Method for measuring a capacitance value

A method for measuring a capacitance value CM of a capacitive sensor using an integration capacitor with a terminal of the capacitive sensor and a first terminal of the integration capacitor being electrically connected at a shared circuit node and the integration capacitor having a known capacitance value CI that is greater than the capacitance value CM of the capacitive sensor, the method comprising the following steps:

• (a) initializing a voltage sum value UTotal to zero;
• (b) connecting the shared circuit node and a second terminal of the integration capacitor to a ground potential to reset a voltage at the integration capacitor to zero;
• (c) performing an initial integration process involving charge quantities being transferred in N successive integration cycles from the capacitive sensor to the integration capacitor, where N is an integer of at least two;
• (d) measuring immediately after the step (c), by an A/D converter, an initial voltage value at the integration capacitor and adding the initial voltage value to the voltage sum value UTotal;
• (e) performing a subsequent integration process involving one or more charge quantities further being transferred in n further successive integration cycle or cycles from the capacitive sensor to the integration capacitor, where n is an integer of at least one;
• (f) measuring after performing the step (e), by an A/D converter, a subsequent voltage value at the integration capacitor and adding the subsequent voltage value to the voltage sum value UTotal;
• (g) repeating the steps (e) and (f) until a total number of all of the performed integration cycles exceeds a predetermined amount;
• and
• (h) evaluating the voltage sum value UTotal as a measurement result, wherein the voltage sum value UTotal is indicative of the capacitance value CM of the capacitive sensor.

A system for measuring a capacitance value CM of a capacitive sensor, the system comprising:

• an integration capacitor having a known capacitance value CI that is greater than the capacitance value CM of the capacitive sensor, wherein a first terminal of the integration capacitor is electrically connected at a shared circuit node to a terminal of the capacitive sensor;
• an A/D converter;
• a first switch configured to selectively connect the shared circuit node to a fixed supply voltage, an open circuit, or a ground potential;
• a second switch configured to selectively connect a second terminal of the integration capacitor to the fixed supply voltage, the A/D converter, or the ground potential;
• and
• a controller configured to control the first switch, the second switch, and the A/D converter to
• (a) perform an initial integration process involving charge quantities being transferred in N successive integration cycles from the capacitive sensor to an integration capacitor, where N is an integer of at least two;
• (b) measure immediately after the step (a), using the A/D converter, an initial voltage value at the integration capacitor and add the initial voltage value a voltage sum value UTotal;
• (c) perform a subsequent integration process involving one or more charge quantities further being transferred in n further successive integration cycle or cycles from the capacitive sensor to the integration capacitor, where n is an integer of at least one;
• (d) measure immediately after the step (c), by an A/D converter, a subsequent voltage value at the integration capacitor and adding the subsequent voltage value to the voltage sum value UTotal;
• (e) repeat the steps (c) and (d) until a total number of integration cycles of all of the performed integration processes exceeds a predetermined amount;
• and
• evaluate the voltage sum value UTotal as a measurement result, wherein the voltage sum value UTotal is indicative of the capacitance value CM of the capacitive sensor.