SENSOR SENSITIVITY ADJUSTING DEVICE

PROBLEM TO BE SOLVED: To reduce a number of parts by packaging a voltage applying means having a fixed resistance identically to other components to miniaturize a device, by adjusting sensor sensitivity by resistance adjustment of a variable resistor. SOLUTION: A voltage Vs, which is equivalent to a reference voltage Vr that a power voltage is divided by resistors R1, R2 of a power supply IC 3, is applied to a terminal of an OP amplifier 6. Consequently, a current described as 'a voltage Vs/a resistance value of a variable resistor 4' is flowed and a current of the same value is flowed in a sensor 2. That is, a current based on the voltage Vs and the resistance of the variable resistor 4 is made to flow in the sensor 2. Therefore, sensitivity adjustment of the sensor 2 is done by the resistance value of the variable resistor 4 so as to flow the current value Is. As a result, a measured material is detected by activating the sensor 2, and a detected signal amplified by an amplifying circuit 5 is output 7. Packaging an OP amplifier 6, and resistances R1, R2 in an IC 3 identically can reduce to 3 parts, the IC 3, variable resistor 4, and amplifying circuit 5.