Patent ID: 8525722

Claim:
An AD converting device comprising: a double integral AD converter having an integrator which when a first integrated voltage is input to the integrator, performs a first integration in which a difference between the first integrated voltage and a reference voltage is integrated, after the first integration is performed and when a second integrated voltage is input to the integrator, performs a second integration in which a difference between the second integrated voltage and the reference voltage is integrated, and outputs an integrated voltage according to at least the second integration; and an output part which receives the integrated voltage output from the integrator and the reference voltage, counts time from when the second integration is started to when the integrated voltage becomes equal to the reference voltage, and outputs the counted time as a digital value; a variable resistance; and a resistance-voltage conversion circuit which changes the first integrated voltage in proportion to a product of a resistance value of the variable resistance after being varied in the variable resistance and a value of an electrical current applied to the variable resistance and changes the second integrated voltage and the reference voltage in proportion to a product of a total resistance value of the variable resistance and the electrical current applied to the variable resistance.