Patent ID: 8632667

Claim:
A deterioration signal generation device for generating a deterioration signal simulating a deteriorated state of an oxygen sensor from a detection signal of the oxygen sensor, the oxygen sensor outputting a detection signal which abruptly changes in signal value around a specific air-fuel ratio in response to concentration of oxygen in an exhaust gas of an internal combustion engine, the deterioration signal generation device outputting the deterioration signal to an external device, and the deterioration signal generation device being supplied with electric power from a power supply different than a power supply connected to the external device, the deterioration signal generation device comprising: a connector which electrically connects a ground line of a first power supply supplying electric power to the external device and a ground line of a second power supply supplying electric power to the deterioration signal generation device; an interface which electrically connects the deterioration signal generation device to a first output line at a reference potential side of the oxygen sensor and to a second output line at a sensor potential side of the oxygen sensor that changes in potential in response to oxygen concentration, and that acquires a first potential of the first output line and a second potential of the second output line; a calculator configured to calculate a first differential value between the first potential and the second potential; a processor configured to perform one or more operations on the first differential value in response to a target deterioration state to thereby obtain a second differential value; an operational amplifier configured to acquire a third potential of a first input line at a reference potential side of the external device, wherein the first input line is connected to the first output line in a case where the oxygen sensor is connected to the external device; and an output circuit configured to generate the deterioration signal having as a signal value a fourth potential obtained by superposing the second differential value on the third potential, to thereby output the deterioration signal to a second input line at a sensor potential side of the external device, wherein the second input line is connected to the second output line in a case where the oxygen sensor is connected to the external device.