So2 concentration detection device

PROBLEM TO BE SOLVED: To provide an SOconcentration detector capable of detecting SOconcentration in exhaust gas without using a dedicated sensor.SOLUTION: As shown in Fig. 4, the current value Iflowing when a voltage (0.3 V) in a limit current region is applied indicates a constant value (limit current value) regardless of the elapsed time. While, the current value Iflowing when a voltage (0.6 V) in an overcurrent region is applied decreases with the elapsed time and approaches a limit current value after 30 seconds from the start of application of the voltage. In the present embodiment, the current value difference |I-I| is defined as "SOreduction current", and detects the SOconcentration around the sensor on the basis of the integrated value of the SOreduction current.