Patent ID: 7655121

Claim:
An interface device for a gas sensor, the gas sensor being capable of producing a current output responsive to the concentration of a specific gas component in measurement gas, the interface device comprising: a detection resistor having first and second resistor ends through which the current output of the gas sensor flows to generate voltages of opposite polarity at the first and second resistor ends; a differential amplifier having first and second input terminals to receive the voltages of the first and second resistor ends, respectively, and an output terminal to output a voltage according to a difference between the voltages of the first and second resistor ends; a first switching element switched between a transmission state and an interruption state so as to transmit the voltage of the first resistor end to the first input terminal of the differential amplifier in the transmission state and interrupt transmission of the voltage of the first resistor end to the first input terminal of the differential amplifier in the interruption state; and a second switching element turned on to establish continuity between the first and second input terminals of the differential amplifier when the first switching element is in the interruption state.