Patent ID: 8854063

Claim:
A method that determines one of a capacitance or a change in capacitance of a capacitive sensor element, the method comprising: a) discharging an average value capacitor; one of b1) discharging the capacitive sensor element and c1) charging an operating capacitor to a charging voltage, or b2) discharging the operating capacitor and c2) charging the capacitive sensor element to the charging voltage; d) connecting the operating capacitor to the capacitive sensor element; e) connecting the operating capacitor to the average value capacitor; f) evaluating a voltage established one of across the operating capacitor or across the average value capacitor in order to determine one of the capacitance or the change in capacitance, wherein the method is further carried out using a microprocessor, the microprocessor comprising an internal capacitor which forms the operating capacitor, an A/D converter which is connected to the internal capacitor, a plurality of ports including a first port, a second port and a third port, each of the plurality of ports capable of being configured as one of an input or an output, the capacitive sensor element being connected to the second port, and the average value capacitor being connected to the third port, and a multiplexer which is connected, on the input side, to the plurality of ports and is connected, on the output side, to the internal capacitor, wherein the microprocessor being configured to further perform the method comprising the following steps in succession, g) configuring the first port as an output and outputting a high signal at the first port; h) configuring the third port as an output and outputting a low signal at the third port; i) configuring the third port as an input; j) configuring the second port as an output and outputting a low signal at the second port; k) configuring the second port as an input; l) setting the multiplexer in such a manner that the internal capacitor is connected to the first port; m) setting the multiplexer such that the internal capacitor is connected to the second port; n) setting the multiplexer such that the internal capacitor is connected to the third port; o) digitizing a voltage present across the internal capacitor into a digital voltage value using the A/D converter; and p) evaluating the digitized voltage value in order to determine one of the capacitance or the change in capacitance.