A. Product overview
The Duct-Mount Temperature and Humidity Transmitter is an HVAC and building-automation grade instrument designed to measure relative humidity and temperature directly inside air ducts. It uses a capacitive humidity sensor (0–100% RH) and a temperature sensor (0–50°C) and provides separate two-wire 4–20 mA outputs for RH and temperature. The transmitter is built for stable, long-term performance with fast response, service-friendly construction, and a replaceable sensor assembly. Its IP65 ABS enclosure and 150 mm duct probe make it suitable for AHU ducting, ventilation systems, cleanrooms, pharma environments, and office climate control where accurate duct measurements are required.
B. Working principle
Humidity measurement (capacitive sensor):
A capacitive RH sensing element changes capacitance as moisture content in the air varies. The transmitter electronics convert this change into a humidity reading, then linearize and scale it.Temperature measurement:
The transmitter measures the RTD resistance and converts it into an accurate temperature value.Two-wire 4–20 mA signal outputs:
The processed RH and temperature values are converted into two independent 4–20 mA current-loop signals (one for RH, one for temperature). Current loops are preferred in HVAC/industrial sites because they handle long cable runs and electrical noise better than voltage signals.Duct installation for representative air sampling:
The 150 mm duct probe places the sensing elements into the moving airstream, helping measure supply/return air conditions accurately for HVAC control.
C. Why it is used
To measure supply air or return air temperature and humidity for accurate HVAC control
To improve AHU performance by enabling correct humidification/dehumidification actions
To support building automation (BMS/BAS) with stable 4–20 mA inputs for monitoring and alarms
To reduce comfort issues and prevent condensation by controlling dew point-related conditions
To maintain controlled environments in pharma labs, cleanrooms, and office buildings
To ensure long-term reliability with replaceable sensor assembly, service-friendly design, and stable sensing performance
D. Suitable buyers
HVAC contractors and AHU system integrators
Building automation / BMS / BAS integrators
Panel builders and automation integrators using PLC, DCS, or SCADA
Facility managers handling large HVAC systems in commercial buildings
Pharmaceutical manufacturing and laboratory facility teams
Cleanroom consultants and maintenance teams
Hospitals, IT parks, data centers, and office building HVAC maintenance contractors
OEMs making HVAC equipment, air handling units, or ventilation control panels
FAQ (SEO-friendly)
1. What is a duct-mount temperature and humidity transmitter used for?
It measures temperature and relative humidity inside HVAC ducts (supply or return air) and sends signals to BMS/PLC/controllers for monitoring, alarms, and climate control.
2. What are the outputs of this transmitter?
It provides two-wire 4–20 mA outputs for both RH and temperature (separate loops), making it compatible with most HVAC controllers, PLC analog inputs, and BMS systems.
3. What ranges does it measure?
Humidity: 0–100% RH
Temperature: 0–50°C
4. What is the accuracy of the transmitter?
Humidity accuracy is ±2% RH with ±0.6% RH repeatability and response time under 15 seconds. Temperature accuracy is ±0.2% of full span using a Class A Pt100 sensor.
5. What power supply is required?
It operates on 12–36 VDC, commonly powered from 24 VDC control panels in HVAC and automation installations.
6. Is it suitable for HVAC and building automation systems?
Yes. Duct-mount installation and 4–20 mA outputs are ideal for AHU control, HVAC monitoring, and integration with BMS/BAS systems.
7. What is the enclosure protection rating?
The enclosure is IP65, which helps protect the transmitter electronics against dust and water splashes in typical HVAC plantroom environments.
8. Can the sensor be replaced if it fails?
Yes. The design includes a replaceable sensor assembly, which reduces downtime and makes maintenance easier.
9. Can it be used in high humidity environments?
It is designed for 0–100% RH in non-condensing conditions. Avoid direct condensation or water droplets on the sensing element for best performance and life.
10. Where is duct mount preferred over wall mount?
Duct mount is preferred when you need actual supply/return air measurements inside ducts for AHU control, ventilation monitoring, and accurate humidity/temperature control in HVAC systems.