Importance

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Abstract

The invention relates to a humidity sensor for capacitive measurement of the humidity contained in a material, predominantly a bulk product. For parallel operation of several humidity sensors, one individual humidity sensor has to fulfil particularly high requirements with regard to accuracy, sensitivity and interchangeability. These requirements are fulfilled by the humidity sensor as per the invention firstly in that at least one pole of a stray field condenser arranged in the humidity sensor is fitted as a conductive layer on the side of a closer plate in the casing of the humidity sensor which is turned away from the material or bulk product. Furthermore, there is arranged in the casing a digital arithmetic-logic unit which exhibits a calibration table stored in a digital memory for determination of humidity levels as a function of measurement signals in a capacity measurement circuit which measures the capacity of the stray field condenser and of interference values affecting the humidity sensor. A further increase in precision, finally, is achieved in that the capacity measurement circuit exhibits an amplitude stabilizer such that the voltage on the stray field condenser is constant over time.

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First Claim