Computer process control system

Claim 1

A process control system for performing process control connected to at least one detecting section for detecting a process variable and generating a corresponding detection signal and to at least one actuator section for changing the process status, said process control system comprising: at least one microcomputer controlling means, housed in a first case member, for comparing the process variable with a preset target value in response to the detection signal and for subjecting a difference between the process variable and the preset target value, if any, to predetermined operations to produce a first electrical signal for minimizing the difference in a first operation mode; man-machine interface means, disposed in a second case member and connected to a connector through a first cable extending from said second case member to outside said second case member, for displaying the process variable and the preset target value in response to the detection signal and for allowing an operator to manually adjust a second electrical signal for minimizing the difference in a second operation mode, said second electrical signal being transmitted through said first cable to outside said process control system; output means, housed in a third case member which has a first surface with a receptacle detachably engaging with said connector of said man-machine interface means and a second surface, for receiving the first and second electrical signals and for selecting and holding one of the first and second electrical signals as an operation signal in accordance with one of the first and second operation modes, said second surface having a signal terminal which is exposed and which electrically transmits the operation signal to outside said process control system; and signal relaying means, having a connection panel to which at least said detecting section, said actuator section and said signal terminal of said output means are detachably connected, for transmitting the detection signal to said microcomputer controlling means and said man-machine interface means and for transmitting the operation signal from said output means to said actuator section connected to said connection panel, said signal relaying means, when another controlling means is provided for another control loop, performing its signal transmission operation also for said another controlling means.