JPS5736302A - Controller - Google Patents

Abstract

PURPOSE:To switch an operation mode from AUTO to CASCADE with a simple operation by executing changeover if a fault of an external set value signal is not detected or suspending it if detected at the changeover command from an automatic operation mode to a cascade one. CONSTITUTION:A controller 1 applies operation such as PID to the deviation between a measured value PV and a set value SV to obtain operation output MV. When a mode select button C is depressed and a select command signal S2 is generated in order to switch an operation mode from automatic AUT to cascade CAS mode, a control circuit 6 turns a switch 3 to the CAS side if a falt detecting circuit 4 does not detect the fault of an external setting signal SV2, and the operation mode is transferred to CASCADE. On the contrary, when the circuit 4 detects the fault of the signal SV2, the circuit 6 suspends the changeover of the switch 3 to the CAS side to hold the automatic operation mode and displays the suspension of the operation of the operation mode changeoveron a display device 9 to inform the contents to the operator.