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Humidity and temperature sensor (wall transmitter) · BACnet points list
Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP) BACnet points list
Updated 4 November 2026
The digital HMW95 transmitter measures relative humidity and temperature and calculates dewpoint, wet bulb, absolute humidity, mixing ratio and enthalpy. On BACnet MS/TP each value is an Analog Input; two writable Analog Values set the operating pressure or altitude used in the humidity calculations.
This page lists 11 BACnet objects for the Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP) — 2 of them writable — with each object’s type, instance number, name, engineering units and access. It is re-typed from Vaisala’s own free documentation, linked below.
- Manufacturer
- Vaisala
- Model
- HMW90 series humidity and temperature transmitter (BACnet MS/TP)
- Equipment
- Humidity and temperature sensor (wall transmitter)
- Equipment type
- Thermostats, sensors & meters
- BACnet objects
- 11 (2 writable)
- Transport
- BACnet MS/TP
- Firmware
- Application software 1.0.28 (firmware 1.0.0.0)
- Default device instance
- Unique value set at the factory
- Also known as
- HMW95, HMW90 BACnet, XMW90, Vaisala humidity transmitter BACnet, M211399EN
Reference only, provided as-is: verify against Vaisala’s current documentation and the live device before use. Not official Vaisala information. Terms of use.
BMS integration notes: Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP)
Set the protocol, baud rate and MAC address on the DIP switches, give the transmitter a unique device instance, then read relative humidity (AI 2) and temperature (AI 3), plus dewpoint (AI 4) or enthalpy (AI 10) if the control sequence needs them. Write the site altitude (AV 2) once for accurate calculated values.
Minimum points to map
The short list most integrators start with — enough to run the unit from a BMS. Map more as the job needs.
| Object | Name | Why | Access |
|---|---|---|---|
| AI 2 | RH | Relative humidity, % | Read |
| AI 3 | T | Temperature | Read |
| AI 4 | Td | Dewpoint | Read |
| AI 10 | h | Enthalpy | Read |
Sensors & values from the BMS
AV 1 (operating pressure, hPa) or AV 2 (altitude) can be written by the BMS for the humidity calculations; the two are linked.
Network setup
- BACnet MS/TP on RS-485. DIP switches select the protocol (BACnet or Modbus) and baud rate: Automatic (default), 9600, 19200, 38400, 57600, 76800 or 115200.
- MAC address 0-255 on the 8-way address DIP switch; below 128 the transmitter is an MS/TP master, 128 and up a slave.
- The device instance is set to a unique value at the factory; change it, the device name, description, location and Max_Master with the BACNET service-port command.
- With automatic baud the transmitter listens 10 s at each rate and locks to the first valid traffic until reset or power cycle.
Watch out for
- Baud rate 4800 is not available with BACnet.
- OPER P and OPER Altitude are linked; write only one of them (writing one updates the other).
Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP) BACnet objects
Type: AI, AO, AV, BI, BO, BV, MI/MO/MV (multi-state) · Access: Read read-only, Write writable, Command writable with a priority array.
| Description | States | |||||
|---|---|---|---|---|---|---|
| AImin | 2 | RH | Relative humidity | %RH | Read | |
| AImin | 3 | T | Temperature | °C or °F | Read | |
| AImin | 4 | Td | Dewpoint | °C or °F | Read | |
| AI | 5 | Tdf | Dewpoint | °C or °F | Read | |
| AI | 6 | dTd | Dewpoint depression | K or °F (delta) | Read | |
| AI | 7 | Tw | Wet bulb temperature | °C or °F | Read | |
| AI | 8 | a | Absolute humidity | g/m³ or gr/ft³ | Read | |
| AI | 9 | x | Mixing ratio | g/kg or gr/lb | Read | |
| AImin | 10 | h | Enthalpy | kJ/kg or BTU/lb | Read | |
| AV | 1 | OPER P | Operating pressure for humidity calculations, default 1013.25 | hPa | Write | |
| AV | 2 | OPER Altitude | Operating altitude; linked to OPER P | m or ft | Write |
No points match these filters.
Object ID lookup: Vaisala HMW90 series humidity and temperature transmitter point IDs by name
Integration notes
- Calculated humidity objects (AI 4-10) exist only on the digital HMW95 models.
- AV 1 OPER P and AV 2 OPER Altitude are linked: writing one recalculates the other.
- Analog Input Present_Value can be written only when Out_Of_Service is set.
- The manual prints the same description 'Dewpoint' for both Td (AI 4) and Tdf (AI 5).
- Source: HMW90 Series User's Guide M211399EN-H, Appendix A (BACnet reference).
Check it against the live device. A points list tells you what the controller can expose; the unit in front of you may differ by firmware or installed options. This list is provided as-is for reference only and may contain mistakes — confirming it before you write, map or commission anything is up to you (terms). Easy BACnet scans a network for BACnet IP devices from an Android phone, reads every object on the HMW90 series humidity and temperature transmitter (BACnet MS/TP) and exports what it actually has to Excel — free. New to BACnet? Start with what a BACnet points list is and what the object types mean.
Questions about the Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP)
How many BACnet points does the Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP) have?
This list has 11 BACnet objects: 9 analog inputs, 2 analog values. The exact set on a given unit depends on its firmware, installed options and configuration.
Which Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP) BACnet points are writable?
2 of the 11 objects accept a write. Points marked Command have a priority array: a write holds until it is released, so release it back to automatic when you are done.
Where is the official Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP) BACnet documentation?
The source is HMW90 Series Transmitters User's Guide (M211399EN-H), revision 2016-04, published free by Vaisala at https://docs.vaisala.com/api/khub/documents/Nz9Rxwoq_FgzXgpFHM~8Yw/content.
What are the minimum BACnet points to integrate the Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP)?
Start with AI 2 RH (Relative humidity, %); AI 3 T (Temperature); AI 4 Td (Dewpoint); AI 10 h (Enthalpy).
Can the BMS supply sensor values to the Vaisala HMW90 series humidity and temperature transmitter (BACnet MS/TP)?
AV 1 (operating pressure, hPa) or AV 2 (altitude) can be written by the BMS for the humidity calculations; the two are linked.
How do I check these points on the real HMW90 series humidity and temperature transmitter (BACnet MS/TP)?
Scan the network with a BACnet IP browser such as Easy BACnet, open the device and compare its object list with this table. Anything missing is usually an option that isn't installed or a point that is disabled in the controller's configuration.
More Vaisala BACnet points lists
- CO2, temperature and humidity sensor (wall transmitter)
Vaisala GMW90 series CO2, temperature and humidity transmitter (BACnet MS/TP)
Vaisala GMW90 series wall transmitters with digital output (GMW95 models), set to the BACnet MS/TP protocol.
Also known as: GMW95, GMW95D, GMW95R, GMW95RD, GMW90 BACnet, XMW90, Vaisala CO2 transmitter BACnet, M211659EN - Humidity and temperature sensor (duct transmitter)
Vaisala HMD65 humidity and temperature duct transmitter (BACnet MS/TP)
Vaisala HMD65 duct-mounted relative humidity and temperature transmitters with the RS-485 port set to BACnet MS/TP.
Also known as: HMD65, Vaisala HMD65, HMD65 BACnet, M212243EN
Source: HMW90 Series Transmitters User's Guide · M211399EN-H · rev. 2016-04. Object names, instances and units are reproduced as published; descriptions are our own.