| 摘要 |
PURPOSE:To carry out the fault diagnosis of the process input and output devices without causing the change of the process state but by opening the exciting power source of the process unit via the relay circuit. CONSTITUTION:Electronic computer 1 gives the switching command to switching unit 4 via process output device 2. Relay contact 10-0 is turned on by the switching command, and accordingly relay contact 13-0 is turned off along with the exciting power sources of relays 14-1-14-n turned off each. As a result, no control output is given to the process unit. Under these conditions, the OFF command is given first to all contacts 10-1-10-n and then the input is given to contacts 12-1-12-n. If device 2 and input device 3 are normal, contacts 12-1-12-n are all turned off. And in case even one of the contacts is turned on, the fault is detected for the output or input at that point. Thus the error process is given. After this, computer 1 gives the ON command to all contacts 10-1-10-n, and then carries out the error process in the same way in case even one of the contacts is turned off. |
