Capacitive Moisture Sensors
A great way to detect and distinguish objects and fluids is through their interference with electrical fields. In many cases it is sufficient to measure the change on the near static capacitance to discern if buttons are pressed or if containers are filled. More challenging applications may require asymmetric sensitivity, RF analysis to distinguish between fluids or enhanced detection distances.
We applied this functionality to realize a moisture sensor that is integrated with the potting material of a power electronic module (picture). The system comprises an application-specific sensing element and the read-out electronics that can be integrated with the device controller. It is used for the detection of safety critical states i.e. the moisture increase due to high external humidity, dewing or ruptures of the encapsulant.
Fraunhofer IISB offers the whole development chain from definition of application concept, electro-magnetic field simulation, sensors printing until the implementation and test of readout circuitry in conventional as well as thin-film electronics.