Humidity sensor using conductivity type transducer

The alternating current conductance of ammonium paratungstate pentahydrate (APT⋅5H2O) is found to change sensitively (response time ∼3 min) with changes in relative humidity, but to remain practically independent over a wide range of frequency (100 Hz–10 KHz) and temperature (up to 80 °C). This property of APT⋅5H2O has been utilized to design a sensitive humidity sensor. A circuit has been developed whose output is a voltage varying with relative humidity.