| 摘要 |
PURPOSE:To prevent an apparatus from being damaged, and to execute continuously a control by providing a signal suppressing circuit in the rear of a digital controlling circuit so that a prescribed control can be executed even in case when an output of the digital controlling circuit has been varied remarkably. CONSTITUTION:In a digital controlling circuit 3, an output is limited so that it does not have a rate of change exceeding some value by an operator of the inside and outputted. In this state, when the operator itself has failed, a rate-of-change detector 2 limits a rate of change of an output signal of that time to some value by a rate-of-change limiter 7, a difference of this limited value and an output signal of the circuit 3 is detected by the rate-of-change detector, and when its value is larger than a set value, the output signal of the circuit 3 is suppressed by outputting an output signal of the detector 2 by a relay switch 11. At the same time, an alarm 15 is raised. In accordance with it, an operator switches a changeover switch 10 which has been provided on an analog controlling circuit 1 to a manual setting device side, by which the circuit 3 is detached, and a control valve 4 is controlled by the circuit 1 singly.
|
