| 摘要 |
PURPOSE:To secure synthetic safety of gas supplying by a method wherein a driving unit is worked automatically to close a shut-off valve by detecting at an electric current detecting section when an abnormal consumed electric current flows in a micro-computer. CONSTITUTION:In case the micro-computer 5 is under a normal condition, the current flowing into the point (a) of the resistance 12 at the current detecting unit 11 is small and the voltage of the resistance 12 hardly drops while the voltage thereof is almost same as a battery 6 voltage. However, the micro-computer 5 becomes abnormal condition due to noise and aging stress or the like for example and the electric current consumption thereof becomes large; as a result, the voltage drop of the resistance 12 is increased and the potential at the point (a) drops. The output of an AND gate 13 becomes low due to the drop of the potential at the point (a) to drive a driving unit 7 and the shut- off valve 10 is operated. The fail safe may be realized by providing the electric current detecting section when the micro-computer becomes abnormal and the current thereof increases in the circuit. |
