Vaisala DRYCAP DMT152 User Manual
M210865EN-J
User Guide
Vaisala DRYCAPâ Dew Point Transmitter
DMT152
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 Oyj 2019
No part of this document may be
reproduced, published or publicly
displayed in any form or by any means,
electronic or mechanical (including
photocopying), nor may its contents be
modified, translated, adapted, sold or
disclosed to a third party without prior
written permission of the copyright holder.
Translated documents and translated
portions of multilingual documents are
based on the original English versions. In
ambiguous cases, the English versions are
applicable, not the translations.
The contents of this document are subject
to change without prior notice.
Local rules and regulations may vary and
they shall take precedence over the
information contained in this document.
Vaisala makes no representations on this
document’s compliance with the local
rules and regulations applicable at any
given time, and hereby disclaims any and
all responsibilities related thereto.
This document does not create any legally
binding obligations for Vaisala towards
customers or end users. All legally binding
obligations and agreements are included
exclusively in the applicable supply
contract or the General Conditions of Sale
and General Conditions of Service of
Vaisala.
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...........................................................................7
1.4 Trademarks........................................................................................................ 8
2. Product Overview...........................................................................................9
2.1 Introduction to DMT152....................................................................................9
2.1.1 Basic Features and Options......................................................................9
2.1.2 Transmitter Structure.............................................................................. 10
2.1.3 Safety..........................................................................................................11
2.1.4 ESD Protection...........................................................................................11
2.1.5 Regulatory Compliances.......................................................................... 11
3. Functional Description................................................................................ 12
3.1 Advanced DRYCAP Technology.................................................................... 12
3.1.1 Auto-Calibration.......................................................................................12
3.1.2 Sensor Purge.............................................................................................12
4. Installation........................................................................................................ 13
4.1 Selecting the Location....................................................................................13
4.2 Installing the Transmitter................................................................................13
4.3 Wiring................................................................................................................15
4.3.1 Output Noise Minimization Option........................................................ 17
4.3.2 Connection Cables................................................................................... 18
4.3.3 Power Supply Requirements.................................................................. 19
4.4 Loop-Powered Display................................................................................... 19
4.5 Sampling from Process..................................................................................20
4.6 Sampling Accessories..................................................................................... 21
4.6.1 DMT242SC Sampling Cell........................................................................21
4.6.2 DMT242SC2 Sampling Cell with Swagelok Connectors...................... 21
4.6.3 DSC74 Sampling Cell with Quick Connector and Leak Screw........... 22
4.6.4 DSC74B Two-Pressure Sampling Cell................................................... 23
4.6.5 DSC74C Two-Pressure Sampling Cell with Coil...................................25
4.6.6 NW40 Mounting Flange......................................................................... 28
5. Serial Line Operation.................................................................................. 29
5.1 Connecting to Serial Interface......................................................................29
5.1.1 Installing Driver for USB Service Cable................................................ 29
5.1.2 Terminal Application Settings............................................................... 29
5.1.3 List of Serial Commands..........................................................................31
5.2 Device Information.........................................................................................33
5.2.1 Show Device Information.......................................................................33
5.2.2 Show Transmitter Status........................................................................ 33
5.2.3 Show Firmware Version..........................................................................34
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DMT152 User Guide M210865EN-J
5.3 Configuring Analog Outputs.........................................................................35
5.3.1 Limit Alarm.............................................................................................. 36
5.3.2 Purge Status Alarm................................................................................. 37
5.3.3 Malfunction Alarm...................................................................................38
5.3.4 Select Analog Output Parameter and Scaling.....................................39
5.4 Configuring Serial Line Operation................................................................39
5.4.1 Set Serial Line Settings...........................................................................39
5.4.2 Set Serial Line Response Time.............................................................. 40
5.4.3 Set Transmitter Address........................................................................ 40
5.4.4 Set Measurement Output Format.........................................................40
5.4.5 Select Unit................................................................................................42
5.4.6 Set Serial Line Operating Mode.............................................................43
5.5 Configuring Measurement Parameters........................................................43
5.5.1 Enable or Disable Sensor Purge............................................................ 43
5.5.2 Set Pressure Value for ppm Calculation...............................................44
5.5.3 Set Molar Mass for ppmw Calculation...................................................45
5.6 Serial Line Output Commands..................................................................... 46
5.6.1 Start Measurement Output....................................................................46
5.6.2 Stop Measurement Output.....................................................................47
5.6.3 Set Output Interval..................................................................................47
5.6.4 Output a Reading Once..........................................................................47
5.7 Troubleshooting and Maintenance Commands..........................................48
5.7.1 Display Currently Active Errors.............................................................48
5.7.2 Test Analog Outputs...............................................................................48
5.7.3 Calibrate Analog Output........................................................................49
5.7.4 Extend Analog Output Range...............................................................49
5.8 Other Commands...........................................................................................50
5.8.1 Opening the Transmitter in POLL Mode...............................................50
5.8.2 Closing the Connection to a Transmitter in POLL Mode....................50
5.8.3 Display Command List.............................................................................51
5.8.4 Set Time.....................................................................................................51
5.8.5 Reset Transmitter..................................................................................... 51
5.8.6 Set LED Voltage........................................................................................51
5.8.7 Restore Factory Settings........................................................................52
6. Maintenance....................................................................................................53
6.1 Cleaning the Transmitter............................................................................... 53
6.2 Changing the Filter.........................................................................................53
6.3 Calibration and Adjustment..........................................................................54
6.3.1 Field Check Using DM70........................................................................ 54
7. Troubleshooting............................................................................................ 57
7.1 Typical Problems.............................................................................................57
7.2 Unknown Serial Settings................................................................................57
7.3 Error State........................................................................................................57
7.4 Error Codes..................................................................................................... 58
2
Table of Contents
8. Technical Data............................................................................................... 60
8.1 Specifications................................................................................................. 60
8.2 Spare Parts and Accessories.........................................................................63
8.3 Dimensions......................................................................................................65
Warranty............................................................................................................ 67
Technical Support............................................................................................67
Recycling...........................................................................................................67
3
DMT152 User Guide M210865EN-J
List of Figures
Figure 1 DMT152 Probe Parts.........................................................................................10
Figure 2 DMT152 Installed Directly to Pipeline (Max. 50 bar)............................... 13
Figure 3 Connectors I and II............................................................................................16
Figure 4 Connector Pinout..............................................................................................16
Figure 5 Output Noise Minimization Wiring Option................................................ 17
Figure 6 Nokeval 301 Loop-Powered Display...........................................................20
Figure 7 DMT152 Nokeval 301/302 Wiring Diagram...............................................20
Figure 8 Sampling Cells DMT242SC2 (Left) and DMT242SC (Right).................22
Figure 9 DSC74 Sampling Cell with Accessories......................................................23
Figure 10 DSC74B............................................................................................................... 24
Figure 11 Removing the Leak Screw............................................................................. 25
Figure 12 Default Assembly of DSC74C....................................................................... 26
Figure 13 Alternative Assembly of DSC74C (for Tight Spaces).............................27
Figure 14 NW40 Mounting Flange.................................................................................28
Figure 15 NW40 Mounting Flange Dimensions......................................................... 28
Figure 16 Filter Structure..................................................................................................53
Figure 17 Accuracy Over Temperature Range.............................................................61
Figure 18 DMT152 Dimensions........................................................................................ 65
4
List of Tables
Table 1 Document Versions (English).......................................................................... 7
Table 2 Related Manuals...................................................................................................7
Table 3 DMT152 Measurement Parameters.................................................................9
Table 4 Standard Wiring Pinouts and Wire Colors..................................................15
Table 5 Output Noise Minimization Wiring Option Pinouts and
Wire Colors..........................................................................................................17
Table 6 Connection Cable Options.............................................................................. 18
Table 7 Default Serial Interface Settings...................................................................29
Table 8 List of Serial Commands.................................................................................. 31
Table 9 ? command......................................................................................................... 33
Table 10 STAT command................................................................................................. 34
Table 11 VERS command................................................................................................ 34
Table 12 AMODE command............................................................................................ 35
Table 13 ALARM command.............................................................................................36
Table 14 STATUS command............................................................................................ 38
Table 15 AERR command................................................................................................ 38
Table 16 ASEL command.................................................................................................39
Table 17 SERI command.................................................................................................. 39
Table 18 FORM Command Parameters.........................................................................41
Table 19 FORM Command Modifiers.............................................................................41
Table 20 UNIT command..................................................................................................42
Table 21 SMODE Command............................................................................................43
Table 22 Selection of Output Modes............................................................................ 43
Table 23 XPUR command................................................................................................44
Table 24 PRES and XPRES command..........................................................................44
Table 25 Pressure Conversion Coecients.................................................................45
Table 26 MOL command.................................................................................................. 46
Table 27 R Command........................................................................................................46
Table 28 INTV Command................................................................................................. 47
Table 29 ERRS command................................................................................................ 48
Table 30 ATEST command.............................................................................................. 48
Table 31 ACAL command................................................................................................49
Table 32 AOVER command.............................................................................................49
Table 33 OPEN command................................................................................................50
Table 34 CLOSE command..............................................................................................50
Table 35 TIME command...................................................................................................51
Table 36 LED command....................................................................................................52
Table 37 Error Codes.........................................................................................................58
Table 38 Measurement Performance........................................................................... 60
Table 39 Operating Environment................................................................................... 61
Table 40 Inputs and Outputs........................................................................................... 61
Table 41 Mechanical Specifications.............................................................................. 62
Table 42 Output Cable Specifications.......................................................................... 62
Table 43 Accessories.........................................................................................................63
List of Tables
5
DMT152 User Guide M210865EN-J
6
Chapter 1 – About This Document
1. About This Document
1.1 Version Information
Table 1 Document Versions (English)
Document Code Date Description
M210865EN-J October 2019 This manual.
• Added information on Nokeval display support.
• Corrected the dew point measurement range upper limit
specification from −10 °C to −20 °C.
• Added information on the minimum valid pressure
setting in the PRES/XPRES
• Updated the document template.
M210865EN-H October 2017 Previous version. IP class specification of the probe
M210865EN-G October 2015 Updated the dew point temperature measurement
updated to IP66 (applies to probes manufactured from
March 2017 onwards). Added information about the
output noise minimization wiring option.
accuracy
specification.
1.2 Related Manuals
commands.
Table 2 Related Manuals
Document Code Description
M210866EN DMT152 Quick Reference Guide
1.3
Documentation Conventions
WARNING!
follow instructions carefully at this point, there is a risk of injury or even death.
CAUTION!
follow instructions carefully at this point, the product could be damaged or
important data could be lost.
Warning alerts y
Caution w
ou to a serious hazard. If you do not read and
arns you of a potential hazard. If you do not read and
7
DMT152 User Guide M210865EN-J
Note highlights important information on using the product.
1.4 Trademarks
DRYCAPâ is a registered trademark of Vaisala Oyj.
All other product or company names that may be mentioned in this publication are trade
names, trademarks, or registered trademarks of their respective owners.
8
Chapter 2 – Product Overview
2. Product Overview
2.1 Introduction to DMT152
The Vaisala DRYCAPâ dew point transmitter DMT152 measures dew point temperature
accurately in a measurement range from −80 °C to −20 °C (−112 … −4 °F). The maximum
output range of the transmitter is −100 … 20 °C (−148 … +68 °F).
DMT152 is designed for a wide range of OEM applications. The transmitter is easy to install, and
the mechanics have been designed for harsh environments requiring protection against dust,
dirt, and splashed water.
The excellent stability and reliability of the transmitter’s performance is based on advanced
DRYCAP polymer sensor technology. The DRYCAP technology has low maintenance needs due
to its excellent long-term stability and durability against condensation. For more information
on DRYCAP technology, see Advanced DRYCAP Technology (page 12).
DMT152 Measurement Parameters
Table 3 DMT152 Measurement Parameters
Parameter Abbreviation Metric Unit Non-Metric Unit
Dew point / frost point
temperature
Parts per million H2O ppmv/ppm
TDF °C °F
w
ppmv/ppm
w
2.1.1 Basic Features and Options
• Calibrated dew point measurement range −80 … −20 °C Td, output range
−100 … +20 °C T
• Output in Td 1) and ppm
• DRYCAP polymer sensor with auto-calibration and sensor purge ensures long-term
stability
• Small size to fit in tight installations
• Two analog output channels, selectable from 0 … 20 mA / 4 … 20 mA and 0 … 5 V /
0 … 10 V
• Configurable alarm modes for analog outputs
• Digital output: RS-485
• Serial line connection also via USB serial interface cable
• Simultaneous use of analog and digital output possible
• Field check suitability with DM70 handheld meter
• Sampling cells with dierent installation options available as optional accessories
1) When the dew point is below 0 °C, the transmitter outputs frost point for T
d
d
9
1
2
3
4
5
DMT152 User Guide M210865EN-J
• LED cable option that enables a visual indication of transmitter status: LED lit when
measurement is frozen (for example, purge active), blinking for malfunction alarm
2.1.2 Transmitter Structure
When the transmitter is delivered, the filter is protected by a yellow transport protection cap
that keeps the sensor dry. The transport protection cap should be left on the transmitter
during storage. Remove the transport protection cap before installing the transmitter.
The transmitter body does not have user serviceable parts inside, and is not designed to be
opened. Opening the transmitter will void the warranty.
Figure 1 DMT152 Probe Parts
4-pin M8 connector I: analog output channels and operating power
1
2 4-pin M8 connector II (shown with protective cap): digital output (RS-485) and operating
power
3 Tightening nut (30 mm)
4 Connection thread, alternatives:
• ISO G1/2"
• NPT 1/2"
• UNF 3/4"-16 2A
5 DRYCAP sensor protected with stainless steel mesh filter (see Changing the Filter
When installing a DMT152 transmitter with ISO or UNF thread, use a sealing ring to achieve a
tight installation. Three copper sealing rings are provided with the transmitter, and more can
be ordered from Vaisala. Note that the sealing rings for ISO and UNF threads are dierent. See
Spare Parts and Accessories (page 63).
10
• UNF 5/8"-18
(page 53))
Chapter 2 – Product Overview
Do not use a sealing ring with the NPT thread. Instead, seal the thread using PTFE
tape or PTFE sealant paste.
2.1.3 Safety
This product has been tested for safety. Note the following precautions:
CAUTION!
product or lead to malfunction.
CAUTION!
and is not designed to be opened. Opening the transmitter will void the
warranty.
Do not modify the unit. Improper modification can damage the
The transmitter body does not have user serviceable parts inside,
2.1.4 ESD Protection
Electrostatic Discharge (ESD) can cause immediate or latent damage to electronic circuits.
Vaisala products are adequately protected against ESD for their intended use. However, it is
possible to damage the product by delivering an electrostatic discharge when touching,
removing or inserting any objects inside the equipment housing.
Avoid touching component contacts or connectors when working with the device.
2.1.5 Regulatory Compliances
This product is in conformity with the provisions of the following EU directives:
• EMC-Directive
• RoHS-Directive
Conformity is shown by compliance with the following standards:
• EN 61326-1: Electrical equipment for measurement, control, and laboratory use – EMC
requirements – for use in industrial locations.
• EN 550022: Information technology equipment – Radio disturbance characteristics –
Limits and methods of measurement
11
DMT152 User Guide M210865EN-J
3. Functional Description
3.1 Advanced DRYCAP Technology
Dew point transmitter DMT152 utilizes an advanced, patented measurement technology to
ensure accurate measurement with excellent long-term stability. This results in very low
maintenance requirements for the transmitter. The lasting performance is achieved with
microprocessor technology and software that automatically performs self-diagnostic functions
in addition to the normal dew point measurement. The self-diagnostic procedures that are
conducted are called auto-calibration, sensor purge, and sensor warming.
3.1.1 Auto-Calibration
The auto-calibration feature of the DMT152 transmitter is an automatic procedure that greatly
reduces the possible drift in the dry end of the dew point measurement.
Auto-calibration is performed:
• at 45-minute intervals
• at shorter intervals if Td is near the dry end of the measurement range
• when the transmitter is powered up
• when the measured environment changes rapidly.
During auto-calibration the sensor is warmed for a short period (< 1 min) and the sensor
capacitance values are evaluated at the elevated temperature. The possible dry end drift is
then corrected to correspond to the calibrated values. Measurement and output remain active
during auto-calibration.
Auto-calibration is carried out only if several criteria for the measurement environment are
fulfilled. This ensures the reliability of the adjustments, and maintains the excellent long-term
stability.
3.1.2 Sensor Purge
Sensor purge is also an automatic procedure that minimizes the drift at the wet end readings
of the dew point measurement. Sensor purge is performed once a week or when the power is
switched on. The sensor is heated for several minutes, which will then evaporate all excess
molecules out of the sensor polymer. This, together with the auto-calibration, results in a very
small drift. The measurement output of the transmitter is frozen to the last measured value for
the duration of the sensor purge.
12
Chapter 4 – Installation
4. Installation
4.1 Selecting the Location
It is important that the conditions at the point of installation represent well the gas to be
measured. Temperature changes do not aect the dew point measurement, but pressure
changes will have an eect on the measurement. All leaks in the system must be eliminated to
avoid ambient humidity aecting the measurement.
Direct installation to the measured gas is the recommended installation method if the
temperature of the gas is suitable for DMT152 and no additional filtering is needed due to very
dusty or oily gas. Oil as such is not harmful for the DRYCAP sensor, but response time may be
slower if there are oil particles in the system, or if oil is collected to the filter over a longer
period of time. The maximum measurement pressure is 50 bara / 725 psia (absolute pressure)
for direct measurement.
If the gas temperature is higher than the specified maximum operating temperature of the
transmitter, gas sampling and cooling it to ambient temperature (for example, 10 °C / 18 °F) is
recommended. Note that the dew point temperature must be clearly lower than the ambient
temperature to avoid condensation in the sampling line. Sampling from the process is easy by
using Vaisala sampling cell options; see Sampling Accessories (page 21).
DMT152 is light in weight, which means that it can be installed in a sample pipeline in the
sampling cells without the need for any additional mechanical support.
4.2
Installing the Transmitter
Figure 2 DMT152 Installed Directly to Pipeline (Max. 50 bar)
13
30 mm
DMT152 User Guide M210865EN-J
After selecting a suitable measurement location, install the transmitter as instructed here.
1. Remove the yellow transport protection cap from the transmitter. Do not touch the filter
with your hands.
2. Prepare the sealing of the connection:
a. If the transmitter has a parallel ISO G1/2" thread or UNF 3/4"-16 thread, place the
sealing ring at the base of the thread. Always use a new sealing ring; do not reuse a
previously installed one.
b. If the transmitter has an NPT 1/2" thread, do not use the sealing ring. Instead, apply
PTFE tape or suitable sealant paste to the thread. Follow the application instructions
of the paste.
3. Make sure that the threads on the mounting point are of the correct type, and fasten the
transmitter to the measurement point. Use your hands to turn the probe until it feels tight.
Do not use force at this point, and check that the sealing ring (if used) remains centered.
4. Use a 30 mm wrench to tighten the connection to 25 Nm. If you do not have a 30 mm
wrench, use a 1 3/16" wrench or an adjustable wrench.
CAUTION!
NOT apply force to other points in the probe body.
Only tighten the probe from the 30 mm tightening nut. Do
14
Chapter 4 – Installation
5. Connect the wires of the connection cable. When using cables provided with DMT152, see
Wiring (page 15) and Power Supply Requirements (page 19).
6. Plug in the cable to the transmitter. Be sure to use the correct connector; see Wiring
(page 15).
7. Cover the unused connector on the transmitter with the rubber plug that is attached to
the transmitter.
8. Turn on the power supply. DMT152 performs self-diagnostics at startup, and the output is
frozen for several minutes. The transmitter will output an approximated reading after one
minute, but accurate measurement will only be available after the startup procedure is
complete.
Normal operation is typically achieved in 10 … 15 minutes. If the measurement environment
changes during the startup, the startup may take up to 15 minutes.
The transmitter always performs the self-diagnostic procedure and sensor purge
when starting up. Keep the transmitter continuously powered to optimize its
measurement performance and availability.
4.3 Wiring
Table 4 Standard Wiring Pinouts and Wire Colors
Pin Connector I Connector II Wire Color
1 VDC supply+ VDC supply+ Brown
2 Signal Ch 1+ RS-485 - / B White
3 GND GND Blue
4 Signal Ch 2+ / LED RS-485 + / A Black
15
1
3
4
2
1
342
+
-
Vs
1
3
+
-
V/m A
4
+
-
V/m A
2
+
-
Vs
1
3
+ / A
4
2
RS485
- / B
DMT152 User Guide M210865EN-J
Figure 3 Connectors I and II
Figure 4 Connector Pinout
CAUTION!
one of them, but do not connect more than one supply voltage in permanent
installations. Temporary simultaneous use with the USB serial interface cable or
DM70 handheld dew point meter (which also provide operation power) is OK.
16
The power supply lines are internally connected. You can use either
4.3.1 Output Noise Minimization Option
1
3
4
2
1
342
3
+
-
V/m A
4
+
-
V/m A
2
+
-
Vs
1
3
+ / A
4
2
RS485
- / B
To minimize the output noise:
• Wire only the analog outputs (V/mA) to Port I
• Connect the power supply only to Port II
Avoid connecting the Port I and Port II grounds (pin #3) together
Chapter 4 – Installation
Figure 5 Output Noise Minimization Wiring Option
The wiring of pinouts 1 … 4 in ports I and II in the output minimization option is described in
the following table.
Table 5 Output Noise Minimization Wiring Option Pinouts and Wire Colors
Pin Connector I Connector II Wire Color
1 Not wired VDC supply+ Brown
2 Signal Ch 1+ RS-485 - / B White
3 GND GND Blue
4 Signal Ch 2+ / LED RS-485 + / A Black
17
DMT152 User Guide M210865EN-J
4.3.2 Connection Cables
The following connection cable options are available for DMT152:
• Unshielded cable with M8 female straight snap-on connector
• Shielded cable with M8 female straight threaded connector
• Unshielded cable with LED indicator for analog channel 2, 90° angled M8 female threaded
connector
• USB serial interface cable
For cable order codes, see Spare Parts and Accessories (page 63).
Avoid using long cables (over 2 m) with voltage output.
Table 6 Connection Cable Options
DMT152 Connection Cable Options
Cable with Snap-On Connector Cable with Threaded Connector
LED Cable USB Serial Interface Cable
18
Chapter 4 – Installation
4.3.3 Power Supply Requirements
The DMT152 transmitters are designed to operate with a supply voltage of 15 … 28 VDC
(voltage output version) or 21 … 28 VDC (current output version). When only the RS-485
output is used, 11 … 28 VDC is enough in typical measurement conditions.
When measuring in pressures 20 … 50 bara (290 … 725 psia) or in temperatures −40 … 0 °C
(−40 … 32 °F), a supply voltage of 21 … 28 VDC is required.
The power supply should maintain the voltage for all load conditions. Voltage fluctuations
must be smaller than 0.3 V, as continuous supply voltage fluctuation may interfere with the
auto-calibration function.
• If auto-calibration has failed due to voltage fluctuation, you can verify it using the STAT
command on the serial line. See Show Transmitter Status (page 33).
• If auto-calibration fails repeatedly, the Autocal error code will be activated. See Error
Codes (page 58).
Current consumption during normal operation is 20 mA. Consumption increases during autocalibration and sensor purge. The maximum current consumption is 220 mA pulsed current.
DMT152 can be powered by the MI70 indicator or the Vaisala USB cable. However,
the power supplied by these devices may not be enough for all functions of the
transmitter (for example, the current output).
If you are using a separate power supply in connector I, connect the power supply
first before connecting the USB cable or the MI70 indicator. The order is
important, since the transmitter will use the power supply that is connected first.
4.4 Loop-Powered Display
DMT152 can be connected to a loop-powered external LED display. The display provides a
reading of the output parameter. The display is powered by the 4 ... 20 mA current signal, so
there is no need for an external power supply.
Two models are available:
• Nokeval 301 (Vaisala order code 226476)
• Nokeval 302 (with alarm relays, Vaisala order code 234759)
The display is delivered at its default settings. Configure the display functions and scaling
according to the documentation delivered with the display. For a wiring example, see Figure 7
(page 20) .
The loop resistance of the display must be included in the loop resistance
calculation for the complete current loop. For the loop resistance of the display,
refer to the manufacturer’s documentation.
19
134
2
DMT152
Analog connector
4 ... 20 mA output
4 Ch2+ (black)
2 Ch1+ (white)
3 GND (blue)
1 VDC+ (brown)
Power supply
21 ... 28 VDC
301/302Nokeval
-
+
1
2
mA+
mA-
301/302Nokeval
1
2
mA+
mA-
DMT152 User Guide M210865EN-J
Figure 6 Nokeval 301 Loop-Powered Display
Figure 7 DMT152 Nokeval 301/302 Wiring Diagram
4.5
Sampling is needed when direct measurement of the air or gas is not possible or desirable.
This may be related to, for example, a high process temperature, protecting the sensor from
water spikes, the need to easily detach the instrument from a pressurized process without
running the whole process down, or wanting to make the measurement at a more convenient
location. To get a representative sample of the process gas and avoid error sources caused by
the sampling system, the following aspects should be considered:
20
Sampling from Process
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