The Smartec humidity sensor is a two terminal capacitor, which increases in value as water molecules are absorbed into its active polymer dielectric. The capacitor consists of a base plate and a water permeable platinum top plate.

The measuring of humidity is rather complex. Generally the humidity in air is measured as the fraction of the maximum amount of water that can be absorbed at a certain temperature. In air, at a given temperature, this fraction can vary between 0 (absolute dry) and 100 % (the point where condensation will begin to form).

Many classical sensing techniques, such as mechanical devices and resistive type sensors, are temperature dependent and the wet bulb thermometer is also pressure dependent. With the Smartec humidity sensor, Relative Humidity (RH) can be measured without the complicating factors of temperature and pressure compensation.