| 摘要 |
PURPOSE:To continue the operation of a plant without interruption even if single equipment has a fault by comparing a process signal with a set value signal in a device and thus detecting a fault of a control system, and smoothly converting control to a normal operating system. CONSTITUTION:An arithmetic circuit 12 for the variation rate of deviation calculates the deviation between pressure signals A and B from respective pressure detectors and the variation rate of the signals A and B; when the deviation exceeds a predetermined value, a status signal C is sent to an intermediate value arithmetic circuit 14 and a delay switching circuit 16. On receiving the status signal C, the intermediate value arithmetic circuit 14 uses three signals, i.e. the pressure signals A and B and a set value signal D from a sett circuit to calculate the intermediate value, which is supplied to a fault diagnosing circuit 15. |
