The HUMI.sens® is based on a capacitive humidity sensor. This sensor consists of a hygroscopic polymer material into which the water vapour from the sample gas is deposited. This embedding changes the dielectric property of the polymer material. This polymer material is located between the electrodes of an electrical capacitor and therefore also changes the capacitance of the capacitor. The capacitance increases almost linearly with the humidity. An equilibrium is created between the humidity in the sample gas and the humidity in the polymer, which adapts reversibly with varying humidity.
Principle structure
The humidity sensor is built up in a layered structure. The bottom layer forms the carrier. This consists of ceramic. A base electrode is then applied to this carrier. The hygroscopic polymer layer is applied over this base electrode. A gas-permeable layer must be applied as a counter electrode so that the water vapour can reach this sensitive layer from the outside.