| 摘要 |
PURPOSE:To secure a pressure sensing circuit with ability of stable, accurate, and certain sensing of pressure, and enhance the reliance upon the foreign matter pinch sensing. CONSTITUTION:A first amplifier 1 has a pressure sensor 2, which is connected between the inversive input terminal and the output terminal and whose resistance value Rs varies in compliance with the pressur force P, wherein inversive input terminal 1a is grounded through a grounding resistance 3, and the output terminal is connected with output terminal 5 and a second amplifier 6 inversive input end. At the non-inversive input end of this second amplifier 6, a reference voltage source 7 is connected which generates a constant reference voltage Eref, and output end is connected with a grounding capacitor 10 through a resistance 8 and analog switch 9 and also with a voltage follower 11 whose output end is in connection with the No.1 amplifier 1 non-inversive input terminal. A voltage holding means to hold the input voltage Ei of No.1 amplifier 1 is composed of these named voltage follower 11, capacitor 10, and analog switch 9 opened and closed at certain timings in conformity to switch control signals SW. |
