| 摘要 |
PROBLEM TO BE SOLVED: To make the sensor characteristics in high and low concentration areas to be linear by making the sensor resistance variable and making the amplification factor of an amplifier variable also. SOLUTION: When an oxygen sensor is inserted into an atmosphere to be measured, a sensor output current I flows according to its concentration, and a sensor output voltage V2 is generated at both ends of the resistance VR. First, an adjusting resistance VR2 is adjusted so that the sensor output voltage may become an A characteristic in ideal characteristic when the concentration at an adjusting point 1 is low. Next, an adjusting resistance VR3 is adjusted so that the sensor output voltage may become a B characteristic in sensor characteristic. Accordingly, the gain of an operation amplifier OP2 becomes high and the in-advance adjusted A characteristic is changed upward, so the resistance VR2 is adjusted again so as to make the sensor output voltage to be an A characteristic in ideal characteristic when the adjusting point 1 is at low concentration. Thus, the output voltage of the operation amplifier decreases again, and the resistance VR3 is adjusted again. Such an adjustment is repeated alternately so as to match with an idela characteristic finally. |
