Circuit device for evaluating and testing capacitive sensor

PURPOSE: To perform self test of a sensor without varying the switching sequence. CONSTITUTION: In a measuring mode, the difference of a measuring capacitance 3 formed by a central electrode 1 and each measuring electrode 2 and connected with a capacitance measuring bridge 5 produces a signal representative of the displacement of the central electrode 1. In a test mode, a reference capacitance 4 connected with the capacitance measuring bridge 5 is connected in place of one measuring capacitance and a potential difference can be applied between the central electrode 1 and the measuring capacitance substituted by the reference capacitance. Furthermore, a displacement of the central electrode 1 thus caused can be measured by the other measuring capacitance 3. COPYRIGHT: (C)1993,JPO