This humidity sensor consists of 2 copper conductors that are located at small distance from each other. The relay switches as soon as the moisture makes a connection that is more or less electrically ...

The resulting current flow is then converted to a dc value by the signal-conditioning circuits of the sensor. Nominal operating temperatures for resistive RH sensors range from 40 to 100°C.

The circuit shown in the figure measures relative humidity in air at the low temperatures found in applications like cold storage of food items and greenhouses.