| 摘要 |
<p>PURPOSE:To keep safety even for a fault in a temperature signal input circuit by monitoring whether or not an energizing time on a load continues for more than a prescribed time by providing a timer circuit. CONSTITUTION:The timer circuit 7 is used for monitoring the time of the turn-on state of a control relay Ry1, etc., and the counting of an turn-on time is started from a time when the relay Ry1 is turned on by the circuit 7. When the energizing time on a heater H1 continues for more than the prescribed time, a processing different from an ordinary processing is started assuming the above fact as that the fault may happen in the temperature input circuit 3. In other words, temperature signals before and after are compared by stopping the energizing of the load for the prescribed time, and it is judged as normal when the temperature signal goes down, then, the processing is returned to the ordinary processing, and when it is judged that no change is observed, it is judged as that the fault is generated in the circuit 3, then, the energizing is stopped. In such a way, it is possible to detect the fault in the circuit 3 effectively, and to secure the safety.</p> |
