Method for measuring capacitance and capacitive sensor unit

摘要

A method measures a capacitance. According to the method, a first detection measurement for the capacitance which is to be measured is detected by a first measurement method during a first measurement phase. In this case, a second measurement phase is started when the first detection measurement satisfies a transition criterion. A second detection measurement for the capacitance which is to be measured is detected during the second measurement phase by a second measurement method which differs from the first measurement method. The second measurement method has higher measurement accuracy than the first measurement method but also greater energy expenditure.

主权项

1. A method for measuring a capacitance, which comprises the steps of:
during a first measuring phase, detecting a first measured quantity of the capacitance via a first measuring method, the first measuring method includes performing one of the further steps for detecting the first measured quantity:
detecting a measurement of a charging speed of a sensor electrode;detecting an amplitude of an alternating voltage present on a voltage divider containing a sensor electrode; ordetecting a phase angle between the alternating voltage and a strength of a flow of current caused by the alternating voltage; starting a second measuring phase when the first measured quantity satisfies a transition criterion; and during the second measuring phase, detecting a second measured quantity of the capacitance to be measured via a second measuring method being different from the first measuring method, the second measuring method having a higher level of measuring accuracy compared to the first measuring method, and the first measuring method having a lower expenditure of energy compared to the second measuring method, the second measuring method includes performing one of the further steps of:
detecting a measurement of a charge quantity on the sensor electrode as the second measured quantity; ordetecting a frequency of a voltage which is generated by an RC oscillator containing the sensor electrode.