| 摘要 |
PURPOSE:To enable a press sensitivity to be constant regardless of size of resistance of a pressure-sensitive sensor for withstanding use at a cold area. CONSTITUTION:A pressure-sensitive sensor 2 whose resistance Rs changes is connected between an inverted input terminal and an output terminal of an inversion amplifier 1 and then a reference resistor 3 is connected to the inverted input terminal. On the other hand, an output terminal 5 and a non-inverted input terminal of a second amplifier 6 are connected to the output terminal. A reference voltage source 7 generating a reference voltage Eref is connected to the inverted input terminal of the second amplifier 6 and then a voltage follower 11 is connected to the output terminal through a time-constant circuit 8. The time-constant circuit 8 is provided with a hold means 12 between input and output, allows an input to be connected to an output terminal of the second amplifier 6 and a resistor 9, the other terminal of the resistor 9 to be connected to a fixed contact of a switch 12, and then the other fixed contact of the switch 12 to the non-inverted input terminal and a capacitor 10 of the voltage follower 11. The other terminal of the capacitor 10 is grounded. The other terminal of the reference resistor 3 is connected to the output terminal of the voltage follower 11. |
