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M212259EN-A
User Guide
Vaisala HUMICAPâ Humidity and Temperature
Module
HMM170
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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.
This product contains software developed
by Vaisala or third parties. Use of the
software is governed by license terms and
conditions included in the applicable
supply contract or, in the absence of
separate license terms and conditions, by
the General License Conditions of Vaisala
Group.
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Table of Contents
Table of Contents
1. About This Document................................................................................... 5
1.1 Version Information..........................................................................................5
1.2 Related Manuals................................................................................................5
1.3 Documentation Conventions...........................................................................5
1.4 Trademarks........................................................................................................ 6
2. Product Overview........................................................................................... 7
2.1 Introduction to HMM170...................................................................................7
2.2 Basic Features and Options.............................................................................7
2.3 Sensor Types..................................................................................................... 8
2.4 Output Parameters........................................................................................... 9
2.5 Probe Head...................................................................................................... 10
2.6 Chemical Purge............................................................................................... 10
2.7 Filter Types........................................................................................................11
2.8 LED Indicator.....................................................................................................11
2.9 Safety................................................................................................................12
2.9.1 ESD Protection..........................................................................................12
2.10 Regulatory Compliances.................................................................................13
3. Installation........................................................................................................14
3.1 Installing Module............................................................................................. 14
3.2 Installing Probe................................................................................................15
3.3 Vaisala Insight Software................................................................................. 16
3.3.1 Connecting to Insight Software..............................................................16
3.3.2 Configuration Options............................................................................. 16
4. Operation.......................................................................................................... 18
4.1 Using Service Port...........................................................................................18
4.1.1 Installing the Driver for the USB Service Cable....................................18
4.2 Modbus.............................................................................................................19
4.3 Operating with MI70 Indicator.......................................................................19
4.3.1 MI70 Indicator Parts............................................................................... 20
4.3.2 Connecting HMM170 to MI70 Indicator................................................ 20
4.3.3 Basic Display............................................................................................. 21
4.3.4 Graphical Display......................................................................................21
4.3.5 Main Menu................................................................................................ 22
4.3.6 Holding and Saving the Display.............................................................22
4.3.7 Recording Data........................................................................................23
5. Maintenance....................................................................................................24
5.1 Cleaning Probe............................................................................................... 24
5.2 Replacing Filter...............................................................................................24
5.3 Calibration and Adjustment.......................................................................... 25
5.3.1 Adjustment Points and Requirements..................................................26
5.3.2 Adjusting Measurement with Insight Software...................................26
5.3.3 Calibration and Adjustment Using MI70...............................................27
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HMM170 User Guide M212259EN-A
6. Technical Data................................................................................................29
6.1 HMM170 Specifications.................................................................................. 29
6.2 Spare Parts and Accessories......................................................................... 32
Appendix A: Modbus Reference................................................................. 33
A.1 Default Communication Settings................................................................. 33
A.2 Function Codes...............................................................................................33
A.3 Data Encoding.................................................................................................33
A.3.1 32-Bit Floating Point or Integer Format...............................................34
A.3.2 16-Bit Integer Format............................................................................. 34
A.4 Modbus Registers...........................................................................................34
A.4.1 Measurement Data Registers.................................................................35
A.4.2 Configuration Registers..........................................................................37
A.4.3 Device Identification Objects..................................................................41
A.4.4 Test Value Registers................................................................................. 41
A.4.5 Modbus Communication Examples...................................................... 42
Warranty............................................................................................................45
Technical Support........................................................................................... 45
Recycling...........................................................................................................45
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List of Figures
Figure 1 HMM170 Probe Head Dimensions................................................................ 10
Figure 2 HMM170 Component Board...........................................................................14
Figure 3 HMM170 Probe Installation.............................................................................15
Figure 4 Connecting Module to Insight.......................................................................16
Figure 5 MI70 Indicator Parts........................................................................................20
Figure 6 MI70 Basic Display............................................................................................21
Figure 7 Recording/Viewing Menu..............................................................................23
Figure 8 Accuracy over Temperature Range in Temperature Measurement... 30
Figure 9 Probe Head Dimensions..................................................................................31
Figure 10 Component Board Dimensions.....................................................................31
List of Figures
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HMM170 User Guide M212259EN-A
List of Tables
Table 1 Document Versions (in English).......................................................................5
Table 2 Related Manuals....................................................................................................5
Table 3 HMM170 Sensor Types.........................................................................................8
Table 4 Availability of Output Parameters................................................................... 9
Table 5 Filter Types and Properties...............................................................................11
Table 6 LED Indicator States...........................................................................................12
Table 7 Measurement Performance.............................................................................29
Table 8 Operating Environment................................................................................... 30
Table 9 Inputs and Outputs........................................................................................... 30
Table 10 Spare Parts and Accessories...........................................................................32
Table 11 Default Modbus Serial Communication Settings.......................................33
Table 12 Modbus Function Codes...................................................................................33
Table 13 16-bit Signed Integer Format Details........................................................... 34
Table 14 Modbus Measurement Data Registers (Read-Only).................................35
Table 15 Modbus Configuration Data Registers (Writable).....................................37
Table 16 Device Identification Objects.......................................................................... 41
Table 17 Modbus Test Registers (Read-Only)..............................................................41
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Chapter 1 – About This Document
1. About This Document
1.1 Version Information
This document provides instructions for installing, operating, and maintaining Vaisala
HUMICAPâ Humidity and Temperature Module HMM170.
Table 1 Document Versions (in English)
Document Code Date Description
M212259EN-A June 2019 First version.
1.2 Related Manuals
Table 2 Related Manuals
Document Code Name
M212260EN HMM170 Quick 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.
Note highlights important information on using the product.
Tip gives information for using the product more eciently.
Warning alerts you to a serious hazard. If you do not read and
Caution warns you of a potential hazard. If you do not read and
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HMM170 User Guide M212259EN-A
Lists tools needed to perform the task.
Indicates that you need to take some notes during the task.
1.4 Trademarks
Vaisalaâ and HUMICAPâ are registered trademarks 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.
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Chapter 2 – Product Overview
2. Product Overview
2.1 Introduction to HMM170
Vaisala HUMICAPâ Humidity and Temperature Module HMM170 is an open frame OEM module
for integration into demanding environmental chambers and harsh conditions. The module
provides a digital RS-485/Modbus RTU output and three freely configurable analog output
channels. The module provides relative humidity, temperature, dew point, and other calculated
parameters.
HMM170 probe covers the full temperature range -70 ... +180 °C (-94 ... +356 °F) used in
climate chambers and the whole humidity range up to condensation. The small probe and
compact component board oer easy and flexible installation. The probe cable options (2, 5,
or 10 m (6.5, 16.4, or 32.8 ft)) oer excellent cost optimization and flexibility to any OEM
application. By ordering HMM170 with the appropriate sensor, you can use the module in
environments that are frequently sterilized with vaporized hydrogen peroxide (H2O2) or to
measure humidity in oil medium, for example, for transformer and engine monitoring
applications.
The latest general purpose HUMICAPâ R2 sensor has an improved corrosion resistance. The
sensor can tolerate typical chemicals, such as cleaning agents used in climate chambers. The
automatic sensor chemical purge function keeps the sensor clean from typical chemical fumes
and the additional probe warming function prevents condensation. In case HMM170 gets in
contact with water, the automatic heating rapidly dries the sensor to enable fast and accurate
humidity measurement.
HMM170 is easy to install and convenient to use. It provides both digital and analog outputs for
multiple needs. An integrated service port enables a quick and simple way to configure, check,
and calibrate the module with the help of a USB cable and Vaisala Insight software.
2.2
Basic Features and Options
• Three humidity sensor types:
• Vaisala HUMICAPâ R2C (general use)
• Vaisala HUMICAPâ 180VC (for H2O2 use)
• Vaisala HUMICAPâ 180L2 (for moisture in oil)
• Sensor purge provides superior chemical resistance
• Probe and sensor warming functions minimize condensation on probe
• Analog output options:
• 0/4 ... 20 mA
• 0/1 ... 5 V
• 0 ... 5/10 V
• Probe cable lengths:
• 2, 5, or 10 m (6.5, 16.4, or 32.8 ft)
• Various filter types
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HMM170 User Guide M212259EN-A
• Service port for maintenance
• Supports Vaisala MI70 Handheld Measurement Indicator
• Optional USB cable for easy connection to Vaisala Insight software for configuration,
diagnostics, and temporary online monitoring
2.3 Sensor Types
HMM170 is available with three dierent sensor types.
Table 3 HMM170 Sensor Types
Sensor Type Description
HUMICAPâ R2C A general purpose industrial humidity sensor with high humidity
HUMICAPâ 180L2 A sensor that is optimized for measurement of humidity in oil
HUMICAPâ 180VC A composite humidity sensor with catalytic surface for use in
durability, good long term stability, and good tolerance against
chemical exposure.
medium. It has good tolerance against chemicals and moderate
humidity durability.
The HUMICAPâ 180L2 sensor measures moisture in oil in terms
of the water activity (aw) and temperature (T). Water activity
indicates directly whether there is a risk of free water formation.
The measurement is also independent of oil type and age. In
addition to water activity, the HMM170 can output ppm, the
average mass concentration of water in oil.
The HUMICAPâ 180L2 sensor does not support probe heating or
chemical purge.
applications where the sensor is exposed to H2O2 (hydrogen
peroxide).
Catalytic HUMICAPâ 180VC sensor is a good choice when you
want to measure RH between bio-decontamination cycles and
you are not interested in saturation level of the air mixture during
the bio-decontamination phase. Catalytic layer protects the
sensor during the bio-decontamination phase. Catalytic layer
catalyzes H2O2 into water vapor and oxygen. Therefore, the
sensing polymer detects only water vapor and shows correct
Relative Humidity value.
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Chapter 2 – Product Overview
2.4 Output Parameters
Output parameter is available
Value of output parameter is locked unless temperature is written to register 0334
external source
Value of output parameter is locked
Output parameter is not valid for sensor type
Table 4 Availability of Output Parameters
from an
hex
Output Parameter HUMICAPâ R2C and 180VC Sensor HUMICAPâ
Normal
Operation
Relative humidity
Temperature
Dew point temperature
Dew/frost point temperature
Dew/frost point temperature at 1 atm
Dew point temperature at 1 atm
Absolute humidity
Mixing ratio
Wet-bulb temperature
Water concentration
Water vapor pressure
Water vapor saturation pressure
Enthalpy
Water activity
Dew point temperature dierence
Absolute humidity at NTP
Water concentration in oil
Relative saturation
Water mass fraction
During
Heating
During
Purge
180L2
Sensor
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mm
[in]
Ø 12
[0.47]
99.5 [3.92]
79.5 [3.13]
37.5 [1.48]
Groove for
lock ring
Ø 12
[0.47]
Ø 5
[0.2]
HMM170 User Guide M212259EN-A
2.5 Probe Head
Figure 1 HMM170 Probe Head Dimensions
HMM170 is designed for applications that involve constant high humidity or rapid changes in
humidity, such as drying and test chambers, combustion air, and other humidifiers and
meteorological measurements, where measurement performance and chemical tolerance are
essential.
• Temperature measurement range −70 ... +180 °C (−94 ... +356 °F)
• Operating temperature range for probe −70 ... +180 °C (−94 ... +356 °F)
• Probe and sensor warming functions minimize condensation on probe
• Vapor and pressure proof construction
• Stainless steel mesh filter standard in delivery
Probe Heating
HMM170 supports probe heating. Probe heating heats up not only the sensor, but the entire
probe head. When probe temperature is heated above dew point temperature, condensation
on the probe can be avoided while measuring the dew point temperature of the process.
Probe heating is normally disabled. If you select to enable probe heating, output parameters
that are dependent on temperature measurement (such as relative humidity) are disabled,
unless the true temperature of the measured environment is updated to the temperature
compensation register of the probe from another measurement instrument. Output
parameters that can be measured or calculated without this external temperature information
(such as dew point temperature) are available even without the temperature input.
2.6
Chemical Purge
Chemical purge is a 4-minute process where the sensors are heated to remove possible
contamination. The purge is essential for the long-term performance and accuracy of the
probe. During the purge, measurements are not available.
Depending on the selected sensor, the purge is automatically performed:
• At probe start-up
• At probe start-up and after every 24 hours
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Chapter 2 – Product Overview
The HUMICAPâ 180L2 sensor does not support chemical purge.
You can trigger a purge manually at any time with Vaisala Insight software or Modbus, or by
closing the external purge trigger on the component board.
2.7 Filter Types
All filters available for the HMM170 are 12 mm (0.47 in) in diameter. Note the operational
temperature range of each filter.
Table 5 Filter Types and Properties
Filter Type Diameter Pore Size Temperature Range
PPS plastic grid
with stainless steel
net
12 mm
(0.47 in)
15 µm −70 ... +180 °C
(−94 ... +356 °F)
Stainless steel
sintered
Stainless steel
filter for moisture
in oil
Porous PTFE
(general purpose)
More Information
‣
Spare Parts and Accessories (page 32)
2.8
LED Indicator
12 mm
(0.47 in)
12 mm
(0.47 in)
12 mm
(0.47 in)
38 µm −70 ... +180 °C
(−94 ... +356 °F)
3.15 mm −70 ... +180 °C
(−94 ... +356 °F)
8 µm −70 ... +180 °C
(−94 ... +356 °F)
The LED indicator on the component board provides a visual indication of the status of the
HMM170. The alarm LED functionality is preset at the factory according to order form.
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HMM170 User Guide M212259EN-A
Table 6 LED Indicator States
LED Color Meaning
Not lit Module is powered o or LED functionality is disabled.
Green Module is powered on and ready for operation.
Green and blinking Module is powering up or communicating with the probe.
Red Module is in error state.
You can use Vaisala Insight software to disable the LED indicator.
2.9 Safety
This product has been tested for safety. Note the following precautions:
WARNING!
to minimize shock hazard.
CAUTION!
documentation. Improper modification may lead to safety hazards, equipment
damage, failure to perform according to specification, or decreased equipment
lifetime.
Ground the product and verify installation grounding periodically
Do not modify the unit or use it in ways not described in the
2.9.1 ESD Protection
Electrostatic Discharge (ESD) can damage electronic circuits. Vaisala products are adequately
protected against ESD for their intended use. However, it is possible to damage the product by
delivering electrostatic discharges when touching, removing, or inserting any objects in the
equipment housing.
To avoid delivering high static voltages to the product:
• Handle ESD-sensitive components on a properly grounded and protected ESD workbench
or by grounding yourself to the equipment chassis with a wrist strap and a resistive
connection cord.
• If you are unable to take either precaution, touch a conductive part of the equipment
chassis with your other hand before touching ESD-sensitive components.
• Hold component boards by the edges and avoid touching component contacts.
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Chapter 2 – Product Overview
2.10 Regulatory Compliances
HMM170 is in conformity with the provisions of the following EU directive(s):
• RoHS Directive
• WEEE Directive
Electromagnetic compatibility of HMM170 has been tested according to the following product
family standard:
EN61326-1 Electrical equipment for measurement, control and laboratory use - EMC
requirements - for use in light industrial environments.
The Electrostatic Discharge test (EN 61000-4-2) was not applied to the open frame module. In
the final product the module PC-board should be installed in a user restricted location /
enclosure for continued ESD protection.
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SERVICE
D+ D− GND
GND
+ VIN − + CH1 − + CH2 − + CH3 − PURGE
1 2
3
4
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HMM170 User Guide M212259EN-A
3. Installation
3.1 Installing Module
The measurement probe with cable is attached to the component board at
Vaisala. Do not disconnect and reconnect the cable.
1. Attach the module securely using the mounting holes on the corners of the component
board.
CAUTION!
other applicable standos to attach the module to the minimum height of
6 mm (0.24 in).
2. Make sure that the module has a good earth connection from the plated mounting hole.
If you are replacing HMM100, the mounting holes in the grey area are compatible
with HMM100.
The module is delivered with a set of standos. Use these or
Figure 2 HMM170 Component Board
1 Power input (12 ... 35 VDC)
2 Active analog outputs (0/4 ... 20 mA,
1 ... 5 V, 0 ... 5/10 V)
3 External purge trigger (closing
activates purge)
4 Grounding point
5 LED Indicator
6 Digital RS-485 (Modbus) port
7 Service port (temporary connection,
MI70, USB cable with Vaisala Insight
Software)
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Chapter 3 – Installation
3.2 Installing Probe
In humidity measurement and especially in calibration it is essential that temperature of the
probe and measuring environment is the same. Even a small dierence in temperature
between the environment and the probe causes an error. For example, if the temperature is
+20 °C (68 °F) and the relative humidity 100 %RH, a dierence of ±1 °C (±1.8 °F) between the
environment and the probe causes an error of ±6 %RH.
Figure 3 HMM170 Probe Installation
1. Select the mounting location for the probe.
• The probe should be entirely in the measurement environment, with sucient
distance to the outer walls of the chamber or duct. Air should flow freely around the
probe.
• The probe location should represent well the environmental or process conditions,
and it should be as clean as possible.
2. Mount the probe head horizontally to prevent any water condensing on the probe head
from running to the sensors.
3. Let the cable hang loosely to prevent condensed water from running along the cable to
the probe head.
4. Seal the cable pass-through using the Vaisala installation accessories.
If the temperature of the measured environment diers greatly from ambient
temperature, the whole probe and preferably plenty of cable must be inside the
process. This prevents measurement inaccuracy caused by heat conduction along
the cable.
More Information
‣
Spare Parts and Accessories (page 32)
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SERVICE
D+ D− GND
GND
+ VIN − + CH1 − + CH2 − + CH3 − PURGE
HMM170 User Guide M212259EN-A
3.3 Vaisala Insight Software
Vaisala Insight software is a configuration software for Indigo-compatible devices. The
supported operating systems are Windows 7 (64-bit), Windows 8.1 (64-bit), and Windows 10
(64-bit).
With the Insight software, you can:
• See device information and status
• See real-time measurement
• Calibrate and adjust the device
• Configure device features such as measurement filtering, chemical purge, heating, and
serial communication
Download Vaisala Insight software at www.vaisala.com/insight.
HMM170 can be connected to Vaisala Insight software using a Vaisala USB cable (no. 219690).
3.3.1 Connecting to Insight Software
• Computer with Vaisala Insight software installed
• USB connection cable (order code 219690)
Figure 4 Connecting Module to Insight
1. Open the Insight software.
2. Connect the USB cable to a free USB port on the PC.
3. Connect the USB cable to the service port of the module. The USB cable powers up the
module.
3.3.2 Configuration Options
Select > Configure Device to access configuration options in Insight software.
The available configuration options correspond to the Modbus configuration registers. Insight
software is the recommended way to change the device configuration.
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You can restore the device back to its default settings using the Factory Default
Settings > Restore Settings function. Doing this will also clear any user
adjustment and restore the latest factory calibration.
More Information
‣
Modbus Reference (page 33)
Chapter 3 – Installation
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HMM170 User Guide M212259EN-A
4. Operation
4.1 Using Service Port
The HMM170 has a 4-pin M8 service port connector on the component board. Vaisala oers an
optional USB cable (Vaisala order code 219690) for connecting the module to your PC.
The service port is intended for short-term use such as calibration. For permanent
installation, use the permanent digital Modbus and/or analog terminals.
If you have not used the HMM170 USB cable before, first install the driver.
More Information
‣
Installing the Driver for the USB Service Cable (page 18)
4.1.1 Installing the Driver for the USB Service Cable
Only Windowsâ operating systems are supported by the driver of the USB
service cable.
1. Connect the USB service cable to a USB port on your computer. Windowsâ detects the
new device and installs the appropriate driver.
2. Open Devices and Printers from the Windowsâ Start menu. Use search to find it if
necessary (search for "devices").
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Chapter 4 – Operation
3. Locate the cable in the list of devices:
• If the device is listed as Vaisala USB Device with a COM port number in brackets, the
cable is ready for use. Note the COM port number, you will need it later.
• If the device is listed as Vaisala USB Instrument Cable without a COM port number
listed, you must install the driver manually.
4. To install the driver manually:
a. Disconnect the USB service cable from the computer.
b. Download the Vaisala USB driver at http://www.vaisala.com/software (select the
appropriate USB Instrument Driver Setup for your cable).
c. Run the USB driver installation program Vaisala USB Device Driver
Setup.exe. Accept the installation defaults.
d. Go back to step 1 and verify that the driver installation works as expected.
4.2
Modbus
The module can be accessed using the Modbus serial communication protocol. The supported
Modbus variant is Modbus RTU (Serial Modbus) over RS-485 interface.
More Information
‣
Modbus Reference (page 33)
4.3
Operating with MI70 Indicator
HMM170 is compatible with the MI70 handheld indicator. The MI70 indicator is a convenient
service tool for viewing the measurement readings, adjusting the environmental compensation
settings, and performing calibration and 1- or 2-point adjustment. MI70 is compatible with
various Vaisala probes, transmitters, and modules.
You can use the MI70 indicator for the following tasks with HMM170:
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HMM170 User Guide M212259EN-A
• Measurement viewing and logging
• Calibration and 1- or 2-point adjustment
• Viewing information about the module
To connect HMM170 to an MI70 indicator, you need the optional MI70 connection
cable (Vaisala order code 219980SP).
4.3.1 MI70 Indicator Parts
Figure 5 MI70 Indicator Parts
1 Charger socket
2 Function key shortcut buttons . The
functions change according to what
you are doing with the indicator.
3 Arrow buttons:
Move up in a menu
Move down in a menu
Enter a sub-menu
Return to previous menu level
4 Power On/O button
5 Battery compartment at the back of
the indicator
6 Two 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 arrow buttons.
4.3.2 Connecting HMM170 to MI70 Indicator
• MI70 connection cable (Vaisala order code 219980SP)
1. If the MI70 indicator is on, turn it o.
2. Connect HMM170 to port I of the MI70 indicator using the MI70 connection cable.
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2
3 4 5
Chapter 4 – Operation
3. Turn on the MI70 indicator. MI70 detects the HMM170 and proceeds to show the
measurement screen. After a few seconds, MI70 will start to show valid measurement
results from the module.
4.3.3 Basic Display
Figure 6 MI70 Basic Display
1 Battery indicator. Shows current status (charge) of the battery.
2 Measured parameter and compensations (up to three items on display simultaneously).
You can change the shown items in Main menu > Display > Quantities and units.
3 Function key Graphic shows the readings as a curve.
4 Function key Hold/Save freezes the display and you can save the reading in the MI70
memory.
5 Function key Record is a quick access to the Recording/Viewing menu.
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.
4.3.4 Graphical Display
The graphical display shows you the measurements as a curve (the curve of the uppermost
quantity 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 quantities, press Next. To get the curves of all the
quantities, press Next until the text All appears, and then select All.
To zoom in and out, press the up/down arrow keys.
To move back and forward in the timeline, use the left/right arrow keys.
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HMM170 User Guide M212259EN-A
4.3.5 Main Menu
In the main menu, you can configure the MI70 settings and basic display options, view
information about the connected device, 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.
2. Press any arrow key, then select Open (must be pressed within 5 seconds or the
indicator returns to the basic display).
3. Move in the menus using the
4. Select an item with the button.
5. To return to the previous level, press .
6. To return to normal operation, press Exit.
buttons.
4.3.6 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
4. Select the saved display based on date and time by pressing the right arrow key.
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Chapter 4 – Operation
4.3.7 Recording Data
With MI70, you can record measurement data over a certain period at chosen intervals. These
recordings are saved in MI70 memory and are available even after MI70 is disconnected from
the module. To start recording, select the Record function key in the basic display, or navigate
to the recording menu: Main menu > Recording/Viewing > Record data.
Figure 7 Recording/Viewing Menu
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HMM170 User Guide M212259EN-A
5. Maintenance
5.1 Cleaning Probe
• Lint-free cloth
• Isopropyl alcohol (70 %)
Do not attempt to clean the sensors under the filter in any way.CAUTION!
1. Moisten a lint-free cloth with isopropyl alcohol (70%).
2. Wipe the probe head and cable with the lint-free cloth.
Do not spray anything directly on the probe head or immerse the probe head
in liquid, since that may deposit impurities on the sensors.
Do not wipe the filter: wiping the filter may block its pores and/or deposit
residue on the filter. If the filter is heavily contaminated, replace it.
3. After cleaning the probe, it is recommended to perform a chemical purge.
More Information
‣
Chemical Purge (page 10)
‣
Replacing Filter (page 24)
5.2
Replacing Filter
• New compatible filter
• Clean lint-free gloves
CAUTION!
the probe head carefully.
24
Without the filter in place, the sensor is easily damaged – handle
Page 27
Chapter 5 – Maintenance
1. Put on clean gloves before touching the filter.
2. Turn the filter counter-clockwise to loosen it.
3. Remove the filter from the probe head. Be careful not to touch the sensor with the filter.
4. Install a new filter on the probe head. Tighten the filter properly (recommended force
5 Nm).
More Information
‣
Filter Types (page 11)
‣
Spare Parts and Accessories (page 32)
5.3 Calibration and Adjustment
The module is fully calibrated and adjusted as shipped from the factory. To maintain the
accuracy of the measurement, calibrate and adjust the module as needed. Typical calibration
interval is one year, but depending on the application it may be necessary to check the
accuracy more frequently.
When adjustment is necessary, you can have Vaisala calibrate and adjust the module. To order
calibration services from Vaisala, visit store.vaisala.com. You can also do the adjustment
yourself using the Insight software.
WARNING!
has not been exposed to dangerous contamination, and is safe to handle
without special precautions.
If you think the device is not measuring correctly, calibration and adjustment is
not the first thing to do. Check the following first:
• Make sure nothing is interfering with the measurement: heat sources,
temperature dierences, or condensation.
• Check that there is no moisture on the probe. If the sensor has become wet,
wait for it to dry.
• Always wait for the measurement to stabilize.
Calibration means comparing the measurement output of the device to a known
reference, such as a known environment in a calibration chamber or the output of
a reference instrument. Correcting the reading of the device so that it measures
accurately is referred to as adjustment.
When returning a product for calibration or repair, make sure it
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HMM170 User Guide M212259EN-A
5.3.1 Adjustment Points and Requirements
You can adjust the humidity measurement in 1 ... 5 points, and temperature measurement in 1 ...
2 points. Note the following:
• Humidity adjustment in more than two points is available when using Insight software in
Advanced Mode.
• If you are adjusting in more than one humidity point, make sure the first two points are at
least 10 %RH apart.
• The module will reject adjustments that are too large, that is, greater than 10 %RH for
humidity and 0.5 °C (0.9 °F) for temperature. If the module appears to need such a large
correction, perform a sensor purge and repeat the adjustment procedure. Make sure the
measurement has stabilized and the reference environment is reliable. If the required
adjustment is still too large, the module needs to be serviced by Vaisala.
When adjustment of humidity measurement is necessary, Vaisala recommends
adjusting in two points, 11 %RH and 75 %RH. These humidities can be produced
using the Vaisala HMK15 Humidity Calibrator.
Adjustment of temperature measurement is typically not necessary.
5.3.2 Adjusting Measurement with Insight Software
• Computer with Windows operating system and Vaisala Insight software
installed
• Vaisala USB cable 219690 for connecting the module
• Reference environment(s) for producing the desired humidity and/or
temperature
This procedure can be used to adjust the module's humidity or temperature measurement. If
you want to adjust both, repeat the procedure.
Because stabilization of temperature and humidity takes time, you should expect the
adjustment procedure to take at least 30 minutes for each adjustment point.
1. Connect the module to Insight. See Connecting to Insight Software (page 16).
2. If you intend to adjust humidity measurement, first select
chemical purge to condition the sensor. Wait a few minutes for purge to complete.
3. Select > Calibrate > Yes to switch the module to calibration mode.
In calibration mode, the device will not use functions that may interfere with calibration
and adjustment.
4. Select the type of adjustment to perform: RH adjustment or T adjustment.
26
> Purge to perform a
Page 29
Chapter 5 – Maintenance
5. Define the needed adjustment for the first measurement point:
a. Insert the probe head in the reference environment for the first calibration point.
b. Wait for the measurement to stabilize fully.
c. Click the Reference value, point 1 text box and enter the reference value of the
calibration point. Press ENTER or click outside the text box when done.
d. The module automatically enters the measured values for the calibration point.
6. If you want to adjust in more than one point, repeat step 5 for all desired calibration
points.
You can adjust humidity measurement in up to five points when Insight is set
to Advanced mode.
7. Select
8. Check the message that appears at the top of the screen. If the message indicates that
9. Select the Calibration information tab and update the Calibration date and Calibration
10. Select Close > Yes to exit the calibration mode.
Activate adjustment > Yes to store the adjustment in the module.
the adjustment is activated successfully, your adjustment is stored in the module.
text.
5.3.3 Calibration and Adjustment Using MI70
• Vaisala MI70 Measurement Indicator
• Connection cable for MI70 Measurement Indicator (Vaisala item 219980SP)
• Reference environments for the desired calibration points
You can calibrate and adjust the HMM170 module in 1 or 2 points using the MI70 indicator. For a
2-point calibration, you need two reference environments. Note that when performing a 2point RH calibration, the first point requires a < 50% RH humidity reference, and the second
point must be > 50% RH. The dierence between the two humidity references must be at least
30% RH.
Using the MI70 indicator, you can also do the 1-point calibration so that you compare the
reading of the module to any MI70-compatible Vaisala device that provides the same
measurement parameter.
1. Connect the HMM170 to port I of the MI70 indicator using the handheld connection cable.
2. If you want to calibrate by comparing to the reading of a reference probe, connect it to
port II of the MI70 indicator.
3. Turn on the MI70 indicator.
4. Start the adjustment sequence from Main menu > Functions > Adjustments. If you have
another device connected, make sure to start the adjustment sequence for device I.
27
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HMM170 User Guide M212259EN-A
5. MI70 notifies you that automatic power o is disabled during adjustment mode. Select
OK to acknowledge.
6. Select RH or T parameter for adjustment and select OK. This procedure assumes you are
adjusting relative humidity, but the same principles apply for temperature adjustment.
7. Insert the probe to be calibrated in the reference environment. If you are calibrating
relative humidity using two reference environments, use the dry reference first. If you have
a reference probe, insert that in the same environment. If you are comparing against the
reading of a reference probe, you can also use the ambient condition as the reference
environment, as long as its conditions are stable.
8. Wait for the measurement to stabilize. You can follow the stabilization from the GRAPH
display. Select ADJUST when the reading is stabilized in the reference.
9. To perform the adjustment using one reference environment (1-point adjustment),
perform these steps:
a. Select 1-point adjustment > SELECT > OK.
b. When the measurement is stable, select READY.
c. Give the reference RH value by using the arrow buttons and select OK.
d. To confirm the adjustment, select YES. If you select NO, you return to the adjustment
mode display and no changes are made.
e. Continue from step 12.
10. To perform the adjustment using two reference environments (two-point adjustment),
perform these steps:
a. Select 2-point adjustment > SELECT > OK.
b. When the measurement is stable, select READY.
c. Give the reference RH value by using the arrow buttons and select OK.
d. Insert the probe to be calibrated in the second reference environment.
e. When the measurement is stable, select READY.
f. Give the reference RH value by using the arrow buttons and select OK.
g. To confirm the adjustment, select YES. If you select NO, you return to the adjustment
mode display and no changes are made.
h. Continue from step 12.
11. To perform the adjustment using a reference probe, perform these steps:
a. Select To same as RH[II].
b. To confirm the adjustment, select YES. If you select NO, you return to the adjustment
mode display and no changes are made.
12. Calibration and adjustment is now completed. Select BACK to exit the adjustment mode
and EXIT to return to the basic display.
13. Disconnect the module from the MI70 indicator.
28
Page 31
Chapter 6 – Technical Data
6. Technical Data
6.1 HMM170 Specifications
Table 7 Measurement Performance
Property Description/Value
Relative Humidity
Measurement range 0 ... 100 %RH
Accuracy
at +15 ... +25 °C (59 ... +77 °F) ±1 %RH (0 ... 90 %RH)
at -20 ... +40 °C (-4 ... +104 °F) ± (1.0 + 0.008 × reading) %RH
at -40 ... +180 °C (-40 ... +356 °F) ± (1.5 + 0.015 × reading) %RH
Factory calibration uncertainty at
+20 °C (+68 °F)
Humidity sensor types Vaisala HUMICAPâ R2C
Response time (90 %) at +20 °C (+68 °F) in 0.1 m/s air flow with Vaisala HUMICAPâ R2C sensor:
with steel netting filter
with sintered filter
Temperature
Measurement range -70 ... +180 °C (-94 ... +356 °F)
Temperature sensor Pt100 RTD Class F0.1 IEC 60751
Typical accuracy at +20 °C (+68 °F) ±0.2 °C (± 0.36 °F)
1)
±1.7 %RH (90 ... 100 %RH)
2)
±0.6 %RH (0 ... 40 %RH)
±1.0 %RH (40 ... 90 %RH)
±1.1 %RH (90 ... 95 %RH)
Vaisala HUMICAPâ 180L2
Vaisala HUMICAPâ 180VC
50 s
60 s
1) Including non-linearity, hysteresis and repeatability.
2) Defined as ±2 standard deviation limits. Small variations possible; see also calibration
certificate.
29
Page 32
°C
0
0-80 -60 -40 -20 20 40 60 80 100 120 140 160
180
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.1
0.2
0.3
0.4
0.5
0.6
0.7
°C
HMM170 User Guide M212259EN-A
Figure 8 Accuracy over Temperature Range in Temperature Measurement
Table 8 Operating Environment
Property Description/Value
Operating temperature for component board -40 ... +60 °C (-40 ... +140 °F)
Operating humidity range for component board 0 ... 100 %RH, non-condensing
Storage temperature -55 ... +80 °C (-67 ... +176 °F)
Operating pressure 0 ... 10 bar
Table 9 Inputs and Outputs
Property Description/Value
Three analog outputs (selectable and scalable) 0 ... 20 mA, 4 ... 20 mA
0 ... 1 V, 0 ... 5 V, 1 ... 5 V, or 0 ... 10 V
Typical accuracy of analog output at +20 °C
±0.05 % full scale
(+68 °F)
Typical temperature dependence of analog
0.005 %/˚C (0.003 %/°F) full scale
output
Digital output RS-485 serial, Modbus
Service port M8 connector for USB cable
Operating voltage 15 ... 35 VDC
Power Consumption
Analog outputs 12 mA (voltage)
50 mA (current)
30
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Property Description/Value
mm
[in]
Ø 12
[0.47]
99.5 [3.92]
79.5 [3.13]
37.5 [1.48]
Groove for
lock ring
Ø 12
[0.47]
Ø 5
[0.2]
SERVICE
D+ D− GND
GND
+ VIN − + CH1 − + CH2 − + CH3 − PURGE
87.4 [3.44]
81.4 [3.20]
32.4 [1.28]
58.3 [2.30]
21.8 [0.86]
68.3 [2.69]
mm
[in]
Chemical purge at 24 VDC +220 mA
Warmed probe at 24 VDC +240 mA
External load RL < 500 Ω
Start-up time 3 s at power-up
Maximum wire size
Figure 9 Probe Head Dimensions
0.5 ... 1.5 mm2 (AWG)
Chapter 6 – Technical Data
Figure 10 Component Board Dimensions
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HMM170 User Guide M212259EN-A
6.2 Spare Parts and Accessories
Table 10 Spare Parts and Accessories
Item Order Code
USB cable for PC connection 219690
MI70 connection cable 219980SP
Feedthrough HMP247CG
Swagelok NPT 1/2" adapter SWG12NPT12
Swagelok ISO 1/2" adapter SWG12ISO12
Duct installation kit for probe 210697
PPS Plastic grid and stainless steel netting DRW010281SP
Stainless steel sintered filter HM47280SP
Sintered PTFE filter with 20 μm pore size 219452SP
Stainless steel filter HM47453SP
32
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Appendix A – Modbus Reference
Appendix A. Modbus Reference
A.1 Default Communication Settings
Table 11 Default Modbus Serial Communication Settings
Property Description/Value
Serial bit rate 19200
Parity None
Number of data bits 8
Number of stop bits 2
Flow control None
Modbus device address 240
You can use up to ten probes on the same RS-485 line. You must configure each probe on the
line to have a dierent Modbus address.
A.2
Function Codes
Table 12 Modbus Function Codes
Function Code
(Decimal)
03 03
16 10
43 / 14 2B
Function Code
(Hexadecimal)
hex
hex
/ 0E
hex
hex
Name Notes
Read Holding
Registers
Write Multiple
Registers
Read Device
Identification
Class 0
Class 0
A.3 Data Encoding
In the data registers, the numeric values are available in one or two formats with separate
register addresses: 32-bit IEEE floating point format and/or 16-bit signed integer format.
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HMM170 User Guide M212259EN-A
A.3.1 32-Bit Floating Point or Integer Format
Least significant 16 bits of floating point or integer numbers are placed at the smaller Modbus
address as specified in Open Modbus TCP Specification, Release 1.0. This is also known as
"little-endian" or "Modicon" word order. Floating point values are represented in standard IEEE
32-bit floating point format.
Despite the specification, some Modbus masters may expect "big-endian" word
order (most significant word first). In such case, you must select "word-swapped"
floating point format in your Modbus master for the Modbus registers of the
device.
A "quiet NaN" value is returned for unavailable values. A quiet NaN is, for example,
7FC00000
; however, the master should understand any NaN value.
hex
A complete 32-bit floating point or integer value should be read and written in a
single Modbus transaction.
A.3.2 16-Bit Integer Format
Some 16-bit integer values in the data registers are scaled to include the necessary decimals.
The scaling factors for those values are shown in the register tables.
Table 13 16-bit Signed Integer Format Details
Value Description
0000
8002
8000
hex
hex
hex
… 7FFE
… FFFF
hex
hex
Value in range 0 … 32766
Value in range -32766 … -1 (2’s complement)
Value is not available (quiet NaN)
Some values may exceed the signed 16-bit range even in normal operation. To
access such values, use the floating point registers instead.
A.4 Modbus Registers
CAUTION!
addresses in actual Modbus messages (Modbus Protocol Data Unit (PDU) are in
hexadecimal and start from zero. Subtract 1 from the register number presented
in this manual to get the address used in the Modbus message (for example,
register number 1 corresponds to address 0
34
Registers are numbered in decimal, starting from 1. Register
in the actual Modbus message).
hex
Page 37
Appendix A – Modbus Reference
Accessing unavailable (temporarily missing) measurement data does not generate an
exception. “Unavailable” value (a quiet NaN for floating point data or 8000
for integer data)
hex
is returned instead. An exception is generated only for any access outside the applicable
register ranges.
A.4.1 Measurement Data Registers
Table 14 Modbus Measurement Data Registers (Read-Only)
Register
Number
(Decimal)
Floating Point Values
Address
(Hexadecimal)
1 0000
3 0002
7 0006
9 0008
11 000A
13 000C
15 000E
17 0010
19 0012
21 0014
23 0016
25 0018
27 001A
29 001C
31 001E
33 0020
35 0022
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
Register Description Data Format Metric Unit
Relative humidity 32-bit float %RH
Temperature 32-bit float °C
Dew point temperature 32-bit float °C
Dew/frost point
32-bit float °C
temperature
Dew/frost point
32-bit float °C
temperature at 1 atm
Dew point temperature
32-bit float °C
at 1 atm
Absolute humidity 32-bit float
g/m
3
Mixing ratio 32-bit float g/kg
Wet-bulb temperature 32-bit float °C
Water concentration 32-bit float ppm
v
Water vapor pressure 32-bit float hPa
Water vapor saturation
32-bit float hPa
pressure
Enthalpy 32-bit float kJ/kg
Water activity 32-bit float a
Dew point temperature
32-bit float °C
w
dierence
Absolute humidity at
32-bit float
g/m
3
NTP
Water concentration in
oil
32-bit float ppm
w
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HMM170 User Guide M212259EN-A
Register
Number
(Decimal)
Floating Point Values
Address
(Hexadecimal)
41 0028
65 0040
Integer Values
257 0100
258 0101
260 0103
261 0104
262 0105
263 0106
264 0107
265 0108
266 0109
267 010A
268 010B
269 010C
270 010D
271 010E
272 010F
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
Register Description Data Format Metric Unit
Relative saturation 32-bit float %
Water mass fraction 32-bit float ppm
Relative humidity 16-bit signed
w
%RH * 100
integer
Temperature 16-bit signed
°C * 100
integer
Dew point temperature 16-bit signed
°C * 100
integer
Dew/frost point
temperature
Dew/frost point
temperature at 1 atm
Dew point temperature
at 1 atm
Absolute humidity 16-bit signed
16-bit signed
integer
16-bit signed
integer
16-bit signed
integer
°C * 100
°C * 100
°C * 100
g/m3 * 100
integer
Mixing ratio 16-bit signed
g/kg * 100
integer
Wet-bulb temperature 16-bit signed
°C * 100
integer
Water vapor
concentration
Water vapor pressure 16-bit signed
16-bit signed
integer
ppm
v
hPa * 10
integer
Water vapor saturation
pressure
Enthalpy 16-bit signed
16-bit signed
integer
hPa * 10
kJ/kg * 100
integer
Water activity 16-bit signed
integer
Dew point temperature
dierence
16-bit signed
integer
a
w
°C * 10
36
Page 39
Integer Values
273 0110
274 0111
277 0114
289 0120
hex
hex
hex
hex
Absolute humidity at
NTP
Parts per million in oil 16-bit signed
Relative saturation 16-bit signed
Water mass fraction 16-bit signed
A.4.2 Configuration Registers
Table 15 Modbus Configuration Data Registers (Writable)
Appendix A – Modbus Reference
16-bit signed
g/m3 * 100
integer
ppm
integer
w
% * 100
integer
ppm
integer
w
Register
Number
(Decimal)
General
Register
Address
(Hexadecimal)
1287 0506
1289 0508
2561 0A00
hex
hex
hex
Register Description Data Format Unit / Valid
Extra heat on/o.
16-bit boolean 0 = O (default)
Enables heating of
humidity sensor when
Range
1 = On
close to saturation.
Measurement is disabled
for the duration of
heating and cooling.
Probe heating on/o.
When on, output
16-bit boolean 0 = O (default)
1 = On
parameters that depend
on temperature
measurement (for
example, relative
humidity) are disabled
unless temperature is
written to register
0334
from an external
hex
source.
User information Text Text string of 24
bytes in UTF-8
encoding
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HMM170 User Guide M212259EN-A
Compensation Setpoints
769 0300
hex
Pressure compensation
setpoint
32-bit float Unit: hPA
Default: 1013.25
hPa
821 0334
hex
Temperature
compensation setpoint. If
32-bit float Unit: °C
a value is written to this
register, the device uses
it instead of its own
temperature
measurement.
When probe heating is in
use, temperature must be
written to this register to
enable output
parameters that depend
on temperature
measurement (for
example, relative
humidity).
Purge
773 0304
hex
Purge interval 32-bit float Unit: min
10 ... 14400
1283 0502
hex
Interval purge on/o 16-bit boolean 0 = O
1 = On
1284 0503
hex
Startup purge on/o 16-bit boolean 0 = O
1 = On
38
Page 41
Filtering
795 031A
1281 0500
1282 0501
Communication
1537 0600
hex
hex
hex
hex
Appendix A – Modbus Reference
Measurement filtering
factor
32-bit float Range: 0.000 ...
1.000
1.000 = Reading
shows 100 % of
the most recent
measured value
(no filtering,
default).
0.01 ... 0.99 =
Reading shows
1 ... 99 % of the
most recent
measured value
and part of the
previous
reading
(filtering is
applied). For
example, "0.9"
means that the
filtered
measurement
reading = 90 %
of the most
recent
measured value
+ 10 % of the
previous
reading.
Filtering on/o 16-bit boolean 0 = O
1 = On
Enable or disable
measurement filtering
using the user-defined
16-bit boolean 0 = O
1 = On
filtering factor (register
031A
)
hex
Modbus address 16-bit integer 1 ... 247
Default: 240
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HMM170 User Guide M212259EN-A
Communication
1538 0601
hex
Bit rate enum 0 = 300
1 = 600
2 = 1200
3 = 2400
4 = 4800
5 = 9600
6 = 19200
7 = 38400
8 = 57600
9 = 115200
1539 0602
hex
Parity, data, stop bits enum 0 = None, 8, 1
1 = None, 8, 2
2 = Even, 8, 1
3 = Even, 8, 2
4 = Odd, 8, 1
5 = Odd, 8, 2
(default: 1 =
None, 8, 2)
1540 0603
hex
Response delay 16-bit integer Unit: ms
Range: 0 ...
1000
Functions
1285 0504
hex
Purge 16-bit function
status
When writing to
register:
1 = Activate
purge
1542 0605
hex
Restart device 16-bit function
status
When writing to
register:
1 = Restart the
device
40
Page 43
A.4.3 Device Identification Objects
Table 16 Device Identification Objects
Appendix A – Modbus Reference
Object Id
(Decimal)
0 00
1 01
3 03
4 04
Object Id (Hexadecimal) Object Name Example Contents
hex
hex
hex
hex
VendorName “Vaisala”
ProductCode "HMM170"
VendorUrl “http://www.vaisala.com/”
ProductName "Vaisala HUMICAP(R) Humidity
and Temperature Module
HMM170"
128 80
129 81
130 82
hex
hex
hex
SerialNumber "NOT SET"
CalibrationDate
CalibrationText
A.4.4 Test Value Registers
Read the known test values from the test registers to verify the functionality of your Modbus
implementation.
Table 17 Modbus Test Registers (Read-Only)
Register Number
(Decimal)
7937 1F00
7938 1F01
7940 1F03
Register Address
(Hexadecimal)
hex
hex
hex
Register
Description
Signed integer
Data Format Test Value
16-bit integer -12345
test
Floating point
32-bit float -123.45
test
Text string test text Text string
"-123.45"
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HMM170 User Guide M212259EN-A
A.4.5 Modbus Communication Examples
Reading Relative Humidity Value
Device address used in the following examples is 240 (F0
hex
).
The values returned by the device dier depending on the ambient conditions
and/or device settings. Your device might not return exactly the same values.
Request Response
Bytes on the Line
(Hexadecimal)
(silence for 3.5 bytes) Start of Modbus RTU
F0
hex
03
hex
00
hex
00
hex
00
hex
02
hex
D1
hex
2A
hex
(silence for 3.5 bytes) End of Modbus RTU
Description Bytes on the Line
(Hexadecimal)
(silence for 3.5 bytes) Start of Modbus RTU
frame
Device address F0
Function (Read
Holding Registers)
Register address 04
Number of 16-bit
registers to read (2)
Modbus RTU
checksum
frame
03
7A
E1
41
F4
05
06
hex
hex
hex
hex
hex
hex
hex
hex
hex
Description
frame
Device address
Function (Read
Holding Registers)
Number of data bytes
Value of first register
(least significant
word)
Value of second
register (most
significant word)
Modbus RTU
checksum
(silence for 3.5 bytes) End of Modbus RTU
frame
Communication Description
Register address 1 (1-based Modbus documentation format) =
0000
(0-based format used in actual
hex
communication).
Data format Two 16-bit Modbus registers interpreted as IEEE
754 binary32 floating point value, least
significant word first.
Returned value 41F47AE1
, which is binary32 representation of
hex
30.56 (%RH).
42
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Writing Pressure Compensation Value
Request Response
Bytes on the Line
(Hexadecimal)
(silence for 3.5 bytes) Start of Modbus RTU
Description Bytes on the Line
(Hexadecimal)
(silence for 3.5 bytes) Start of Modbus RTU
frame
F0
10
03
00
00
02
04
6E
14
44
75
AB
4E
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
hex
Device address F0
Function (Write
10
Multiple Registers)
Register address 03
00
Number of registers to
write (2)
00
02
Number of data bytes AD
Value for first register
54
(least significant
word)
Value for second
(silence for 3.5 bytes) End of Modbus RTU
register (least
significant word)
Modbus RTU
checksum
hex
hex
hex
hex
hex
hex
hex
hex
(silence for 3.5 bytes) End of Modbus RTU
frame
Appendix A – Modbus Reference
Description
frame
Device address
Function (Write
Multiple Registers)
Register address
Number of 16-bit
registers written (2)
Modbus RTU
checksum
frame
The response to a write
function informs that the
function was correctly received
by the device. It does not
guarantee that the written
value was accepted by the
device (for example, in case of
out-of-range values).
To verify that the value was
really accepted by the device,
read the register value after
writing.
Communication Description
Register address 769 (1-based Modbus documentation format) =
0300
(0-based format used in actual
hex
communication).
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HMM170 User Guide M212259EN-A
Communication Description
Data format Two 16-bit Modbus registers interpreted as IEEE
754 binary32 floating point value, least
significant word first.
Value to write 44756E14
= 981.72 (hPa)
hex
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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.
Technical Support
Contact Vaisala technical support at helpdesk@vaisala.com. Provide at least the
following supporting information:
• Product name, model, and serial number
• 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.
Recycling
Recycle all applicable material.
Follow the statutory regulations for disposing of the product and packaging.
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