| 摘要 |
PURPOSE:To repair a controller while keeping a normal output to a process at all times by using an output switch circuit to select one or normal controllers and giving an output when a faulty controller is repaired. CONSTITUTION:If any of controllers 2A-2C is faulty and repaired, one of relays 9A-9C corresponding thereto is excited and relays 10A-10C switch an output of an output switch circuit 6 to that of a normal controller. A relay 7 is excited at the same time to switch an output signal 5 of the process controller from an output of an intermediate value selection circuit 4 to an out-put 6' of the circuit 6. A relay 7' is excited at the same time to hold the relays 10A-10C. Then the output of the controller switched by the relays 10A-10C is held as the output 6' during repair of the faulty controller. Thus, the faulty controller is repaired and the output 6' is compared with that of the other controller not switched to complete the repair of the faulty controller without using the signal 5 as a faulty signal. |
