Circuit Project Electronic

A humidity sensor with temperature compensation built-in. Never apply a DC voltage to the sensor, even measuring the sensor with an ohmmeter will damage the device, always ensure that an AC voltage is applied. Avoid condensation, freezing, dust, mist, oil, alcohol, etc. To set up this circuit replace the H14DL with Min Res 22Kohm and Min Res 51Kohm as shown, Acjust RV1 until a voltmeter between output and ground reads 1.40V. The output will then be as shown in the table to an accuracy of about ~5%.

Source:http://www.next.gr/inside-circuits/
Humidity-Sensor-with-the-H14DL-l5867.html