Method for operating a pressure measuring cell of a capacitive pressure sensor

A method for operating a pressure measuring cell (10) of a capacitive pressure sensor (1);

• wherein the pressure measuring cell (10) comprises a pressure-dependent measuring capacitor (CM) and a reference capacitor (CR), which have an internal excitation voltage UE0 applied to them in the form of an alternating square-wave signal, and the pressure measured value p is obtained from the capacitance values of the measuring capacitor (CM) and the reference capacitor (CR);
• wherein the measurement signal is supplied in the form of an alternating square-wave signal UR to an evaluation unit, the pulse level of said signal being dependent on the quotient of the capacitance values of the reference capacitor (CR) and the measuring capacitor (CM) and the period duration of said signal being determined by way of the capacitance value of the measuring capacitor (CM), characterized in that the alternating square-wave signal UR is supplied to an amplifier unit (VE) for the purpose of signal amplification and offset correction, the signal amplification being performed by means of an amplitude adjustment for the internal excitation voltage UE0 and the offset compensation being performed by way of a further square-wave signal UOF;
• and in that respective fixed voltage values have been stored in a memory unit (40) in a comparison procedure for the purpose of gain and offset correction;
• wherein these stored voltage values together with a predefined clock are used to form the two square-wave signals UE0 and UOF;
• and wherein the gain correction is performed by way of the multiplicative influencing of the quotient of the capacitance values of the reference capacitor (CR) and the measuring capacitor (CM), and the offset correction is performed by virtue of the square-wave signal UOF being supplied to the amplifier unit (VE) and thus being added to the square-wave signal UR.