Inspection method of sensor device and sensor device

A sensor device, comprising:

• a sensor unit including:
• a first capacitive sensor element connected between a first driving terminal and a signal terminal;
• and
• a second capacitive sensor element connected between a second driving terminal and the signal terminal;
• a first driving circuit configured to output a first driving voltage or a second driving voltage to the first driving terminal;
• a second driving circuit configured to output the first driving voltage or the second driving voltage to the second driving terminal;
• a capacitor having a first end connected to the signal terminal and a second end;
• an amplifier circuit configured to output an amplified voltage to the second end of the capacitor, by amplifying a difference between a voltage of the signal terminal and a reference voltage, such that the voltage of the signal terminal becomes close to the reference voltage;
• a switching circuit configured to discharge electric charges accumulated in the capacitor;
• and
• a control circuit configured to control the first driving circuit, the second driving circuit, and the switching circuit such that the amplified voltage output from the amplifier circuit corresponds to a difference between a capacitance of the first capacitive sensor element and a capacitance of the second capacitive sensor element,
• wherein the control circuit is further configured to perform a first inspection stage in which the control circuit:
• controls, in a first step, the switching circuit to discharge the capacitor, and both of the first and second driving circuits to output to the first driving voltage to the first and second driving terminals, respectively;
• controls, in a second step, the switching circuit to stop the discharge of the capacitor to make the capacitor available for charging, and both of the first and second driving circuits to output the second driving voltage to the first and second driving terminals, respectively;
• and
• determines, in a third step, whether or not the amplified voltage output from the amplifier circuit in the second step is within a first normal range between a first threshold voltage and a power supply voltage, wherein the first threshold voltage is higher than the reference voltage and lower than the power supply voltage.