| 摘要 |
<p>PURPOSE:To enhance detection accuracy by preventing erroneous detection caused by environmental change or secular change by generating the pressure detection voltage having the magnitude corresponding to the pressure applied to a pressure-sensitive element and performing the detection based on the fluctuation of said voltage. CONSTITUTION:A variable resistor whose resistance value changes corresponding to pressure is provided to a pressure-sensitive sensor 1 as a pressure-sensitive element 4. A pressure change detection circuit 10 detects the magnitude of the pressure applied to the sensor 1 on the basis of the resistance value Rv of the element 4 to output the detection voltage Vs corresponding thereto. Fur ther, a condensor 14 cuts off the DC component of the voltage Vs outputted from the circuit 10 to take out the same. The output voltage VQ of the con denser 14 is not outputted when the resistance value Rv of the element 4 changes gently but outputted only when the change of the resistance value Rv is sudden. Therefore, when detection is performed on the basis of the voltage VQ, detection based on a change of pressure but not on the magnitude of pressure becomes possible and, even when the resistance value Rv is changed by secular change or temp. change, the erroneous detection due to said change can be prevented.</p> |
