Patent ID: 7724000

Claim:
A method of automatically testing an electronic circuit with a capacitive sensor, wherein the capacitive sensor includes two differential mounted capacitors whose common first electrode is able to move relative to each fixed second electrode of the two capacitors to alter capacitive value of each capacitor during measurement of a physical parameter, and the electronic circuit includes the capacitive sensor and an electronic interface of the sensor, wherein the electronic interface includes a charge transfer amplifier unit connected to a moving third electrode common to the two capacitors of the sensor, an integrator unit connected to an output of the amplifier unit to integrate charges provided by the amplifier unit and to provide a measurement output voltage, and an excitation unit arranged between an output of the integrator unit and the sensor for inversely polarizing each fixed second electrode of the capacitors in operating mode at a high voltage or a low voltage of a constant voltage source relative to a median rest voltage of the sensor between the high voltage and the low voltage, or for discharging each capacitor by an output voltage of the integrator unit, wherein the automatic test method includes, in normal operating mode, several successive measuring cycles, each divided into at least two successive phases, wherein the at least two successive phases comprise: (a) in a first phase, in discharging the two capacitors by the output voltage provided by the integrator unit; and (b) in a second phase, in polarizing the fixed second electrode of a first capacitor of the two differential mounted capacitors by the high voltage or the low voltage of the voltage source and in inversely polarizing the fixed second electrode of a second capacitor of the two differential mounted capacitors by the low voltage or the high voltage of the voltage source, wherein in a test mode, the method further includes a test phase replacing a polarizing second phase, wherein the test phase occurs in at least one cycle every several measurement cycles, and in the test phase only one fixed second electrode of one of the two capacitors is polarized at each test phase by a polarizing voltage higher than the low voltage and lower than the high voltage, wherein the polarizing voltage is obtained on the basis of a constant reference voltage that is added to or subtracted from the median rest voltage of the sensor or to or from the output voltage of the integrator unit, the constant reference voltage is programmed or adjusted as a function of a desired electrostatic force to be generated deliberately for an automatic test of the electronic circuit and is independent of any variation in the high voltage or low voltage.