Method for Measuring a Capacitance Value

摘要

A method for measuring a capacitance value of a capacitive sensor uses an integration process. For the integration process, the sensor is connected to an integration capacitor having a known capacitance value greater than the capacitance value of the sensor and a voltage UCI of the integration capacitor is measured by an A/D converter after a number IZ of executed integration cycles of the integration process. The method includes carrying out the integration process until the number IZ of executed integration cycles has reached the number N of integration cycles to be executed, adding a voltage value UCI (N) of the integration capacitor, which is determined by the A/D converter, to the total voltage value Utotal, increasing the number N, and repeating until the number N exceeds a predetermined value. The final total voltage value Utotal is indicative of the capacitance value of the capacitive sensor.

主权项

1. A method for measuring a capacitance value of a capacitive sensor using an integration process, wherein for the integration process a terminal of the sensor is electrically connected at a shared circuit node to a first terminal of an integration capacitor having a known capacitance value greater than the capacitance value of the sensor and a voltage UCI of the integration capacitor is measured by an A/D converter after a number IZ of executed integration cycles of the integration process, the method comprising:
(a) setting a number N of integration cycles to be executed to a start value Nstart and determining an end value Nend for the number N of integration cycles to be executed; (b) initializing a total voltage value Utotal to a value zero; (c) initializing a number IZ of executed integration cycles to a value zero; (d) carrying out the integration process until the number IZ of executed integration cycles has reached the number N of integration cycles to be executed; (e) adding a voltage value UCI (N) of the integration capacitor, which is determined by the A/D converter, to the total voltage value Utotal; (f) increasing the number N by a value n, wherein n is greater than or equal to one and is less than Ndiff=Nend−Nstart, and repeating steps (c), (d), (e), and (f), beginning with step (c), until the number N exceeds the determined end value Nend; and (g) evaluating the total voltage value Utotal as a measurement result indicative of the capacitance value of the capacitive sensor.