Method for monitoring the operation of a pressure measuring cell of a capacitive pressure sensor

A method for monitoring the operation of a pressure measuring cell of a capacitive pressure sensor,

• wherein the pressure measuring cell comprises a pressure-dependent measuring capacitor and a pressure-dependent reference capacitor and the pressure measurement value (p) is obtained as a measurement signal from the capacitance values of the measuring capacitor and the reference capacitor,
• wherein the measurement signal is fed to an evaluation unit in the form of an alternating square-wave signal, the pulse height of which depends on the quotient of the capacitance values of the reference capacitor and the measuring capacitor and the period duration of which is determined by the capacitance value of the measuring capacitor so that in the nominal pressure range of the pressure sensor there is a fixed relationship between pulse height and period duration,
• wherein the pressure sensor comprises a microcontroller with a timer, a memory and a processing unit,
• characterized by the following method steps:
• defining and storing the functional relationship between the pulse height hx and the period duration dx in the form of a polynomial in the memory;
• the timer determines the period duration dx of the alternating square-wave signal and forwards it as the value dx-IST to the processing unit;
• determining the period duration dx-SOLL associated with a measured pressure value px with the pulse height hx-IST based on the polynomial;
• comparing the value for the period duration dx-SOLL determined based on the polynomial with the actual, measured period duration dx-IST and generating an error signal in the case of a significant deviation between dx-IST and dx-SOLL.