Integration of a humidity sensor with power electronic applications

Humidity sensing inside power electronic modules is an important condition monitoring tool, as humidity induced corrosion processes can lead to the failure of devices and whole electronic systems. A humidity sensor based on capacitive characterization of interdigitated metal electrode structures was developed together with the corresponding readout electronics. FEM simulation was used to elaborate an optimized sensor structure with a maximal gain in capacitance and appropriate basic capacitance. Electric field simulations show that the measurement of humidity in air as well as in water absorbing solid-state materials is possible in the vicinity of the sensor. Experiments in a climatic chamber verify the functionality of the sensing system and proof its suitability for the detection of humidity uptake in silicone potting gel that is used as insulation material in power electronics.