| 摘要 |
PURPOSE:To prevent an erroneous shut-off operation when the valve is manually returned back to its original position by a method wherein a main control unit is constituted by an input part of sensor, a return signal input part, a memory part and a timer circuit etc. CONSTITUTION:When a valve 22 is set again to its open condition under a manual returning operation, a reed switch 19 is turned on and an output of a return sensor circuit 20 becomes ''Lo''. A microcomputer 16 acknowledges that the valve is opened and checks if a signal is fed from a flow sensor 15 within a certain time. If a signal from the flow sensor 15 is not detected, it becomes a normal gas flow supervising condition. When it is operated to return, an output from an invertor 29 becomes ''Hi'' and a charging current is flowed in a capacitor 27 through a resistor 28. An output from a voltage comparator 26 keeps ''Lo'' until a potential in the capacitor 27 is higher than a certain input potential in the voltage comparator 26 and then prohibits a signal from the flow sensor 15. Thereby, it is possible to prevent leakage in pipings and also cocks from being left unclosed. |
