HOW THE ABS-300 ABSOLUTE HUMIDITY SENSOR WORKS

The ABS-300 is a thermal conductivity absolute humidity sensor. This sensor measures the absolute humidity by quantifying the difference in thermal conductivity of dry air and air containing water vapor. The sensor consists of two matched NTC thermistor elements in a bridge circuit. One sensor is hermetically encapsulated in dry nitrogen while the other sensor is exposed to the environment. As current passes through the thermistors, resistive heating increases their temperatures. The sealed sensor dissipates more heat than the exposed sensor. This difference in heat dissipation results in the two thermistors having a difference in resistance. This difference is directly proportional to the absolute humidity. If temperature and pressure are known the absolute humidity easily converts to relative humidity.

For more information, call OHMIC’s technical support at 800-626-7713.