| 摘要 |
PURPOSE:To prevent erroneous operation based upon inter-wiring capacity to electrodes, by turning on SCR with a prescribed phase of a signal voltage from a detection electrode. CONSTITUTION:In a water tank, electrodes E1-E3 are provided and on the basis of the secondary induced voltage of transformer 1, an electric current flows to resistance R3 via electrode E3. This current varies with a liquid level and the voltage developed across resistance R3 is synthesized by the circuit including contact 21 via the inverting amplifying circuit including OP amplifier 31; and the synthesized voltage is passed through gate circuit 4 and then has its polarity and magnitude detected by diode 32 and SCR33 to drive relay 2. Only 0-90 deg. phase components of the input voltage are passed through circuit 4 and applied to the gate of SCR33. As a result, the malfunction of the detector due to electrostatic capacity in wiring for electrodes can be prevented. |
