factor Is Set to 3 When the Crest Factor Is Set to 6

1. (Display C) 3. 1. (Display C) 3.

2. 2.
2
Confirm the Confirm the
setting. setting.

The unit is A. The unit is A.
3

4
There are more ranges to choose from on models with the /EX1 or /EX2 option. For details, see section 2.4
in the User’s Manual, IM WT310-01EN.

Operating the WT300 series

WT332/WT333 Current Ranges 5
When the Crest Factor Is Set to 3 When the Crest Factor Is Set to 6

1. (Display C) 3. 1. (Display C) 3.

2. 2. 6
Confirm the Confirm the
setting. setting.

The unit is A. The unit is A.

App
There are more ranges to choose from on models with the /EX1 or /EX2 option. For details, see section 2.4
in the User’s Manual, IM WT310-01EN.

Note Index
In addition to the above operation, you can also change the current range without displaying the current
range setup menu. For details, see section 2.3 in the User’s Manual, IM WT310-01EN.

IM WT310-02EN 4-3
 4.2 Configuring the Wiring System Settings
(Only on the WT332/WT333)
For details, see section 2.2 in the User’s Manual, IMWT310-01EN.

On the WT332/WT333, you can set a wiring system that matches the connected circuit under
measurement.
The wiring system on the WT310/WT310HC is a single-phase, two-wire system.

If you set the displayed function to input element Σ, the average current and voltage of each of the
wired input elements and the total power of each of the input elements are displayed in accordance
with the selected wiring system.*
* The current and voltage values do not have any physical meaning.

See appendix 1 for the formula that is used to determine the total power.
For the procedure for selecting input element Σ, see section 4.4.

Configuring the Wiring System Settings

Wiring system indicators

Press to select “3P3W” as the wiring system.

When you press , the wiring system indicators light in the following order.

4-4 IM WT310-02EN
 4.3 Displaying the Voltage, Current, and Active 1
Power on the WT310/WT310HC
For details, see section 4.1 in the User’s Manual, IMWT310-01EN.
2
After you select the measurement ranges (the voltage and current ranges), select the measurement
items that you want to show in each display.

3
Displaying the Voltage in Display A on the WT310/WT310HC
Function keys

Operating the WT300 series

5

6
Press the key for display A, and select V.
When you press , the function and unit indicators for display A light in the following order. To display the
voltage on display A, press the key until V lights.
7
Display A

V
Apparent Reactive Integration App
Voltage Current Active power
power power time
V VA
A var
W TIME

Index
The WT310/WT310HC moves the decimal point so that the measured value can be displayed using the
number of digits available in display A. The unit prefix changes in accordance with the position of the
decimal point.
–3
• m: 10
3
• k: 10
6
• M: 10

IM WT310-02EN 4-5
 4.4 Displaying Voltages, Currents, and Active
Powers on the WT332/WT333
For details, see section 4.1 in the User’s Manual, IMWT310-01EN.

After you select the measurement ranges (the voltage and current ranges), select the measurement
items that you want to show in each display.

Displaying a Voltage in Display A on the WT332/WT333

Function key Element key and indicators

1. Press the key for display A, and select V.

When you press , the function and unit indicators for display A light in the following order. To display a
voltage on display A, press the key until V lights.

Display A

V
Apparent Reactive Integration
Voltage Current Active power power
power time
V VA
A var
W TIME

The WT3330 moves the decimal point so that the measured value can be displayed using the number of
digits available in display A. The unit prefix changes in accordance with the position of the decimal point (m:
–3 3 6
10 ), k: 10 , M: 10 ).

2. Press the key for display A to select input element 1, 2, 3, or Σ.

When you press , the element indicators for display A light in the following order.

Display A

1 2 3
1 2 3

* On the WT332 (the two input element model) element indicator 2 is skipped.

For example, in a three-phase, three-wire system, the circuit under measurement will be connected to input
elements 1 and 3 on the WT332/WT333.
• The display for input element 1 shows the line voltage between phases R-S (see page 2-28).
• The display for input element 3 shows the line voltage between phases T-S (see page 2-28).
• The display for input element Σ shows the average of the line voltage between phases R-S and T-S.
This value does not have any physical meaning.

4-6 IM WT310-02EN
Chapter 5 External I/0 (Option)

5.1 External I/O Connector Pin Arrangement and 1

Pinout
If you select the /DA4 or /DA12 option, D/A output and remote control features are installed in the
2
WT300 series.
You can use the external I/O connector on the rear panel to control the WT300 series remotely and
produce D/A output.

Recorder
3
WT332/WT333 D/A output

4
Remote signal Remote control
signal source

5
WT310/WT310HC

External I/0 (Option)

6
Remote Control
7
CAUTION
Only apply voltages that are within the range of 0 V to 5 V to the remote control input pins.
Do not short or apply external voltages to the output pins. Doing so may damage the WT300
App
series.

D/A Output Index

CAUTION
• Do not short or apply an external voltage to the D/A output terminal. Doing so may damage
the WT300 series.
• When connecting the D/A output to another device, do not connect the wrong signal pin.
Doing so may damage the WT300 series or the connected instrument.

D/A Cable (B9879SX)

Cut the D/A cable to the necessary length, strip the insulation around the internal core wires, and
connect the cable to another device.

IM WT310-02EN 5-1
5.1 External I/O Connector Pin Arrangement and Pinout

Connector Pin Arrangement

WT310/WT310HC WT332/WT333

14 26

WT rear panel 26 13 13 26
1 13

1 13
14 1 1 14
Cable connector
14 26
WT rear panel Cable connector

Pinout
/DA4 (WT310/WT310HC)
Pin No. Core Wire Color Signal Name Pin No. Core Wire Color Signal Name
1 Orange (Red 1) EXT COM 14 Gray (Black 2) EXT SINGLE (input)
2 Orange (Black 1) EXT HOLD (input) 15 White (Red 2) EXT STOP (input)
3 Gray (Red 1) EXT START (input) 16 White (Black 2) INTEG BUSY (output)
4 Gray (Black 1) EXT RESET (input) 17 Yellow (Red 2) No Connection
5 White (Red 1) No Connection 18 Yellow (Black 2) No Connection
6 White (Black 1) No Connection 19 Pink (Red 2) No Connection
7 Yellow (Red 1) No Connection 20 Pink (Black 2) No Connection
8 Yellow (Black 1) No Connection 21 Orange (Red 3) No Connection
9 Pink (Red 1) No Connection 22 Orange (Black 3) DA 4ch (output)
10 Pink (Black 1) DA 3ch (output) 23 Gray (Red 3) DA 2ch (output)
11 Orange (Red 2) DA 1ch (output) 24 Gray (Black 3) DA COM
12 Orange (Black 2) DA COM 25 White (Red 3) No Connection
13 Gray (Red 2) DA COM 26 White (Black 3) No Connection

/DA12 (WT332/WT333)
Pin No. Core Wire Color Signal Name Pin No. Core Wire Color Signal Name
1 Orange (Red 1) EXT COM 14 Gray (Black 2) EXT SINGLE (input)
2 Orange (Black 1) EXT HOLD (input) 15 White (Red 2) EXT STOP (input)
3 Gray (Red 1) EXT START (input) 16 White (Black 2) INTEG BUSY (output)
4 Gray (Black 1) EXT RESET (input) 17 Yellow (Red 2) No Connection
5 White (Red 1) No Connection 18 Yellow (Black 2) DA 12ch (output)
6 White (Black 1) DA 11ch (output) 19 Pink (Red 2) DA 10ch (output)
7 Yellow (Red 1) DA 9ch (output) 20 Pink (Black 2) DA 8ch (output)
8 Yellow (Black 1) DA 7ch (output) 21 Orange (Red 3) DA 6ch (output)
9 Pink (Red 1) DA 5ch (output) 22 Orange (Black 3) DA 4ch (output)
10 Pink (Black 1) DA 3ch (output) 23 Gray (Red 3) DA 2ch (output)
11 Orange (Red 2) DA 1ch (output) 24 Gray (Black 3) DA COM
12 Orange (Black 2) DA COM 25 White (Red 3) No Connection
13 Gray (Red 2) DA COM 26 White (Black 3) No Connection

Note
The EXT COM and DA COM signals are connected internally.

Remote Control I/O Circuit

Input circuit Output circuit
+5 V +5 V

10 kΩ
10 kΩ 100 Ω

0.01 μF 0.01 μF

L level: 0 V to 1 V L level: 0 V to 1.5 V (8 mA)

H level: 4 V to 5 V H level: 2.8 V to 5 V (–8 mA)

5-2 IM WT310-02EN
 5.2 Controlling the WT300 series Remotely 1
Through external control, you can hold values, perform single measurements, and start, stop, and
reset integration.
2
Controlling Integration Remotely
Apply signals according to the following timing chart.
3
Start Stop Reset Start Stop

Approx. 25 ms or more
EXT START 4
Approx. 25
ms or more
EXT STOP
Approx. 25 5
ms or more
EXT RESET Approx. 200 Approx. 200 Approx. 200 Approx. 200

External I/0 (Option)

ms or more ms or more ms or more ms or more

INTEG BUSY 6
The INTEG BUSY output signal is set to low level during integration.
Use this signal when you are observing integration.
7
Holding the Updating of Displayed Data
This produces the same effect as pressing HOLD. Apply an EXT HOLD signal as shown in the
following figure.
App
Display hold
Approx. 25 ms or more
EXT HOLD
Index

Updating Held Display Data

This produces the same effect as pressing SINGLE. While the display is being held, you can update it
by applying an EXT SINGLE signal.

Display update Display update

Data update interval or longer

Approx. 25 ms or more Approx. 25 ms or more

EXT SINGLE

Note
If the period of the EXT SINGLE signal does not meet the conditions shown in the above figure, the signal
may not be detected by the WT300 series.

IM WT310-02EN 5-3
 5.3 Producing D/A Output

Procedure
Follow the procedure indicated by the thick lines in the following menu.

Setting the D/A Output Format

Select the D/A output feature.
1. (Display B)

2.

Select the output format.

3. (Display C) 5. 6.

4. Confirm the setting. Close menu.

(Default setting)

(original
configuration)

Set the output

channel. Set the output item.
(Display B) 7. (Display C) 11. 2

6, 12. 8.
Confirm Confirm
the setting. the setting.

Only on the
1
WT332/WT333

13. 14.

Confirm Close menu.

the setting. A B
8. Press and to set area A (the output function).

On the WT332/WT333, select the element in the following steps 9 and 10.

9. Press to move to area B.

3
10. Press and to select an element (you cannot select an element for ).

1 The number of channels varies depending on the specific option that is installed.
• /DA4 option on the WT310/WT310HC: 4 channels
• /DA12 option on the WT332/WT333: 12 channels
2 When you press SET in step 11, the output channel shown in display B changes to the next channel. For
example, ch1 changes to ch2.
3 The numbers (element numbers) that you can select vary depending on the model. For details, see
“Explanation” in this section.

5-4 IM WT310-02EN
 5.3 Producing D/A Output

Rated Integration Time 1

Select the rated integration time.
1. (Display B)

2.
3.
Hours
(Display B) 5. 2

4. Press and to set the number.

Press to move the digit. 3

Minutes Seconds
(Display C) 7. (Display D) 9. 10.
4
6. The same as 8. The same as Confirm the Close menu.
operation 4. operation 4. setting.

Note
If you operate the WT300 series frequently to configure settings such as the D/A output items and rated
integration time, you can connect the WT300 series to a PC and use WTViewerFreePlus to easily configure
5
settings from the PC.

External I/0 (Option)

Explanation 6
D/A Output
You can output voltage, current, active power, apparent power, reactive power, power factor, phase
angle, frequency, voltage peak, current peak, and integrated values using a ±5 V FS DC voltage.
7
Number of Channels
The number of channels varies depending on the specific option that is installed.
• /DA4 option on the WT310/WT310HC: 4 channels
App
• /DA12 option on the WT332/WT333: 12 channels

Output Format
You can select a preconfigured output format or configure your own original format.
Index
Using the Default Settings
Select one of the default settings to output preconfigured (default) items.
Default Values for Normal Measurement: dFLt-n
Select this setting to output normal measured values. The output settings are as follows:
Suffix Code /DA4 /DA12
Product Name WT310 WT332 WT333
WT310HC
Output Channel ch1 U1 U1 U1
ch2 I1 - U2
ch3 P1 U3 U3
ch4 fU UΣ UΣ
1
ch5 I1 I1
ch6 - I2
ch7 I3 I3
ch8 IΣ IΣ
ch9 P1 P1
ch10 - P2
ch11 P3 P3
ch12 PΣ PΣ
1 These channels cannot be set.
2 The numbers are used to indicate input elements 1, 2, and 3.

IM WT310-02EN 5-5
5.3 Producing D/A Output

Default Values for Integration: dFLt-i

Select this setting to output integrated values. The output settings are as follows:
Suffix Code /DA4 /DA12
Product Name WT310 WT332 WT333
WT310HC
Output Channel ch1 P1 P1 P1
ch2 WP1 - P2
ch3 q1 P3 P3
ch4 fU PΣ PΣ
1
ch5 WP1 WP1
ch6 - WP2
ch7 WP3 WP3
ch8 WPΣ WPΣ
ch9 q1 q1
ch10 - q2
ch11 q3 q3
ch12 qΣ qΣ
1 These channels cannot be set.
2 The numbers are used to indicate input elements 1, 2, and 3.

Configuring an Original Output Format

You can specify output items (output functions and elements) for each output channel.

Output Functions (Area A in step 8 in the procedural explanation

for setting the D/A output format)
You can select from the following options.
u (voltage U), i (current I), P (active power P), VA (apparent power S),
VAr (reactive power Q), PF (power factor λ), dEG (phase angle Φ),
uFrq (voltage frequency fU), iFrq (current frequency fI),
uP (peak voltage value Upk), iP (peak current value Ipk),
Ph (sum of watt hours Wp), Ph+ (positive watt hour Wp+), Ph– (negative watt hour Wp–),
Ah (sum of ampere hours q), Ah+ (positive ampere hour* q+), Ah– (negative ampere hour* q-),
MATH (integration), ---- (0 V D/A output; no element is specified)

* For more information about positive and negative ampere hours, see page 5-4 of the User’s
Manual, IM WT310-01EN.

Elements (Area B in step 10 in the procedural explanation for setting the D/A output
format)
Product Name Element
WT310 or WT310HC 1
WT332 1, 3, or 4
WT333 1, 2, 3, or 4
Element number 4 represents Σ.

5-6 IM WT310-02EN
 5.3 Producing D/A Output

Rated Integration Time 1

In the D/A output of integrated values, 5.0 V FS represents the integrated value when the rated range
value is applied for the rated integration time. The same is true if scaling is enabled or the value for Σ
is being measured. The default setting is 1.00.00 (1 h, 0 min, 0 s).
• Range: 0.00.00 (00 h, 00 min, 00 s) to 10000.00.00 (10000 h, 00 min, 00 s)
2
If you set the rated integration time to 0.00.00, the D/A output value will be 0 V.

Note 3
• When the MAX hold feature (see section 4.6 in the User’s Manual, IM WT310-01EN) is enabled, the
maximum held values (MAX values) for the following items are displayed. The maximum held values (MAX
values) are also output in D/A output.
Voltage, current, active power, apparent power, peak voltage, peak current 4
• D/A output is performed for each output item with 5.0 V FS representing the application of the rated range
value for voltage, current, and power.
• Even when scaling constants are set for voltage, current, and power, the D/A output of 5.0 V FS
represents the application of the rated range value. 5
• Even if the elements have different scaling constants, when you set the element to Σ, 5.0 V FS of D/A
output represents the application of the rated range value to each element.

External I/0 (Option)

• The D/A output for all math functions except for those indicated below is 0 V.
Efficiency, average active power during integration 6

App

Index

IM WT310-02EN 5-7
5.3 Producing D/A Output

Relationship between Output Items and D/A Output Voltage

Frequency
D/A output
Approx. 7.5 V

5.0 V

2.5 V

0.5 V
Displayed value
0.5 Hz 10 Hz 1 kHz 100 kHz
1 Hz 100 Hz 10 kHz

Integrated Value
D/A output
Approx. 7.0 V
When 140% of
the rated input is applied.
5.0 V

When the rated input is applied.

0 Integration time
t0
t0: Rated integration time

Other Items
D/A output
Approx. 7.5 V
Approx. 7.0 V
5.0 V

Displayed Value Output

140% Approx. 7.0 V –140 –100
100% 5.0 V 0 100 140 Displayed value (%)
0% 0V
–100% –5.0 V
–140% pprox. –7.0 V –5.0V
Approx. –7.0 V
Approx. –7.5 V

• The range between +5 to +7 V and –5 to –7 V is not output for λ and Φ. When an error occurs, the output
is approximately ±7.5 V.
• For the efficiency math function, +5 V represents 100%.
• For Upk and Ipk, ±5 V represents the application of 3 times the rated range value (6 times the rated range
value when the crest factor is 6).
• When the selected output function is “----” or there is no numerical data, the output is 0 V.

5-8 IM WT310-02EN
 5.3 Producing D/A Output

Examples of D/A Output 1

Voltage
When the voltage range is set to 150 V and 150 V (the rated range value) is applied, the D/A output is
+5 V. 2
When 100 V is applied, the output is 100 V/150 V × 5 V = 3.3 V.

Power 3
When the voltage range is set to 150 V and the current range is set to 5 A, the rated power range is
150 V × 5 A = 750 W.
If the measured power value is 750 W, the D/A output is +5 V.
When the measured power value is 300 W, the output is 300 W/750 W × 5V = 2.0 V. 4

Three-Phase Power (WT332/WT333)

When the voltage range is set to 150 V, the current range is set to 5 A, and a three-phase, three-wire
system is connected to elements 1 and 3, the rated power range of wiring unit Σ will be as follows.1
5

External I/0 (Option)

(Rated power range of element 1) + (rated power range of element 3)
= 150 V × 5 A + 150 V × 5 A
=1500 W 6
If the measured power value for Σ is 1500 W, the D/A output is +5 V.
When the measured power value is 600 W, the output is 600 W/1500 W × 5V = 2.0 V.

1 For information about the power range of wiring unit Σ, see the table of Σ function expressions on
7
the second page of the appendix in the User’s Manual, IM WT310-01EN (PDF). This table shows
the expressions that the WT332/WT333 uses to internally calculate the measured values. This table
also shows how to think about wiring unit measurement ranges. In this example, PΣ in the table App
corresponds to P1 + P3 in the three-phase, three-wire (3P3W) column.

Integrated Power Values

When the voltage range is set to 150 V and the current range is set to 5 A, the rated power range is Index
150 V × 5 A = 750 W. In manual integration mode, when the rated integration time is set to 1 hour, the
rated electrical energy value is 750 W × 1 h = 750 Wh.
If you perform integration for 1 hour and the measured electrical energy is 750 W, the D/A output one
hour after integration starts is + 5 V.
If the measured electrical energy over 1 hour is 300 Wh, the output one hour after integration starts is
300 Wh/750 Wh × 5 V = 2.0 V.
The output 30 minutes after integration starts is 150 Wh/750 Wh × 5 V = 1.0 V.

IM WT310-02EN 5-9
Chapter 6 Troubleshooting, Maintenance, and Inspection

6.1 Troubleshooting 1

Faults and Corrective Actions 2

• If an error code appears on the 7-segment LED display, see section 5.2. Also, for information about
communication error messages, see the appendix of the Communication Interface User’s Manual,
IM WT310-17EN.
• If servicing is necessary, or if the instrument does not operate properly even after you have
3
attempted to deal with the problem according to the instructions in this section, contact your nearest
YOKOGAWA dealer.

Problems and Solutions Refer To

4
Nothing appears on the 7-segment LED display when you turn on the power.
Securely connect the power cord to the WT300 series and to the power outlet. 2.3
Set the supply voltage and frequency to within the permitted range. 2.3
The displayed data is not correct. 5
Confirm that the ambient temperature and humidity are within their specified 2.2
ranges.
Confirm that the display is not being affected by noise. 2.1, 2.5
Check the measurement cable wiring.
Check the wiring system. (Applies to the WT332/WT333.)
2.8 to 2.11
2.8 to 2.11,
6
2.21

Troubleshooting, Maintenance, and Inspection

Confirm that the line filter is off. 2.91
Check the measurement period settings. 2.81
Check the FAQ at the following URL. ― 7
http://tmi.yokogawa.com/
Turn the power off and then on again. 2.4
Keys do not work.
Check the REMOTE indicator. If the REMOTE indicator is illuminated, press ―
SHIFT (LOCAL) to turn it off.
App
Confirm that the keys are not locked. 8.51
Unable to make harmonic measurements.
Check the PLL source settings. 6.31
Confirm that the input signal that you have selected as the PLL source meets the 6.31 Index
specifications.
Unable to configure or control the instrument through the communication interface.
Check to make sure that the GP-IB address setting matches the specifications. ―2
Check to make sure that the TCP/IP settings match the specifications. ―2
Check to make sure that the serial (RS-232) interface parameter settings match ―2
the specifications.
Confirm that the interface meets the electrical and mechanical specifications. ―2
1 See the User’s Manual, IM WT310-01EN.
2 See the Communication Interface User’s Manual, IM WT310-17EN.

IM WT310-02EN 6-1
 6.2 Error Code Descriptions
and Corrective Actions
Information That Is Displayed When the Power Is Turned On (Display: Code.##)
Code Description Corrective Action Refer To
3 You turned on the power while holding SET, so all the 3.3
settings have been initialized.
80 The system structure has changed, so all the settings ―
have been initialized.
87 The WT310/WT310HC/WT330 firmware has ―
changed, so all the settings have been initialized.

Setting and Execution Errors (Display: Err.###)

Code Description Corrective Action Refer To
759 Network initialization failed. Check the network settings. Chapter
41
812 The setting or command is not available during data ―
storage.
813 The setting is not available when an integration Reset the integration operation. 5.32
operation is being carried out or aborted.
823 Cannot be changed during CAL. Wait until CAL finishes. 8.32
832 You tried to load an empty setup parameter file. Select a file that has had setup parameters saved 7.22
to it.
840 The setting or command is not available when auto
range is on.
841 You tried to start integration after the integration time Reset the integration operation. 5.32
reached the specified timer time.
842 You tried to start integration during an integration 5.32
operation.
843 The integrated value overflowed during integration or Reset the integration operation. 5.32
ended abnormally because of power failure or some
other reason.
844 You tried to stop integration when no integration 5.32
operation was taking place.
845 You tried to reset integration when the mode was not 5.32
integration mode or during integration.
846 You tried to start integration despite a peak ―
overrange.
847 When you tried to start integration in continuous Set the integration timer correctly. 5.22
integration mode, the integration timer time was set
to zero.
865 The setting is not available when an integration Abort or reset the integration operation. 5.32
operation is being carried out.

System Errors (Display: Err.###)

Code Description Corrective Action Refer To
901 The setup data could not be backed up, and the The battery for backing up the setup data may have ―
settings have been initialized. worn out.
Servicing is required.
915 This is an EEPROM SUM error. The EEPROM may be corrupted. ―
Servicing is required.
919 The currently installed modules and the setup data Servicing is required. ―
conflict with each other. The setup data has been
initialized.

1 Communication Interface User’s Manual, IM WT310-17EN

2 User’s Manual, IM WT310-01EN

6-2 IM WT310-02EN
 6.3 Recommended Part Replacement 1

YOKOGAWA guarantees the WT300 series for the period and under the conditions of the product
warranty. The warranty does not cover the following expendable items. The replacement period for 2
expendable items varies depending on the conditions of use. Refer to the table below as a general
guideline. Contact your nearest YOKOGAWA dealer to have parts replaced.

Part Name Recommended Replacement Interval 3

Current input relay A relay for switching the current input circuit. The relay’s specifications indicated below.
(only for the WT310) • Electrical life: Approximately 50,000 operations (at the rated capacity)
• Mechanical life: Approximately 1,000,000 operations
Backup battery
(lithium)
3 years
4

Troubleshooting, Maintenance, and Inspection

7

App

Index

IM WT310-02EN 6-3
 6.4 Calibration and Adjustment
For calibration and adjustment, contact your nearest YOKOGAWA dealer.

6-4 IM WT310-02EN
Chapter 7 Specifications

7.1 Input 1

Item Specifications
Input terminal type Voltage 2
Plug-in terminal (safety terminal)
Current
• Direct input: Large binding post

Input format
• External current sensor input (option): isolated BNC connector
Voltage
3
Floating input through resistive voltage divider
Current
Floating input through shunt
Measurement range Voltage 4
Crest factor 3: 15 V, 30 V, 60 V, 150 V, 300 V, 600 V
Crest factor 6: 7.5 V, 15 V, 30 V, 75 V, 150 V, 300 V
Current
• Direct input
• Crest factor 3: 5
• WT310/WT332/WT333: 0.5 A, 1 A, 2 A, 5 A, 10 A, 20 A
• WT310 Only: 5 mA, 10 mA, 20 mA, 50 mA, 100 mA, 200 mA
• WT310HC: 1 A, 2 A, 5 A, 10 A, 20 A, 40 A
• Crest factor 6:
• WT310/WT332/WT333: 0.25 A, 0.5 A, 1 A, 2.5 A, 5 A, 10 A 6
• WT310 Only: 2.5 mA, 5 mA, 10 mA, 25 mA, 50 mA, 100 mA
• WT310HC: 0.5 A, 1 A, 2.5 A, 5 A, 10 A, 20 A
• External current sensor input (/EX1, /EX2)
• Crest factor 3:
EX1 “2.5 V, 5 V, 10 V” or 7
EX2 “50 mV, 100 mV, 200 mV, 500 mV, 1 V, 2 V”

Specifications
• Crest factor 6:
EX1 “1.25 V, 2.5 V, 5 V” or
EX2 “25 mV, 50 mV, 100 mV, 250 mV, 500 mV, 1 V”
Input impedance Voltage
App
Input resistance: Approx. 2 MΩ, input capacitance: Approx. 13 pF in parallel with the resistance
Current
• Direct input
• WT332/WT333 Index
Crest factor 3: 0.5 A, 1 A, 2 A, 5 A, 10 A, 20 A
Crest factor 6: 0.25 A, 0.5 A, 1 A, 2.5 A, 5 A, 10 A
Input resistance: Approx. 6 mΩ, input inductance : Approx.0.1 μH in series with the
resistance
• WT310
Crest factor 3: 0.5 A, 1 A, 2 A, 5 A, 10 A, 20 A
Crest factor 6: 0.25 A, 0.5 A, 1 A, 2.5 A, 5 A, 10 A
Input resistance: Approx. 6 mΩ + 10 mΩ (max)* Factory setting
Input inductance: Approx. 0.1 μH in series with the resistance
• WT310
Crest factor 3: 5 mA, 10 mA, 20 mA, 50 mA, 100 mA, 200 mA
Crest factor 6: 2.5 mA, 5 mA, 10 mA, 25 mA, 50 mA, 100 mA
Input resistance: Approx. 500 mΩ, input inductance : Approx.0.1 μH in series with the
resistance
• WT310HC
Crest factor 3: 1 A, 2 A, 5 A, 10 A, 20 A, 40 A
Crest factor 6: 0.5 A, 1 A, 2.5 A, 5 A, 10 A, 20 A
Input resistance: Approx. 5 mΩ, input inductance : Approx.0.1 μH in series with the
resistance
• External current sensor input (/EX1):
Crest factor 3: 2.5 V, 5 V, 10 V
Crest factor 6: 1.25 V, 2.5 V, 5 V
Input resistance: Approx. 100 kΩ
• External current sensor input (/EX2):
Crest factor 3: 50 mV, 100 mV, 200 mV, 500 mV, 1 V, 2 V
Crest factor 6: 25 mV, 50 mV, 100 mV, 250 mV, 500 mV, 1 V
Input resistance: Approx. 20 kΩ

IM WT310-02EN 7-1
7.1 Input

Item Specifications
Instantaneous maximum Voltage
allowable input Peak value of 2.8 kV or RMS value of 2.0 kV, whichever is less
(1 period, for 20 ms) Current
• Direct input
• WT310/WT332/WT333
Crest factor 3: 0.5 A, 1 A, 2 A, 5 A, 10 A, 20 A
Crest factor 6: 0.25 A, 0.5 A, 1 A, 2.5 A, 5 A, 10 A
Peak value of 450 A or RMS value of 300 A, whichever is less
• WT310
Crest factor 3: 5 mA, 10 mA, 20 mA, 50 mA, 100 mA, 200 mA
Crest factor 6: 2.5 mA, 5 mA, 10 mA, 25 mA, 50 mA, 100 mA
Peak value of 150 A or RMS value of 100 A, whichever is less
• WT310HC
Crest factor 3: 1 A, 2 A, 5 A, 10 A, 20 A, 40 A
Crest factor 6: 0.5 A, 1 A, 2.5 A, 5 A, 10 A, 20 A
Peak value of 450 A or RMS value of 300 A, whichever is less
• External current sensor input
Peak value less than or equal to 10 times the rated range
Instantaneous maximum Voltage
allowable input Peak value of 2 kV or RMS value of 1.5 kV, whichever is less
(for 1 s) Current
• Direct input
• WT310/WT332/WT333
Crest factor 3: 0.5 A, 1 A, 2 A, 5 A, 10 A, 20 A
Crest factor 6: 0.25 A, 0.5 A, 1 A, 2.5 A, 5 A, 10 A
Peak value of 150 A or RMS value of 40 A, whichever is less
• WT310
Crest factor 3: 5 mA, 10 mA, 20 mA, 50 mA, 100 mA, 200 mA
Crest factor 6: 2.5 mA, 5 mA, 10 mA, 25 mA, 50 mA, 100 mA
Peak value of 30 A or RMS value of 20 A, whichever is less
• WT310HC
Crest factor 3: 1 A, 2 A, 5 A, 10 A, 20 A, 40 A
Crest factor 6: 0.5 A, 1 A, 2.5 A, 5 A, 10 A, 20 A
Peak value of 150 A or RMS value of 44 A, whichever is less
• External current sensor input
Peak value less than or equal to 10 times the rated range
Continuous maximum Voltage
allowable input Peak value of 1.5 kV or RMS value of 1 kV, whichever is less
Current
• Direct input
• WT310/WT332/WT333
Crest factor 3: 0.5 A, 1 A, 2 A, 5 A, 10 A, 20 A
Crest factor 6: 0.25 A, 0.5 A, 1 A, 2.5 A, 5 A, 10 A
Peak value of 100 A or RMS value of 30 A, whichever is less
• WT310
Crest factor 3: 5 mA, 10 mA, 20 mA, 50 mA, 100 mA, 200 mA
Crest factor 6: 2.5 mA, 5 mA, 10 mA, 25 mA, 50 mA, 100 mA
Peak value of 30 A or RMS value of 20 A, whichever is less
• WT310HC
Crest factor 3: 1 A, 2 A, 5 A, 10 A, 20 A, 40 A
Crest factor 6: 0.5 A, 1 A, 2.5 A, 5 A, 10 A, 20 A
Peak value of 100 A or RMS value of 44 A, whichever is less
• External current sensor input
Peak value less than or equal to 5 times the rated range
Continuous maximum 600VrmsCAT II
common-mode voltage
(during 50/60 Hz input)

7-2 IM WT310-02EN
 7.1 Input

Item Specifications
1
Influence of common mode When 600 Vrms is applied between the input terminal and case with the voltage input terminals shorted,
voltage current input terminals open and external current sensor input terminals shorted.
Double the following values when the crest factor is set to 6.
2
• At 50/60 Hz
–80 dB or more (±0.01% of range or less)

• Up to 100 kHz (reference value)

0.01% of range or more. f is frequency of input signal in kHz. 3
• 15 V, 30 V, 60 V, 150 V, 300 V, 600 V ranges, 0.5 A, 1 A, 2 A, 5 A, 10 A, 20 A ranges of WT310/
WT332/WT333, 1 A, 2 A, 5 A, 10 A, 20 A, 40A ranges of WT310HC and, external current sensor
input (/EX2 Option)
4
Within ± (Maximum rated range) × 0.001 × f% of range
(Rated range)
The maximum rated range is 600 V for the voltage input terminal and 20 A for the current input
of WT310/WT332/WT333 and 40 A for the current input terminal of WT310HC and 2 V for option
/EX2. 5
• 5 mA, 10 mA, 20 mA, 50 mA, 100 mA, and 200 mA ranges of WT310

Within ± (Maximum rated range) × 0.0002 × f% of range

(Rated range)
The maximum rated range is 20 A.
6
• External current sensor input (/EX1 Option) ranges

Within ± (Maximum rated range) × 0.01 × f% of range

(Rated range) 7
The maximum rated range is 10V.

Specifications
Line filter Select OFF or ON (cutoff frequency at 500 Hz).
Frequency filter Select OFF or ON (cutoff frequency at 500 Hz).
A/D converter Simultaneous conversion of voltage and current inputs. Resolution: 16 bits App
Maximum conversion rate: Approx. 10 μs

Index

IM WT310-02EN 7-3
 7.2 Measurement Items

Item Specifications
Displayed items

During normal measurement

Item Indicator Displayed On Meaning
U V A, B, C, D voltage
I A A, B, C, D current
P W A, B, C, D active power
S VA A apparent power
Q var A reactive power
TIME TIME A elapsed integration time
λ PF B, D power factor
Φ ° B phase angle
U+pk V pk C Maximum voltage
U-pk V pk C Minimum voltage
I+pk A pk C Maximum current
I-pk A pk C Minimum current
P+pk W pk C Maximum active power
P-pk W pk C Minimum active power
WP Wh C sum of watt hours
WP+ W h± C positive watt hour
WP- W h± C negative watt hour
q Ah C sum of ampere hours
q+ A h± C positive ampere hour
q- A h± C negative ampere hour
MATH MATH C Result of efficiency computation, crest factor computation,
four arithmetic operations, and average active power during
integration
fU V Hz D voltage frequency
fI A Hz D current frequency
Uthd THD V % D total harmonic distortion of voltage
Ithd THD A % D total harmonic distortion of current

During harmonic measurement

Item Indicator Displayed On Meaning
U V A, B, C, D harmonic voltage
I A A, B, C, D harmonic current
P W A, B, C, D harmonic active power
k or. (in 7 segment display) A harmonic order
Uhdf V% B relative harmonic content of each harmonic voltage
Ihdf A% B relative harmonic content of each harmonic current
Phdf W% B relative harmonic content of each harmonic power
ΦU V° B phase angle of each harmonic component of voltage
ΦI A° B phase angle of each harmonic component of current
λ PF D power factor of fundamental signal
fU V Hz D frequency of the voltage set to be the PLL synchronization
source
fI A Hz D frequency of the current set to be the PLL synchronization
source
Uthd THD V % D total harmonic distortion of voltage
Ithd THD A % D total harmonic distortion of current

Element Select the input element or Σ on the WT332/WT333. Displays the display item of the selected
element.

7-4 IM WT310-02EN
 7.3 Accuracy 1

7.3.1 Voltage and Current Accuracy 2

Item Specifications
Accuracy Requirements
• Temperature: 23 ± 5°C
• Humidity: 30 to 75%RH
• Input waveform: Sine wave 3
• Crest factor: 3
• Common-mode voltage: 0 V
• Scaling function: OFF
• Number of displayed digits: 5 digits
• Frequency filter: Turn ON to measure voltage or current of 200 Hz or less.
4
• After warm-up time has passed
• After zero-level compensation or after measurement range is changed

Accuracy (at 12 months)

(The accuracy shown below is the sum of reading and range errors.)
5
* f in the read error equation is the input signal frequency in kHz.
WT310/WT332/WT333 WT310HC WT310HC
(Voltage/Current) (Voltage, Current EXT sensor input) (Direct current input) 6
±(0.1% of reading ±(0.1% of reading ±(0.2% of reading
DC
+ 0.2% of range) + 0.2% of range) + 0.2% of range)
±(0.1% of reading ±(0.1% of reading ±(0.1% of reading
0.5 Hz ≤ f< 45 Hz
+ 0.2% of range) + 0.2% of range) + 0.2% of range)
±(0.1% of reading ±(0.1% of reading ±(0.1% of reading
7
45 Hz ≤ f ≤ 66 Hz
+ 0.1 % of range) + 0.1 % of range) + 0.1 % of range)

Specifications
±(0.1% of reading ±(0.1% of reading ±(0.1% of reading
66 Hz < f ≤ 1 kHz
+ 0.2 % of range) + 0.2 % of range) + 0.2 % of range)

1 kHz < f ≤ 10 kHz

±{(0.07×f)% of reading ±{(0.07×f)% of reading+ 0.3 % of ±{(0.13×f)% of reading+ 0.3 % of App
+ 0.3 % of range} range} range}
±{(0.13×f)% of reading + 0.5 % of
10 kHz < f ≤ 20 kHz
range}
±(0.5 % of reading ±(0.5 % of reading
10 kHz < f ≤ 100 kHz +0.5 % of range) + 0.5 % of range)
Index
±[{0.04×(f–10)}% of reading] ±[{0.04×(f–10)}% of reading]
• Influence of temperature changes after zero-level compensation or range change
Add 0.02% of range/°C to the DC voltage accuracy.
Add the following value to the DC current accuracies.
WT310 (5mA/10mA/20mA/50mA/100mA/200mA ranges): 5 μA/°C
WT310 (0.5A/1A/2A/5A/10A/20A ranges) and WT332/WT333 direct current input: 500 μA/°C
WT310HC direct current input: 1 mA/°C
External current sensor input (/EX1): 1 mV/°C
External current sensor input (/EX2): 50 μV/°C

• Accuracy of the waveform display data, Upk and Ipk

Add the following value to the above accuracy (reference value).
The effective input range is within ±300% of range (within ±600% for crest factor 6)
Voltage input: 1.5 × √(15/range) % of range
Direct current input range:
WT310 (5mA/10mA/20mA/50mA/100mA/200mA range): 3 ×√(0.005/range) % of range
WT310 (0.5A/1A/2A/5A/10A/20A range) and WT332/WT333 direct current input: 3 ×√(0.5/
range) % of range
WT310HC direct current input: 3 ×√(1/range) % of range
External current sensor input range:
/EX1 Option: 3 ×√(2.5/range) % of range
/EX2 Option: 3 ×√(0.05/range) % of range

IM WT310-02EN 7-5
7.3 Accuracy

• Influence of self-generated heat caused by voltage input

Add 0.0000001 ×U2% of reading to the AC voltage accuracies.
Add 0.0000001 ×U2% of reading + 0.0000001 ×U2% of range to the DC current accuracies. U is
the voltage reading (V).

Influence of self-generated heat caused by voltage input lasts until falling the temperature of the
input resistor even if voltage input decreases.

• Influence of self-generated heat caused by current input

WT310:
Add 0.00013 × I2% of reading to the AC current accuracies.
Add 0.00013 × I2% of reading + 0.004 × I2 mA (0.5 A, 1 A, 2 A, 5 A, 10 A, and 20 A ranges) or
0.00013 × I2% of reading + 0.00004 × I2 mA (5 mA, 10 mA, 20 mA, 50 mA, 100 mA, and 200
mA ranges) to the DC current accuracies.
I is the current reading (A).
WT310HC:
Add 0.00006× I2% of reading to the AC current accuracies.
Add 0.00006 × I2% of reading + 0.001 × I2 mA to the DC current accuracies.
I is the current reading (A).
WT332/WT333:
Add 0.00013 × I2% of reading to the AC current accuracies.
Add 0.00013 × I2% of reading + 0.002 × I2 mA to the DC current accuracies.
I is the current reading (A).

Influence of self-generated heat caused by current input lasts until falling the temperature of the
shunt resistor even if current input decreases.

• Accuracy changes caused by data update interval

When the data update interval is 100 ms, add 0.05% of reading to the 0.5 Hz to 1 kHz
accuracies.
• Guaranteed accuracy ranges for frequency, voltage, and current (direct input)
All accuracy figures for 0.5 Hz to 10 Hz are reference values.
The current accuracy figures for DC, 10 Hz to 45 Hz, and 400 Hz to 30 kHz when the
current exceeds 20 A are reference values.
WT310 only
The maximum current input is 6 A when the frequency is over 30 kHz up to 100 kHz.
Input range 1 to 130% with respect to the rated range of voltage or current. (It displays up to 140%.)
WT310HC: 40 A Range Only 1 to 100% (display is 110%)
(Add the reading error × 0.5 to above accuracies for the range of 110% to 130% of the rated
range.)
Measurement frequency Data update interval Measurement Frequency Range
range 0.1 s DC, 25 Hz ≤ f ≤ 100 kHz
0.25 s DC, 10 Hz ≤ f ≤ 100 kHz
0.5 s DC, 5 Hz ≤ f ≤ 100 kHz
1s DC, 2.5 Hz ≤ f ≤ 100 kHz
2s DC, 1.5 Hz ≤ f ≤ 100 kHz
5s DC, 0.5 Hz ≤ f ≤ 100 kHz
Only for direct current input of WT310HC, the maximum measurement range is 20kHz.
When the line filter is turned 45 to 66 Hz: Add 0.2% of reading.
ON Less than 45 Hz: Add 0.5% of reading.
Temperature coefficient Add ±0.03% of reading/°C within the range of 5 to 18°C or 28 to 40°C.
Accuracy when the crest Accuracy obtained by doubling the measurement range error for the accuracy when the crest factor
factor is set to 6 is set to 3.

7-6 IM WT310-02EN
 7.3 Accuracy

7.3.2 Active Power Accuracy 1

Item Specifications
Accuracy Requirements
Same as the conditions for voltage and current.
• Power factor: 1 2
Accuracy (at 12 months)
(The accuracy shown below is the sum of reading and range errors.)

* f in the read error equation is the input signal frequency in kHz. 3

WT310/WT332/WT333
WT310HC (Direct current input)
WT310HC (Current EXT sensor input)
DC ±(0.1% of reading + 0.2% of range) ±(0.3% of reading + 0.2% of range)
0.5 Hz ≤ f < 45 Hz
45 Hz ≤ f ≤ 66 Hz
±(0.3% of reading + 0.2% of range)
±(0.1% of reading + 0.1 % of range)
±(0.3% of reading + 0.2% of range)
±(0.1% of reading + 0.1 % of range)
4
66 Hz < f ≤ 1 kHz ±(0.2% of reading + 0.2 % of range) ±(0.2% of reading + 0.2 % of range)
±(0.1% of reading + 0.3 % of range)
1 kHz < f ≤ 10 kHz ±((0.13×f)% of reading + 0.3 % of range)
±[{0.067×(f–1)}% of reading]
10 kHz < f ≤ 20 kHz ±((0.13×f)% of reading + 0.5 % of range) 5
±(0.5 % of reading + 0.5 % of range)
10 kHz < f ≤ 100 kHz
±[{0.09×(f–10)}% of reading]

• Influence of temperature changes after zero-level compensation or range change

Add the product of the voltage influence and the current influence listed below to the DC power 6
accuracies.
DC voltage accuracy: 0.02% of range/°C
DC current accuracies
WT310 (5mA/10mA/20mA/50mA/100mA/200mA ranges): 5μA/°C
WT310 (0.5A/1A/2A/5A/10A/20A ranges) and WT332/WT333 direct current input: 500 μA/°C 7
WT310HC direct current input: 1mA/°C
External current sensor input (/EX1): 1mV/°C

Specifications
External current sensor input (/EX2): 50μV/°C

• Influence of self-generated heat caused by voltage input App

Add 0.0000001 ×U2% of reading to the AC power accuracies.
Add 0.0000001 ×U2% of reading + 0.0000001 ×U2% of range to the DC power accuracies. U is the
voltage reading (V).

Influence of self-generated heat caused by voltage input lasts until falling the temperature of the input Index
resistor even if voltage input decreases.

• Influence of self-generated heat caused by current input

WT310:
Add 0.00013 × I2% of reading to the AC power accuracies.
Add 0.00013 × I2% of reading + 0.004 × I2 mA (0.5 A, 1 A, 2 A, 5 A, 10 A, and 20 A ranges) or 0.00013
× I2% of reading + 0.00004 × I2 mA (5 mA, 10 mA, 20 mA, 50 mA, 100 mA, and 200 mA ranges) to
the DC power accuracies.
I is the current reading (A).
WT310HC:
Add 0.00006 × I2% of reading to the AC power accuracies.
Add 0.00006 × I2% of reading + 0.001 × I2 mA to the DC power accuracies.
I is the current reading (A).
WT332/WT333:
Add 0.00013 × I2% of reading to the AC power accuracies.
Add 0.00013 × I2% of reading + 0.002 × I2 mA to the DC power accuracies.
I is the current reading (A).
Influence of self-generated heat caused by current input lasts until falling the temperature of the shunt
resistor even if current input decreases.

• Accuracy changes caused by data update interval

When the data update interval is 100 ms, add 0.05% of reading to the 0.5 Hz to 1 kHz accuracies.

• Guaranteed accuracy ranges for frequency, voltage, and current (direct input)
All accuracy figures for 0.5 Hz to 10 Hz are reference values.
The power accuracy figures for DC, 10 Hz to 45 Hz, and 400 Hz to 30 kHz when the current
exceeds 20 A are reference values.
WT310 only
The maximum current input is 6 A when the frequency is over 30 kHz up to 100 kHz.

IM WT310-02EN 7-7
7.3 Accuracy

Item Specifications
Power factor influence When power factor (λ) = 0 (S: apparent power)
• ±0.2% of S for 45 Hz ≤ f ≤ 66 Hz.
• ±{(0.2 + 0.2 × f)% of S} for up to 100 kHz as reference data.
f is frequency of input signal in kHz.
When 0 < λ < 1 (φ: phase angle of the voltage and current)
(power reading) × [(power reading error %) + (power range error %) × (power range/indicated
apparent power value) +
{tanφ × (influence when λ = 0)%}]
When the line filter is turned 45 to 66 Hz: Add 0.3% of reading.
ON Less than 45 Hz: Add 1% of reading.
Temperature coefficient Same as the temperature coefficient for voltage and current
Accuracy when the crest Accuracy obtained by doubling the measurement range error for the accuracy when the crest factor
factor is set to 6 is set to 3.
Accuracy of apparent power Voltage accuracy + current accuracy
S
Accuracy of reactive power Accuracy of apparent power +(√(1.0004−λ2)−√(1−λ2)) × 100 % of range
Q
Accuracy of power factor λ ±[(λ–λ/1.0002) + |cosf – cos{f + sin−1(influence from the power factor
when λ= 0%/100)}|] ± 1 digit
when voltage and current are at the measurement range rated input
Accuracy of phase ±[|f – cos−1(λ/1.0002)| + sin−1{(influence from the power factor
differenceφ when λ= 0%)/100}] deg ± 1 digit
when voltage and current are at the measurement range rated input

7-8 IM WT310-02EN
 7.4 Functions 1

7.4.1 Voltage, Current, and Active Power Measurements 2

Item Specifications
Measurement method Digital sampling method
Crest factor 3 or 6
Wiring system WT310, WT310HC (One element model)
Single-phase, two-wire (1P2W)
3
WT332 (Two element model)
Select single-phase, two-wire (1P2W); single-phase, three-wire (1P3W); or three-phase, three-
wire (3P3W).
WT333 (Three element model)
Select single-phase, two-wire (1P2W); single-phase, three-wire (1P3W); three-phase, three-wire
4
(3P3W); three-phase, four-wire (3P4W); or three-voltage, three-current (3V3A).
Range select Select manual or auto ranging.
Auto range Range increase
The range is increased when any of the following conditions is met. 5
• Urms or Irms exceeds 130% of the currently set measurement range.
• Crest factor 3: Upk , Ipk value of the input signal exceeds 300% of the currently set
measurement range.
• Crest factor 6: Upk , Ipk value of the input signal exceeds 600% of the currently set
measurement range. 6
On the WT332/WT333, when any of those input elements meets the above condition, the
range is increased the next time the measured value is updated.

Range decrease 7
The range is decreased when all of the following conditions are met.

Specifications
• Urms or Irms is less than or equal to 30% of the measurement range.
• Urms or Irms is less than or equal to 125% of the next lower measurement range.
• Crest factor 3: Upk , Ipk value of the input signal exceeds 300% of the currently set
measurement range.
App
• Crest factor 6: Upk , Ipk value of the input signal exceeds 600% of the currently set
measurement range.

On the WT332/WT333, when all of the input elements meet the above conditions, the range is Index
decreased the next time the measured value is updated.
Display mode switching Select RMS (the true RMS value of voltage and current), VOLTAGE MEAN(the rectified mean value
calibrated to the RMS value of the voltage and the true RMS value of the current), or DC (simple
average of voltage and current).
Measurement Select voltage, current, or the entire period of the data update interval for the signal used to achieve
synchronization source synchronization during measurement.
Line filter Select OFF or ON (cutoff frequency at 500 Hz).
Peak measurement Measures the peak (max, min) value of voltage, current, or power from the instantaneous voltage,
instantaneous current, or instantaneous power that is sampled.
Zero-level compensation Removes the internal offset of the WT300 series.

IM WT310-02EN 7-9
7.4 Features

7.4.2 Frequency Measurement

Item Specifications
Measured item Voltage and current frequencies applied to the selected input element can be measured.

WT332 (two element model)

Select voltage (U1)/current (I1) of input element 1 or voltage (U3)/current (I3) of input element 3.

WT333 (three element model)

Select voltage (U1)/current (I1) of input element 1, voltage (U2)/current (I2) of input element 2 or
voltage (U3)/current (I3) of input element 3.
Method Reciprocal method
Frequency measuring range Varies depending on the data update interval (see description given later) as follows:

Data Update Interval Measurement Range

0.1 s 25 Hz ≤ f ≤ 100 kHz
0.25 s 10 Hz ≤ f ≤ 100 kHz
0.5 s 5 Hz ≤ f ≤ 100 kHz
1s 2.5 Hz ≤ f ≤ 100 kHz
2s 1.5 Hz ≤ f ≤ 50 kHz
5s 0.5 Hz ≤ f ≤ 20 kHz

Only for the direct current input of the WT310HC, the maximum measurement range is 20 kHz.
Measurement range Auto switching among six types: 1 Hz, 10 Hz, 100 Hz, 1 kHz, 10 kHz, and 100 kHz
Frequency filter Select OFF or ON (cutoff frequency at 500 Hz).
Accuracy Requirements
• When the input signal level is 30% or more of the measurement range if the crest factor is set
to 3 (60% or more if the crest factor is set to 6)
• Frequency filter is ON when measuring voltage or current of 200 Hz or less.

Accuracy: ±(0.06% of reading)

7.4.3 Computation
Item Specifications
Computing equation of apparent power (S), reactive power (Q), power factor (λ), and phase angle (Φ)

i : Input element number

Single-Phase, Three- Three-Phase, Three- Three-Phase, Three- Three-Phase, Four-
Wire (1P3W) Wire (3P3W) Wire (3V3A) Wire (3P4W)
UΣ[V] (U1+U3)/2 (U1+U2+U3)/3
IΣ[A] (I1+I3)/2 (I1+I2+I3)/3
PΣ[W] P1+P3 P1+P2+P3
SΣ[VA] Si=Ui×Ii S1+S3 3 ( S1 + S3 ) 3 ( S1+ S2+ S3 ) S1+S2+S3
2 3
QΣ[var] Qi= S2i − Pi2 Q1+Q3 Q1+Q2+Q3

λΣ λi = Pi/Si PΣ
SΣ
Φ[°] −1 Pi −1 PΣ
Φi = cos ( S i ) cos ( )
SΣ

• On the WT300 series, S, Q, λ, and Φ are derived through the computation of the measured values of voltage, current, and
active power. Therefore, for distorted signal input, the value obtained on the WT300 series may differ from that obtained on
other instruments that use a different method.

• If the voltage or current is less than 0.5% (less than or equal to 1% if the crest factor is set to 6) of the rated range, zero is
displayed for S or Q, and error is displayed for λ and Φ.

• For Q[var], when the current leads the voltage, the Q value is displayed as a negative value; when the current lags the voltage,
the Q value is displayed as a positive value. The value of QΣ may be negative, because it is calculated from the Q of each
element with the signs included.

7-10 IM WT310-02EN
 7.4 Features

Lead and lag detection The lead and lag of the voltage and current inputs can be detected correctly for the following: 1
(Phase angle Φ’s D (lead) • Sine waves
and G (lag)) • When the measured value is 50% or more (100% or more when the crest factor is 6) of the
measurement range
• Frequency: 20 Hz to 2 kHz(WT310HC: to 1 kHz)
• Phase difference: ±(5° to 175°)
2
Scaling Set the current sensor transformation ratio, VT ratio, CT ratio, and power factor when applying the
external current sensor, VT, or CT output to the instrument.
• Significant digits: Selected automatically according to significant digits in the voltage and current
ranges. 3
• Selectable range: 0.001 to 9999
Averaging Select the method from the following two types.
• Exponential averaging method
• Moving average method
Select the attenuation constant for exponential averaging; select the sample number from 8, 16, 4
32,and 64 for moving average.
Efficiency Computation of efficiency is possible on the WT332/WT333.
Crest factor Computes the crest factor (peak value/RMS value) of voltage and current.
Four arithmetic operation Six types of four arithmetic operations possible
(A+B, A–B, A*B, A/B, A2/B, and A/B2)
5
Average active power during Computes the average active power within the integrated period.
integration

6
7.4.4 Integration
Item Specifications
Mode
Timer
Select manual integration mode, standard integration mode, or repetitive integration mode.
Automatically stop integration by setting a timer.
7
Selectable range: 0 hours 00 minutes 00 seconds to 10000 hours 00 minutes 00 seconds

Specifications
(Set automatically to manual integration mode for 0 hours 00 minutes 00 seconds)
Count overflow Holds the elapsed integration time and integration value and stops integration when the elapsed
time of integration reaches the maximum integration time of 10000 hours or when the integrated App
value reaches the maximum or minimum displayable integration value (999999M or –99999M).1
1 WP: 999999 MWh/-99999 MWh, q: 999999 MAh/-99999 MAh
Accuracy ±(Power accuracy (or current accuracy) + 0.1% of reading) (fixed range)
* In the case of auto range, the measurement is not carried out during a range change.
The first measurement data after the range change is added for the period which measurement Index
was not carried out.
Range setting Auto range or fixed range for Integration is available.
For details on range switching, see section 7.4.1, “Voltage, Current, and Active Power
Measurements.”
Valid Frequency Ranges for Active power
Integration DC to 45 kHz
Current
When the measurement mode is RMS:
DC, lower limit frequency determined by the data update interval to 45 kHz
When the measurement mode is VOLTAGE MEAN:
DC, lower limit frequency determined by the data update interval to 45 kHz
When the measurement mode is DC:
DC to 45 kHz
Timer accuracy ±0.02%
Remote control Start, stop, and reset operations are available using an external remote signal.
(applies to products with the /DA4 or /DA12 option)

IM WT310-02EN 7-11
7.4 Features

7.4.5 Harmonic Measurement (/G5 Option)

Item Specifications
Measured item All installed elements
Method PLL synchronization method
Frequency range Fundamental frequency of the PLL source is in the range of 10 Hz to 1.2 kHz.
PLL source • Select voltage or current of each input element.
• Input level
50% or more of the rated measurement range when the crest factor is 3.
100% or more of the rated measurement range when the crest factor is 6.
• The frequency filter must be turned on when the fundamental frequency is less than or equal to 200Hz.
FFT data length 1024
Window function Rectangular
Sample rate, window width, and upper limit of harmonic analysis
Fundamental Frequency Sample Rate Window Width Upper Limit of Harmonic Analysis*
10 Hz to 75 Hz f×1024 1 50
75 Hz to 150 Hz f×512 2 32
150 Hz to 300 Hz f×256 4 16
300 Hz to 600 Hz f×128 8 8
600 Hz to 1200 Hz f×64 16 4
f in the equation is the input fundamental frequency.
* The upper limit of harmonic order can be decreased.
Accuracy
(The accuracy shown below is the sum of reading and range errors.)
When Line Filter is OFF
<WT310/WT332/WT333>
Frequency Voltage Current Power
10 Hz ≤ f < 45 Hz 0.15% of reading 0.15% of reading 0.35% of reading
+0.35% of range +0.35% of range +0.50% of range
45 Hz ≤ f ≤ 440 Hz 0.15% of reading 0.15% of reading 0.25% of reading
+0.35% of range +0.35% of range +0.50% of range
440 Hz < f ≤ 1 kHz 0.20% of reading 0.20% of reading 0.40% of reading
+0.35% of range +0.35% of range +0.50% of range
1 kHz < f ≤ 2.5 kHz 0.80%+ of reading 0.80%+ of reading 1.56% of reading
+0.45% of range +0.45% of range +0.60% of range
2.5 kHz < f ≤ 5 kHz 3.05% of reading 3.05% of reading 5.77% of reading
+0.45% of range +0.45% of range +0.60% of range
<WT310HC>
Frequency Voltage Current Power
10 Hz ≤ f < 45 Hz 0.15% of reading 0.15% of reading 0.35% of reading
+0.35% of range +0.35% of range +0.50% of range
45 Hz ≤ f ≤ 440 Hz 0.15% of reading 0.15% of reading 0.25% of reading
+0.35% of range +0.35% of range +0.50% of range
440 Hz < f ≤ 1 kHz 0.20% of reading 0.20% of reading 0.40% of reading
+0.35% of range +0.35% of range +0.50% of range
1 kHz < f ≤ 2.5 kHz 0.80%+ of reading 0.95%+ of reading 1.68% of reading
+0.45% of range +0.45% of range +0.60% of range
2.5 kHz < f ≤ 5 kHz 3.05% of reading 3.35% of reading 6.05% of reading
+0.45% of range +0.45% of range +0.60% of range
• When the crest factor is set to 3.
• When λ (the power factor) is 1.
• Power figures that exceed 1.2 kHz are reference values.
• For a direct current range, add 10 μA to the current accuracy and (10 μv/direct current range) × 100% of range to the power
accuracy.
• For the external current sensor range, add 100 μA to the current accuracy and (100 μV/external current sensor range rating) ×
100% of range to the power accuracy.
• For nth harmonic component input, add ({n/(m + 1)}/50)% of (the nth harmonic reading) to the n + mth harmonic and n – mth
harmonic of the voltage and current, and add ({n/(m + 1)}/25)% of (the nth harmonic reading) to the n + mth harmonic and n –
mth harmonic of the power.
• Add (n/500)% of reading to the nth component of the voltage and current, and add (n/250)% of reading to the nth component
of the power.
• The accuracy when the crest factor is 6 is the same as the accuracy when the crest factor is 3 after doubling the measurement
range.
• The guaranteed accuracy ranges for frequency, voltage, and current, are the same as the guaranteed ranges for ordinary
measurement. If the amplitude of the high frequency component is large, influence of approximately 1% may appear in certain
harmonics. Because the influence depends on the size of the frequency component, if the frequency component is small with
respect to the range rating, the influence is also negligible.
7-12 IM WT310-02EN
 7.4 Features

7.4.6 Display 1
Item Specifications
Display type 7-segment LED
Simultaneous display 4 items
Maximum display During normal measurement 2
(display range) Displayed item When the number of When the number of displayed
displayed digits is 5 digits is 4
U, I, P, S*, Q* 99999 9999
λ* 1.0000 to –1.0000 1.000 to –1.000 3
Φ* G180.0 to d180.0 G180.0 to d180.0
fU*, fI* 99999 9999
WP, WP±, q, q±
When the unit is MWh or 999999 999999
MAh (–99999 for negative watt hour and ampere hour.) 4
When the unit is other than 99999 99999
MWh or MAh
TIME Elapsed integration time Display A Display
indication resolution 5
0 to 99 hours 59 minutes 59 0.00.00 to 1s
seconds 99.59.59
100 hours to 9999 hours 59 100.00 to 1 minute
minutes 59 seconds 9999.59 6
10000 hours 10000 1 hour
Efficiency (WT332/WT333 0.000 to 99.999 to 0.00 to 99.99 to
only) 100.00 to 999.99% 100.0 to 999.9%
Crest factor 99999 9999 7
Four arithmetic operation 99999 9999
Average active power 99999 9999

Specifications
Voltage peak 99999 9999
Current peak 99999 9999
Power peak 99999 9999 App
* The computation accuracy (the value calculated from the measured value) is one-half the
display resolution.
Maximum display During harmonic measurement
(display range) Displayed item When the number of displayed When the number of displayed Index
digits is 5 digits is 4
U, I, P 99999 9999
λ 1.0000 to –1.0000 1.000 to –1.000
Uhdf, Ihdf, Phdf 0.000 to 99.999 to 0.00 to 99.99 to
100.00 to 999.99% 100.0 to 999.9%
Uthd, Ithd 0.000 to 99.999 to 0.00 to 99.99 to
100.00 to 999.99% 100.0 to 999.9%
ΦU, ΦI
Phase angle of the G180.0 to d180.0 G180.0 to d180.0
fundamental current with
respect to the fundamental
voltage
Phase angle of the 2nd –180.0 to 180.0 –180.0 to 180.0
harmonic and higher
harmonics of voltage with
respect to the fundamental
voltage
Phase angle of the 2nd –180.0 to 180.0 –180.0 to 180.0
harmonic and higher
harmonics of current with
respect to the fundamental
current

Unit symbols m, k, M, V, A, W, VA, var, °, Hz, h±, TIME, %

IM WT310-02EN 7-13
7.4 Features

Number of displayed digits Select 5 or 4 digits.

Data update interval Select 0.1 s, 0.25 s, 0.5 s, 1 s, 2 s, or 5 s.
Response time Data update rate × 2 or less
(The time it takes to reach the accuracy of the final value when the displayed value changed from 0
to 100% or 100 to 0% of the rated range)
Auto range monitor The indicator illuminates when the input signal meets the conditions for auto range switching.
Overrange display Overrange “- - - oL -” is displayed for the following conditions.
When the measured value exceeds 140% of the rated range
* WT310HC:40 A range
When the measured value exceeds 110% of the rated range
Hold Holds the displayed value.
Single update Updates the displayed value once each time the SINGLE key is pressed during Hold.
MAX hold Holds the maximum displayed value of U, I, P, S, Q, U±pk, I±pk, and P±pk.

7.4.7 Internal Memory

Item Specifications
Measured data Recall the stored measurement data by a communication command.
Storage interval
Data update interval or in the range of 1 s to 99 hrs 59 min 59 s.
There is no backup function for stored measurement data.
Setup information Saves/Loads four patterns of setup information.
Number of blocks which can be stored
Model normal measurement normal +harmonic measurement
WT310/WT310HC 9000 700
WT332 4000 300
WT333 3000 200
* Harmonic Measurement (/G5 Option)
Harmonic measurement function is turned ON.

7.5 External Current Sensor Input

(/EX1 and /EX2 options)
Item Specifications
Allows input of voltage output type current sensor signal. For detailed input specifications, see section 7.1, “Input.”
• Measurement range of the /EX1 option
Crest factor 3: 2.5 V, 5 V, 10 V
Crest factor 6: 1.25 V, 2.5 V, 5 V
• Measurement range of the /EX2 option
Crest factor 3: 50 mV, 100 mV, 200 mV, 500 mV, 1 V, 2 V
Crest factor 6: 25 mV, 50 mV, 100 mV, 250 mV, 500 mV, 1 V

7.6 D/A Output (/DA4, /DA12 Options)

Item Specifications
Output voltage ±5 V FS (approx. ±7.5 V maximum) against each rated value
Number of output channels 4 outputs for products with the /DA4; 12 outputs for products with the /DA12 option
Output items Set for each channel.
U, I, P, S, Q, λ, Φ, fU, fI, Upk, Ipk, WP, WP±, q, q±, MATH
Accuracy ±(accuracy of each measurement item + 0.2% of FS) (FS = 5 V)
D/A conversion resolution 16 bits
Minimum load 100 kΩ
Update interval Same as the data update interval.
Temperature coefficient ±0.05%/°C of FS

7-14 IM WT310-02EN
 7.7 Remote Control Input/Output Signal 1
(/DA4, /DA12 Options)
Item Specifications
Remote control input signal EXT HOLD, EXT TRIG, EXT START, EXT STOP, EXT RESET 2
Remote control output signal INTEG BUSY
I/O level TTL
I/O logic format Negative logic, falling edge

3
7.8 GP-IB Interface (Standard on -C1)
4
Item Specifications
Usable devices National Instruments Corporation
• PCI-GPIB or PCI-GPIB+
• PCIe-GPIB or PCIe-GPIB+
• PCMCIA-GPIB or PCMCIA-GPIB+
5
(not supported on Windows Vista or Windows 7.)
• GPIB-USB-HS
Use driver NI-488.2M Ver. 2.8.1 or later.
Electrical and mechanical Complies with IEEE St’d 488-1978 (JIS C 1901-1987) 6
Functional specifications SH1, AH1, T6, L4, SR1, RL1, PP0, DC1, DT1, C0
Protocol Complies with IEEE St’d 488.2-1992
Code ISO (ASCII) codes
Mode Addressable mode 7
Addresses 0 to 30
Clear remote mode Press LOCAL to clear remote mode (except during Local Lockout).

Specifications
App
7.9 Serial (RS-232) Interface (Standard on -C2)

Item Specifications Index

Connector type D-Sub 9-pin (plug)
Electrical specifications Complies with EIA-574 (EIA-232 (RS-232) standard for 9-pin)
Connection Point to point
Transmission mode Full duplex
Synchronization Start-stop synchronization
Baud rate Select from 1200, 2400, 4800, 9600, 19200, 38400 or 57600 bps.

7.10 USB PC Interface

Item Specifications
Number of ports 1
Connector Type B connector (receptacle)
Electrical and mechanical Complies with USB Rev. 2.0
specifications
Supported transfer modes HS (High Speed; 480 Mbps) and FS (Full Speed; 12 Mbps)
Supported protocols USBTMC-USB488 (USB Test and Measurement Class Ver. 1.0)
PC system requirements A PC with a USB port, running the English or Japanese version of Windows 7 (32 bit/64bit),
Windows Vista (32 bit), or Windows XP (32 bit, SP2 or later)

IM WT310-02EN 7-15
 7.11 Ethernet Interface(/C7 Option)

Item Specifications
Ports 1
Connector type RJ-45
Electrical and mechanical Complies with IEEE802.3
specifications
Transmission system Ethernet (100BASE-TX/10BASE-T)
Transfer rate 100 Mbps max.
Communication protocol TCP/IP
Supported services DHCP, remote control (VXI-11)

7.12 Safety Terminal Adapter

Item Specifications
Maximum allowable current 36 A
Dielectric strength 1000 V CATIII
Contact resistance 10 mΩ or less
Contact section Nickel plating on brass or bronze
Insulator Polyamide
Maximum core wire diameter 1.8 mm
Maximum insulation diameter 3.9 mm

7-16 IM WT310-02EN
 7.13 General Specifications 1

Item Specifications
Warm-up time Approx. 30 minutes 2
Operating environment Temperature: 5°C to 40°C
Humidity: 20%RH to 80%RH (no condensation)
Elevation: 2000 m or less
Installation location
Storage environment
Indoors
Temperature: -25°C to 60°C
3
Humidity: 20%RH to 80%RH (no condensation)
Rated supply voltage 100 VAC to 240 VAC
Permitted supply voltage 90 VAC to 264 VAC
range 4
Rated supply frequency 50/60 Hz
Permitted supply voltage 48 Hz to 63 Hz
frequency range
Maximum power WT310, WT310HC: 50 VA, WT332/WT333: 70 VA
consumption 5
External dimensions WT310, WT310HC: Approx. 213 (W) × 88 (H) × 379 (D) mm
(excluding protrusions) WT332/WT333: Approx. 213 (W) × 132 (H) × 379 (D) mm
Weight WT310, WT310HC: Approx. 3 kg

Battery backup
WT332/WT333: Approx. 5 kg
Setup parameters are backed up with a lithium battery.
6
Standard accessories • Power cord: 1 piece
• D/A cable: 1 piece (included in products with the /DA4, /DA12 options)
• Current input protection cover: 1 piece that matches the main unit
• Hind feet rubber: 1 set 7
• User’s manual: 1 piece (this manual)
• Safety terminal adapter:

Specifications
WT310, WT310HC: Red/Black 1 set
WT332: Red/Black 2 sets
WT333: Red/Black 3 sets App
Safety standard1 Compliant standard: EN61010-1
Installation category (overvoltage category) CAT II2
Measurement Category CAT II3
Pollution degree 24
Emission1 Compliant standards Index
EN61326-1 Class A
EN55011 ClassA, Group1
EN61000-3-2
EN61000-3-3
C-tick EN55011 Class A, Group1
Korea Electromagnetic Conformity Standard ( 한국 전자파적합성기준 )
This product is a Class A (for industrial environment) product. Operation of this product in a
residential area may cause radio interference in which case the user will be required to correct
the interference.
Cable conditions
• Serial (RS-232) interface connector
Use shielded serial cables.5
• GP-IB interface connector
Use shielded GP-IB cables.5
• USB port (PC)
Use shielded USB cables.5
• Ethernet port
Use category 5 or better Ethernet cables (STP).6
• D/A output terminal
Use shielded cables.5
• Connecting cables may cause radio interference in which case the user is required to
correct the interference.
Immunity1 Compliant standard
EN61326-1 Table 2 (for industrial locations)
However, the measured values may receive noise effects.
Cable conditions
Same as the cable conditions for emission above.

IM WT310-02EN 7-17
7.13 General Specifications

1 Applies to products with CE marks. For information on other products, contact your nearest YOKOGAWA dealer.
2 The overvoltage category (installation category) is a value used to define the transient overvoltage condition and includes the
rated impulse withstand voltage. CAT II applies to electrical equipment that is powered through a fixed installation, such as a
wall outlet wired to a distribution board.
3 This instrument is measurement category II product. Do not use for Measurement Categories III and IV.
Measurement category O applies to measurement of other circuits that are not directly connected to a main power source.
Measurement Category II applies to electrical equipment that is powered through a fixed installation, such as a wall outlet
wired to a distribution board, and to measurement performed on such wiring.
Measurement category III applies to measurement of facility circuits, such as distribution boards and circuit breakers.
Measurement category IV applies to measurement of power source circuits, such as entrance cables to buildings and cable
systems, for low-voltage installations.
4 Pollution Degree applies to the degree of adhesion of a solid, liquid, or gas that deteriorates withstand voltage or surface
resistivity.
Pollution Degree 2 applies to normal indoor atmospheres (with only non-conductive pollution).
5 Use cables of length 3 m or less.
6 Use cables of length 30m or less.

7-18 IM WT310-02EN
 7.14 External Dimensions 1

Unit: mm
2

Rear view
3

5
250 73 23 359
213 356

6
88
179

19

7
480 ±1
JIS rack mount dimensions
460 ±1

Specifications
Mounting surface 20

11
App
99 -0.3
50 ±0.2
0

6
24.5

480 ±1
460 ±1
Index
Mounting surface 20

11
99 -0.3
50 ±0.2
0

6
24.5

EIA rack mount dimensions 482.6 ±1

460 ±1
Mounting surface 20
76.2 ±0.2
88 -0.3
0

7.1
5.9

482.6 ±1
463 ±1
Mounting surface 20
76.2 ±0.2
88 -0.3
0

7.1
5.9

Unless otherwise specified, tolerances are ±3%

(however, tolerances are ±0.3 mm when below 10 mm).

IM WT310-02EN 7-19
7.14 External Dimensions

Unit: mm

Rear view

13 213 23 327 34
28.5
132
20

JIS rack mount dimensions 480 ±1

Mounting surface 20 460 ±1

17
149 -0.3
100 ±0.2
0

6
24.5

480 ±1
Mounting surface 20 460 ±1

17
149 -0.3
100 ±0.2
0

6
24.5

EIA rack mount dimensions 482.6 ±1

Mounting surface 20 460 ±1
132 -0.3
0

57.2 ±0.2

7.1
37.4

482.6 ±1
Mounting surface 20 463 ±1
132 -0.3
0

57.2 ±0.2

7.1
37.4

Unless otherwise specified, tolerances are ±3%

(however, tolerances are ±0.3 mm when below 10 mm).

7-20 IM WT310-02EN
Appendix

Appendix 1 How to Make Accurate Measurements 1

Effects of Power Loss 2

By wiring a circuit to match the load, you can minimize the effects of power loss on measurement
accuracy. We will discuss the wiring of the DC power supply (SOURCE) and a load resistance (LOAD)
below.
3
When the Measured Current Is Relatively Large
Connect the voltage measurement circuit between the current measurement circuit and the load.
The current measurement circuit measures the sum of iL and iV. iL is the current flowing through the
load of the circuit under measurement, and iV is the current flowing through the voltage measurement 4
circuit. Because the current flowing through the circuit under measurement is iL, only iV reduces
measurement accuracy. The input resistance of the voltage measurement circuit of the WT300 series
is approximately 2 MΩ. If the input voltage is 600 V, iV is approximately 0.3 mA (600 V/2 MΩ). If the
load current iL is 3 A or more (the load resistance is 200 Ω or less), the effect of iV on the measurement 5
accuracy is 0.01% or less. If the input voltage is 100 V and the current is 5 A, iV = 0.05 mA (100 V/2
MΩ), so the effect of iV on the measurement accuracy is 0.001% (0.05 mA/5 A).

SOURCE
6
V LOAD
V iV
SOURCE U LOAD ±
±
±
I
C 7
iL
± C
WT300 series App
As a reference, the relationships between the voltages and currents that produce effects of 0.01%,

Appendix
0.001%, and 0.0001% are shown in the figure below.

0.01% effect 0.001% effect Index

600
Measured voltage (V)

400

200 Smaller effect

0.0001% effect

0
0 3 5 10 15 20 25 30 35 40
Measured current (A)

When the Measured Current Is Relatively Small

Connect the current measurement circuit between the voltage measurement circuit and the load.
In this case, the voltage measurement circuit measures the sum of eL and eI. eL is the load voltage,
and eI is the voltage drop across the current measurement circuit. Only eI reduces measurement
accuracy. For example, the input resistance of the current measurement circuit of the WT332/WT333
is approximately 6 mΩ. If the load resistance is 600 Ω, the effect on the measurement accuracy is
approximately 0.001% (6 mΩ/600 Ω). For the input resistances of the WT310 and WT310HC, see
chapter 7.

SOURCE LOAD
V
V eL
SOURCE U LOAD ±
±
± C
± C
I
eI
WT300 series

IM WT310-02EN App-1
Appendix 1 How to Make Accurate Measurements

Effects of Stray Capacitance

The effects of stray capacitance on measurement accuracy can be minimized by connecting the
WT300 series current input terminal to the side of the power supply (SOURCE) that is closest to its
earth potential.

The internal structure of the WT300 series is explained below.

The voltage and current measurement circuits are each enclosed in shielded cases. These shielded
cases are contained within an outer case. The shielded case of the voltage measurement circuit is
connected to the positive and negative voltage input terminals, and the shielded case of the current
measurement circuit is connected to the positive and negative current input terminals.
Because the outer case is insulated from the shielded cases, there is stray capacitance, which is
expressed as Cs. Cs is approximately 40 pF. The current generated by stray capacitance Cs causes
errors.

Shielded case of the voltage

measurement circuit
V
Cs Outer case
± Grounding

C
Cs
±
Shielded case of the current
measurement circuit

As an example, we will consider the case when the outer case and one side of the power supply are
grounded.
In this case, there are two conceivable current flows, iL and iCs. iL is the load current, and iCs is the
current that flows through the stray capacitance. iL flows through the current measurement circuit, then
through the load, and returns to the power supply (shown with a dotted line). iCs flows through the
current measurement circuit, the stray capacitance, and the earth ground of the outer case, and then
returns to the power supply (shown with a dot-dash line).
Therefore, the current measurement circuit ends up measuring the sum of iL and iCs, even if the
objective is just to measure iL. Only iCs reduces measurement accuracy. If the voltage applied to Cs is
VCs (common mode voltage), iCs can be found using the equation shown below. Because the phase
of iCs is ahead of the voltage by 90°, the effect of iCs on the measurement accuracy increases as the
power factor gets smaller.
iCs = VCs × 2πf × Cs

iL V

iCs C Cs LOAD

iL
±
SOURCE
iL

iCs

App-2 IM WT310-02EN
 Appendix 1 How to Make Accurate Measurements

Because the WT300 series measures high frequencies, the effects of iCs cannot be ignored. 1
If you connect the WT300 series current input terminal to the side of the power supply (SOURCE) that
is close to its earth potential, the WT300 series current measurement circuit positive and negative
terminals are close to the earth potential, so VCs becomes approximately zero and very little iCs flows.
This reduces the effect on measurement accuracy. 2

App

Appendix
Index

IM WT310-02EN App-3