Electronic controller having a detachable front panel

Claim 1

In an electronic controller for controlling an external process, the controller being of the type having a main housing for control circuitry for controlling at least one of a plurality of process variables and at least one of a plurality of control parameters associated with the process, a front panel unit on which are arranged means for incrementally changing a value of at least one process variable controlled by the controller in discrete magnitude steps, means for selecting a control parameter controlled by the electronic controller, means for incrementally changing a value of the selected control parameter in discrete magnitude steps, means for indicating the value of the process variable, means for indicating the selected control parameter and means for indicating the value of the selected control parameter, the improvement comprising: means for electrically detachably connecting the front panel unit from said main housing of the electronic controller; means for mechanically detachably connecting the front panel unit from said main housing of the electronic controller; a master microprocessor included in said control circuitry contained in said main housing for controlling the process, said master microprocessor receiving inputs associated with said at least one process variable and said control parameters from said controlled process and transmitting outputs associated with said at least one process variable and said control parameters to said controlled process; and a slave microprocessor contained in said front panel unit and permanently electrically coupled to said means for selecting a control parameter, said means for incrementally changing a value of the selected control parameter, said means for incrementally changing a value of the at least one process variable, said means for indicating the selected control parameter, said means for indicating the value of the at least one process variable and said means for indicating the value of the selected control parameter, said slave microprocessor coupled to said master microprocessor in said main housing through said means for electrically detachably connecting and said means for mechanically detachably connecting, said slave microprocessor being responsive to signals received from said master microprocessor via said means for electrically detachably connecting for updating values of said at least one process variable and said control parameters and transmitting signals to said master microprocessor via said means for electrically detachably connecting for changing the value of said selected control parameter and said at least one process variable in response to actuation of said respective means for incrementally changing the value of said selected control parameter and said at least one process variable; said control circuitry in said main housing comprising means for independently controlling the process whereby said front panel unit may be detached from said main housing without interrupting the control of the process.