| 摘要 |
<p>PURPOSE:To surely prevent a controller from being malfunction or malunfunction by detecting whether input signals contradict each other or not and deciding the occurrence of abnormality of an input circuit to raise an alarm when they do not contradict each other and holding the preceding control state then. CONSTITUTION:A limit switch 1 as the input circuit has a moving contact point connected to a DC power source 2 and has contact points (a) and (b) connected to a digital controller 3. The controller 3 is provided with a digital input circuit 5, a control and arithmetic circuit 6, a digital output circuit 11, and an output connector 12, and the control and arithmetic circuit 6 consists of an exclusive OR circuit 7 as a logical contradiction detecting circuit and an abnormality deciding circuit consisting of a NOT circuit 8, a flip-flop circuit 10, etc. In case of the abnormal state where no contradictions are not caused, an alarm signal AS or the like from an output connector 12 is supplied to an alarm device 13 and a control signal CS is supplied to an electromagnetic relay 14 to control a final control element.</p> |
