Abstract: A capacitive humidity sensor circuit in which a one-shot circuit produces pulses having a pulse duration determined by the capacitance of a capacitive sensing element, the one-shot circuit being triggered by the trailing edges of pulses in a pulse train produced by a multivibrator. The multivibrator is adjustable to produce a pulse train of variable repetition rate independent of the value of the measured parameter. The pulses produced by the one-shot circuit are integrated to produce a voltage indicative of the time average value of the pulses, the voltage being supplied to an amplification and offset compensation circuit whose output signal is used to adjust the supply voltage to the multivibrator so as to effectively achieve compensation for nonlinear response of the capacitive sensing element to increasing relative humidity.

Abstract: A dialogue system uses a three wire bus connecting a central station with a plurality of substations with two of the wires carrying an AC supply voltage and a third one of the wires carrying data by means of a closed loop of the AC carrying wires and the third wire. The central station uses a series connection of a data transmitter and a data receiver with the third data wire and each substation includes a data receiver in series with the data wire and a data transmitter between the data wire and both AC wires.