SENSOR DEVICE

A sensor device includes an electrically conductive base substrate defining a first electrode kept at a reference potential, a membrane defining a second electrode that changes a position thereof in response to a change of surrounding pressure and faces the base substrate, a casing that is kept at the reference potential and is outside the membrane, a capacitance detection circuit to amplify a signal from the membrane and detect an electrostatic capacitance between electrodes 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 AC with a predetermined threshold value Cta, and when ΔC≥Cta, determine that a foreign object is attached to the casing. Thus, the attachment of a foreign object can be reliably detected.