HVAC Temperature Sensor Selection Guide

Start with the control system

The best HVAC sensor depends on what it connects to. A building controller may expect a 10 kΩ NTC thermistor, a Pt100 or Pt1000 RTD, a 0–10 V signal, a 4–20 mA loop or a digital RS485 value. Check the controller input before choosing the sensor.

Pt100 vs thermistor vs thermocouple

Pt100 / Pt1000 RTD: stable and accurate over a wide range, good for chillers, boilers, hot water and critical air handling. Requires a matching 2-, 3- or 4-wire input.
NTC thermistor: low cost and high sensitivity around room temperature; common in HVAC controls and duct sensors. The resistance curve is non-linear and the usable range is narrower.
Thermocouple: fast and suitable for high temperature, but less accurate at room temperature and needs cold-junction compensation. Less common for normal HVAC air and water measurement.

For most commercial HVAC applications, a Pt100 or a matched NTC is the practical choice.

Duct, pipe or immersion?

Duct sensor: use a probe long enough to reach the airstream, with a mounting flange and a sealed cable entry.
Pipe sensor: use a threaded probe or a thermowell; match the thread and insertion depth to the pipe.
Immersion sensor: protect the probe with a thermowell where maintenance or isolation is needed.
Room sensor: choose a representative location away from sunlight, drafts and heat sources.

Output and wiring

A bare Pt100 or NTC element needs a matching controller input. If the controller only accepts 4–20 mA or 0–10 V, use a temperature transmitter. A 4–20 mA loop is robust over long cables; 0–10 V is common in HVAC panels; RS485 is useful for digital networks.

Our RTD sensors include duct, pipe, surface and immersion versions. For panel integration, see temperature transmitters.

Accuracy and calibration

HVAC control usually does not need laboratory accuracy, but chilled-water and boiler sensors benefit from a calibrated Pt100. A Class A or Class B probe is normally sufficient; for critical validation, request a calibration certificate.

Use the Pt100 calculator to check resistance at a temperature, and the 4–20 mA calculator to verify a transmitter loop.

Selection checklist

Controller input type and range
Air, water or surface measurement
Probe length, thread and mounting
Cable length and insulation
Accuracy class and calibration requirement
Local display or transmitter needed?

Send us the controller input, measurement point and range, and we will recommend a standard or custom HVAC sensor. Contact our engineers.