Vaisala HMDW110 Series
Duct, wall and outdoor humidity and temperature transmitters with dew point, wet bulb and enthalpy.
The Vaisala HMDW110 series are humidity and temperature transmitters for ducts, walls and outdoor use, together with the TMI110 immersion transmitter for heating and cooling water. This Modbus RTU template reads relative humidity, temperature, dew point, wet-bulb temperature, enthalpy and the error code, and lets you set the filtering and the serial settings from ModbusCloud.
- Protocol
- Modbus RTU
- Connection
- RS485, 19200 baud
- Registers
- 18, read and write
- Brand
- Vaisala
- Key readings
- Relative humidity · Temperature · Dew/frost point · Wet-bulb temperature · Enthalpy · Device status · Error code
- Available commands
- Measurement filtering factor · Modbus address · Bit rate and parity · Response delay · Transmitter restart
- Compatible models
- HMD110 · HMW110 · HMS110 · TMI110
- Last updated
Registers (18)
17 read, 7 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Relative Humidity | %RH | Read | |||
| Temperature | °C | Read | |||
| Dew/Frost Point Temperature | °C | Read | |||
| Wet-Bulb Temperature | °C | Read | |||
| Enthalpy | Read | ||||
| Device Status | Read | ||||
| Error Code | Read | ||||
| Security Hash | Read | ||||
| Measurement Filtering Factor | Read and write | ||||
| Modbus Address | Read and write | ||||
| Bit Rate | Read and write | ||||
| Parity, Data and Stop Bits | Read and write | ||||
| Response Delay | ms | Read and write | |||
| Protocol | Read and write | ||||
| Restart Device | Write | ||||
| Signed Integer Test | Read | ||||
| Floating Point Test | Read | ||||
| Text String Test | Read |
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Use cases
- Show humidity, temperature and dew point from each transmitter on a dashboard and keep 365 days of history.
- Get an email, in-app or webhook alert when the relative humidity in a duct or greenhouse compartment rises above a threshold you set.
- Put the outdoor humidity and temperature of an HMS110 next to the indoor values to compare the climate inside and outside.
- Follow the heating or cooling water temperature from a TMI110 and get an alert when it drops below a set value.
- Raise an alert when Error Code is not 0, for example on a wet humidity sensor or a supply voltage out of range.
- Set more measurement filtering from the portal when short swings in the reading need to be averaged out.
Installation
Connect terminal 1 (RS485+) and terminal 2 (RS485-) to the RS485 port of the ModbusCloud Gateway, and the RS-485 common to terminal 3 (Pwr-). On an HMW110 with M12 connector use pins 4, 2 and 3.
Power the transmitter with 10 to 28 V DC on terminal 4 (Pwr+) and terminal 3 (Pwr-). In Modbus mode, pull out the terminal block of the current outputs (terminals 5 to 8).
Check that the transmitter was ordered with Modbus output and uses address 240, 19200 baud, no parity, 8 data bits and 2 stop bits. Change the settings with Vaisala Insight if needed, and give each transmitter its own address.
In ModbusCloud, add a Modbus device on the gateway with these settings and import the Vaisala HMDW110 Series template.
Check that Floating Point Test reads -123.45 and that Relative Humidity and Temperature show plausible values.
Things to watch for
The transmitter does not answer on the RS485 bus. What should I check?
Check 19200 baud, no parity, 8 data bits and 2 stop bits at address 240. Many masters default to 1 stop bit. Check that RS485+ is on terminal 1, RS485- on terminal 2 and the common on terminal 3. A transmitter delivered with current output, such as the standard HMD112, HMW112 and HMS112, is not set up for Modbus. Modbus works only at 9600 baud or higher.
The values look plausible but do not match my reference. How do I check the readout?
Read Floating Point Test. It must show -123.45, and Signed Integer Test -12345. The transmitter sends 32-bit values low word first, and a wrong word order can still give values that look right. The template already uses the order of the transmitter. On the TMI110 only Temperature carries a measurement, the humidity values do not apply.
Device Status does not show 1. What does that mean?
Device Status 1 means no errors. For any other value read Error Code, which gives the cause as a sum of codes, for example 2 for a humidity measurement error, which usually means a wet sensor, or 2048 for a supply voltage out of range. An alert on Error Code not equal to 0 catches every error.
How do I connect several transmitters to one bus?
Every transmitter with Modbus output leaves the factory at address 240. Give each one its own address from 1 to 247 before you connect them together, for example with Vaisala Insight, and use the same bit rate and serial format on all of them. Connect the RS-485 common to terminal 3 of every transmitter.
Writing a setting returns an error or has no effect. Why?
The transmitter only accepts writes as write multiple (function code 16). The filtering factor is 32-bit and always goes that way. If writing a single 16-bit setting such as the address or the bit rate returns an error, change it with Vaisala Insight. New bit rate and parity settings only apply after a restart. Writing registers in ModbusCloud is off by default and is enabled per gateway on request.
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