Humidity Sensors & Transmitters for HVAC Explained
Humidity control is as important as temperature control in most commercial buildings — too dry and static/comfort problems appear, too humid and mold risk rises. A humidity sensor gives the BMS the data it needs to manage that balance. Jaideo Automation supplies an extensive humidity sensor range including the HSH-R Series Indoor Wall-Mounted Sensor, H7012 Room Humidity Sensor, H77 Series Humidity and Temperature Sensors, and RH-15xP Series Duct Humidity Transmitter.
How a Humidity Sensor Works
Most modern HVAC humidity sensors use a capacitive sensing element whose electrical capacitance changes in proportion to the moisture in the surrounding air. That change is converted into a relative humidity (%RH) reading, output as a signal the BMS can read for monitoring, alarming, or control.
Sensor vs Transmitter
A humidity sensor typically provides a raw measurement signal, while a humidity transmitter conditions that signal into a standardized output (such as 4-20mA or 0-10V) suitable for direct integration into a building automation system over longer wire runs without signal degradation.
Sensor Formats by Installation Location
- Wall-mounted (room) sensors — like the HSH-R series, measure occupied-space humidity directly, the most common format for comfort control
- Duct sensors — like the RH-15xP series, measure humidity in the supply or return airstream rather than the room itself, useful for monitoring the air handling process
- Outdoor sensors — measure ambient outdoor conditions, feeding economizer and outdoor air control strategies
- Remote/RF sensors — wireless options for locations where running sensor wiring is impractical
Combined Temperature and Humidity Sensors
Many of Jaideo’s humidity sensors, including the H77 and HSH series, measure both temperature and humidity from a single device — reducing installation points and giving the BMS both readings from one location. See our Temperature Sensors for HVAC guide for the temperature side of these combined sensors.
Applications
- Comfort control in offices, hotels, and residential buildings
- Humidity-sensitive spaces — server rooms, museums, pharmaceutical storage
- Economizer and demand-controlled ventilation strategies
- Humidification and dehumidification equipment control
Frequently Asked Questions
How does a humidity sensor work?
Most HVAC humidity sensors use a capacitive sensing element whose electrical capacitance changes in proportion to moisture in the air, which is converted into a relative humidity reading.
What is the difference between a humidity sensor and a humidity transmitter?
A humidity sensor provides a raw measurement signal, while a humidity transmitter conditions that signal into a standardized output like 4-20mA or 0-10V for reliable integration into a building automation system over longer wire runs.
Can one sensor measure both temperature and humidity?
Yes. Many combined sensors, such as the H77 and HSH series, measure both temperature and humidity from a single device, reducing installation points.