PURPOSE: To simplify the structure of a sensor part and to attain to enhance temp. detecting preciseness, by performing the detection of oxygen concn. output and the detection of the impedance of a temp. detecting element by a same electrode.
CONSTITUTION: A voltage applying circuit 9 applying prescribed voltage (voltage obtained by applying high frequency AC current to predetermined DC voltage in a piled-up state) and a current detecting resistor 10 detecting radio wave passing through an oxygen concn. sensor 8 are provided to said sensor 8 and the AC component of a current (a detecting current) flowed through the resistor 10 is taken out by a bypass filter 13 and thereafter detected by a wave detecting comparator 4 to be compared to reference voltage. In addition, ON-and-OFF of the oxygen concn. heater 11 mounted in the sensor 8 is carried out by the output thereof to adjust the sensor 8 to a predetermined temp. On the other hand, the detected current is passed through a low pass filter 15 to be brought to a DC component which is, in turn, transmitted to machinery such as a computer from an oxygen concn. detecting terminal 16 showing a current value corresponding to oxygen concn.
SUZUKI MASATOSHI
HARADA TAKASHI
SANO HIROMI
SAITOU TOSHITAKA
SHIBATA SHINKOU
YAMAKAWA MICHIHIRO
