Sensor device

A sensor device comprising:

• a first electrode being kept at a reference potential;
• a second electrode that changes a position thereof in response to a change of surrounding pressure and faces the first electrode;
• a casing being kept at the reference potential and provided outside the second electrode;
• a capacitance detection circuit to amplify a signal from the second electrode and detect an electrostatic capacitance between the first electrode and the second electrode at a predetermined sampling cycle;
• and
• a signal processing circuit to measure a difference ΔC of electrostatic capacitance values before and after a sampling, compare the difference ΔC with a predetermined threshold value Cta, and when ΔC>Cta, determine that a foreign object is attached to the casing;
• wherein
• when the signal processing circuit determines that a foreign object is attached, a gain of the capacitance detection circuit, or a gain of the signal processing circuit, or gains of both the capacitance detection circuit and the signal processing circuit, are adjusted.