.png)
HVAC Sensors and Transmitters for Building Automation
Better building control starts with trustworthy measurements
An HVAC controller can only respond to the values it receives. When a room sensor drifts, a duct transmitter is installed in the wrong place or an outdoor sensor is affected by solar radiation, the building may use more energy while occupants still feel uncomfortable.
Vaisala HVAC transmitters measure humidity, temperature, carbon dioxide and differential pressure for commercial buildings, hospitals, laboratories, cleanrooms, data centres and industrial facilities. The range includes wall, duct, outdoor and DIN-rail options with analogue or Modbus communication for building-management systems.
This guide helps consultants, contractors and facility teams choose the measurement, mounting style and product family that fit each part of the building.
What should an HVAC system measure?
| Parameter | Why it matters | Typical control use |
|---|---|---|
| Temperature | Directly affects comfort, processes and equipment reliability | Cooling, heating, supply-air and water-loop control |
| Relative humidity | Influences comfort, condensation, static electricity and material stability | Humidification, dehumidification and economiser control |
| Carbon dioxide | Provides a practical indication of occupancy-related ventilation demand | Demand-controlled ventilation and indoor-air-quality monitoring |
| Differential pressure | Confirms airflow direction or restriction across a filter and fan | Cleanroom pressure cascades, isolation rooms and AHU maintenance |
Choose by measurement location
| Location | Product | Recommended Vaisala family | Best fit |
|---|---|---|---|
| Occupied room |  |
HMW80, HMW90 or HMW110 | Wall-mounted humidity and temperature measurement |
| Room with CO2 control |  |
GMW80, GMW90 or XMW85 | Demand-controlled ventilation with optional humidity and temperature |
| Wall-mounted measurement in demanding indoor environments |  |
Vaisala HMW90 Series | Humidity and temperature measurement for indoor HVAC applications requiring accuracy and stability. Confirm the display and output configuration for the selected model. |
| Compact sensing and modular installations |  |
Vaisala XMP10 Series | Compact probes with different sensor and accuracy options, for standalone use or compatible Origo10 transmitters. Select the probe and interface together. XMP10T measures temperature only. |
| Indoor air quality and ventilation monitoring |  |
Vaisala XMW85 Series | Configurable indoor transmitters for CO₂, humidity and temperature. Suitable for reviewing smart-building and ventilation requirements. Confirm the measurements included in the selected configuration. |
| Accurate compact sensing for equipment and data loggers |  |
Vaisala HMP110 | Compact HUMICAP humidity and temperature probe for equipment integration and environmental monitoring. Select the output, filter, cable and mounting accessories for the application. |
| Cost-conscious equipment integration and general monitoring |  |
Vaisala HMP60 | Compact humidity and temperature probe with an interchangeable INTERCAP sensor. Consider it for general monitoring and equipment integration, checking the required accuracy, operating conditions and output before selection. |
| Ventilation duct |  |
HMD60, HMD80 or HMD110 | Supply, return or extract-air humidity and temperature |
| Duct CO2 |  |
GMD110 | CO2 measurement in a representative ventilation-air stream |
| Outdoor air | |
HMS80 or HMS110 | Humidity and temperature with a weather-resistant arrangement |
| Room or AHU differential pressure |  |
PDT101 or PDT102 | Pressure cascades, filter loading and fan monitoring |
| Flexible multi-parameter point |  |
Origo10 Series | Interchangeable probes and modules for demanding buildings |
Room transmitters for comfort and indoor air quality
Wall-mounted transmitters should represent the occupied zone, not the temperature of the wall or a nearby heat source. For routine humidity and temperature control, the HMW80 family provides a practical selection of analogue and Modbus models. HMW90 raises the measurement performance for museums, archives, laboratories, data centres and other spaces where long-term accuracy matters.
When ventilation needs to respond to occupancy, use a CO2 transmitter. The GMW80 family provides cost-effective room measurement, while GMW90 is suited to projects that need higher performance, flexible outputs and optional humidity measurement. XMW85 combines CO2, humidity and temperature with Modbus RTU in one compact wall transmitter.
Place a room sensor where the room actually lives
Avoid direct sunlight, exterior walls, supply-air jets, doorways, local heaters and enclosed corners. Mount the sensor at a representative occupied-zone height and allow air to circulate around its enclosure.
Duct and outdoor measurement
Duct transmitters are useful when the controller needs a representative value for the air stream rather than one room. HMD80 supports routine duct applications, HMD110 provides higher accuracy and traceable calibration, and HMD60 is designed for demanding projects that need high measurement performance, a robust metal enclosure or BACnet integration.
For CO2 in ventilation ducts, GMD110 is the purpose-built choice. Install it in a section with a well-mixed air stream and sufficient straight duct, away from sharp bends, dampers and zones where outdoor and return air have not mixed properly.
Outdoor humidity and temperature measurement needs protection from rain and solar heating. HMS80 and HMS110 use an outdoor arrangement with a radiation shield and can be mounted to a wall or pole. Do not substitute an ordinary indoor wall sensor in an exposed outdoor location.
Compare the Main Vaisala HVAC Humidity Families
| Family | Mounting | Main strength | Typical selection reason |
|---|---|---|---|
| 80 Series | Wall, duct or outdoor, depending on model | Cost-effective range with multiple mounting and output options | Routine commercial HVAC and installations with many measurement points |
| 110 Series | Wall, duct or outdoor, depending on model | Higher accuracy with traceable calibration | Demanding buildings and critical measurement locations |
| HMW90 Series | Indoor wall | High-accuracy room measurement with a replaceable measurement module | Laboratories, museums, data centres and controlled rooms |
| XMP10 Series | Compact probe; installation depends on equipment or compatible transmitter | Multiple sensor and accuracy options in a compact format | Equipment integration, confined measurement points and compatible Origo10 installations |
| XMW85 Series | Indoor wall | Modbus RTU with configurable CO₂, humidity and temperature measurement | Room air-quality and ventilation monitoring; confirm the parameters included in the selected model |
| HMP110 | Compact probe with application-specific mounting accessories | Accurate HUMICAP humidity and temperature measurement | Equipment integration, environmental chambers and compatible data loggers |
| HMP60 | Compact probe with application-specific mounting accessories | Cost-effective measurement with an interchangeable INTERCAP sensor | General environmental monitoring, data loggers and volume equipment integration |
| HMD60 Series | Duct | High-performance measurement, robust metal enclosure and model-dependent digital interfaces | Demanding air-handling and building-automation projects, including configurations requiring BACnet MS/TP |
Select the complete model configuration rather than the family name alone. Measurement parameters, accuracy, outputs and accessories vary. XMP10T is temperature-only; CO₂ measurement is not included in every XMW85 configuration.
Differential pressure completes the HVAC picture
Humidity, temperature and CO2 describe air condition; differential pressure helps show where the air is moving. PDT101 can monitor bidirectional room pressure or unidirectional pressure drop across fans and filters. PDT102 is intended for high-accuracy low-pressure applications such as regulated cleanrooms and critical spaces.
- Positive-pressure room: Helps protect a clean space from contaminants entering.
- Negative-pressure room: Helps contain airborne contaminants within the room.
- Filter pressure drop: Shows increasing restriction and supports condition-based replacement.
- Fan or AHU monitoring: Confirms that the expected pressure is being produced.
Analogue, Modbus or BACnet?
Choose the communication method around the controller, cabling strategy and maintenance plan—not simply the newest protocol.
- 4–20 mA: Robust for long cable runs and easy to troubleshoot with standard instruments.
- 0–10 V: Common in building automation, but voltage drop and grounding deserve attention.
- Modbus RTU: Carries several parameters and diagnostics on one RS-485 network.
- BACnet MS/TP: Useful when native integration with the building-management system is required.
Confirm the exact output, supply voltage, display, enclosure and calculated-parameter requirements before selecting the full model code.
Common HVAC sensor mistakes
- Selecting the transmitter before deciding what the control sequence actually needs.
- Mounting a room sensor where sunlight, doors or supply air distort the reading.
- Installing a duct probe before outdoor and return air are fully mixed.
- Using indoor equipment outdoors without the required radiation and weather protection.
- Ignoring condensation risk in chilled areas or high-humidity rooms.
- Specifying CO2 range, outputs or display without checking the controller points list.
- Commissioning the BMS value without comparing it with the transmitter reading.
- Leaving calibration access and future sensor replacement out of the design.
Commissioning and maintaining reliable measurements
At commissioning, verify the installation location, wiring, scaling, network address and engineering units. Compare the local or controller value with a suitable reference and record the result as a baseline.
Maintenance frequency depends on the building, required accuracy and environmental exposure. Clean sites may need only periodic verification, while dusty ducts, wet areas and critical facilities require closer attention. Field-replaceable sensing modules and calibration access can reduce downtime over the life of the building.
Five-year warranty
Vaisala states a standard five-year warranty for its HVAC transmitters. Confirm the warranty coverage, applicable model and order terms with Seacom when specifying or purchasing equipment.
Vaisala HVAC sensor supplier in Malaysia
Seacom Process Instruments supplies and supports Vaisala HVAC measurement products in Malaysia. We can help consultants, contractors, system integrators and facility teams compare models, select outputs, review installation locations and match instruments to the building-management system.
Send us the measured parameter, room or duct location, expected range, required accuracy, output signal, supply voltage, display preference, enclosure requirement and controller details. We will help narrow the selection before the final model code is ordered.
All comments