| 摘要 |
PURPOSE:To monitor faults of a gate circuit so as to output signals of the normal gate circuit from a process controller, by providing a reference gate circuit having the same function as the gate circuit has and comparing the output of the gate circuit with that of the reference gate circuit. CONSTITUTION:Tripled controllers 2A, 2B, and 2C are used for controlling a process 1 and a redundancy gate circuit section 3 selects one of the controllers 2A-2C and outputs the selection to the process 1. The circuit 3 consists of gate circuits 4A and 4B, a gate circuit 5 for reference, and output switching circuit 6. When no faults occurs in the gate circuits 4A, 4B, and 5, inputs of comparator circuits 7A and 7B coincide with each other and their outputs become zero. When the gate circuit 4A is faulty, a relay circuit 10 is not excited and the output of the gate circuit 4B is selected and, accordingly, this device is normally operated. Moreover, when the circuit 5 is out of order, the relay circuit 10 is excited and the output of the circuit 4A is fetched. In case when the circuit 6 is faulty, one of the outputs of the gate circuits 4A and 4B is outputted. |
