Method for monitoring the function of a capacitive pressure measuring cell

A method for monitoring a function of a capacitive pressure measuring cell (10) comprising a measuring capacitor (CM) and a reference capacitor (CR) as well as a temperature element,

• wherein a pressure measurement value p is obtained by forming a quotient Q from the capacitance values of the reference capacitor (CR) and the measuring capacitor (CM),
• the method comprising the following method steps:
• in a matching procedure, determining and storing in a lookup table a characteristic curve of values of the quotient Q and the corresponding capacitance of the measuring capacitor (CM) versus pressures at different temperature scenarios, so as to define an expected behavior of a course in which corresponding absolute values of the quotient Q and the capacitance of the measuring capacitor (CM) are compared with each other at the different temperature scenarios;
• then in an operation step, continuously assigning each of the corresponding absolute values of the quotient Q and the corresponding capacitance of the measuring capacitor (CM) from the lookup table with a pressure measurement value p at a temperature detected at a respective moment by the temperature element;
• continuing with the operation step, determining a behavior of a course in which corresponding absolute values of the quotient Q and the capacitance of the measuring capacitor (CM) are compared with each other at the temperatures detected by the temperature element;
• wherein:
• in the case of a significant deviation of the determined behavior from the expected behavior, the evaluation unit is temporarily switched into a safety mode while a temperature gradient detected by the temperature element is evaluated;
• then
• if there is a significant increase in the detected temperature gradient, a temperature compensation is initiated;
• and
• if there is no significant increase in the detected temperature gradient, an error signal is generated.