M010091EN-G

User Guide
â
Vaisala DRYCAP Handheld Dew Point Meter
DM70
PUBLISHED BY

Vaisala Oyj
Vanha Nurmijärventie 21, FI-01670 Vantaa, Finland
P.O. Box 26, FI-00421 Helsinki, Finland
+358 9 8949 1

Visit our Internet pages at www.vaisala.com.

© Vaisala 2020

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 Table of contents

Table of contents

1. About this document.....................................................................................7

1.1 Version information.......................................................................................... 7
1.2 Related manuals................................................................................................7
1.3 Documentation conventions........................................................................... 8
1.4 Trademarks........................................................................................................ 8

2. Product overview............................................................................................ 9
2.1 Introduction to DM70....................................................................................... 9
2.2 Basic features and options.............................................................................10
2.3 Parts description...............................................................................................11

3. MI70 indicator................................................................................................. 12
3.1 MI70 indicator parts........................................................................................ 12
3.2 Installing and recharging MI70 batteries...................................................... 12
3.2.1 MI70 battery status information.............................................................13
3.3 MI70 first start-up settings.............................................................................14
3.4 Changing the rechargeable battery pack.....................................................14

4. Dew point measurement............................................................................ 16

4.1 Measurement in dry environments................................................................16
4.2 Taking dew point measurements.................................................................. 16
4.3 Measuring multiple parameters simultaneously..........................................17

5. User interface.................................................................................................. 19
5.1 Basic display.....................................................................................................19
5.2 Main menu........................................................................................................ 19
5.3 MI70 status icons............................................................................................ 22
5.4 Display menu...................................................................................................23
5.4.1 Selecting parameters and units.............................................................23
5.4.2 Rounding.................................................................................................. 24
5.4.3 Holding and saving the display............................................................. 24
5.4.4 Graphical display..................................................................................... 25
5.5 Functions menu.............................................................................................. 25
5.5.1 Setting an alarm...................................................................................... 25
5.5.2 Selecting and scaling analog output.................................................... 26
5.5.3 Autocalibration........................................................................................ 27
5.5.4 Sensor purge.............................................................................................31
5.6 Recording/Viewing menu..............................................................................33
5.6.1 Recording data........................................................................................ 33
5.6.2 Viewing recorded data........................................................................... 34
5.6.3 Checking MI70 memory status..............................................................34
5.6.4 Clearing data memory............................................................................34
5.6.5 Transferring recorded data to PC with MI70 Link............................... 35
5.7 Environment menu......................................................................................... 35
5.7.1 Configuring pressure settings................................................................35

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DM70 User Guide M010091EN-G

5.8 Settings menu.................................................................................................36

5.8.1 User interface settings............................................................................36
5.9 Date and time..................................................................................................38
5.10 Measurement settings................................................................................... 39
5.11 Setting calibration reminder......................................................................... 39
5.12 Device information........................................................................................ 40
5.13 Factory settings...............................................................................................41

6. Field calibration check of fixed transmitters.................................... 42

6.1 Field calibration check of DMT340/DMT242/DMT143.............................. 42

7. Sampling from processes..........................................................................44

7.1 Sampling cells.................................................................................................44
7.1.1 DSC74....................................................................................................... 44
7.1.2 DSC74B.....................................................................................................45
7.1.3 DSC74C.....................................................................................................46
7.1.4 DMT242SC and DMT242SC2..................................................................47
7.2 Connecting to pressurized processes using DSC74 sampling cell........... 48
7.3 DSS70A sampling system...............................................................................51
7.3.1 DSS70A sampling procedure.................................................................52
7.3.2 Recharging DSS70A battery..................................................................53
7.3.3 Changing DSS70A battery.....................................................................54
7.3.4 Changing DSS70A filter..........................................................................56
7.3.5 Changing DSS70A fuses.........................................................................57

8. Measuring moisture in SF6 gas-insulated equipment .................. 58

8.1 Overview..........................................................................................................58
8.2 Operating environment................................................................................. 59
8.3 Measuring........................................................................................................ 59

9. Calibration and adjustment....................................................................... 61

9.1 Calibration........................................................................................................ 61
9.2 User calibration and adjustment................................................................... 61
9.3 Adjusting DM70............................................................................................... 61
9.4 Adjusting DMT340 series transmitters using DM70 as
reference or terminal......................................................................................62
9.5 Adjusting dew point.......................................................................................62
9.5.1 Making a 2-point relative humidity adjustment.................................. 62
9.5.2 Making a 2-point %RH adjustment of DMT340 series
transmitters using DM70........................................................................64
9.5.3 Td/f adjustment of DM70....................................................................... 65
9.5.4 Td/f adjustment of DMT340 series transmitters using DM70........... 66
9.6 Adjusting temperature...................................................................................68
9.6.1 Temperature adjustment of DM70........................................................ 68
9.6.2 Temperature adjustment of DMT340 series using DM70.................. 70

10. Technical data................................................................................................ 73

10.1 DM70 and DMP74 specifications.................................................................. 73

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 Table of contents

10.2 MI70 specifications.........................................................................................78

10.3 Dimensions..................................................................................................... 80
10.4 Spare parts and accessories......................................................................... 80

Maintenance and calibration services........................................................ 83

Technical support............................................................................................ 83

Warranty............................................................................................................ 83

Recycling........................................................................................................... 83

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DM70 User Guide M010091EN-G

List of figures

Figure 1 DM70 parts......................................................................................................... 11

Figure 2 MI70 indicator parts........................................................................................ 12
Figure 3 Display example with carbon dioxide and temperature
and humidity probes connected simultaneously....................................18
Figure 4 DM70 basic display..........................................................................................19
Figure 5 DM70 menus......................................................................................................21
Figure 6 Quantities and units menu............................................................................23
Figure 7 Analog output menu...................................................................................... 27
Figure 8 Sensor purge displays....................................................................................33
Figure 9 Recording/Viewing menu.............................................................................34
Figure 10 User interface settings menu.......................................................................36
Figure 11 Hold/Save replaced by AutoCal..................................................................38
Figure 12 Measurement settings menu....................................................................... 39
Figure 13 Calibration reminder menu..........................................................................40
Figure 14 Device information menu.............................................................................40
Figure 15 Indicator and probe information................................................................. 41
Figure 16 DSC74 sampling cell with adapters........................................................... 45
Figure 17 DSC74B..............................................................................................................46
Figure 18 Default assembly of DSC74C.......................................................................46
Figure 19 Alternative assembly of DSC74C for tight spaces................................. 47
Figure 20 DMT242SC and DMT242SC2 sampling cells............................................47
Figure 21 Turning sampling cell valve screw with flathead screwdriver............ 50
Figure 22 DSSA70A portable sampling system.........................................................52
Figure 23 Lifting the system........................................................................................... 54
Figure 24 Sampling system upside down....................................................................55
Figure 25 Changing the filter..........................................................................................56
Figure 26 Gas collection option..................................................................................... 58
Figure 27 Removing the leak screw..............................................................................59
Figure 28 DMP74A dew point accuracy vs. measurement conditions................ 75
Figure 29 DMP74B and DMP74C dew point accuracy vs.
measurement conditions.............................................................................. 75
Figure 30 Dimensions of MI70 indicator, DMP74 probe, DSC74
sampling cell, and DSC74C sampling cell (left to right
and top to bottom)........................................................................................ 80

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 List of tables

List of tables

Table 1 Document versions (English)............................................................................ 7

Table 2 Related manuals................................................................................................... 7
Table 3 Display parameters.............................................................................................. 9
Table 4 MI70 battery status indicator.......................................................................... 13
Table 5 MI70 status icons................................................................................................22
Table 6 DM70 handheld meter general specifications........................................... 73
Table 7 DMP74A, DMP74B, and DMP74C measurement performance.............. 73
Table 8 DMP74A, DMP74B, and DMP74C general specifications.........................75
Table 9 DMP74A, DMP74B, and DMP74C mechanical specifications................. 76
Table 10 Sampling cell specifications............................................................................76
Table 11 MI70 measurement indicator..........................................................................78
Table 12 MI70 battery operation time...........................................................................79
Table 13 DM70 spare parts and accessories............................................................... 80

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DM70 User Guide M010091EN-G

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 Chapter 1 – About this document

1. About this document

1.1 Version information
This document provides detailed instructions for using and maintaining Vaisala DRYCAPâ
Handheld Dew Point Meter DM70.

Table 1 Document versions (English)

Document code Date Description

M010091EN-G October This document.

2020
• The following sections added:
• MI70 battery status information (page 13)
• MI70 status icons (page 22)
• Setting calibration reminder (page 39)
• The following sections updated:
• Sections introducing the MI70 indicator
• Measuring multiple parameters simultaneously (page 17)
• Connecting to pressurized processes using DSC74 sampling
cell (page 48)
• Calibration (page 61)
• DM70 and DMP74 specifications (page 73)
• Spare parts and accessories (page 80)
• References to DMP248 removed
• Document format and layout update, quality improvements,
and content reorganization.
M010091EN-F September Previous version.
2007

1.2 Related manuals
Table 2 Related manuals

Document code Name

M210704EN Vaisala DRYCAPâ Dewpoint and Temperature Transmitter Series DMT340 User's
Guide

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DM70 User Guide M010091EN-G

1.3 Documentation conventions
WARNING! Warning alerts you to a serious hazard. If you do not read and
follow instructions carefully at this point, there is a risk of injury or even death.

CAUTION! Caution warns you of a potential hazard. If you do not read and
follow instructions carefully at this point, the product could be damaged or
important data could be lost.

Note highlights important information on using the product.

Tip gives information for using the product more efficiently.

Lists tools needed to perform the task.

Indicates that you need to take some notes during the task.

1.4 Trademarks
Vaisalaâ and DRYCAPâ are registered trademarks of Vaisala Oyj.
Windowsâ is either a registered trademark or trademark of Microsoft Corporation in the
United States and other countries.

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 Chapter 2 – Product overview

2. Product overview

2.1 Introduction to DM70
Vaisala DRYCAPâ Handheld Dew Point Meter DM70 measures dew point temperature
accurately in a measurement range from −60 °C up to +60 °C (−76 ... +140 °F) depending on
the probe model. DM70 incorporates the advanced DRYCAPâ technology, which enables
reliable and high-performance dew point measurement. DM70 measures the following
parameters:

Table 3 Display parameters

Parameter Abbreviation Metric unit Non-metric unit

Relative humidity RH %RH %RH

Temperature T °C °F
Dew point/frost point Td/f °C °F
temperature 1)
Dew point temperature Td °C °F
2)

Dew point in the Td °C atm °F atm

atmospheric pressure
Dew point/frost point Td/f °C atm °F atm
in the atmospheric
pressure
Absolute humidity a g/m3 gr/ft3
Mixing ratio x g/kg gr/lb
Water concentration / H2O ppmv / ppmw ppmv / ppmw
Water mass fraction

1) Td/f shows dew point temperature above the freezing point (0 °C/32 °F) and frost point
temperature Tf (dew point over ice) below the freezing point. This is considered as the
industry standard.
2) Td shows dew point over water throughout the entire measurement range.

DM70 consists of 2 main units: the MI70 indicator and DMP74 probe, models A, B, or C. DM70
can be used with the optional sampling cell to measure process dew point. With DSS70A,
DM70 forms a part of a complete portable sampling system for measuring process dew point.

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DM70 User Guide M010091EN-G

More information
‣ DM70 and DMP74 specifications (page 73)
‣ Parts description (page 11)
‣ Sampling cells (page 44)

2.2 Basic features and options

DM70 has the following basic features and options:
• Numerical and graphical multilingual displays
• Data recording possibility
• Three probe models, temperature measurement range −60 … +60 °C (−76 … +140 °F),
depending on the model
• A tool for checking the reading of fixed transmitters DMT340, DMT242, and DMT143
• A possibility for an analog output (voltage signal 0 ... 1 V)
• Multiprobe operation; any combination of 2 Vaisala DM70, GM70, HM70, and MM70 series
probes can be used, for example, for simultaneous dew point and relative humidity
measurements
• The optional, ready-to-use MI70 Link Microsoft Windowsâ software, which allows an easy
way to handle measurement data using a serial line or a USB instrument cable
• The optional sampling system DSS70A

More information
‣ DSS70A sampling system (page 51)
‣ Transferring recorded data to PC with MI70 Link (page 35)

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 Chapter 2 – Product overview

2.3 Parts description
1

Figure 1 DM70 parts

1 Charger socket
2 MI70 indicator
3 Connector ports for probes and cables
4 Calibration button
5 Sampling cell DSC74 (optional)
6 DMP74 probe

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DM70 User Guide M010091EN-G

3. MI70 indicator

3.1 MI70 indicator parts

Figure 2 MI70 indicator parts
1
1 Charger socket
2 Function key shortcut buttons . The
functions change according to what
you are doing with the indicator.
3 Arrow buttons:
2
Move up in a menu
3
Move down in a menu
4 Enter a sub-menu
Return to previous menu level
4 Power On/Off button
5 Battery compartment at the back of
5 the indicator
6 2 ports (labeled I and II) for
connecting probes and instruments.

To open menus, press an arrow button and then press the shortcut buttons. To activate a
function shown above the shortcut button, press the shortcut button. To navigate in the
menus, press the arrow buttons.

3.2 Installing and recharging MI70 batteries

If you are using alkaline batteries, unscrew the back plate of the indicator and insert the
batteries. Do not attempt to recharge standard alkaline batteries.
If you ordered MI70 with a rechargeable battery, it is already in place as shipped from the
factory. The delivered batteries have been pre-charged.
To recharge the battery:

1. Plug in the charger connector to the indicator. The socket is located at the top of the
indicator, covered by a rubber seal.

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 Chapter 3 – MI70 indicator

2. Connect the charger to a wall socket. An animated battery icon in the left corner of the
display indicates that the battery is charging. The recharge duration (typically 4 ... 5 h)
depends on the charge level of the battery.

A new battery takes approximately 3 charging cycles to reach its maximum

battery life.

Do not store the batteries empty. Empty batteries may not charge after an
extended storage period.

3.2.1 MI70 battery status information

The status of the MI70 battery is shown by the battery icon in the upper left corner of the
display. Possible statuses are listed in the following table.

Table 4 MI70 battery status indicator

Battery status indicator Description

graphic

Battery status icon. The icon can show the following info:
• 0 ... 8 bars, no animation:
• batteries are in use, a charger is not connected
• if a charger is connected: non-rechargeable batteries installed
• if a charger is connected: waiting for the battery temperature to
settle between 0 ... +40 °C (+32 ... +104 °F)
• if a charger is connected and the icon remains at 8/8 bars: the
battery is full
• Animated battery status icon: battery is charging (or recovering
after emptying out completely). The charging animation is shown
also when the indicator is powered off.
• Battery icon not present: batteries are not installed
An empty battery icon with an X over it means that the battery
cannot be recharged and must be replaced. If the indicator is
powered on, a notification about not being able to charge the
battery is shown on the MI70 screen.
You can order replacement batteries from Vaisala (item code 26755).

To keep the rechargeable MI70 battery in good working condition, recharge MI70
monthly if the indicator is not in use.

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DM70 User Guide M010091EN-G

More information
‣ Spare parts and accessories (page 80)

3.3 MI70 first start-up settings

When you switch on MI70 for the first time, configure the basic settings (time, date, language)
as instructed below.

1. Connect the probe to either one of the base connectors in the indicator. To ensure a
durable connection, screw the metal ring clockwise until it tightens up. (Respectively,
when disconnecting the cable, first screw the metal ring counterclockwise until it loosens
and then pull out the plug.)
2. Press the Power On/Off button.
3. Press any of the arrow buttons and open the menu by pressing Open.
4. Select Settings using the buttons and press .
5. Select User interface and press .
6. Select Language and press Set.
7. Select the language using the buttons. Confirm the selection by pressing Select.
8. If you want to set the date at this point, return to the Settings menu by pressing .

The language can be selected also later. For instructions, see Selecting
language (page 36).

9. To change the date, select Date and press Set. Then change the date using the
buttons. To confirm the selection, press Select. As a default, the date format is year-
month-day. You can select from 2 other alternative formats.
10. To change the time, select Time and press Set. Then change the time by using the
arrow buttons. Confirm the selection by pressing OK. As a default, the time format is
based on the 24-hour clock. If you want to use the 12-hour clock, select 12-hour clock and
then press On.
11. To return to the basic display, press Exit.

3.4 Changing the rechargeable battery pack

• New rechargeable battery pack
• Medium-sized flathead screwdriver

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 Chapter 3 – MI70 indicator

In case you are installing a battery pack and you have a device with alkaline batteries, remove
the metal contact from the probe port end of the battery compartment before installing the
battery pack.

1. Open the back plate of the indicator by opening the screw of the back plate.
2. Remove the old battery pack. Detach the black connector by carefully pulling it up from
the wires.
3. Connect the black connector of the new battery pack. Make sure the position of the
connector is as shown in the following figure (red and black wires are on the upper edge
of the connector). Do not push the connector with conducting material.

4. Place the battery pack in the compartment.

5. Close the back plate and tighten the screw.
6. Recharge the indicator before use.

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DM70 User Guide M010091EN-G

4. Dew point measurement

4.1 Measurement in dry environments

The following recommendations should be taken into account when measuring in very dry
environments:
• A clean environment is always best for humidity measurements.
• The number of connections should be minimized to avoid leaks.
• The flow rate must be adequate.
• Dead ends must be avoided as they cannot be flushed easily.
• The tube temperature must never lie under the dew point of the sample gas. This may
lead to condensation and false results.
• The sample tubing should be of as short length as possible. The surface area should be
minimized using the narrowest tubing that the flow conditions allow.
• The surface finish of the pipework is important. Polished or electro-polished steel is
recommended for best results.
• Hygroscopic materials should be avoided in the sampling lines. Use stainless steel
membranes instead of rubber membranes.
• Impermeable materials should be selected to avoid inward diffusion of moisture through
the sampling tubes and enclosures. Such impermeable materials are, for example, high-
quality stainless steel and metals. Avoid PVC or nylon tubes.

4.2 Taking dew point measurements

When you start to use DM70 for the first time, see MI70 first start-up settings (page 14).
Otherwise follow the instructions below.

1. Connect the probe to the MI70 indicator.

2. Press the Power On/Off button.
3. Install the probe to the measuring position. If you are measuring in pressurized processes,
see Connecting to pressurized processes using DSC74 sampling cell (page 48). When
using other sampling cells than DSC74, make sure that the threads are compatible with
the probe threads (G ½" ISO228/1). Be careful not to damage the sintered filter when
installing the probe.
4. Before measuring, make sure that the air pressure settings of DM70 are correct and that
autocalibration has taken place (see Automatic autocalibration (page 28)).

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 Chapter 4 – Dew point measurement

5. The basic display opens. Let the reading stabilize.

CAUTION! If you need to disconnect the probe from the indicator, first
press the Power On/Off button to turn the indicator off. This ensures that
all the settings and data are saved properly

When measuring low dew points, the stabilization times can be long, for
example, 1 ... 2 hours. Therefore, turn off the automatic power-off function,
turn on the automatic autocalibration, and turn on the automatic sensor
purge.
This allows monitoring the stabilization, the autocalibration ensures an
accurate measurement, and the purge ensures the shortest possible response
times.

More information
‣ Configuring automatic power off (page 37)
‣ Turning automatic autocalibration on and off (page 28)
‣ Turning automatic sensor purge on and off (page 31)

4.3 Measuring multiple parameters simultaneously

MI70 is a generic indicator that can be used with Vaisala interchangeable dew point
(DM70 series), humidity (HM70 series), carbon dioxide (GM70 series), and moisture in oil
(MM70 series) probes. Two different types of probes can be connected to MI70 simultaneously.

1. Switch off the MI70 indicator.

2. Connect the 2 probes to the connector ports (port I and II) on the bottom of the indicator.
3. Switch on MI70.
4. Check that the environment settings of the probes (port I and II) are the same if you are
taking measurements from the same condition. In this case, select Yes when MI70
prompts you to check the environment settings.

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DM70 User Guide M010091EN-G

5. The reading of the probe in port I is now displayed on the upper row(s) and the reading of
the probe in port II on the lower row(s) of the MI70 display.

Figure 3 Display example with carbon dioxide and temperature and humidity probes
connected simultaneously

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 Chapter 5 – User interface

5. User interface

5.1 Basic display

1 2

4 5 6
Figure 4 DM70 basic display

1 Battery indicator. Shows the current status (charge) of the battery.

2 Pressure setting.
3 Measured parameter (up to 3 items on display simultaneously). You can change the shown
items in Main menu > Display > Quantities and units.
4 Function key Graphic shows the readings as a curve.
5 Function key Hold/Save freezes the display and you can save the reading in the MI70
memory.
6 Function key Record is a quick access to the Recording/Viewing menu. (This is the
default shortcut button. In the figure it has been changed to Start/S).

You can change the default function key shortcuts (Graphic, Hold/Save, Record) to other
menus or functions in Main menu > Settings > User interface > Program shortcut keys.

5.2 Main menu
In the main menu, you can configure the MI70 settings and basic display options, view
information about the probe, access recordings and clear the memory, set alarms, start
adjustments, and use the analog output option of the MI70 indicator.
To open the main menu and navigate in the menus:

1. Go to the basic display.

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DM70 User Guide M010091EN-G

2. Press any arrow button, then select Open (must be pressed within 5 seconds or the
indicator returns to the basic display).
3. Move in the menus using the buttons.
4. Select an item with the button.
5. To return to the previous level, press .

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 Chapter 5 – User interface

6. To return to normal operation, press Exit.

Figure 5 DM70 menus

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DM70 User Guide M010091EN-G

5.3 MI70 status icons

Icons that inform you about the status of MI70 (for example, battery status and alarm
notification) are shown on the upper left corner of the display. Multiple icons can be shown
simultaneously.

Table 5 MI70 status icons

Icon Description

Battery status icon. The icon can show the following info:
• 0 ... 8 bars, no animation:
• batteries are in use, a charger is not connected
• if a charger is connected: non-rechargeable batteries installed
• if a charger is connected: waiting for the battery temperature to settle
between 0 ... +40 °C (+32 ... +104 °F)
• if a charger is connected and the icon remains at 8/8 bars: the battery is
full
• Animated battery status icon: battery is charging (or recovering after
emptying out completely). The charging animation is shown also when the
indicator is powered off.
• Battery icon not present: batteries are not installed
The battery can no longer be charged and must be replaced.

Recording icon. Shows that the measurements are being recorded. The bar
shows for how long the recording will continue (a set time limit or until the
memory runs out). The recording icon and bar are shown also when the
indicator is powered off.
Calibration reminder icon. Appears when a calibration reminder has been set
to inform that a user-defined interval has passed and calibration is due.

Analog output icon. Shown when the analog output mode is in use.

PC connection icon. Shown when the indicator is connected to a PC with a

cable.

Alarm icon. Shown when the measurement has reached a user-defined alarm
limit.

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 Chapter 5 – User interface

More information
‣ MI70 battery status information (page 13)
‣ Recording data (page 33)
‣ Setting calibration reminder (page 39)
‣ Selecting and scaling analog output (page 26)
‣ Transferring recorded data to PC with MI70 Link (page 35)
‣ Setting an alarm (page 25)

5.4 Display menu

5.4.1 Selecting parameters and units

In the MI70 user interface, measurement parameters are referred to as quantities.

Figure 6 Quantities and units menu

The unit of parameters (Td/f, Td, or T) can be selected between °C or °F. The default is °C.

1. Open the menu by pressing Open.

2. Select Display and press .
3. Select Quantities and units and then press .
4. To select a parameter, move on the desired parameter using the arrow buttons and then
press Select.
5. To change the unit, move on the desired parameter using the arrow buttons and then
press Unit.
6. To hide a parameter, move on the desired parameter using the arrow buttons and then
press Hide.
7. To return to the basic display, press Exit.

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DM70 User Guide M010091EN-G

8. If you want to check the environment settings, press Yes. Otherwise press No.

Units °C atm and °F atm indicate that the dew point or frost point is
converted from process pressure to atmospheric pressure.

5.4.2 Rounding
1. Open the menu by pressing Open.
2. Select Display and then press .
3. Select Rounding.
4. To return to the basic display, press Exit.

Rounding does not affect the measurement accuracy defined in the device
specifications.

5.4.3 Holding and saving the display

With the Hold/Save function, you can freeze a certain display reading. This reading can be
saved in the MI70 memory and it will be available even after MI70 is disconnected from the
transmitter.

1. In the basic display, select Hold/Save. Alternatively, select Main menu > Display > Hold/
Save display > Hold.
2. Press Save.
3. To view the saved display, go to basic display and select Record > View recorded data.
Alternatively, select Main menu > Recording/Viewing > View recorded data.
A list of saved displays and data recordings appears. The icons on the left of the date and
time indicate whether the file is a saved display or a longer recording of data:
Saved display

Data recording

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 Chapter 5 – User interface

4. Select the saved display based on date and time by pressing the right arrow button.

5.4.4 Graphical display
The graphical display shows you the measurements as a curve (the curve of the uppermost
parameter shown in the basic display). From the curve you can examine the data trend and
history of the last minutes.
To open the graphical display, select Graphic in the basic display or select Main menu >
Display > Graphic history > Show.
To get the statistical info on the graph area (minimum, maximum, and average values), press
Info.
To get the curve of the other selected parameters, press Next. To get the curves of all the
parameters, press Next until the text All appears, and then select All.
To zoom in and out, press the up/down arrow buttons.
To move back and forward in the timeline, use the left/right arrow buttons.

5.5 Functions menu

5.5.1 Setting an alarm

In the MI70 user interface, measurement parameters are referred to as quantities.

When an alarm is triggered, the indicator beeps and the display backlight blinks. The alarm is
triggered when the measured value is not between the alarm limits, that is, the permitted area.
The alarm level(s) can be set for only 1 parameter at a time.

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DM70 User Guide M010091EN-G

1. Open the menus by pressing Open.

2. Select Functions and press .
3. Select Alarm and press .
4. Select Quantity and press Set to select the parameter.
5. Select the parameter and press Select. Only 1 active parameter can be selected at a
time. To change which parameters are active, go to Menu > Display > Quantities and
units.
6. Select the first limit and and press Set (if the alarm function is on, turn it off). Use the
arrow buttons to set the alarm level. To select the sign for the alarm level, press the +/-
button. To save the settings, press OK.
7. Select the second limit and follow the instructions in step 6. The alarm is triggered when
either the upper or lower limit is exceeded.

If you want to use only 1 limit, for example, if you want to detect if the dew
point rises above −40 °C, do the following:
Set the upper limit to −40 °C and the value of the lower limit so low that it is
never reached, for example, to −80 °C. With this configuration, DM70 alerts
when Td rises above −40 °C.

8. To activate the alarm and to return to the basic display, select Alarm On/Off and press
On. The note icon ♫ appears in the upper left corner of the display.
9. When the alarm level is reached, you can stop the alarm by pressing OK. To reactivate
the alarm, press Yes. To discard the alarm, press No.

The alarm does not work when the device is powered off.

5.5.2 Selecting and scaling analog output

To get analog measurement data, an analog signal cable is needed (Vaisala item code
27168ZZ).

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 Chapter 5 – User interface

Figure 7 Analog output menu

1. Connect the signal cable connector of the analog output to the base connector of the
MI70 indicator. Connect the screw terminal block as follows:

Wire Connect to

Brown wire Common wire (−)

Yellow-green wire Signal (+)

2. Open the menu by pressing Open.

3. Select Functions and press .
4. Select Analog output and press .
5. To set the value for the 0.0 V output signal, select 0.0 V and press Set. If the analog
output is on, turn it off. Set the low value using the arrow buttons. To select the sign for
the value, press +-. To confirm the setting, press OK.
6. To set the value for the 1.0 V output signal, select 1.0 V and press Set. Set the high
value using the arrow buttons. To select the sign for the value, press +-. To confirm the
setting, press OK.
7. To activate the analog output and to return to the basic display, select Analog output on/
off and On. The wave icon appears in the upper left corner of the basic display.
8. To deactivate analog output, go to Menu > Functions > Analog output -
Analog output on/off and press Off.

5.5.3 Autocalibration
To obtain the best possible accuracy in measurements taken in dry environments, DM70 has
built-in automatic calibration. During the autocalibration, DM70 adjusts the dry-end reading to
correspond to the calibrated values. This is a unique and patented method to avoid errors in
accuracy when monitoring low dew points.
The autocalibration is carried out if the following criteria for the measurement environment are
fulfilled:
• Relative humidity must be
• < 5 % (DMP74A)
• < 2 % (DMP74B/DMP74C)
• Temperature must be 0 < T < 60 °C

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DM70 User Guide M010091EN-G

• Humidity environment must be stable. The maximum change in the dew point can be 1 °C
within 30 seconds.

Autocalibration cannot operate if the above criteria are not met.

If the adjustment in the autocalibration reaches a preset, maximum value or if the

autocalibration correction fails, for example, because of unstable conditions, a new
autocalibration may take place later (if the automatic autocalibration is turned on).
Autocalibration can be either automatic or manual.

5.5.3.1 Automatic autocalibration
As a default, the automatic autocalibration in DM70 is turned on. In this mode, the calibration
takes place automatically if the dew point or temperature changes significantly, typically more
than 10 °C. However, if there are no changes in the conditions, the calibration will take place at
an interval of 1 hour (or maximum 1 hour after the previous autocalibration).

5.5.3.2 Turning automatic autocalibration on and off

If the automatic autocalibration is turned off, the autocalibration should be

started when starting measuring after the probe has not been used for a while
and always at least once every hour.

To turn off automatic autocalibration:

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select Measurement settings and press .
4. To turn off automatic autocalibration, press Off. To reactivate automatic
autocalibration, press On.
5. To return to the basic display, press Exit.

5.5.3.3 Performing manual autocalibration

To check that autocalibration has taken place for obtaining the most accurate measurement in
a very dry environment, you can autocalibrate manually before measuring as follows:

1. Open the menu by pressing Open.

2. Select Functions and press .
3. Select AutoCal and press Start.

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 Chapter 5 – User interface

4. If you want to start autocalibration, press Yes. If the autocalibration conditions are not
fulfilled, a note appears on the display informing that the calibration cannot be made or
that a new attempt will be made later.

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DM70 User Guide M010091EN-G

5. When the autocalibration is completed, the display returns to the basic display
automatically.

If it is too humid, autocalibration will not start.

a. Display during the adjustment period (< 15 seconds).

b. Adjustment period is completed and stabilization period will start.

c. After successful autocalibration, the corrected readings are shown during the
stabilization period. If the autocalibration fails, no readings are shown, only lines are
displayed.

d. Display during the stabilization period (1 ... 2 minutes).

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 Chapter 5 – User interface

e. Autocalibration is completed.

5.5.4 Sensor purge
Sensor purge feature is only available in the DMP74B/DMP74C probe. The purge should be
carried out to achieve the shortest response times and the best long-term stability.
Sensor purge is an automatic procedure, in which the sensor is dried. Thus, the sensor will
response very fast when installing the probe from an ambient to a dry gas. This will also ensure
together with autocalibration the best measurement accuracy and long-term stability.
The purge is performed automatically if humidity changes significantly or quickly and if the
dew point is low enough.
As a default, the automatic sensor purge is turned on automatically in DM70. It is
recommended not to turn it off. The automatic sensor purge can also be started manually,
which is necessary if the purge has not been performed during the last 24 hours. If the power
is continuously turned on in DM70, or if DM70 has been left in logging mode (display on or
off), the automatic sensor purge will be performed at set interval (default = 24 hours).

5.5.4.1 Turning automatic sensor purge on and off

Performing the sensor purge on a regular basis provides the best measurement
accuracy and fastest response time. Perform the sensor purge when starting to
take measurements after the probe has been in storage, and always at least once
every 24 hours.

To turn off automatic sensor purge:

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DM70 User Guide M010091EN-G

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select Measurement settings and press .
4. Select Autom. Purge and press .
5. To turn the automatic sensor purge off, press Off. To reactivate the automatic sensor
purge, press Off.
6. To return to the basic display, press Exit.

5.5.4.2 Changing automatic sensor purge interval

If there are high chemical concentrations present in the measurement environment, some
sensor drift can occur. If you experience this kind of drift, it can be necessary to perform the
sensor purge more often. The purge interval can be varied between 1 ... 48 hours. However,
note that frequent sensor purges reduce battery operation time.
To change the automatic sensor purge interval:

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select Measurement settings and press .
4. Select Purge interval and press Set.
5. Set the desired purge interval with the arrow buttons. Press Ok to confirm.
6. To return to the basic display, press Exit.

5.5.4.3 Performing manual sensor purge

Although the sensor purge is in the automatic mode, it can also be performed
manually.

To check that the sensor purge has been performed to ensure the best possible response times
or before calibration, start the purge manually as follows:

1. Open the menu by pressing Open.

2. Select Functions and press .
3. Select Purge and press Start. Confirm the selection by pressing Yes.

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 Chapter 5 – User interface

4. When the sensor purge is completed, the display returns to the basic display
automatically. The stabilization of the temperature reading can take a few minutes.

If the dew point is low, automatic autocalibration will take place immediately
after the sensor purge.

The purge takes up to 5 minutes to complete. During the purge, there are no readings on
the display. A message appears on the display every 15 seconds to inform of the time
required to complete the purge. The purge icon also appears in the upper left corner of
the display.

Figure 8 Sensor purge displays

You can also change one of the shortcut keys to point to the sensor purge:
for instructions, see Programming shortcut keys (page 37).

5.6 Recording/Viewing menu

5.6.1 Recording data
With MI70, you can record transmitter measurement data over a certain period at chosen
intervals. These recordings are saved in the MI70 memory and are available even after MI70 is
disconnected from the transmitter. To start recording, select the Record function key in the
basic display, or navigate to the recording menu: Main menu > Recording/Viewing > Record
data.

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DM70 User Guide M010091EN-G

Figure 9 Recording/Viewing menu

5.6.2 Viewing recorded data

1. Open the menu by pressing Open.
2. Select Recording/Viewing and press .
3. Select View recorded data and press .
4. Select the file you want to view and press . The files are identified according to the
starting date and time of recording.
5. To go to the graphical view, press Graph. To view the recording time stamps, press
Times. To return to the recording values, press Values.
6. To return to the basic display, press Exit.

5.6.3 Checking MI70 memory status

1. Open the menu by pressing Open.
2. Select Recording/Viewing and press .
3. To view the amount of memory that is in use and the estimated free space left, select
Memory status and press Show.
4. To return to the basic display, press OK and Exit.

The estimate of available free space is calculated for the current number of
active parameters. If you change the displayed parameters, the estimate will
change accordingly.

5.6.4 Clearing data memory

1. Open the menu by pressing Open.
2. Select Recording/Viewing and press .
3. Select Clear data memory and press Clear. To confirm the deletion, press Yes.

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4. To return to the basic display, press Exit.

5.6.5 Transferring recorded data to PC with MI70 Link

PC data transfer requires the MI70 Link Windowsâ software and a Vaisala USB cable (item
code 219687). The serial connection cable can also be used for MI70 Link data transfer. The
MI70 Link software is available from the Vaisala website: www.vaisala.com/mi70link.
Recorded data can be transferred to a PC using the MI70 Link program that allows examining
the recorded data easily in the Microsoft Windowsâ environment and processing it further on
a spreadsheet program such as Microsoft Excelâ. Both logged and real-time measurement
data can be transferred.
To set up an MI70 Link connection:

1. Install the MI70 Link software according to the instructions on the installation wizard. Do
not connect the USB cable before the installation has completed.
2. After the installation completes, connect the MI70 indicator to the PC with the USB/serial
cable. Windows detects the new device automatically.
3. You can now access the readings from the PC with MI70 Link. If MI70 Link cannot discover
the instrument, check the following:
• the device is powered on
• the cable is properly connected
• another application has not reserved the connection

5.7 Environment menu

5.7.1 Configuring pressure settings

In pressurized environments, the actual process pressure value must be set for DM70. The
pressure can be given in the following units:
Pbarg Gauge pressure is given in the unit of bar. It indicates the pressure difference between
the normal atmospheric pressure and the actual process pressure.
Pbara Absolute process pressure is given in the unit of bar.
Ppsig Gauge pressure is given in the unit of psi. It indicates the pressure difference between
the normal atmospheric pressure and the actual process pressure.
Ppsia Absolute pressure is given in the unit of psi.

To set the pressure values:

1. Open the menu by pressing Open.

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DM70 User Guide M010091EN-G

2. Select Environment with and press .

3. To change the pressure unit, press Unit. The default unit is barg.
4. To change the ambient pressure value, press Set.
5. Set the value using the arrow buttons. To change the sign of the pressure value, press
+/-. To save the value, press OK.
6. To return to the basic display, press Exit.

5.8 Settings menu

5.8.1 User interface settings

Figure 10 User interface settings menu

5.8.1.1 Selecting language
You can select any of the following languages for the user interface: English, Finnish, Chinese,
Russian, Japanese, Swedish, French, German, or Spanish.

1. Open the menu by pressing Open.

2. Select Settings and then press .
3. Select User interface and then press .
4. Select Language and press Set.
5. Choose the correct language and press Select.

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6. To return to the basic display, press Exit.

5.8.1.2 Correcting language selection

1. Return to the basic display by pressing the rightmost button until the basic display
appears.
2. Go to the Language selection menu by pressing first and then the button in the
middle.
3. Then press , then , then again, and finally press the button in the middle.
4. Reselect the language.

5.8.1.3 Configuring automatic power off

As a default, MI70 powers off after 15 minutes of inactivity. This also saves battery. The
inactivity setting can be changed to 60 minutes or completely turned off.

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select User interface and press .
4. Select Auto power off and press Set.
5. Choose an inactivity time option and press Select.
6. To return to the basic display, press Exit.

5.8.1.4 Programming shortcut keys

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select User interface and press .
4. Select Program shortcut keys and press Start.
5. Press the shortcut key you want to change, for example, Hold/Save.
6. If you want to replace Hold/Save with the autocalibration function, select AutoCal with
the arrow buttons and then press Select. To confirm your selection, press Yes.
Otherwise press No and continue from step 4.

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7. To return to the basic display, press Exit.

Figure 11 Hold/Save replaced by AutoCal

5.8.1.5 Configuring button tones and backlight

To turn on or off the backlight or the sound effects for the buttons:

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select User interface and press .
4. To turn the sound effect on or off, select Key Click and press On/Off.
5. To turn the backlight on or off, select Backlight on key press and press On/Off.
6. To return to the basic display, press Exit.

5.9 Date and time

As a default, the time format is based on the 24-hour clock. Also a 12-hour clock can be used.
The default date format is day.month.year, for example, 25.4.2020. The date format can be
changed to month.day.year. or year.month.day.

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select Date and time and press .
4. For the desired date, select Date and then press Set. Use the arrow buttons to change
the date. Confirm the selection by pressing Select. To change the date format, select
an option and press Select.

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5. For the desired time, select Time and press Set. Use the arrow buttons to change the
time. To confirm the selection, press OK. To change the time format, select 12-hour
clock and press On/Off.
6. To return to the basic display, press Exit.

5.10 Measurement settings

Figure 12 Measurement settings menu

Menu Description

Automatic autocalibration To turn the feature on, press On. To turn the
feature off, press Off.

Automatic purge To turn the feature on, press On. To turn the
feature off, press Off.

Molecular weight The ppmw M setting is used to give the

molecular weight of the measured gas. This
value is required in ppmw (weight) calculation.
The default values are 28.96 for DMP74A/B (air)
and 146.06 for DMP74C (SF6).
Purge interval The time interval at which the automatic sensor
purge is performed: can be selected between
1 ... 48 hours. For instructions, see Changing
automatic sensor purge interval (page 32).

5.11 Setting calibration reminder

You can set a calibration reminder to notify when calibration is due. Choose an interval of 3, 6,
12, or 24 months. By default, the reminder is off.

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DM70 User Guide M010091EN-G

Figure 13 Calibration reminder menu

Make sure the MI70 date and time settings are correct when using the calibration
reminder.

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select Calibr. reminder and press Set.
4. Choose a reminder interval option and press Select.
5. To return to the basic display, press Exit.

5.12 Device information

Figure 14 Device information menu

To view basic information about the indicator and probe:

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select Device information and press Show.
4. The first display gives information on the MI70 indicator. For details on the probe, press
More.

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 Chapter 5 – User interface

5. To return to the basic display, press Exit.

1 4

2 5

Figure 15 Indicator and probe information

1 Software version of the MI70 indicator

2 Serial number of the MI70 indicator
3 Probe type
4 Software version of the probe
5 Serial number of the probe

5.13 Factory settings
Factory settings can be restored to clear all the changed settings and data memory of the
indicator. Restoring factory settings does not affect the probe calibration.

1. Open the menu by pressing Open.

2. Select Settings and press .
3. Select Factory Settings and press Revert. To confirm the selection, press Yes. MI70
powers off automatically.

When MI70 is switched on after a factory reset, the language, date, and time
settings must be set again.

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DM70 User Guide M010091EN-G

6. Field calibration check of fixed

transmitters
To compare measurement readings or to read the output of a fixed transmitter directly on the
DM70 display, connect DM70 to a fixed Vaisala transmitter using the connection cable
accessories.
Vaisala DRYCAPâ Dew Point and Temperature Transmitter Series DMT340 can be adjusted in
laboratory conditions using DM70 as a reference. For more information on calibration and
adjustment, see Calibration (page 61).

6.1 Field calibration check of DMT340/DMT242/

DMT143
You can use DM70 to display the reading of DMT340, DMT242, or DMT143 transmitter, and to
compare the readings of DM70 and the transmitter.
Use the following cables to connect DM70 to the transmitter:
• Connection cable 211339 with DMT340
• Connection cable 27160ZZ with DMT242
• Connection cable 219980SP with DMT143
To carry out a field calibration check:

1. Turn off DM70.

2. Connect the cable between DMT340 (service port) or DMT242/DMT143 (serial port) and
DM70 (connector I or II). Turn on both devices.
3. If you are requested to check the environment settings, press Yes. Then check the
pressure settings. For instructions on setting the ambient pressure, see Configuring
pressure settings (page 35).
4. Check that the pressure units of DM70 and DMT340/DMT242/DMT143 are the same. If
not, and you are checking DMT242/DMT143, change the DM70 pressure unit to bara by
pressing Unit on the corresponding row. You cannot change the pressure unit for
DMT242/DMT143. Adjust the values as instructed in Configuring pressure settings
(page 35).
When using DM70 to check DMT340, you can change the pressure unit of DMT340 by
pressing Unit on the corresponding row. It is also possible to change the pressure unit
of DMT340 through the transmitters local display/keypad interface (for instructions, see
DMT340 User's Guide). Then adjust the values as instructed in Configuring pressure
settings (page 35).

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 Chapter 6 – Field calibration check of fixed transmitters

5. When the pressure settings are correct, press Exit. Now the display shows the dew
point readings Td/f of DM70, DMT340/DMT242/DMT143, and the difference between the
readings ∆Td/f. Roman numerals (I and II) after the parameter abbreviations indicate from
which port the readings are coming. You can follow the measurement trend from the
graphical display.
6. Wait until the readings are stabilized. This can take up to 1 hour in very low dew points. If
the difference between the dew point readings is less than 3 ˚C, there is no immediate
need for adjustment. However, in applications where optimum accuracy is essential, it is
recommended to send the DMT340/DMT242/DMT143 transmitter to Vaisala if the
difference is considered significant.
7. Press the Power On/Off button.
8. Disconnect the connection cable.

More information
‣ Spare parts and accessories (page 80)
‣ Maintenance and calibration services (page 83)

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7. Sampling from processes

7.1 Sampling cells
When the dew point of a process needs to be measured using DM70, the process can be
sampled using one of the following devices:
• DSC74
• DSC74B
• DSC74C
• DSS70A
• DMT242SC
• DMT242SC2
Use the DSC74 sampling cell when the sample is taken from the pressurized process, where
the process pressure forces the sample gas into the sample cell.
Use the DSC74B sampling cell as DSC74. DSC74B is enhanced version of DSC74. With version
B, harmful gases can be recovered.
DSC74C complements DSC74B with a diffusion coil, which allows measuring in the
atmospheric pressure.
Use the DSS70A sampling system when the process is not pressurized, that is, the sample
must be pumped from the process and when the process is dirty or too hot for direct
measurements.
Use the DMT242SC sampling cell when only the body (thread 3/8"G and 1/4"G) of the main
sampling cell is needed.
Use the DMT242SC2 sampling cell with the welded Swagelok connectors. This is ideal for
sampling in a 1/4" pipeline.

7.1.1 DSC74
• Sampling cell with a leakage screw, thread 3/8"G
• Quick coupling, type NIP08, type D
• Thread adapter, type 3/8" - 1/4"G
• Thread adapter, type 3/8" - 1/2"G (for DMT242 fittings)

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 Chapter 7 – Sampling from processes

Figure 16 DSC74 sampling cell with adapters

1 Thread adapter type 3/8" - 1/2"G

2 Thread adapter type 3/8" - 1/4"G
3 NIP08, type D
4 Leakage screw
5 Sampling cell DSC74

7.1.2 DSC74B
• Sampling cell, thread 3/8"G
• Connection part with a needle valve and an integrated leakage screw
• Reducing nipple (thread adapter), 3/8"G - 1/2"G
• Reducing adapter (thread adapter), 3/8"G - 1/4"G

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Figure 17 DSC74B

1 Gas goes in
2 Gas comes out

7.1.3 DSC74C
• Sampling cell, thread 3/8"G
• Connection part with a needle valve and an integrated leakage screw
• Reducing nipple (thread adapter), 3/8"G - 1/2"G
• Reducing adapter (thread adapter), 3/8"G - 1/4"G
• Diffusion coil (for measurements in atmospheric pressure)

Figure 18 Default assembly of DSC74C

1 Gas goes in. Also the coil can be used

here.
2 Gas comes out
3 Coil
4 Valve

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 Chapter 7 – Sampling from processes

Figure 19 Alternative assembly of DSC74C

for tight spaces
1
1 Gas comes out
2 Coil
2 3 Thread, max. size 7 mm
4 Gas goes in
5 Valve

7.1.4 DMT242SC and DMT242SC2

• DMT242SC is a sampling cell with threads 3/8"G and 1/4"G.
• DMT242SC2 is a sampling cell with 1/4" welded Swagelok connectors.

Figure 20 DMT242SC and DMT242SC2 sampling cells

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7.2 Connecting to pressurized processes using

DSC74 sampling cell
DSC74 is a Vaisala sampling cell for connecting DM70 to pressurized processes (optional
accessory). With DSC74B and DSC74C, measuring can be done in overpressure or atmospheric
pressure. This depends on whether the sample gas is let into the sample cell before the needle
valve or after that. See Figure 17 (page 46) and Figure 18 (page 46).
The DSC74 sampling cell comes with a quick connector that fits to industry standard
compressed air line connectors (suitable for type D, Quick08, NIP08). This allows for easy
installation and detachment of the probe without having to shut down the process. Alternative
ways to connect are through the 2 different thread adapters (G3/8" to G1/2" and G3/8" to
G1/4" ISO) that are supplied with each DSC74 unit.

CAUTION! If you use the thread adapters, the process pressure must be shut
down for the installation or removal of the probe. If you use the quick connector,
the process pressure can be maintained during the installation or removal of the
sampling cell. Take a firm hold of the device to keep it in your hands while
removing it.

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To connect to a pressurized process using DSC74:

1. Check that the HM70 pressure setting is correct (same as the process pressure). For
instructions, see Configuring pressure settings (page 35).
2. Select the quick connector or thread adapter that matches your process fitting.
3. Carefully seal the threads of the quick connector or thread adapter with PTFE thread seal
tape.
4. Attach the quick connector or thread adapter onto the sample cell threads. Tighten the
fitting with a fork wrench.
5. Connect the sample cell to the process fittings. Seal the fitting with PTFE thread seal tape.
6. Install the gasket (delivered with the probe) to the nut of probe thread.
7. Set the probe into the sample cell. Tighten the probe by turning it from the thread nut. Do
not tighten the probe from the handle.

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8. Make sure that the valve of the sampling cell is open. First close the valve, then turn it
halfway open again. You can also first open the valve more to ventilate the parts, then
readjust it to allow only a small leakage.

Figure 21 Turning sampling cell valve screw with flathead screwdriver

To verify that the leak screw is open, close the screw and then listen for a
barely audible hiss when reopening the screw (1/2 turn). A light air flow can
be felt when placing a hand over the opened valve.

9. If the sample cell is installed correctly, there is no leakage in the connections. You can test
this by closing the valve temporarily.

CAUTION! Do not open the leak screw more than 1/2 turn to limit the
pressure drop in the sampling cell. If the pressure drops too much,
measurement accuracy can be affected significantly.

More information
‣ Spare parts and accessories (page 80)

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 Chapter 7 – Sampling from processes

7.3 DSS70A sampling system

DSS70A is a portable sampling system for taking gas samples from hot, dirty, or pressurized
processes. The gas collecting system is built in the briefcase including the DM70 meter. The
system consists of a sample pump that draws out the sample gas, a filter to clean the sample
from particles (> 7µm), and a sample valve and flowmeter to adjust the flow rate.

Sample Cell
Filter for Td Probe Sample valve Flowmeter Sample Pump

Sample Gas Sample Gas

Inlet Outlet

The sample gas going into the system must meet the following requirements:
• The temperature must be < 40 ˚C (104 ˚F). Thus, when using the PTFE tube of 2 meters
(provided), the temperature of the process gas should be less than 200 ˚C (392 ˚F).
When the temperature of the sample gas is over 200 ˚C, a stainless steel tube (not
provided) should be used.
• The sample gases must be: Air, N2, non-toxic gases, inert, non-flammable gases.
• If the sample is taken from a pressurized process (1.2 ... 20 bar), the sample pump must be
turned off and the tube from the flowmeter to the pump must be detached.
The DSS70A sampling system can be ordered from Vaisala separately or in connection with
the DM70 meter.

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Figure 22 DSSA70A portable sampling system

1 Fuses
2 Inline filter (7 µm)
3 MI70 recharger adapter
4 Pump on/off
5 MI70 indicator
6 Sample valve
7 Sampling tube
8 Sample gas inlet and outlet
9 Flowmeter
10 Detach this tube when sampling from pressurized processes

7.3.1 DSS70A sampling procedure

To take a sample from a process using DSS70A:

1. Before you start, make sure the pump is switched off. Lift the flowmeter to a vertical
position.
2. Close the sample valve by turning it clockwise as far as it goes.
3. If the process is not pressurized (600 ... 1200 mbar), continue from step 3. If the process is
pressurized (1.2 ... 20 bar), detach the flexible tube from the flowmeter. See Figure 22
(page 52).

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4. Remove the inlet/outlet plugs.

5. Insert the 1/4" tubing into the IN fitting. Tighten the nut 11/4 turns with an open-ended, 14-
mm spanner to make a gas-tight fitting. In future, only slight tightening with an open-
ended spanner is needed to make a gas-tight fitting. Insert the tubing into the OUT fitting,
if needed.
6. If the process is not pressurized, turn on the pump. If the process is pressurized, do not
turn the pump on.
7. Adjust the sample flow using the sample valve, for example, 150 l/h = 2.5 l/min.
8. Turn on the MI70 indicator.
9. Set the pressure to represent the sample pressure. For instructions, see Configuring
pressure settings (page 35).
10. Wait until the reading has stabilized.
11. After the measurements, turn off the pump, remove the tubes, and put the inlet/outlet
plugs back into their places.

CAUTION! Be careful when taking samples from hot processes. Do not

touch the hot sampling lines without suitable protective clothing.

The measured dew points must always be lower than the ambient
temperature or DSS70A probe temperature to avoid condensation in the
system. If condensation occurs, stop sampling and dry the system by
circulating ambient air in the system.
Prevent liquids from entering the DSS70A sampling line as this may damage
the product.

7.3.2 Recharging DSS70A battery

The battery must be recharged when the charger meter shows 10.5 V or less. DSS70A is
powered by a battery, fitted underneath the system. MI70 uses its own battery when it is
connected to DSS70A.
To recharge the DSS70A battery:

1. Detach the MI70 recharger adapter from the socket of the sampling system and plug in
the recharger provided with DM70.
2. Disconnect the recharger when the battery is full and put the MI70 recharger back into
the case.
If you want to recharge the sampling system and MI70 at the same time, connect the MI70
recharger adapter to the recharger socket on top of MI70 and recharge DSS70A as
described above.

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DM70 User Guide M010091EN-G

7.3.3 Changing DSS70A battery

Replacement batteries can be ordered from Vaisala (see Spare parts and accessories
(page 80)).
To change the battery:

1. The battery is fitted underneath the sampling system. To change the battery, lift the
sampling system from the briefcase. To lift the system, use 2 screwdrivers as lever arms
and lift the system from 2 corners (see Figure 23 (page 54)).

Figure 23 Lifting the system

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 Chapter 7 – Sampling from processes

2. Turn the sampling system upside down (see Figure 24 (page 55)).

Figure 24 Sampling system upside down

1 Battery
2 Battery wires
3 Nut of the sample oil

3. Detach the battery wires. Remove the old battery by pulling it up. The battery is attached
to its place with double-sided tape.

The used battery must be disposed of according to the local laws and
regulations.

4. Attach the double-sided tapes provided with the battery to the new battery enclosure.
Place them onto the side without text. For reference, see the old battery.

WARNING! Batteries are electrochemically live at all times. Do not short-

circuit them.

5. Reconnect the wires as follows:

• Red pole: BA + wire
• Black pole: BA - wire

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DM70 User Guide M010091EN-G

6. Press the new battery onto the tapes.

7. Put the system back into the briefcase.

More information
‣ Spare parts and accessories (page 80)

7.3.4 Changing DSS70A filter

The filter should be changed regularly as a part of maintenance. However, the need for
changing the filter depends on how dirty the process is. The filter may need to be changed
after several hundreds of hours or after years. A dry filter may cause increased response times.
A new filter can be ordered from Vaisala (see Spare parts and accessories (page 80)).

1. To change the filter, lift the sampling system out of the briefcase. See Figure 23 (page 54).
2. Unscrew the nut of sample cell. See Figure 25 (page 56).
3. Turn the sampling cell right side up again and undo the nut of the filter cell.
4. Replace the filter and tighten the nuts. The direction of the arrow on the filter must match
the direction of the arrow on DSS70A. See Figure 25 (page 56).
5. Put the sampling system back into the briefcase.

Figure 25 Changing the filter

1 1 Filter direction
2 Nuts of the filter

More information
‣ Spare parts and accessories (page 80)

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 Chapter 7 – Sampling from processes

7.3.5 Changing DSS70A fuses

To change the DSS70A fuses:

1. Press down the fuse button and simultaneously turn it.

2. Replace the old fuse with a new one of same type and rating (glass tube fuse 5 × 20 mm
T 2 A / 250 VAC).
3. Put the fuse button back into place by pressing and turning it.

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DM70 User Guide M010091EN-G

8. Measuring moisture in SF6 gas-

insulated equipment

8.1 Overview
Sulfur hexafluoride (SF6) is an inert, insulating gas of high dielectric strength and thermal
stability. SF6 is used to insulate high voltage lines, circuit breakers, and other equipment used
in transmission and distribution of electricity. Measuring moisture is crucial for the
maintenance of SF6 equipment.

The DMP74C probe has been optimized for measurements in SF6 gas. The measurement is
recommended to be made in pressurized gas for better dew point accuracy. The sensor purge
feature of the DRYCAPâ 180M sensor allows a fast response in low dew points, and only a
small amount of SF6 needs to be drained from the GIE (gas-insulated equipment).

SF6 is a greenhouse gas, with a global warming potential 24900 times that of CO2. For this
reason, the gas should be recycled according to the local laws and regulations. The DSC74B
sampling cell allows the gas to be collected after the measurement (see Figure 26 (page 58)).
When measurement is done in the GIE pressure, the structure of DSC74B eliminates the
adverse effect of pressure fluctuation caused by the collection system.

Figure 26 Gas collection option

1 Gas from GIE

2 Gas to the collecting system

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 Chapter 8 – Measuring moisture in SF6 gas-insulated equipment

8.2 Operating environment
A typical dew point of pure SF6 is usually around −60 °C. The recommendations for the
moisture limit of the equipment insulated with gas (GIE) vary between 70 ... 810 ppmv, which
corresponds to −45 ... −22 °C Td/f in the atmospheric pressure, or −29 ... −3 °C Td/f in 5 barg
pressure.
DM70 is able to measure the dew point directly in the GIE pressure (usually 3 ... 8 barg), or the
gas can be sampled and measured in the atmospheric pressure. If there is a need to measure
high-pressure gas (>10 bar), for example in the recycling bottle, a regulator should be used to
drop the pressure before the measurement.
High-voltage equipment can locate either indoors or outdoors. The operational temperature
range of DM70 is between −10 ... +60 °C.

8.3 Measuring
CAUTION! Before measuring moisture, make sure that hydrofluoric (HF) acid is
not present in the GIE.

With DSC74B, the dew point can be measured at the GIE pressure. If the measurement is done
in the GIE pressure, DM70 is able to show the corresponding dew point in the atmospheric
pressure.
DSC74B limits the flow rate with a leakage screw. The flow rate is optimized for GIE pressures
between 3 ... 10 barg, and no external flow meter is needed. The maximum flow can also be
increased by removing the leak screw and adjusting the flow manually with the valve.
Remove the leak screw as shown in Figure 27 (page 59).

Figure 27 Removing the leak screw

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DM70 User Guide M010091EN-G

Parts per million by volume (ppmv) and parts per million by weight (ppmw) are frequently
used to indicate humidity. The latter depends on the molecular weight of the gas. For SF6, the
molecular weight is 146.06, and the conversion between ppmv and ppmw is the following:

ppmw = ppmv / 8.1

DM70 is able to show the ppmv and ppmw values for moisture.

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 Chapter 9 – Calibration and adjustment

9. Calibration and adjustment

9.1 Calibration
DM70 is fully calibrated and adjusted as shipped from the factory. The typical calibration
interval is 1 year. Calibration must always be done when there is reason to believe that the
device is not within the accuracy specifications.
The device can be sent to Vaisala for calibration and adjustment.

If DM70 is producing incorrect measurements, the recommended first step is to

carry out a few (2 ... 4) sensor purges (available in the DMP74B/DMP74C probes)
to heat and dry the sensor and check if this solves the issue. For instructions on
starting a sensor purge manually, see Performing manual sensor purge (page 32).
If sensor purges fail to correct the issue, move on to calibration and adjustment.

9.2 User calibration and adjustment

In this document, the term "calibration" refers to comparing the device's reading against a
reference value. "Adjustment" refers to changing the device's reading to correspond to the
reference value. After the adjustment, the original calibration certificate shipped with the
product is no longer valid. Read the instructions through carefully before making any
adjustments.

Dew point calibration should be carried out in Vaisala or in other laboratory

conditions.

9.3 Adjusting DM70
The reference condition of the dew point must be traceable to the appropriate standards. The
user adjustment requires a stable humidity generator capable of producing the required
humidities and a calibrated reference dew point meter. For adjustment, the probe and the
reference dew point meter are connected to the humidity generator output, the reference
condition is adjusted and let to stabilize. After the probe and the reference dew point meter
are stabilized, the DM70 reading is adjusted to correspond the reference value.
For the adjustment of the DMP74A probe, the dew point reference temperature should be
between –40 °C and –60 °C (–40 °F ... –76 °F), and for the DMP74B and DMP74C probes, the
dew point reference temperature should be between –57 °C and –67 °C (–70.6 °F ... –88.6 °F).
The optional sampling cell DSC74 (see Figure 16 (page 45)) can be used as a calibration
chamber to be connected with a humidity generator.

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DM70 User Guide M010091EN-G

To ensure the correctness of the adjustment, the reference dew point meter must be calibrated
at a recognized laboratory with a known uncertainty and traceability to national or
international standards.
The Td and H2O parameters can be viewed in the adjustment mode to see the effect of the
adjustment.
To see when the adjustment was made last, select Last adjustment date or check the date
from the Device information view (see Device information (page 40)).

9.4 Adjusting DMT340 series transmitters using

DM70 as reference or terminal
Vaisala DRYCAPâ Dew Point and Temperature Transmitter Series DMT340 can be adjusted
using a correctly adjusted DM70 as a reference dew point meter. Note that dew point
adjustment should be carried out in laboratory conditions and not in the field. The adjustment
procedure for DMT340 using DM70 as a reference is very similar to the adjustment of the
DMP74B/DMP74C probes.
You can also use the MI70 indicator without the reference probe as a terminal to display the
measurement readings and to control the adjustment functions when making adjustment of
DMT340. This is especially useful with transmitters without display. For instructions, see Td/f
adjustment of DMT340 series transmitters using DM70 (page 66).

9.5 Adjusting dew point

Before adjusting dew point, first carry out the 2-point relative humidity calibration, which
ensures the basic adjustment level. When adjusting the DMP74B or DMP74C probe or DMT340
series transmitters with the M-sensor, do the sensor purge before calibration and adjustment.
For instructions, see Sensor purge (page 31).

9.5.1 Making a 2-point relative humidity adjustment

For the DMP74A probe, the wet point humidity reference must be > 20 %RH.
For the DMP74B and DMP74C probes , the wet point humidity reference must be
< 20 %RH.

For DMP74A, humidity references of 0 % (for example nitrogen) and 30 ... 75 % are
recommended. Make sure that the difference between the humidity references is more than
30 %.
For DMP74B and DMP74C, humidity references of 0 % (for example nitrogen) and 11 % are
recommended.
To make a 2-point %RH adjustment:

1. Check that DM70 is turned on.

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 Chapter 9 – Calibration and adjustment

2. When using the DMP74B probe, do the manual sensor purge. For instructions, see
Performing manual sensor purge (page 32) .
3. Remove the screw from the probe handle to expose the calibration button (see Figure 1
(page 11)) and press the button, for example, with a small screwdriver. When pressing the
button, the indicator switches into adjustment mode.
4. To start adjusting, press OK.
5. Select RH and press Select.
6. To check the environmental settings, press Yes. To continue without checking the
settings, press No.
7. To select the adjustment method, press Adjust.
8. Select 2-point adjustment and press Select. Press OK to continue.

9. Set the probe to a lower reference value of relative humidity 1). You can follow the
stabilization from the graph display by pressing Graph. When the reading has
stabilized, press Ready.
10. Use the arrow buttons to give the lower reference value of relative humidity. Then press
OK.

11. Set the probe to a higher reference value of relative humidity 1). You can follow the
stabilization from the graph display by pressing Graph. When the reading has
stabilized, press Ready.
12. Use the arrow buttons to give the higher reference value of relative humidity. Then press
OK.
13. Confirm the adjustment by pressing Yes. If you press No, you return to the
adjustment display and no changes are made.

DMP74A: If the difference between the 2 references is less than 30 %, the

adjustment cannot be done.

14. The adjustment is complete. To exit the adjustment mode, press Back.
15. To return to the basic display, press Exit.
16. Place the screw back onto the calibration button after finishing dew point adjustments.

1) If there is a temperature difference between the generated reference and the probe
temperature, relative humidity must be calculated to correspond to the temperature of the
probe.

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DM70 User Guide M010091EN-G

9.5.2 Making a 2-point %RH adjustment of DMT340 series

transmitters using DM70
DM70 can be used for making a 2-point relative humidity adjustment of DMT340 series
transmitters.
For DMT340 M-sensor, humidity references of 0 % (for example nitrogen) and 10 ... 20 % are
required.

For the DMT340 M-sensor, both reference humidities must be below 20 %RH.

To make a 2-point %RH adjustment of DMT340 using DM70:

1. Turn off DM70.

2. Connect cable 211339 between DMT340 (service port) and DM70 (connector I or II). Turn
on both devices.
3. With DMT340 series transmitters with the M-sensor, perform the manual purge (for
instructions, see Performing manual sensor purge (page 32)). Also, if you are using a
DMP74B probe as reference, perform the manual purge on the reference probe as well.
4. Press the ADJ button on the DMT340 component board to enable the adjustment mode.
5. From the list of parameters, select RHI/II
6. When you are prompted to check the settings, make sure that the pressure units of DM70
and DMT340 are the same. If not, change the unit by pressing Unit on the
corresponding row.
7. Continue with the adjustment by pressing Adjust. Select 2-point adjustment. A note is
displayed on the screen reminding you to follow the adjustment procedure described in
DMT340 User's Guide. Press OK to proceed with the adjustment.

8. Set the probe to a lower reference value of relative humidity 1). You can follow the
stabilization from the graph display by pressing Graph. When the reading has
stabilized, press Ready.
9. Use the arrow buttons to give the lower reference value of relative humidity. Then press
OK.

10. Set the probe to a higher reference value of relative humidity 1). You can follow the
stabilization from the graph display by pressing Graph. When the reading has
stabilized, press Ready.
11. Use the arrow buttons to give the higher reference value of relative humidity. Then press
OK.
12. Confirm the adjustment by pressing Yes. If you press No, you return to the
adjustment display and no changes are made.
13. The adjustment is complete. To exit the adjustment mode, press Back.

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14. To return to the basic display, press Exit.

1) If there is a temperature difference between the generated reference and the probe

temperature, relative humidity must be calculated to correspond to the temperature of the

probe.

9.5.3 Td/f adjustment of DM70

For DMP74B/DMP74C, the sensor purge must be performed manually 1 hour

before adjusting the dew point.

For DMP74A, the reference temperature of the dew point should be −40 ˚C ... −60 ˚C
(−40 ˚F ... −76 ˚F).
For DMP74B/DMP74C, the reference temperature of the dew point should be −57 ˚C ... −67 ˚C
(−70.6 ˚F ... −88.6 ˚F).
To adjust the dew point:

1. Set the probe to the reference condition. Follow the stabilization from the graphic display
by pressing Graph. The minimum recommended stabilization time for this critical
adjustment is 5 hours.
2. Perform the manual purge if necessary.
3. Press the Calibration button on the probe handle (see Figure 1 (page 11)) using, for
example, a small screwdriver. The indicator will switch into adjustment mode. To confirm
calibration, press OK.
4. Select Td/f and press Select.
5. To check the environmental settings, press Yes. To go to calibration directly, press
No.
6. To select 1-point adjustment, press Adjust and then Select.
7. When the reading has stabilized at the reference level, press Ready.
8. Use the arrow buttons to give the reference value. Then press OK.
9. Confirm the adjustment by pressing Yes. If you press No, you return to the
adjustment mode display and no changes are made.
10. Wait until the automatic autocalibration has taken place.
11. When the calibration completes, press Back to exit the adjustment mode.
12. To return to the basic display, press Exit.
13. Place the screw back onto the calibration button.

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14. To seal the calibration, attach a sticker on the calibration button.

Several autocalibrations may be necessary after this adjustment has been

performed until the transmitter reaches full accuracy.

9.5.4 Td/f adjustment of DMT340 series transmitters using

DM70

For DMT340 series transmitters with the M-sensor, the sensor purge must be
performed manually 1 hour before adjusting the dew point.

For DMT340 series transmitters, the reference temperature of the dew point should be
−57 ... −67 ˚C (−70.6 ... −88.6 ˚F).
To adjust DMT340 dew point using DM70, follow the instructions below.

First carry out step 1 ... step 7 . In step 8, choose one of the two alternative
methods for completing the adjustment.

1. Turn off DM70.

2. Connect the cable 211339 between DMT340 (service port) and DM70 (connector I or II).
Turn on both devices.
3. Set the probe to the reference condition. Follow the stabilization from the graphic display
by pressing Graph. The minimum recommended stabilization time for this critical
adjustment is 5 hours.
4. Perform the manual purge if necessary.
5. Press the ADJ button on the DMT340 component board to enable the adjustment mode.
6. From the list of parameters, select Td/f I/II
7. You are prompted to check the settings: make sure that the pressure units of DM70 and
DMT340 are the same. If not, change the unit by pressing Unit on the corresponding
row.
8. At this point you need to select the adjustment method. If the reference probe is
connected, 2 options are displayed: To same as Td/f I/II (see To same as T d/f I/II
(page 67)) or 1-point adjustment (see 1-point adjustment (page 67)). If you are using
DM70 as a terminal, only 1-point adjustment is possible.

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 Chapter 9 – Calibration and adjustment

9.5.4.1 To same as Td/f I/II

This procedure is one of the alternative options for completing the adjustment
described in Td/f adjustment of DMT340 series transmitters using DM70
(page 66).

This adjustment method automatically uses the reading of the reference probe as
the reference value for making the adjustment.

1. Continue with the adjustment by pressing Yes.

2. A note is displayed on the screen reminding you to follow the adjustment procedure
described in the DMT340 User's Guide. Press OK to proceed with the adjustment.
3. Follow the stabilization from the graphic display by pressing Graph. The minimum
recommended stabilization time for this critical adjustment is 5 hours.
4. When the reading has stabilized at the reference level, press Ready. This adjustment
method automatically uses the reading of the reference probe as the reference value.
5. Confirm the adjustment by pressing Yes. If you press No, you return to the
adjustment mode display and no changes are made.
6. Wait until the automatic autocalibration has taken place.
7. When the calibration completes, press Back to exit the adjustment mode.
8. To return to the basic display, press Exit.
9. Place the screw back onto the calibration button.
10. To seal the calibration, attach a sticker on the calibration button.

Several autocalibrations may be necessary after this adjustment has been

performed until the transmitter reaches full accuracy.

9.5.4.2 1-point adjustment

This procedure is one of the alternative options for completing the adjustment
described in Td/f adjustment of DMT340 series transmitters using DM70
(page 66).

This adjustment method allows entering the reference value manually when
making the adjustment.

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DM70 User Guide M010091EN-G

1. A note is displayed on the screen reminding you to follow the adjustment procedure
described in the DMT340 User's Guide. Press OK to proceed with the adjustment.
2. Follow the stabilization from the graphic display by pressing Graph. The minimum
recommended stabilization time for this critical adjustment is 5 hours.
3. When the reading has stabilized at the reference level, press Ready.
4. Use the arrow buttons to give the reference value and press OK.
5. Confirm the adjustment by pressing Yes. If you press No, you return to the
adjustment mode display and no changes are made.
6. Wait until the automatic autocalibration has taken place.
7. When the calibration completes, press Back to exit the adjustment mode.
8. To return to the basic display, press Exit.
9. Place the screw back onto the calibration button.
10. To seal the calibration, attach a sticker on the calibration button.

Several autocalibrations may be necessary after this adjustment has been

performed until the transmitter reaches full accuracy.

9.6 Adjusting temperature

9.6.1 Temperature adjustment of DM70

The temperature adjustment can be done using the 1-point or 2-point adjustment. The 1-point
adjustment should be done within the temperature range in which the device is most often
used.

First carry out steps step 1 ... step 4. In step 5, choose one of the two alternative
methods for completing the adjustment.

To start the adjustment:

1. Press the Calibration button of the probe handle (see number 4 in Figure 1 (page 11))
using a tool with a thin, sharp point, for example, a small screwdriver. The indicator will
switch into the adjustment mode. To confirm calibration, press OK.
2. Select Td/f and press Select.
3. Select T and press Select.

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 Chapter 9 – Calibration and adjustment

4. To select the adjustment method, first press Adjust and then choose the adjustment
method, either 1-point adjustment or 2-point adjustment.
5. Depending on your selection, continue with the instructions in 1-point adjustment
(page 69) or 2-point adjustment (page 69).

9.6.1.1 1-point adjustment

This procedure is one of the alternative options for completing the adjustment
described in Temperature adjustment of DM70 (page 68).

1. After selecting 1-point adjustment, press Select to continue.

2. Set the probe to the reference temperature. You can follow the stabilization from the
graph display by pressing Graph. The minimum recommended stabilization time for
this critical adjustment is 5 hours. When the reading has stabilized, press Ready.
3. Use the arrow buttons to give the reference temperature and then press OK.
4. Confirm the adjustment by pressing Yes. If you press No, you return to the
adjustment mode display and no changes are made.
5. To exit the adjustment mode, press Back.
6. To return to the basic display, press Exit.

9.6.1.2 2-point adjustment

This procedure is one of the alternative options for completing the adjustment
described in Temperature adjustment of DM70 (page 68).

1. After selecting 2-point adjustment, press Select to continue.

2. Set the probe to a lower reference temperature. You can follow the stabilization from the
graphical display by pressing Graph. When the reading has stabilized, press Ready.
3. Use the arrow buttons to give the lower reference temperature value and then press
OK.
4. Set the probe to a higher reference temperature. You can follow the stabilization from the
graphical display by pressing Graph. When the reading has stabilized, press Ready.
5. Use the arrow buttons to give the higher reference temperature value and then press
OK.

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6. Confirm the adjustment by pressing Yes. If you press No, you return to the
adjustment display and no changes are made.

If the difference between the 2 references is less than 30 %, the adjustment

cannot be done.

7. The adjustment is complete. To exit the adjustment mode, press Back.

8. To return to the basic display, press Exit.

9.6.2 Temperature adjustment of DMT340 series using DM70

DM70 can be used for making the temperature adjustment of DMT340 series transmitters.

First carry out steps step 1 ... step 6. From step 6 onwards, choose one of the three
alternative methods for completing the adjustment.

1. Turn off DM70.

2. Connect the cable 211339 between DMT340 (service port) and DM70 (connector I or II).
Turn on both devices.
3. Press the ADJ button on the DMT340 component board to enable the adjustment mode.
4. From the list of parameters, select TI/II.
5. At this point you need to select the adjustment method. If the reference probe is
connected, three options are displayed: To same as TI/II (see To same as T I/II (page 70)),
1-point adjustment (see 1-point adjustment (page 71)) or 2-point adjustment (see 2-
point adjustment (page 71)).
6. You are prompted to check the settings: make sure that the pressure units of DM70 and
DMT340 are the same. If not, change the unit by pressing Unit on the corresponding
row.

9.6.2.1 To same as TI/II

This procedure is one of the alternative options for completing the adjustment
described in Temperature adjustment of DMT340 series using DM70 (page 70).

This adjustment method automatically uses the reading of the reference probe as
the reference value for making the adjustment.

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 Chapter 9 – Calibration and adjustment

1. After selecting To same as TI/II, confirm the adjustment by pressing Yes. If you press
No, a note is displayed on the screen reminding you to follow the adjustment procedure
described in the DMT340 User's Guide. Press OK and the adjustment mode display
returns and no changes are made.

9.6.2.2 1-point adjustment

This procedure is one of the alternative options for completing the adjustment
described in Temperature adjustment of DMT340 series using DM70 (page 70).

1. After selecting 1-point adjustment, press Select to continue.

2. Set the probe to the reference temperature. You can follow the stabilization from the
graphic display by pressing Graph. When the reading has stabilized, press Ready.
3. Use the arrow buttons to give the reference temperature value and press OK.
4. Confirm the adjustment by pressing Yes. If you press No, you return to the
adjustment mode display and no changes are made.
5. The adjustment is now complete. Press Back to exit the adjustment mode.
6. To return to the basic display, press Exit.

9.6.2.3 2-point adjustment

This procedure is 1 of the alternative options for completing the adjustment

described in Temperature adjustment of DMT340 series using DM70 (page 70).

1. After selecting 2-point adjustment, press Select to continue.

2. Set the probe to the lower reference temperature. You can follow the stabilization from
the graphic display by pressing Graph. When the reading has stabilized, press
Ready.
3. Use the arrow buttons to give the lower reference temperature value and press OK.
4. Set the probe to the higher reference temperature. You can follow the stabilization from
the graphic display by pressing Graph. When the reading has stabilized, press
Ready.
5. Use the arrow buttons to give the higher reference temperature value and press OK.

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6. Confirm the adjustment by pressing Yes. If you press No, you return to the
adjustment mode display and no changes are made.

If the difference between the two references is less than 30 °C, the
adjustment cannot be done.

7. The adjustment is now complete. Press Back to exit the adjustment mode.
8. To return to the basic display, press Exit.

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 Chapter 10 – Technical data

10. Technical data

10.1 DM70 and DMP74 specifications

Table 6 DM70 handheld meter general specifications

Property Description/value

Storage temperature −40 … +70 ˚C (−40 … +158 ˚F)

Storage humidity range 0 … 100 % non-condensing
Housing material ABS/PC blend
Total weight 750 g (26 oz)
Electromagnetic compatibility Complies with the following standard:
EN 61326-1:1997 +Am 1:1998, Electrical
equipment for measurement, control, and
laboratory use - EMC requirements: Basic
environment.

Table 7 DMP74A, DMP74B, and DMP74C measurement performance

Property Description/value

Dew point temperature

Measurement range DMP74C: −70 … +30 ˚C (−94 … +86 ˚F)
DMP74A: −50 … +60 ˚C (−58 … +140 ˚F)
DMP74B: −70 … +30 ˚C (−94 … +86 ˚F)
Accuracy ±2 ˚C (±3.6 ˚F), see the accuracy graphs below
Dew point range for ±2 ˚C. Accuracy for DMP74A: −64 … +60 ˚C (−83 … +140 ˚F)
pressure converted dew point (dew point DMP74B: −80 … +20 ˚C (−112 … +68 ˚F)
measured in pressure, calculated to 1 atm dew
point value) DMP74C: −72 … +20 ˚C (−98 … +68 ˚F)

DMP74A:
Response time: 63 % (90 %) at flow rate 0.2 m/s, 1 bar absolute pressure, +20 ˚C
0 … −40 ˚C Td (+32 … +40 ˚F Td) 20 s (120 s)

−40 … ˚C Td (−40 … +32 ˚F Td) 10 s (20 s)

DMP74B/DMP74C:
Response time: 63 % (90 %) at flow rate 0.2 m/s, 1 bar absolute pressure, +20 ˚C
0 … −60 ˚C Td (+32 … −76 ˚F Td) 50 s (340 s)

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DM70 User Guide M010091EN-G

Property Description/value

−60 … 0 ˚C Td (−76 … +32 ˚F Td) 10 s (20 s)

Temperature
Measurement range −10 … 60 ˚C (14 … 140 ˚F)
Accuracy at +20 ˚C (+68 ˚F) ±0.2 ˚C (±0.36 ˚F)
Typical temperature dependence of electronics ±0.005 ˚C/˚C (±0.005 °F/°F)
Temperature sensor Pt100 IEC751 1/3 class B
PPM (ppmv or ppmw)

Measurement range (typical) DMP74A: 40 … 200000 ppm

DMP74B/DMP74C: 10 … 20000 ppm
Accuracy at +20 ˚C (+68 ˚F):
< 40 ppm ±(0.5 ppm + 25.4 % of reading)
> 40 ppm ±(7.3 ppm + 8.3 % of reading)
Absolute humidity (DMP74A probe recommended)
Measurement range (typical) 0.5 … 100 g/m3 (0.2 … 40 gr/ft3)
Accuracy ±(0.2 g/m3 + 10 % of reading)
±(0.1 gr/ft3 + 10 % of reading)
Mixing ratio (DMP74A probe recommended)
Measurement range (typical) 0.2 … 100 g/kg (2 … 700 gr/lbs)
Accuracy ±(0.1 g/kg + 12 % of reading)
±(0.8 gr/lbs + 12 % of reading)
Relative humidity (DMP74A)
Measurement range 0 … 100 %
Accuracy at +20 ˚C (+68 ˚F) RH < 5 %: ±(0.025 % RH + 17.5 % of reading)
RH > 5 %: ±(0.8 % RH + 2 % of reading)
Measurement environment
Temperature −10 … +60 ˚C (+14 … +140 ˚F)
Pressure DMP74A: 0 … 20 bara (0 … 290 psia)
DMP74B: 0 … 20 bara (0 … 290 psia)
DMP74C: 0 … 10 bara (0 … 150 psia)

Sample flow rate No effect on dew point accuracy

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70
60
50
Dew point temperature (°C)

e
40 on lin
turati
30 v a p or sa
r d
20 Wate °C T
< ±1
10 c c u racy
A
0 d
°C T
-10 < ±2
c u racy ied
A c pecif
-20 not s
racy
-30 Accu
-40 it
e lower lim
-50 ment rang
-60 Dew point measure
-70
-80
-10 0 10 20 30 40 50 60
Temperature of measured gas (°C)

Figure 28 DMP74A dew point accuracy vs. measurement conditions

70
60
50
Dew point temperature (°C)

40
t range high limit
30 men
sure
mea
20
point specifie
d
Dew cy not
10 Accura
0
-10
-20 °C Td
cy < ±2
-30 Accura
-40 d
specifie
-50 cy not
-60 Accura
limit
-70 t range lower
-80
Dew point measuremen
-10 0 10 20 30 40 50 60
Temperature of measured gas (°C)

Figure 29 DMP74B and DMP74C dew point accuracy vs. measurement conditions

Dashed line: For DMP74C the ±2 °C accuracy range is limited to −50 °C Td when used in SF6
gas.

Table 8 DMP74A, DMP74B, and DMP74C general specifications

Property Description/value

Sensor DMP74A: Vaisala DRYCAPâ 180S

DMP74B/DMP74C: Vaisala DRYCAPâ 180M

Probe material (wetted parts) Stainless steel (AISI 316L)

Sensor protection Sintered filter, (AISI 316L), item No. HM47280SP

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Property Description/value

Mechanical connection G1/2" ISO2281 thread with bonded seal ring (U-
seal)
Housing classification IP65 (NEMA4)
Storage temperature −40 … +70 ˚C (−40 … +158 ˚F)
Storage humidity 0 … 100 %RH non-condensing
Weight 350 g (12 oz)

Table 9 DMP74A, DMP74B, and DMP74C mechanical specifications

Property Description/value

Materials
Probe housing material PET plastic
Filter PTFE membrane, PET plastic grid
Connector Nickel plated brass, M12 5-pin
Housing classification, probe body IP65
Connector M12 5-pin male
Weight, probe head 45 g (1.6 oz)
Dimensions
Probe diameter 25 mm (0.98 in)
Probe length 96 mm (3.8 in)

Table 10 Sampling cell specifications

Property Description/value

DMT242SC sampling cell

Inlet/outlet thread ISO G 3/8"/G 1/4"
Pressure limit 10 MPa, 100 barg, 1450 psig

Material Stainless steel AISI316

Weight 220 g (7.8 oz)
DMT242SC sampling cell with Swagelok connectors
Inlet/outlet thread 1/4" Swagelok connectors (for 1/4" tubing)
Pressure limit 4 MPa, 40 barg, 580 psig

Material Stainless steel AISI316

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Property Description/value

Weight 285 g (10 oz)

DSC74 sampling cell for pressurized gases
Quick connector Type D/NIP08
Leak screw Screwdriver operated
Inlet/outlet thread ISO G 3/8"/G 1/4"
Thread adapters included A) ISO G 3/8" to G 1/4" (female)
B) ISO G 3/8" to G 1/2" (male)
Pressure limit 1 MPa, 10 barg, 145 psig

Material Stainless steel AISI316

Weight 300 g (11 oz)
DSC74B 2-pressure sampling cell
Inlet/outlet thread ISO G 3/8"/G 3/8"
Flow adjustment Manually operated
Pressure limit 1 MPa, 10 barg, 145 psig

Material Stainless steel AISI316

Weight 390 g (14 oz)
DSC74C
DSC74C is a sampling cell that combines DSC74B with DMCOIL cooling/venting coil.
DMCOIL
Coil pipe size 6 mm (0.24 in)
Connection to sampling cell With ISO G 1/4" and G 3/8" thread adapter
Weight 130 g (4.6 oz)
DSS70A sampling system
Measuring range −60 ˚C (−76 ˚F) Td … Tamb
(max Tamb +40 ˚C (+104 ˚F) Td)

Operating gases Air, N2, non-toxic gases, non-flammable, inert

gases
Inlet/outlet connection 1/4" SWAGELOK
Operating temperature Ambient temperature: 0 … +40 ˚C
(+32 … +104 ˚F)
Gas temperature: max 200 ˚C (392 ˚F) with 2 m
(6.6 ft) PTFE tube at 20 ˚C (68 ˚F)

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Property Description/value

Operating pressure With pump: 0.6 … 1.2 bara (8.7 … 17.4 psia)
Pump disconnected: 0 … 20 bara (0 … 290 psia)

Battery operation time for pump 8 h continuous

Filter 7 mm (0.28 in) inline filter, 1/4" SWAGELOK
SS-4F-7
Wetted parts Stainless steel
Carrying case ABC plastic
Weight 5.5 kg (12 lbs.)
Fuse ratings Glass tube fuse 5 × 20 mm T 2A/250 VAC
(Manufacturer: Littlefuse 218002)

10.2 MI70 specifications
Table 11 MI70 measurement indicator

Property Description/Value

Operating environment
Operating temperature −10 ... +40 °C (+14 … +104 °F)
Operating humidity 0 ... 100 %RH, non-condensing
Storage temperature −40 ... +70 °C (-40 ... +158 °F)
Inputs and outputs
Max. no of probes 2
PC interface MI70 Link software with USB or serial port cable
Analog output 0 ... 1 VDC
Power supply Rechargeable NiMH battery pack with AC adapter or
4 × AA size alkalines, type IEC LR6
Output resolution 0.6 mV
Accuracy 0.2 % full scale
Temperature dependence 0.002 %/˚C (0.01 %/˚F) full scale
Minimum load resistor 10 kΩ to ground
Mechanical specifications
Housing classification IP54
Housing materials ABS/PC blend

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Property Description/Value

Weight 400 g (14 oz)

Compatibility
EMC compliance EN 61326-1, portable equipment
Other
Menu languages English, Chinese, Spanish, Russian, French, Japanese,
German, Swedish, Finnish
Display • LCD with backlight
• Graphic trend display of any parameter
• Character height up to 16 mm (0.63 in)
Alarm Audible alarm function
Data logging capacity 2700 real time data points
Logging interval 1 s to 12 h
Logging duration 1 min ... memory full
Resolution 0.01 %RH, 0.01 °C/°F, 0.01 hPa, 0.01 aw, 10 ppm / 0.01
%CO2

Table 12 MI70 battery operation time

Property Value/Description

Typical charging time 4 hours

Operation times
Continuous use 48 h typical at +20 ˚C (+68 °F)
Data logging use Up to a month

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10.3 Dimensions

Figure 30 Dimensions of MI70 indicator, DMP74 probe, DSC74 sampling cell, and DSC74C sampling
cell (left to right and top to bottom)

10.4 Spare parts and accessories

Information on spare parts, accessories, and calibration products is available
online at www.vaisala.com and store.vaisala.com.

Table 13 DM70 spare parts and accessories

Description Item code

AC adapters
Euro AC adapter MI70EUROADAPTER
UK AC adapter MI70UKADAPTER

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Description Item code

US AC adapter MI70USADAPTER
AUS AC adapter MI70AUSADAPTER
MI70 All adapter MI70ALLADAPTER
Sampling
Portable sampling system with case DSS70A
Sampling cell DMT242SC
Sampling cell with Swagelok connectors DMT242SC2
Sampling cell for pressurized gases DSC74
Two pressure sampling cell DSC74B
Two pressure sampling cell with venting coil DSC74C
Cooling/venting coil for sampling cells DMCOIL
Cables
Analog output signal cable 27168ZZ
Connection cable for DMT152, DMT132, DMT143, DPT145, and DPT146 219980SP
transmitters
Probe extension cable (10 m (33 ft)) 213107SP
Connection cable for DMT242 27160ZZ
Connection cable for DMT340 series 211339
Carrying cases
Weatherproof hard plastic carrying case MI70CASE3
Soft carrying case MI70SOFTCASE
Probe accessories
Sintered filter for the probe HM47280SP
Bonded seal ring 26230
Others
Measurement indicator MI70

USB PC connection cable (for use with MI70 Link software) 1) 219687

Filter for DSS70A 210801

Rechargeable battery for MI70 26755
Rechargeable battery for DSS70A DSS70BAT

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Description Item code

Service kit for DSC74 (all versions) DSC74SERVICEKIT

1) Vaisala MI70 Link software for Windows is available at www.vaisala.com/mi70link.

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Maintenance and calibration services
Vaisala offers comprehensive customer care throughout the life cycle of our
measurement instruments and systems. Our factory services are provided
worldwide with fast deliveries. For more information, see www.vaisala.com/
calibration.
• Vaisala Online Store at store.vaisala.com is available for most countries. You
can browse the offering by product model and order the right accessories,
spare parts, or maintenance and calibration services.
• To contact your local maintenance and calibration expert, see
www.vaisala.com/contactus.

Technical support
Contact Vaisala technical support at helpdesk@vaisala.com. Provide at least the
following supporting information as applicable:
• Product name, model, and serial number
• Software/Firmware version
• Name and location of the installation site
• Name and contact information of a technical person who can provide further
information on the problem
For more information, see www.vaisala.com/support.

Warranty
For standard warranty terms and conditions, see www.vaisala.com/warranty.
Please observe that any such warranty may not be valid in case of damage due to normal wear
and tear, exceptional operating conditions, negligent handling or installation, or unauthorized
modifications. Please see the applicable supply contract or Conditions of Sale for details of the
warranty for each product.

Recycling
Recycle all applicable material.

Follow the statutory regulations for disposing of the product and packaging.

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