A humidity sensor detects and measures moisture content in air, typically reporting relative humidity (RH%) or dew point temperature for HVAC control. Modern humidity sensors are critical components in enthalpy controls, dehumidification systems, and indoor air quality monitoring. Accuracy ratings of ±3% RH are standard in commercial-grade sensors.
Sensor Types and Performance
Capacitive humidity sensors use polymer films whose electrical properties change with moisture absorption, offering response times of 10-30 seconds. Resistance-based sensors (damp-sensing elements) provide lower cost but slower response. Digital sensors with integral transmitters output standard 4-20 mA or 0-10 VDC signals directly to building controls. Sensors typically operate across 0-100% RH and -40 to 185°F temperature ranges.
HVAC Applications
Humidity sensors regulate dehumidification setpoints (maintain 40-60% RH in occupied spaces) and control outdoor air dampers in enthalpy economizers. They trigger alerts for moisture-related problems in data centers (critical at 20-80% RH) and prevent condensation in cold supply ducts. Regular calibration checks every 12 months ensure ±2-3% accuracy.