Patent ID: 8624608

Claim:
A capacitance detecting device comprising: a capacitance element having varying capacitance depending on surrounding circumstances; a charge reading mechanism reading the charge of the capacitance element; an integrator integrating the read charge transmitted from the charge reading mechanism to convert the read charge into a voltage signal; an offset adjustment circuit removing offset from the charge transmitted to the integrator from the charge reading mechanism; and a control circuit controlling the operation of the offset adjustment circuit, wherein the offset adjustment circuit includes: a variable capacitance element switching the number of capacitative elements connected in parallel to a charge transmission line made up of a plurality of the capacitative elements and formed between the charge reading mechanism and the integrator, and setting the number to a predetermined capacitance value; and a capacitative element for adjustment that is connected in parallel to the variable capacitance element with respect to the charge transmission line, and having a capacitance value corresponding to the minimum value of the capacitative elements constituting the variable capacitance element, wherein the control circuit drives the variable capacitance element so that offset removal is performed in the variable capacitance element whenever charge is transmitted from the charge reading mechanism to the integrator, and drives the capacitative element for adjustment so that offset removal is performed only N times (M>N; M and N are natural numbers) in the capacitative element for adjustment while offset removal is repeated M times in the variable capacitance element.