

MICRO-OHMMETER
6250

ENGLISH User Manual

 Statement of Compliance
Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments
certifies that this instrument has been calibrated
using standards and instruments traceable to
international standards.

We guarantee that at the time of shipping your

instrument has met its published specifications.

An NIST traceable certificate may be

requested at the time of purchase, or obtained
by returning the instrument to our repair and
calibration facility, for a nominal charge.

The recommended calibration interval for this

instrument is 12 months and begins on the date of
receipt by the customer. For recalibration, please
use our calibration services. Refer to our repair
and calibration section at www.aemc.com.

Serial #: _________________________________
Catalog #: 2129.81
Model #: 6250

Please fill in the appropriate date as indicated:

Date Received: __________________________________

Date Calibration Due: ________________________

Chauvin Arnoux®, Inc.

d.b.a AEMC® Instruments
www.aemc.com
 READ CAREFULLY BEFORE
USING FOR THE FIRST TIME
Your instrument is equipped with a NiMH battery. This technology offers several
advantages:
• Long battery charge life for a limited volume and weight.
• Possibility of quickly recharging your battery.
• Significantly reduced memory effect: you can recharge your
battery even if it is not fully discharged.
• Respect for the environment: no pollutant materials such as lead
or cadmium, in compliance with the applicable regulations.

After prolonged storage, the battery may be completely discharged. If so, it must
be completely recharged.

Your instrument may not function during part of this recharging operation.

Full recharging of a completely discharged battery may take several hours.

NOTE: In this case, at least 5 charge/discharge cycles will be necessary

for your battery to recover 95% of its capacity.

To make the best possible use of your battery and extend its effective service life:
• Only use the charger supplied with your instrument. Use of
another charger may be dangerous.
• Only charge your instrument at temperatures between 0° and 40°C.
• Comply with the conditions of use defined in the operating manual.
• Comply with the storage conditions specified in the operating
manual.

NiMH technology allows a limited number of charge/discharge cycles depending

significantly on:
• The conditions of use.
• The charging conditions.

Please refer to § 9 for correct replacement of the battery.

Do not dispose of the battery pack with other solid waste. Used batteries
must be entrusted to a qualified recycling company or to a company
specialized in processing hazardous materials.
 Table of Contents

1. INTRODUCTION.................................................................................. 5
1.1 International Electrical Symbols.................................................6
1.2 Definition of Measurement Categories......................................6
1.3 Receiving Your Shipment...........................................................6
1.4 Ordering Information..................................................................7
1.4.1 Accessories and Replacement Parts.............................7

2. PRODUCT FEATURES.......................................................................... 8
2.1 Description.................................................................................8
2.2 Applications...............................................................................9
2.3 Key Features.............................................................................9
2.4 Control Features......................................................................10
2.5 Button Functions...................................................................... 11
2.6 Display Symbols......................................................................12

3. SPECIFICATIONS.............................................................................. 14
3.1 Electrical..................................................................................14
3.2 Mechanical...............................................................................15
3.3 Display.....................................................................................15
3.4 Environmental..........................................................................16
3.5 Safety.......................................................................................16

4. OPERATION...................................................................................... 17
4.1 Quick Summary.......................................................................17
4.2 Instrument Configuration (SET-UP Mode)...............................19
4.2.1 Program Menu Tree.....................................................19
4.2.2 Programming the 9-Pin Interface Port (rS) .................20
4.2.3 Setting the Buzzer Level (bUZZ).................................21
4.2.4 Reading the Internal Serial Number (EdSn)................21
4.2.5 Reading the Internal Software Version (EdPP)............21
4.2.6 Setting Language for Printing Reports (LAnG)............22

2 Micro-Ohmmeter Model 6250

 4.2.7 Setting the Value for Reference Temperature..............22
4.2.8 Selecting the Method/Value for Ambient Temp............23
4.2.9 Selecting the Metal Type (nEtA)..................................24
4.2.10 Programming the Alpha Value (ALPH).........................24
4.2.11 Selecting Temperature Units (dEg)..............................24
4.2.12 Setting Alarm Set Point/Direction/Buzzer Level...........25
4.2.13 Setting the Display Timeout (LlgH)..............................26
4.2.14 Clearing the Memory (nEn)..........................................26
4.3 Operating Procedure...............................................................28
4.3.1 Connections and Readings..........................................28
4.3.2 Test Lead Connection..................................................29
4.3.3 Very Low Resistance...................................................29
4.3.4 Meter Readings...........................................................29
4.3.5 Stand-by (ST BY) State ...............................................30
4.4 Selecting the Test Range.........................................................30
4.5 Measurement Modes...............................................................31
4.5.1 Measurement Safety Warnings....................................31
4.5.2 Inductive Resistance Measurement Mode...................31
4.5.3 Resistance Measurement Mode..................................33
4.5.4 Low Inductive Resistance Measurement Mode...........34
4.6 Ambient Temperature Compensation......................................35
4.6.1 Activating the Compensation Function .......................38
4.7 Activating Alarms.....................................................................39

5. MEMORY / PRINTING....................................................................... 40
5.1 Managing and Printing the Data in Memory ..........................40
5.2 Displaying and Printing Stored Measurements................................41
5.3 Cables and Printers Used with the Interface Port....................43

6. DATAVIEW® SOFTWARE.................................................................... 45
6.1 Installing DataView®.................................................................45
6.2 Connecting the Instrument to your Computer..........................47
6.3 Establishing Communication to the Instrument.......................47
6.4 Configuring the Instrument......................................................47

Micro-Ohmmeter Model 6250 3

7. TROUBLESHOOTING......................................................................... 48
7.1 Fault Indicators........................................................................48

8. APPLICATION EXAMPLES................................................................. 49
8.1 Measuring Winding Resistance of Motors
and Transformers.....................................................................49
8.2 Measuring Resistance on Electric Motors...............................50
8.3 Battery Strap Measurements...................................................56

9. MAINTENANCE................................................................................. 51
9.1 Warning...................................................................................51
9.2 Cleaning...................................................................................51
9.3 Charging/Recharging the Battery............................................52
9.4 Battery and Fuse Replacement...............................................53
Repair and Calibration.....................................................................54
Technical and Sales Assistance.......................................................54
Limited Warranty..............................................................................55
Warranty Repairs.............................................................................55

4 Micro-Ohmmeter Model 6250

 CHAPTER 1

INTRODUCTION

WARNING
These safety warnings are provided to ensure the safety of person-
nel and proper operation of the instrument.
• Do not attempt to perform any tests with this instrument until you
have read the user manual.
• Tests are to be carried out on de-energized circuits only! Never
connect the unit to a live circuit.
• When the unit is measuring resistance showing a high inductive
component (transformers, motors, etc.) after ending the measure-
ment, the unit then discharges the inductive sample and the
warning icon appears for the entire duration. Never disconnect
the connection wires before this icon disappears.
• The micro-ohmmeter should never be used in an explosive
environment (this includes poorly ventilated battery rooms and
enclosures).
• Make sure the internal battery is fully charged prior to testing. If the
instrument has been left unused for several months, recharge the
battery.
• We recommend recharging the micro-ohmmeter every month to
ensure a full battery charge when used.
• When replacing fuses, install only fuses which are direct replace-
ments.
• If the case needs cleaning, do not use any alcohol or oil based
cleaners. Preferably use soapy water with a damp cloth or
sponge.
• The test leads and measuring wires must be in good condition and
should be changed if there is any evidence of deterioration (insula-
tion split, burnt, etc.).
• Never exceed the safety values indicated in the specifications.

Micro-Ohmmeter Model 6250 5

1.1 International Electrical Symbols
This symbol signifies that the instrument is protected by double or rein-
forced insulation.
CAUTION - Risk of Danger! Indicates a WARNING and that the operator must
refer to the user manual for instructions before operating the instrument in all
cases where this symbol is marked.

Important instructions to read and understand completely.

Important information to acknowledge.

Risk of electric shock. The voltage at the parts marked with this symbol may
be dangerous.
Compliance with the Low Voltage & Electromagnetic Compatibility European
directives (73/23/CEE & 89/336/CEE)
In the European Union, this product is subject to a separate collection system
for recycling electrical and electronic components In accordance with directive
WEEE 2002/96/EC

1.2 Definition of Measurement Categories

CAT IV: For measurements performed at the primary electrical supply
(<1000V) such as on primary overcurrent protection devices,
ripple control units, or meters.
CAT III: For measurements performed in the building installation at
the distribution level such as on hardwired equipment in fixed
installation and circuit breakers.
CAT II: For measurements performed on circuits directly connected to
the electrical distribution system. Examples are measurements
on household appliances or portable tools.

1.3 Receiving Your Shipment

Upon receiving your shipment, make sure that the contents are consistent
with the packing list. Notify your distributor of any missing items. If the equip-
ment appears to be damaged, file a claim immediately with the carrier and
notify your distributor at once, giving a detailed description of any damage.
Save the damaged packing container to substantiate your claim.

6 Micro-Ohmmeter Model 6250

1.4 Ordering Information
Micro-ohmmeter Model 6250............................................. Cat. #2129.81
Includes extra large tool bag, set of two 10ft Kelvin clips (10A - Hippo), one RS-232 DB9 F/F
6 ft null modem cable, RS-232 to USB adapter, US 115V power cord, quick reference guide,
one pad of measurement result forms, NiMH rechargeable 6V battery pack, and USB stick
supplied with product user manual and DataView® software.

1.4.1 Accessories and Replacement Parts

Kelvin clips (10A Hippo), 10 ft color-coded leads..............................Cat. #1017.84
Kelvin clips (10A Hippo), 20 ft color-coded leads.............................. Cat. #2118.70
Kelvin probes (1A), spring loaded, 10 ft color-coded leads
with banana plug terminations........................................................... Cat. #2118.73
Kelvin probes (1A), spring loaded, 20 ft color-coded leads
with banana plug terminations........................................................... Cat. #2118.74
Kelvin Probes Pistol Grip 10 ft (10A) Spring Loaded........................ Cat. #2118.75
Kelvin Probes Pistol Grip 20 ft (10A) Spring Loaded........................ Cat. #2118.76
Kelvin Probes 10 ft (10A) Spring Loaded ......................................... Cat. #2118.77
Kelvin Probes 20 ft (10A) Spring Loaded ......................................... Cat. #2118.78
Kelvin Clips 10 ft (1-10A)................................................................... Cat. #2118.79
Kelvin Clips 20 ft (1-10A)................................................................... Cat. #2118.80
Cable, PC RS-232, DB9 F/F 6 ft Null Modem Cable......................... Cat. #2119.45
Replacement Battery 6V, 8.5 Ah rechargeable NiMH..........................Cat. #2129.91
RTD temperature probe.....................................................................Cat. #2129.95
RTD temperature probe with 7 ft (2m) extension cable.....................Cat. #2129.96
Fuse, set of 3, 16A/250V, 1 1/4 x 1/4" (6.3x32mm)
fast blow.......................................................................................................Cat. #2129.98
Fuse, set of 10, 2A/250V, 3/4 x 3/16" (5x20mm) fast blow..................Cat. #2129.99
Extra large classic tool bag...............................................................Cat. #2133.73
Inverter – 12VDC to 120VAC 200 Watt for vehicle use.....................Cat. #2135.43
115V Power Cord..............................................................................Cat. #5000.14
Adapter – RS-232 to USB 2.0...........................................................Cat. #5000.60

Order Accessories and Replacement Parts Directly Online

Check our Storefront at www.aemc.com/store for availability

Micro-Ohmmeter Model 6250 7

 CHAPTER 2

PRODUCT FEATURES

2.1 Description
The Model 6250 Micro-ohmmeter is used to perform low resistance
measurements from 1μΩ to 2500Ω. There are seven ranges with test
currents from 1mA to 10A.
The front end of the micro-ohmmeter employs a four-wire Kelvin configu-
ration, which eliminates test lead resistance for a measurement accuracy
of 0.05%. A built-in circuit filters out AC signals.
The Model 6250 Micro-ohmmeter is packaged in a sealed field case well
suited for shop and field use. Power is supplied by a long-life NiMH battery
pack with a built-in recharger (110/220V).
The large, easy-to-read liquid crystal display is 2.25 x 4.00". It displays
the value of resistance, metal type, reference and ambient temperatures
(if selected), alarm conditions (if selected), test current and range and test
mode (Resistive, Inductive or Auto).
For operator safety and instrument protection, the micro-ohmmeter is
fuse protected at the inputs. Two fuses, accessible behind the front panel,
protect against stored energy in inductive loads.
Enhanced internal circuitry protects against possible inductive kickback
when the current is shut off.
A built-in thermal switch protects the micro-ohmmeter against overheating
on the 10A range when in continuous use.

8 Micro-Ohmmeter Model 6250

2.2 Applications
Some of the more popular and most frequent uses of the micro-ohmmeter
are in applications for:
• Checking metallic coating resistance, especially in aeronautics
• Ground connections and continuity measurement
• Resistance measurements on motors and transformers
• Contact resistance measurements on breakers and switches
• Component measurement
• Electrical cable resistance measurement
• Mechanical bond tests
• Wire to terminal connections
• Aircraft and rail bonds
• Many other very low resistance samples

2.3 Key Features

• Measures from 1µΩ to 2500Ω
• Test current selection from 1mA to 10A
• RTD temperature measurement (optional)
• Automatic or manual temperature compensation
• Two programmable alarms with high or low triggering
• Stores up to 1500 test results
• Selectable Inductive or Resistive test modes
• Operator safety by automatic discharge of residual charge on the
equipment under test
• Instantaneous, continuous or multiple test operation
• Selectable metal type (Copper, Aluminum or other) for
temperature compensation
• Internal, rechargeable batteries conduct up to 5000, 10A tests
• A built-in battery pack recharger recharges the batteries by
connecting to the AC line (90V/264V, 45Hz/420Hz) using a
standard line cord
• 4-Wire measurement with automatic compensation of
undesirable voltages and lead resistance
• Large multi-function backlit display
• Direct display of the measurement with its units, range, measure-
ment mode and, if activated, temperature compensation.
• Measurement can be initiated from the front panel or remotely
through the 9-pin communication port
• Rugged, sealed case
Micro-Ohmmeter Model 6250 9
2.4 Control Features

2 3 4 5

Figure 2-1

1. Kelvin input terminals

2. AC line recharging receptacle
3. Large multi-line backlit liquid crystal display
4. RTD temperature input
5. Communication /remote operation port
6. Range selection switch
7. Test, Start/Stop button
8. Eight program /function buttons

10 Micro-Ohmmeter Model 6250

2.5 Button Functions

In SET-UP mode, selects a function or increments a flashing parameter.

In SET-UP mode, selects a function or decrements a flashing parameter
In SET-UP mode, accesses the function to be modified.
In Wrap-Around mode, selects the parameter to be modified (from left to
right)
In SET-UP mode, shifts the decimal point and selects the unit.
Activates the secondary function of a button. The symbol appears on
the left side of the display.
PRINT Immediate printing of the measurement to a serial printer. If the temperature
compensation function has been activated, the calculated result and the
temperatures involved are also printed.
PRINT Retrieves stored data for printing (this function is independent of the setting
MEM of the switch) except in the OFF and SET-UP positions.
Activates or deactivates the temperature compensation function to calcu-
late the resistance measured at a temperature other than ambient meas-
urement temperature.
ALARM Activates or deactivates the alarms. High or low triggering values are
adjusted in SET-UP.
Selects the desired measurement mode prior to starting one of the follow-
ing measurements: Inductive mode (continuous test), non-inductive mode
(instantaneous test) or non-inductive mode with automatic triggering (mul-
tiple tests).
METAL Selects the metal type for the temperature compensation calculation: Cu,
Al, or Other metal.
MEM Stores the measurement at an address identified by an object number
(OBJ) and a test number (TEST).
Two presses on this button are required, one to select the location (use
the ▲ and ► buttons to change the location) and another to store the
measurement.
MR Retrieves stored data (this function is independent of the selector setting
of the switch) except for the OFF and SET-UP positions. Data is viewed
using the ▲ and ► buttons. The , and ALARM buttons can
be used.
Turns the display backlight ON or OFF.
Activates or deactivates the buzzer and adjusts the sound level.

Micro-Ohmmeter Model 6250 11

2.6 Display Symbols
The display incorporates two lines of characters to display test results, as
well as a library of symbols to assist the operator in determining conditions
at a glance. The symbols that can appear are shown in Figure 2-2 and are
detailed here.

Figure 2-2

Buzzer ON

Battery condition
Temperature compensation ON
Cu Copper metal type selected
Al Aluminium metal type selected
Other metal User defined metal type selected

Communication port active

ALARM 1 ▲ Alarm 1 active with high set point

ALARM 1 ▼ Alarm 1 active with low set point
ALARM 2 ▲ Alarm 2 active with high set point
ALARM 2 ▼ Alarm 2 active with low set point
OBJ. First position locator for data stored in memory
TEST Second position locator for data stored in memory
°C / °F Temperature displayed in either degrees Centigrade or Fahrenheit
PRINT Printing current test result or tests stored in memory
MEM Displayed measurement about to be stored in memory

12 Micro-Ohmmeter Model 6250

REMOTE Instrument under computer control
MR Memory recall

Memory utilization indicator

mV mΩ Units of measure
Resistive material test mode selected
Inductive material test mode selected
AUTO Repetitive test mode selected
ST BY System idle ready to start a test
OPER Test in process

Second function of a button activated

CAUTION! Refer to the user manual before using the instrument.

2500Ω 1mA 2500 ohm, 1 milliamp test range selected

250Ω 10mA 250 ohm, 10 milliamp test range selected
25Ω 100mA 25 ohm, 100 milliamp test range selected
2500mΩ 1A 2500 milliohm, 1 Amp test range selected
250mΩ 10A 250 milliohm, 10 Amp test range selected
25mΩ 10A 25 milliohm, 10 Amp test range selected
5mΩ 10A 5 milliohm, 10 Amp test range selected

Micro-Ohmmeter Model 6250 13

 CHAPTER 3

SPECIFICATIONS

3.1 Electrical
Specifications are given for an ambient temperature of 23°C ± 5°, relative humidity
of 45 to 75% and a supply voltage of 6V ± 0.1V.

Measurement Method:
4-Wire Kelvin resistance measurement with compensation for stray/resid-
ual voltages

Measurement Ranges:
Accuracy over 1 year Measurement Voltage
Range Resolution
23°C ± 5°C Current Drop
5mΩ 0.1µΩ 0.15% ± 1.0µΩ 10A 50mV
25mΩ 1µΩ 0.05% ± 3µΩ 10A 250mV
250mΩ 10µΩ 0.05% ± 30µΩ 10A 2500mV
2500mΩ 0.1mΩ 0.05% ± 0.3mΩ 1A 2500mV
25Ω 1mΩ 0.05% ± 3mΩ 100mA 2500mV
250Ω 10mΩ 0.05% ± 30mΩ 10mA 2500mV
2500Ω 100mΩ 0.05% ± 300mΩ 1mA 2500mV

Temperature Measurement: 3-wire 100Ω Platinum RTD

Accuracy: ± 0.5°C
Resolution: 0.1°C

Influence From Environment Conditions:

Temperature: 0.1% per 10°C typical, 0.25% max
Humidity: 0.5% max from 10 to 90%
Battery Voltage: ± 0.1% from 4.5 to 7.5V
Open Circuit Voltage: 7VDC max

14 Micro-Ohmmeter Model 6250

Operating Voltage: 5 to 6VDC

Power Source:
Rechargeable 6V, 8.5 Ah NiMH battery pack
Built-in 90 to 256V (45 to 420Hz) charger

Battery Life: 5000, 10A tests (typical)

Battery Charging: 120/240VAC ± 20% (45 to 400Hz) line voltage

Auto-Power Off: when battery voltage <5.0V

Low Battery Indication: The symbol is displayed when the battery

needs to be recharged

Overload Input Protection: 250Vrms

Fuses:
F1 - 1 1/4 x 1/4" (6.3x32mm), fast acting, 16A/250V current source
protection
F2 - 3/4 x 3/16" (5x20mm), fast acting, 2A/250V charging circuit
protection

3.2 Mechanical
Dimensions: 10.63 x 9.84 x 7.09" (270 x 250 x 180mm)

Weight: 8.1 lbs (3.69kg approx) without leads

Case Protection: ABS plastic polycarbonate: watertight to IP64 (cover

closed), water resistant to IP53 (cover open).

Color: Safety yellow case with gray faceplate

3.3 Display
Blue Electroluminescent backlit Liquid Crystal Display (LCD), 2.25 x 4.00"
with icons and two numeric fields for data presentation.
One numeric field contains 4 digits for displaying ambient and reference
temperature levels on the top line in “temperature compensation” mode.
The other contains 5 digits and is used to display the measured values on
the bottom line. Error messages are also listed on the bottom line.

Micro-Ohmmeter Model 6250 15

3.4 Environmental
Operating Temperature:
14° to 132°F (-10° to 55°C), 10 to 80% (non-condensing)

Storage Temperature: -40° to 140°F (-40° to 60°C)

3.5 Safety

EN 61010-1, 50V, CAT III, Pollution Degree 2

Conducted and radiated emission:

EN 55022, class B
EN 61000-3-2
EN 61000-3-3

Immunity:
EN 61000-4-2 electrostatic discharges
EN 61000-4-3 radiated fields
EN 61000-4-5 shock
EN 61000-4-6 conducted disturbances
EN 61000-4-11 voltage drops
EN 61000-4-4 bursts

*Specifications are subject to change without notice

16 Micro-Ohmmeter Model 6250

 CHAPTER 4

OPERATION

NOTE: Charge the instrument fully before use.

4.1 Quick Summary

The following is a summary instruction set that will assist the operator in
performing measurements. For complete details on each function and test
method refer to the operating procedure section (§ 4.3) and instrument
configuration section (§ 4.2) in this manual.

WARNING: Read and follow all safety warnings on page 4 before operat-
ing this instrument.

1. Turn the instrument on and select a test range by turning the rotary
switch to the desired position. If the resistance of the device under test
is unknown, start with the highest range (2500Ω) and work down to
increase resolution as necessary.
2. Select the test method best suited for the measurement by press-
ing the button to select inductive (continuous test), resistive
(instantaneous test) or AUTO (multiple testing).

3. Activate the backlight, if necessary, by pressing the button.

4. Activate the buzzer, if desired, by pressing yellow button followed
by the button.
5. Activate alarms, if desired, by pressing the yellow button followed
by the ALARM button. Successive presses of this two-button sequence
will select Alarm 1, Alarm 2 or both.
6. Select the metal type for the device under test by pressing the yellow
button followed by the METAL button. Successive presses of this
two-button sequence will select Copper (Cu), Aluminum (Al) or Other
metal. This will be needed for temperature compensation.

Micro-Ohmmeter Model 6250 17

7. Activate temperature compensation by pressing the button.
The reference temperature will appear followed by the ambient
temperature on the top line of the display.
8. Start the test by pressing the START/STOP button. The resistance
reading will appear on the lower line of the display. The symbol
OPER will appear on the lower left to indicate that a test is in
process. The Stand-by symbol ST BY will appear when the test is
completed. Resistive element tests will stop automatically. Inductive
and AUTO testing will stop when the operator pushes the START/
STOP button a second time.
9. Store the test result in memory by pressing the MEM button at the
conclusion of a test. The next available location will be presented on
the top line of the display. To use this location, press the MEM button
a second time.
10. Recall readings from memory by pressing the yellow button fol-
lowed by the MEM button. The last measurement stored in location
OBJ: X TEST: X will be displayed. Use the ▲, ▼ and ► buttons to
select the object and test memory location to review. All information
from the measurement is available for review including metal type,
ambient and reference temperatures, resistance at ambient and refer-
ence temperatures, test range and test current.

Typical Operational Display

Temperature
compensation active

Buzzer active Metal type (Copper)

Alarm 1 hi set point active Reference temperature

Resistance measurement

Measurement units
Measurement range Test in process

Test current Inductive test mode

Figure 4-1

18 Micro-Ohmmeter Model 6250

4.2 Instrument Configuration (SET-UP Mode)

4.2.1 Program Menu Tree

The menu tree below shows the order in which functions appear in the
Menu and sub-menus of the set up mode.

Set
r5 – OFF – Trig – PC – uT100 – Print
buzz – off – low high
EdSn – displays internal serial number
EdPP – displays firmware number
Lang – Lg Gb – Lg F
trEF – value
tAnb – Prb – nPrb
nEtA – Copper alpha – Aluminum alpha, Other Metal
ALPH – value
dEg – dEgF – dEgC
ALAr – Alarm 1 – Alarm 2
LlgH – t=OFF – t=1 – t=5 – t=10
nEn – dEL – dEL O – Y – n

The cursor buttons ▲, ▼ and ► have the following functions in the

SET-UP menu:
• The up Arrow ▲ button selects the next function to be programmed
in the top level menu and increments the value of the flashing
variable in the sub-menus.
• The down Arrow ▼ button selects the previous function to be pro-
grammed in the top level menu and decrements the value of the
flashing variable in the sub-menus.
• The right arrow ► button selects the function displayed in the top
level menu and moves the cursor one place to the right or validates
the programming in the sub-menus. See Cables and Printer Used
with the Interface Port (§5.3) for proper connections.

Micro-Ohmmeter Model 6250 19

4.2.2 Programming the 9-Pin Interface Port (rS)
The 9-pin interface port on the top right side of the front panel can be pro-
grammed to any of five communication methods. These consist of:
1. Off: Disable input and output functions of the interface port. This
choice saves battery power.
2. Trigger: Enables the remote measurement function.
3. PC: Activates an RS-232 link between a computer and the unit for
configuring the Model 6250 and for conducting tests and storing
results. When activated, the icon will appear on the display.
4. VT100: Activates an RS-232 link between a display terminal and
the Model 6250. When activated, the icon will appear on the
display.
5. Print: Activates the RS-232 link between a printer and the Model
6250 for direct printing of test results. When activated, the icon
will appear on the display.
The RS-232 modes also allow programming of transmission speed. The
baud rate choices are: 4800, 9600, 19200 and 31250.
The required data configuration settings are: 8 bits, no parity, 1 stop bit,
hardware control (CTS).
• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “rS” appears on the top line of the
display.
• Press the ► button, OFF will appear in the display.
• Press the ► button to accept this setting or press the ▲ button
to scroll through the other choices of trigger (trlG), PC, Terminal
(ut100) and Print.
• The choices of PC, terminal and print also require a baud rate
selection.
• After selecting PC, ut100 or Print, pressing the ► button will enter
the baud rate selection menu.
• Press the ▲ button to toggle the choices for 4800, 9600, 19200
and 31250. When the desired baud rate is in the display, validate
it by pressing the ► button to return to the top level rS menu. The
icon will appear in the display.
• Proceed to the next programming variable by pressing the ▲
button.

20 Micro-Ohmmeter Model 6250

4.2.3 Setting the Buzzer Level (bUZZ)
• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “bUZZ” appears on the top line of the
display.
• Press the ► button to scroll through the choices of OFF (no icon
displayed), LOW (small buzzer icon displayed) or HIGH (large
buzzer icon displayed). Each choice will display the corre-
sponding icon in the top left corner of the display along with the
associated audible sound.
• When the desired sound level is displayed, press the ► button to
accept it and return to the top level of buzzer set-up.
• To proceed to the next programming variable, press the ▲ button.

4.2.4 Reading the Internal Serial Number (EdSn)

• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “EdSn” appears on the top line of the
display.
• Press the ► button to scroll through the serial number. There are
10 digits in the serial number. The first press will display the first
five digits. The second press will display the second five digits.
EXAMPLE: First press displays: t0302
Second press displays: 044-0
Third press displays: 0001 A
• Press the ► button again to return to the top level of the Serial
Number set-up menu.
• To proceed to the next programming variable, press the ▲ button.

4.2.5 Reading the Internal Software Version (EdPP)

• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “EdPP” appears on the top line of the
display.
• Press the ► button to display the firmware version.
• Press the ► button again to return to the top level of the Software
Version set-up menu.
• To proceed to the next programming variable, press the ▲ button.
Micro-Ohmmeter Model 6250 21
4.2.6 Setting the Language used for Printing Reports (LAnG)
• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “LAnG” appears on the top line of the
display.
• Press the ► button to enter the language selection sub-menu.
• Next, press the ▲ button to toggle between English (Lg Gb) or
French (Lg F).
• Press the ► button to validate the selection and return to the top
level of the Language set-up menu.
• To proceed to the next programming variable, press the ▲ button.

4.2.7 Setting the Value for the Reference Temperature (trEF)

• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “trEF” appears on the top line of the display.
• Press the ► button to enter the reference temperature sub-menu.
The current reference temperature will be displayed with the lead-
ing digit flashing.
• Use the ▲ button to change the leading digit. The minus (-) symbol
can also be programmed in this location.
• When the desired value is reached, press the ► button to move
the next digit to the right.
• Use the ▲ button to change this digit, then press the ► button to
again move to the next digit to the right.
• Repeat this process for each of the 5 digit locations.
• After the 5th digit is programmed, press the ► button again to return
to the top level of the Reference Temperature set-up menu.
• To proceed to the next programming variable, press the ▲ button.

NOTE: The program limits for the reference temperature are 32.0 to
130.0°F and -10.0 to 130.0°C. Attempting to set values outside these
limits will cause error message “Err23” (Entry Out of Range) to appear in
the display.

22 Micro-Ohmmeter Model 6250

4.2.8 Selecting the Method and Value for Ambient
Temperature (tAnb)
• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “tAnb” appears on the top line of the dis-
play.
• Press the ► button to enter the ambient temperature sub-menu.
• The first choice here is to decide if ambient temperature will be
measured using the RTD temperature probe accessory or if it will
be programmed using the same method as described for refer-
ence temperature. “Prb” (measure the ambient temperature using
the RTD probe accessory) or “nPrb” (no probe, manually enter
the ambient temperature) will be displayed, press the ▲ button to
toggle between the two choices.
• If measuring the ambient temperature is desired, press the ►
button when “Prb” is in the display. The lower display will momen-
tarily show dashes “-----” and then return to the top level ambient
temperature menu.
• If manually entering the ambient temperature is desired, press the
► button when “nPrb” is in the display. The ambient temperature
may now be manually entered.
• The current programmed ambient temperature will be displayed
with the leading digit flashing.
• Use the ▲ button to change the leading digit. The minus (-) symbol
can also be programmed in this location.
• When the desired value is reached, press the ► button to move
the next digit to the right.
• Use the ▲ button to change this digit then press the ► button to
again move to the next digit to the right.
• Repeat this process for each of the 5 digit locations.
• After the 5th digit is programmed, press the ► button again to
return to the top level of the ambient temperature set-up menu.
• To proceed to the next programming variable, press the ▲ button.

NOTE: The program limits for the reference temperature are 32.0 to
130.0°F and -10.0 to 130.0°C. Attempting to set values outside these
limits will cause error message “Err23” (Entry Out of Range) to appear in
the display.

Micro-Ohmmeter Model 6250 23

4.2.9 Selecting the Metal Type (nEtA)
• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “nEtA” appears on the top line of the
display.
• Press the ► button to toggle through the choices of Copper (Cu),
Aluminum (Al) or Other Metal. With each press of the right arrow
button, the metal type icon appears at the top of the display.
“nEtA” appears on the small display and the five digit alpha value
appears on the large display and then automatically returns to the
top level of the metal set-up menu.
• To proceed to the next programming variable, press the ▲
button.

4.2.10 Programming the Alpha Value (ALPH)

• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “ALPH” appears on the top line of the
display.
• Press the ► button to begin programming the alpha value. See
Table 2 in §4.6 for common alpha values.
• The current alpha value will be displayed with the leading digit
flashing.
• Use the ▲ button to change the leading digit. When the desired
value is reached, press the ► button to move the next digit to the
right.
• Use the ▲ button to change this digit, then press the ► button to
again move to the next digit to the right.
• Repeat this process for each of the 5 digit locations.
• After the 5th digit is programmed, press the ► button again to
return to the top level of the alpha set up menu
• To proceed to the next programming variable, press the ▲
button.

4.2.11 Selecting Temperature Units (dEg)

• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “dEg” appears on the top line of the dis-
play.

24 Micro-Ohmmeter Model 6250

 • Press the ► button to enter the degree units sub-menu.
• Use the ▲ button to toggle through the choices of Fahrenheit
(dEgF) or Centigrade (dEgC).
• Press the ► button to validate the selection and return to the top
level of the Temperature units set-up menu.
• To proceed to the next programming variable, press the ▲ button.

4.2.12 Setting Alarm Set Point, Direction and Buzzer Level (ALAr)
• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “ALAr” appears on the top line of the
display.
• Press the ► button, Alarm 1 and its set point, direction and buzzer
level will appear with ALARM 1 flashing.
• To modify the settings of Alarm 1, press the ► button. The direc-
tion arrow will now be flashing. To modify Alarm 2 press the ▲
button, ALARM 2 will then be flashing.
• When the direction arrow is flashing, it may be changed by press-
ing the ▲ button to toggle between HIGH (▲ activates above set
point) and LOW (▼ activates below set point).
• Next, press the ► button to adjust the buzzer level for this alarm.
The buzzer icon will be flashing. The choices are OFF (no
icon displayed), LOW (small buzzer icon displayed ) or HIGH
(large buzzer icon displayed). The selection is made by
pressing the ▲ button while the icon is flashing.
• Next, program the set point value used to trigger the alarm (ignor-
ing the decimal point) by pressing the ► button. The leading digit
will be flashing. Adjust the digit value using the ▲ button then
press the ► button to move to the next digit to the right.
• Repeat the process for each of the five digits.
• Press the ► button when the numeric value is set to the desired
number. The decimal point and units (mΩ or Ω) will be flashing.
• Set the desired resolution and units by pressing the ▲ button.
Each press will move the decimal point one place to the right.
Cycling through milliohms and then through ohms.
• To accept the alarm settings once the decimal point and units
are at the desired values, press the ► button. This will bring you
to Alarm 2. Repeat the process as necessary to set Alarm 2’s
conditions.

Micro-Ohmmeter Model 6250 25

 • When Alarm 2 is set press the ► button to return to the top level
of the alarm programming menu. “ALAr” will again appear on the
top line and the bottom line will be blank.
• To proceed to the next programming variable, press the ▲ button.

4.2.13 Setting the Display Timeout (LlgH)

This setting determines the length of time that the backlight will stay on after
the last button press. The choices are OFF (function disabled, backlight
stays on continuously when activated), 1, 5 or 10 minutes.
• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “LlgH” appears on the top line of the
display.
• Press the ► button, the last programmed value will appear in the
display.
• Press the ▲ button to toggle through the choices of OFF, t=1, t=5
and t=10.
• When the desired length of time is in the display, press the ►
button to validate the selection.
• To proceed to the next programming variable, press the ▲ button.

4.2.14 Clearing the Memory (nEn)

You can choose to clear the entire memory or the contents of a specific
object.
• Turn the rotary switch to the SET-UP position.
• Press the ▲ button until “nEn” appears on the top line of the
display.
• Press the ► button, “dEL” will appear on the lower line of the
display.
• Toggle between clearing the entire memory (dEL) or a specific
object (dEL O) using the ▲ button.
• To clear a specific object, press the ► button when “dEL. O” is in
the display, the top line will display Obj 01 with the “0” flashing.
Use the arrow buttons to select the object to be deleted.
• The lower display will show “dEL.02” for example if object number
2 is selected for deletion. As you press the ▲ button, the selected
object will increment accordingly.

26 Micro-Ohmmeter Model 6250

 • Delete the selected object by first pressing the ► button and
toggling between Yes “dEL. Y” or No “dEL. n”
• Pressing the ► button while “dEL. Y” is in the display will delete
the contents of the selected object. The display will momentarily
display dashes “-----” and then return to display the next highest
object location.
• Pressing the ► button while “dEL. n” is in the display will cancel
the request.
• Repeat this process for each object to be deleted.
• To clear the entire memory contents, turn the rotary switch to the
SET-UP position.
• Press the ▲ button until “nEn” appears on the top line of the
display.
• Press the ► button, “dEL” will appear on the lower line of the
display.
• Delete all data from memory by first pressing the ► button, then
toggling between Yes “dEL. Y” or No “dEL. n”
• Pressing the ► button while “dEL. Y” is in the display will clear all
memory of stored measurements.
• Pressing the ► button while “dEL. n” is in the display will cancel
the request.

NOTE: Only objects with data stored in them can be accessed.

To return to the beginning of the SET-UP menu, press the ▲ button when
“nEn” is on the top line of the display

Micro-Ohmmeter Model 6250 27

4.3 Operating Procedure

WARNING: Before performing the resistance test, verify that the sample
under test is not energized.

4.3.1 Connections and Readings

Clean all surfaces before connecting test leads. Verify a solid connection
between test leads and the sample. Set the range selector switch to the
desired range for the test. If the anticipated resistance is not known, begin
with the highest range (2500Ω) and successively lower the range selection
until adequate resolution is achieved. The START/STOP button will need
to be pressed each time you change ranges. The range selection may be
changed while the instrument is on.
A diagram of the measurement system is shown in Figure 4-2. The
Model 6250 generates a current (I) from the internal voltage source (V).
A voltmeter measures the voltage drop Vx at the Kelvin probe contact
points to the resistance to be measured (Rx) and displays the resistance
measurement (Rx) directly using the formula Rx = Vx / I.
The result is not affected by the other resistances encountered in the cur-
rent loop (Ri, Rf, Rc), as long as the total voltage drop induced across Rx
remains below the voltage supplied by the source which is between 5 to
6V. The maximum admissible lead resistance level is Rf ≈ (V- Vx) / I. The
use of Kelvin probes helps, as they eliminate the effect of the lead resis-
tance (Rf).

Ri C1 Rf

P2 Rc
Rf
I
Vx P2 Rx
Rf
+
V C2 Rc
Rf

Figure 4-2

Ri = Unit internal resistance Rc = Contact resistance

Rf = Lead resistance Rx = Resistance to be measured

28 Micro-Ohmmeter Model 6250

4.3.2 Test Lead Connection
The measurement leads are connected using the four binding posts on the
left side of the front panel as shown in Figure 4-3.
Connect the two red leads to terminals C1 and P1. Connect the two black
leads to terminals C2 and P2.
Any drop in the voltage on the load terminals is measured between the two
“voltage” (V) leads, P1 and P2. The current leads (C1 and C2) can deliver
current from 1mA to 10A.

I U

Figure 4-3

4.3.3 Very Low Resistance

When measuring very low resistive values in the µΩ range, the presence
of stray DC currents may affect the accuracy of the measurements. These
currents can be present due to a variety of reasons including chemical or
thermal EMF in samples made of dissimilar metals. These EMFs are auto-
matically compensated for during the measurement process.
The presence of AC interference in the sample under test may cause the
measured value on the display to fluctuate. This interference may become
more noticeable in the presence of strong electric fields. The effects of this
interference may be reduced by twisting the leads around each other.

4.3.4 Meter Readings

When testing resistive samples, the meter reading will stabilize within the
first few hundred milliseconds. On inductive loads (e.g. transformers), the
measurement reading may take from several seconds to a few minutes
to stabilize and depends greatly on the type of equipment and the imped-
ance of the equipment under test. On very large samples such as utility
transformers, 10 to 15 minutes charging time may be necessary.

Micro-Ohmmeter Model 6250 29

4.3.5 Stand-by (ST BY) State
This is the position that the Model 6250 returns to at the end of a measure-
ment cycle after:
• the operator presses the START/STOP button during a test
• any changes to the position of the rotary switch
• every low inductive mode measurement
• an error is detected

4.4 Selecting the Test Range

The Model 6250 has seven test ranges to choose from. Table 1 lists the
maximum resistance, test current and resolution for each range.

Resistance Range Test Current Resolution

2500Ω 1mA 100mΩ
250Ω 10mA 10mΩ
25Ω 100mA 1mΩ
2500mΩ 1A 0.1mΩ
250mΩ 10A 10µΩ
25mΩ 10A 1µΩ
5mΩ 10A 0.1µΩ

Table 1

Turn the rotary switch to the desired range, the range and test current
will appear on the lower left side of the display.

Figure 4-4

The Model 6250 is now ready to start a test.

30 Micro-Ohmmeter Model 6250

4.5 Measurement Modes

NOTE: For descriptions of all Fault Indicator (Error) codes, refer to

Chapter 7 - “Troubleshooting” in this manual.

4.5.1 Measurement Safety Warnings

WARNING:
• Never use test leads or measuring wires if there is any evidence
of deterioration (insulation split, burnt, etc).
• Never exceed the safety values indicated in the specifications.
• Never connect the unit to a live circuit.
• When the unit is measuring resistance showing a high induc-
tive component (transformers, motors, etc.) after ending the
measurement (with the measurement current cut-off), the unit
then discharges this inductance and displays the icon for this
entire duration.

• Never disconnect the connection wires before the icon dis-

appears.

4.5.2 Inductive Resistance Measurement Mode ( )

This mode is intended for performing measurements on inductive devices.
Press the button until the icon shows on the display.
From the Stand-by state, start a test by performing the following:
• Connect the Kelvin probes to the test specimen.
• Press the START/STOP button.
• If the Kelvin probes are incorrectly connected, the display will show
error message “Err 11” (current leads incorrectly connected), or
“Err 12” (voltage leads incorrectly connected). The unit will then
return to the Stand-by state. When the error is corrected, the test
automatically begins again.

Micro-Ohmmeter Model 6250 31

 • With the current switched off, the residual voltage (V0) across the
resistor terminals is measured and displayed. If this voltage level
is too high, “Err 13” will be displayed.
• The current (I) is switched on at the start of a measurement and
remains on continuously until the unit is manually returned to the
Stand-by state by pressing the START/STOP button.
• The voltage across the resistor terminals (V1) is measured and
the measurement R = (V1 - V0) / I is displayed.
• All subsequent measurements comprise only a Vn measurement
as V0 remains in memory. The timing sequence for measurement
is shown in Figure 4-5.

NOTE: After ending the measurement, with the current turned off, the 6250
will discharge the device under test as long as the test leads are connected
to the device.

OPER
STBY

I C

MES 0 1 2 3 n
100ms
640ms 120ms
1200ms

Figure 4-5
C = connection check
0 = residual voltage measurement (stored)
1,2,3…n = successive voltage measurements across the resistor terminals

• The test is stopped by pressing the START/STOP button.

• Store the measurement by first pressing the MEM button, then
select the object and test location to store the measurement using
the arrow buttons. When the desired location has been selected,
press the MEM button a second time to complete the data storage
process.

32 Micro-Ohmmeter Model 6250

4.5.3 Resistance Measurement Mode ( )
This mode is intended for measuring contact and metal plating resistance
levels, and as a general rule, any resistance level on material with a time
constant that is less than a few milliseconds.
In this mode, only one measurement is performed per cycle. When the
START/STOP button is pressed, the test current is applied for approximately
400 milliseconds. Residual voltage is measured, a resistance measurement
is taken and the test stops automatically.
The advantages of the resistance mode include:
• Reduced power consumption as the test current is off between
measurements.
• Less heating of the measured resistance.
• Improved compensation of stray voltages as these are measured
and compensated before each resistance measurement.

Press the button until the icon shows on the display.

From the Stand-by state, start a test by performing the following:
• Connect the Kelvin probes to the test specimen.
• Press the START/STOP button.
• If the Kelvin probes are incorrectly connected, the display will
show error message “Err 11” (current leads incorrectly connected),
or “Err 12” (voltage leads incorrectly connected). The unit will then
return to the Stand-by state. When the error is corrected, the test
can begin again by pressing the START/STOP button.
• With the current switched off, the residual voltage (V0) across the
resistor terminals is measured. If this voltage level is too high,
the unit displays “Err 13” and returns to Stand-by position. (See
Chapter 7 - “Troubleshooting” for all error message descriptions.)
• The current (I) is switched on when the START/STOP button is
pressed.
• The voltage across the resistor terminals (V1) is measured and
then the current is removed.
• The measurement resistance result R = (V1 - V0) / I is displayed
or error message “Err 07” is displayed, if an over range condition
occurs.

Micro-Ohmmeter Model 6250 33

The Model 6250 then returns to the Stand-by state at the end of the mea-
surement. The unit is ready to perform another measurement.

OPER
STBY

I C C

O M O M
MES

100ms 100ms
240ms 240ms

360ms 360ms

Figure 4-6

C = connection check
0 = residual voltage measurement
M = measurement of the voltage across the resistor terminals.

• Store the measurement by first pressing the MEM button, then

select the object and test location to store the measurement using
the arrow buttons. When the desired location has been selected,
press the MEM button a second time to complete the data storage
process.

4.5.4 Low Inductive Resistance Automatic Triggering

Measurement Mode
This mode is intended only for measuring resistance on material without a
time constant (non-inductive). The use of the spring loaded Kelvin probes
(Cat. #2118.77 or Cat. #2118.78) listed in the accessories section are rec-
ommended for this mode.
From the Stand-by state, start a test by performing the following:
• Press the button until the AUTO icon shows on the display.
• Press the START/STOP button.
• Connect the probes to the specimen. The unit waits until it detects
that the current and voltage leads are connected correctly.

34 Micro-Ohmmeter Model 6250

 • Residual voltage (V0) measurement across the resistor terminals
is measured.
• The measurement current (I) is established, the voltage across
the resistor terminals (V1) is measured and the measurement
resistance result R = (V1 - V0) / I is displayed.
• To start a new measurement cycle, Release at least one
probe, and then reconnect it to the next point or specimen.

NOTE: If the range is exceeded, the unit displays “Err 07”. Changing the
range switch position will stop the test cycle and the unit returns to the
Stand-by state. Each measurement taken during the test cycle can be
temperature compensated and stored while the test cycle is running.

• Store the measurement of each specimen or point by first pressing

the MEM button, then select the object and test location to store
the measurement using the arrow buttons. When the desired loca-
tion has been selected, press the MEM button a second time to
complete the data storage process.
• The test is stopped by pressing the START/STOP button.

4.6 Ambient Temperature Compensation

Principle
The metals used in the windings of certain devices (for example, the copper
wire used in transformer or motor windings) have high temperature coef-
ficients in the order of 0.4%/°C (for copper or aluminum). This results in
resistance measurements that are highly dependent on the temperature of
the device. Activating temperature compensation will correct for this condi-
tion.
The “Temperature Compensation” function can be accessed by pressing
the button before the start of a test in Resistance and Inductive resis-
tance measurement mode. It can also be activated at anytime during Auto
measurement mode.
Its purpose is to compensate the measured or resistance value at the
ambient temperature (whether measured or programmed), to the resis-
tance value that it should have at a reference temperature.

Micro-Ohmmeter Model 6250 35

The compensated resistance level is expressed as follows:
R(Tref) = R(Tamb) * (1 + alpha * Tref )
1 + (alpha * Tamb)
Where:
R(Tamb) = the resistance value measured at ambient temperature
Tamb = the temperature measured by a Pt100 probe or programmed
by the operator
Alpha = the temperature coefficient of the chosen metal (Aluminum,
Copper, “Other metal”)
Tref = the programmed reference temperature to which the
measurement is compensated to

The Temperature Coefficient of Copper (near room temperature) is +0.393

percent per degree C. This means if the temperature increases 1°C the
resistance will increase 0.393%.

Example: You have 100 feet of 20 gage wire and its resistance is 1.015Ω at
20°C (room temp). If the temperature of the wire goes up 10°C the resistance
will change by 0.0399Ω (10° * 0.00393 / ° * 1.015Ω = 0.0399Ω).
The wire resistance will now be 1.015Ω + 0.0399Ω = 1.0549Ω.

The table below provides the temperature coefficients of the more common
metals and alloys.
The Alpha values for Copper and Aluminum are pre-programmed into the
Model 6250. Others may be programmed by selecting Other Metals and
then programming in the alpha constant from the table or other sources.

“alpha” per °C
Material Element/Alloy
X10-3
Aluminum Element 4.030
Copper Element 3.930
Nickel Element 5.866
Iron Element 5.671
Molybdenum Element 4.579
Tungsten Element 4.403
Silver Element 3.819
Platinum Element 3.729
Gold Element 3.715
Zinc Element 0.847
Steel Alloy 3.000
Nichrome Alloy 0.170
Nichrome V Alloy 0.130
Table 2

36 Micro-Ohmmeter Model 6250

A 100Ω platinum RTD can be connected to the front panel of the Model
6250 to perform compensated measurements. The temperature sensor
and extension cable assembly, listed in the Accessories section, are rec-
ommended. The three pin temperature compensation port is located to the
left of the interface port and is configured as shown in Figure 4-7.

Pt100 connector

Figure 4-7

To measure the ambient air temperature at the Model 6250, plug the
optional temperature sensor directly into the temperature port on the front
panel as shown in Figure 4-8.

Figure 4-8

To measure the ambient temperature at the specimen, plug the optional

temperature sensor onto the extension cable and plug the extension cable
into the temperature port on the front panel as shown in Figure 4-9.
Place the temperature sensor in contact with the specimen or in close
proximity to it. Allow 2 minutes for the sensor to normalize to the specimen
temperature before starting a temperature compensated measurement.

Micro-Ohmmeter Model 6250 37

 Figure 4-9

4.6.1 Activating the Compensation Function

Check to ensure that all desired programming and connections are made
correctly. See Setting the Value for Reference Temperature (§4.2.7) and
Selecting the Method for Ambient Temperature (§4.2.8).
• Select the range and the measurement mode.
• Press the button.
The following information will be displayed on-screen:
1.
2. Metal type selected (Cu, Al or Other Metal)
3. Temperature levels Tref followed by Tamb
• Press the START/STOP button.
• The unit performs a measurement cycle and directly displays the
compensated resistance value and, depending on set-up, displays
one of the following:
1. The programmed ambient temperature level
2. The temperature level measured by the temperature
sensor

38 Micro-Ohmmeter Model 6250

 3. “- - - -” if the temperature sensor is activated but is
incorrectly connected or not connected at all
4. The measured temperature is out of range (-10° to 55°C)
If the temperature is out of range or if the sensor leads are disconnected,
the Model 6250 displays “Err 10”.
Temperature compensation can be toggled ON or OFF after the mea-
surement is completed, in resistive and inductive modes or at any time in
AUTO mode.

4.7 Activating Alarms

The alarm programming menu offers the option of choosing one or two
alarm thresholds. An alarm comprises a value, an activation direction
(above ▲ or below ▼ the setpoint) and a sound level setting for the buzzer,
should the alarm become active.

NOTE: Alarms are activated by successively pressing the button fol-

lowed by the ALARM button.

The display will indicate one of the following after each set of button
presses:
• Alarm 1 and the activation direction, ▲ or ▼
• Alarm 2 and the activation direction, ▲ or ▼
• Alarm 1 and Alarm 2 and activation directions, ▲ or ▼ for each
These values and direction parameters are programmable. See Setting
an Alarm Set Point, Direction and Buzzer Levels (§4.2.12). The buzzer will
sound when Alarm 1 and/or Alarm 2 threshold values are reached.

Micro-Ohmmeter Model 6250 39

 CHAPTER 5

MEMORY / PRINTING

5.1 Managing and Printing the Data in Memory

The memory is organized into locations called Objects and Tests.
There are 99 objects, each containing a maximum of 99 tests (measure-
ments). The maximum number of measurements that can be stored is
approximately 1500.
After taking a measurement, it may be stored in memory by pressing the
MEM button. The MEM icon blinks and the first available Object and Test
location for storing this measurement is displayed with the last digit of the
test number blinking.

Example: Object 1 and Test 4 are displayed and the 4 will be blinking.

01:04.
OBJ : TEST

The object and test location can be changed using the arrow buttons.
• FREE is displayed when the location is empty
• OCC is displayed when the location has data stored in it
After choosing the measurement’s memory location, pressing the MEM
button a second time validates memory storage in a FREE location.
If an occupied location is selected, the OCC message blinks to warn
that this memory location is already taken. Storage action in this location
requires pressing the MEM button again. The previous measurement in
this location will be replaced by the new measurement.

40 Micro-Ohmmeter Model 6250

5.2 Displaying and Printing Stored Measurements

NOTE: To display or print a measurement result stored in memory, press

the yellow button followed by the MR button.

The measurement value for the last object and test saved is displayed.

Example: Object 1 and Test 3 are displayed.

01:03.
OBJ : TEST
The test unit number will be blinking. In this example the 3 will be blinking.
Change the object and test numbers using the arrow buttons. As you
change memory locations, the stored measurement value will be dis-
played. The following measurement components are also accessible if
stored.
The selected memory location will display:
• The number of the object and test that correspond to the memory
location
• The active range and current level during the measurement
• The measurement value with any compensation used
• The alarm icon for any active alarms that occurred during the
measurement

The parameters set for the alarm threshold, reference temperature,

ambient temperature and metal correction coefficient are not directly
accessible. They are accessible by pressing the following:
• Press the button to display ambient temperature at the time
of the stored measurement.
• Press the button a second time to display the reference tem-
perature that the measurement was compensated to.
• Press the button to display the type of metal and alpha
value used for compensation at the time of the measurement.
• Press the PRINT button to print the measurement results stored at
the current memory location. An optional serial printer is required
for this feature.
Micro-Ohmmeter Model 6250 41
 NOTE: Only memory locations with stored measurements are accessible.
Measurement data stored in memory can be accessed directly from any
switch position except OFF and SET-UP for printing.
 Press the yellow button followed by the PRINT MEM button
to access measurement results stored in memory for printing. An
optional serial printer is required for this feature. Use the arrow
buttons to select the object and test to be printed.
A typical printed report using the optional DPU-414-30B portable battery
operated printer (Cat. #2140.21) is shown below.

CHAUVIN ARNOUX - CA6250

NUMBER : ...................................

OBJECT: TEST:
DESCRIPTION: ...............................
............................................
............................................

Meas. Date : ___/___/___

Meas. Type : LOW INDUCTIVE
Metal Type : Cu
Coeff. Metal : 3.93
Measurement Temperature : 23.2 C
Reference Temperature : 20.0 C
Resistance Value (Tamb) : 1294.6 Ohm
Resistance Value (Tref) : 1287.2 Ohm

COMMENTS : ...............................
............................................
............................................
Next test date : ___/___/___

Figure 5-1

Enclosed with this manual is a pad containing 50 forms to record the measurement
results manually. They may be photocopied as needed or downloaded from our
website at www.aemc.com/techinfo/index.asp located in the Micro-ohmmeter
section.

42 Micro-Ohmmeter Model 6250

5.3 Cables and Printers Used with the Interface Port
The DB9 interface port can be used to trigger remote measurements
(“TRIG”). Wiring for remote triggering of a test is detailed in Figure 5-2.
The “READY” LED indicates that a measurement can be made.

Figure 5-2

The DB9 interface port can be used for RS-232 communication with a PC,
terminal or a printer. The main connection pins used are detailed in Figures
5-3 and 5-4 respectively.

Connection to a PC or Terminal:

2 2

3 3
5 5

Figure 5-3

Male Connector Female Connector

Printer end     Printer end  
  Pin   6250 end  
Rx 2   3 Tx
Tx 3   2 Rx
Gnd 5   5 Gnd

Micro-Ohmmeter Model 6250 43

For a Direct Printer Connection:

2 2
3 3
8 8
5 5

Figure 5-4

Male Connector Female Connector

Printer end     Printer end  
  Pin    Pin
Rx 2   3 Tx
Tx 3   2 Rx
Gnd 5   5 Gnd
CTS 8 8 CTS

44 Micro-Ohmmeter Model 6250

 CHAPTER 6

DATAVIEW® SOFTWARE

6.1 Installing DataView®

DO NOT CONNECT THE INSTRUMENT TO THE PC BEFORE INSTALLING

THE SOFTWARE AND DRIVERS.

NOTE: When installing, the user must have Administrative access

rights during the installation. The users access rights can be changed
after the installation is complete. DataView® must be reinstalled for
each user in a multi-user system.

1. Insert the DataView thumb drive into an available USB port on your
computer. If Autorun is enabled, an AutoPlay window appears on your
screen. Click “Open folder to view files” to display the DataView folder.
If Autorun is not enabled or allowed, use Windows Explorer to locate
and open the USB drive labeled “DataView.”
2. When the DataView folder is open, find the file Setup.exe located in
the root directory of the USB drive, and double-click it to run the instal-
lation program.
3. The DataView setup screen appears. In the upper left corner of the
screen, choose the language version of the Setup interface. (All Setup
screens and dialogs will immediately appear in the selected language.
In the lower left corner are the available installation options. In addition
to the DataView software, you can select “Adobe Reader.” This links
to the Adobe web site where you can download the latest version of
Reader. This program is required to view DataView .pdf documents.
The option Firmware Upgrades links to the website where you can
check for new firmware updates for the instrument. Finally, User Man-
uals displays a list of .pdf files contained in the USB drive that accom-
panies DataView. (DataView also comes with a Help system that is
installed with the program files.) To install DataView, select DataView
in the Options list and click Install.

Micro-Ohmmeter Model 6250 45

4. Select the language version of DataView you want to install (Eng-
lish, French, or Spanish) then click Next. (By default, the language
selected in step 3 is highlighted.).
5. You are now prompted to select the software you want to install. Each
AEMC product family has its own specially designed Control Panel. If
you are performing a Complete install, by default all available Control
Panels are selected (a check mark next to the Control Panel indicates
it is selected). Control Panels take up disk space on the computer; so
unless you have other types of AEMC instruments, we recommend
that you select MicroOhmmeter and deselect the rest. You should also
check the option DataView Core, which is a requirement if you plan to
create DataView reports.
After you finish selecting and deselecting Control Panels and/or Data-
View Core, click Next..
6. The Setup program now informs you that it is ready to install Data-
View. If you want to review any of your previous selections, click the
Previous button to return to earlier screens. Otherwise, click Install to
begin installation
7. The InstallShield program installs the selected software. If an
earlier version of the software is already installed on your com-
puter, for each selected program the InstallShield program will:
(a) Ask you to confirm the installation of the program. Click Next.
(b) Display a status bar indicating the progress of the installation.
(c) Inform you when the program is installed.
Click Finish to install the next selected program.
If the software is not installed (or if the installed software is the same
version as the selected software), the software is installed without
requesting confirmation.
When all programs are installed, a message appears informing you of
this. Click Finish to return to the Setup screen.
8. You can now select additional Setup options to install (see step 3
above). When finished, click Exit.
9. The DataView folder now appears on your computer desktop, within
which is the MicroOhmmeter icon and the icon(s) for any other
Control Panel(s) you have installed.

46 Micro-Ohmmeter Model 6250

6.2 Connecting the Instrument to your Computer
The Model 6250 is supplied with a serial cable (Cat. #2119.45) necessary
for connecting the instrument to the computer.
To connect the instrument to your computer, connect one end of the serial
cable to the communications port on the Model 6250 and the other end to
the port on the computer.

6.3 Establishing Communication to the Instrument

1. Double-click the Micro-ohmmeter Icon in the DataView folder that
was created during software installation to open the Micro-ohmmeter
Control Panel.
2. From the main menu, go to Instrument > Connect to open the
Connection dialog box.
3. Make sure the Communication port and rate match the port that the
serial cable is plugged into and the baud rate the instrument is config-
ured to (see §4.2.2).
4. From the Instrument model drop-down menu, select the correct model,
if necessary.
5. Once the proper parameters have been specified, click OK.

6.4 Configuring the Instrument

1. Establish a connection to the instrument (see § 6.3).
2. Go to Instrument > Configure from the main menu to open the Con-
figuration Panel dialog box.
This dialog box allows you to configure the Measurement Type, Tem-
perature Correction, Ambient Temperature, Metal type, Lock program-
ming and enable/set the two Alarm thresholds.

NOTE: For additional help on using the software, use DataView’s “Help”
Menu, which is located on the menu bar.

Micro-Ohmmeter Model 6250 47

 CHAPTER 7

TROUBLESHOOTING
The Model 6250 incorporates internal diagnostics and will inform the oper-
ator of any condition needing attention through the use of error messages.
The available messages are described here.

7.1 Fault Indicators

Err 1 Low battery level
Err 2 Internal problem
Err 3 Unable to measure battery
Err 4 Unable to measure temperature
Err 5 Internal temperature too high - let the instrument cool down
Err 6 Unable to establish current measurement
Err 7 Measurement out of range
Err 8 Internal problem
Err 9 Measurement cycle stopped
Err 10 Temperature sensor incorrectly connected or missing
Err 11 Current leads incorrectly connected
Err 12 Voltage leads incorrectly connected or measured resistance
too high
Err 13 Residual voltage too high
Err 21 Adjustment out of range
Err 22 Measured value out of range
Err 23 Entry out of range
Err 24 Unable to write to memory
Err 25 Unable to read memory
Err 26 Memory full
Err 27 Memory empty; no data available
Err 28 Memory check problem
Err 29 Object or test number incorrect

WARNING: If error message 2, 3, 4, or 8 appears, the instrument must be

sent to a qualified organization for repair. See the Repair and Calibration
section for return instructions.

48 Micro-Ohmmeter Model 6250

 CHAPTER 8

APPLICATION EXAMPLES

The proper procedures for using the Model 6250 in some specific applica-
tions are outlined throughout this section.

8.1 Measuring Winding Resistance of Motors

and Transformers

WARNING: Prior to and after testing a transformer winding, the energy

stored in the magnetic field must be dissipated by shorting the trans-
former terminals. For additional safety, the transformer terminals should
be jumpered together before the instrument is disconnected.

One terminal of the sample should be grounded for safety!

Make connections to the transformer as shown in Figure 8-1. On larger
transformers, the measurement stabilization time will increase.

Figure 8-1

Micro-Ohmmeter Model 6250 49

8.2 Measuring Resistance on Electric Motors
For this test, Kelvin probes should be used (Figure 8-2). Make contact
with each segment on the motor commutator. Allow approximately two
seconds for the display to stabilize.

Figure 8-2

8.3 Battery Strap Measurements

Proper battery strap resistance measurements will help ensure proper
voltage output. The resistance on battery strap connections should be
measured using the Kelvin probes (see Figure 8-3). Measurements must
be made with the system power turned off.
The average resistance of all the intercell connections should be
determined by totaling the individual resistances and dividing by the
number of connectors. Each individual cell resistance should not exceed
the average by more than 10%. See the manufacturer’s specifications for
typical resistance values.

Battery Battery

Figure 8-3

50 Micro-Ohmmeter Model 6250

 CHAPTER 9

MAINTENANCE
Use only factory specified replacement parts. AEMC® will not be held
responsible for any accident, incident, or malfunction following a repair
done other than by its service center or by an approved repair center.

9.1 Warning
• To avoid electrical shock, do not attempt to perform any servicing
unless you are qualified to do so.
• Do not perform any service while the micro-ohmmeter is on any
circuit.
• To avoid electrical shock and/or damage to the instrument, do not
get water or other foreign agents into the electronic module.
• Make sure the internal battery is fully charged prior to testing. If
the instrument has been left unused for several months, recharge
the battery.
• We recommend recharging the micro-ohmmeter every month to
ensure a full battery charge when used.
• When replacing fuses, install only fuses which are direct replace-
ments.

9.2 Cleaning

WARNING: Disconnect the instrument from any source of electricity.

• If the case needs cleaning, do not use any alcohol or oil based
cleaners. Preferably use soapy water with a damp cloth or
sponge.
• Dry immediately after cleaning. Avoid water penetration into the
electronic module.
• Make sure the micro-ohmmeter and all leads are dry before fur-
ther use.

Micro-Ohmmeter Model 6250 51

9.3 Charging/Recharging the Battery

AC POWER SELECTION
The Model 6250 may be recharged from 90 to 264VAC (45 to 420Hz). The
instrument includes a 110V line cord, which provides the charging voltage
for the rechargeable battery.

CHARGING THE BATTERY

The Model 6250 should be charged to a full charge before using it for the
first time. Charging to full capacity may take up to 6 hours for a completely
discharged battery
If the battery symbol is flashing, the battery needs to be recharged.
The battery will charge in both the ON and OFF mode.
• In the ON mode, the charging indicators will show on the display.
• In the OFF mode, no display will show during charging.
Connect the Model 6250 to 120VAC using the power cord provided (charg-
ing starts automatically).

NOTE: Testing can not be conducted while charging the batteries. Button
presses are ignored when charging is in process.

CHARGING INDICATORS
• bAt on the small display and CHrg on the main display, signifies
fast charging in progress.
• bAt on the small display and CHrg flashing on the main display,
signifies slow charging (starts off with fast charge, temperature
conditions permitting).
• bAt on the small display and FULL on the main display, signifies
that charging is complete.
If the instrument is turned on and the battery voltage is >5V, then the
normal use of the device is permitted.

52 Micro-Ohmmeter Model 6250

9.4 Battery and Fuse Replacement

NOTE: Make sure that no terminals are connected and that the switch is
in the OFF position before opening the front panel.

BATTERY
• Replacing the battery causes data to be lost from the memory.
• The battery should only be replaced by a qualified technician or
sent back to the factory for replacement and standard calibration.
See the Repair and Calibration section for return instructions.

FUSES
• Before replacing the internal batteries or fuses, the front panel
must first be removed. Use a Phillips Head screwdriver to remove
the four screws from the feet on the bottom of the case.
• Pull out the chassis from the top.
• The two fuses are located on the left side of the chassis.
F1 is located near the C1 and P1 terminals.
F2 is located directly below on the bottom power supply board
assembly.
• Fuse F1, is a 6.3x32 mm, fast acting, 16A/250V, low internal
resistance, protecting the current source from outside voltages on
energized specimens.
• Fuse F2, is a 5.0x20 mm, fast acting, 2A/250V, protecting the
battery charger power supply board.

Micro-Ohmmeter Model 6250 53

Repair and Calibration
To ensure that your instrument meets factory specifications, we recommend
that it be scheduled back to our factory Service Center at one-year intervals
for recalibration, or as required by other standards or internal procedures.

For instrument repair and calibration:

You must contact our Service Center for a Customer Service Authorization
Number (CSA#). This will ensure that when your instrument arrives, it will be
tracked and processed promptly. Please write the CSA# on the outside of the
shipping container. If the instrument is returned for calibration, we need to
know if you want a standard calibration, or a calibration traceable to N.I.S.T.
(Includes calibration certificate plus recorded calibration data).

Ship To: Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments

15 Faraday Drive
Dover, NH 03820 USA
Phone: (800) 945-2362 (Ext. 360)
(603) 749-6434 (Ext. 360)
Fax: (603) 742-2346 or (603) 749-6309
E-mail: repair@aemc.com
(Or contact your authorized distributor)
Costs for repair, standard calibration, and calibration traceable to N.I.S.T. are
available.
NOTE: You must obtain a CSA# before returning any instrument.

Technical and Sales Assistance

If you are experiencing any technical problems, or require any assistance with
the proper operation or application of your instrument, please call, mail, fax or
e-mail our technical support team:

Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments

200 Foxborough Boulevard
Foxborough, MA 02035 USA
Phone: (800) 343-1391
(508) 698-2115
Fax: (508) 698-2118
E-mail: techsupport@aemc.com
www.aemc.com

NOTE: Do not ship Instruments to our Foxborough, MA address.

54 Micro-Ohmmeter Model 6250

Limited Warranty
The Micro-ohmmeter Model 6250 is warranted to the owner for a period of two
years from the date of original purchase against defects in manufacture. This
limited warranty is given by AEMC® Instruments, not by the distributor from
whom it was purchased. This warranty is void if the unit has been tampered
with, abused or if the defect is related to service not performed by AEMC®
Instruments.

Full warranty coverage and product registration is available on our

website at www.aemc.com/warranty.html.

Please print the online Warranty Coverage Information for your records.

What AEMC® Instruments will do:

If a malfunction occurs within the warranty period, you may return the instrument
to us for repair, provided we have your warranty registration information on file
or a proof of purchase. AEMC® Instruments will, at its option, repair or replace
the faulty material.

REGISTER ONLINE AT: www.aemc.com

Warranty Repairs
What you must do to return an Instrument for Warranty Repair:
First, request a Customer Service Authorization Number (CSA#) by phone
or by fax from our Service Department (see address below), then return the
instrument along with the signed CSA Form. Please write the CSA# on the
outside of the shipping container. Return the instrument, postage or shipment
pre-paid to:

Ship To: Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments

15 Faraday Drive • Dover, NH 03820 USA
Phone: (800) 945-2362 (Ext. 360)
(603) 749-6434 (Ext. 360)
Fax: (603) 742-2346 or (603) 749-6309
E-mail: repair@aemc.com

Caution: To protect yourself against in-transit loss, we recommend you insure

your returned material.

NOTE: You must obtain a CSA# before returning any instrument.

56 Micro-Ohmmeter Model 6250
Micro-Ohmmeter Model 6250 57
 11/19

99-MAN 100288 v26

Chauvin Arnoux®, Inc. d.b.a. AEMC® Instruments

15 Faraday Drive • Dover, NH 03820 USA • Phone: (603) 749-6434 • Fax: (603) 742-2346
www.aemc.com