Explain the following terms in a controller? 1) measurement variable 2) desired variable 3) deviation 4) output

Measurement variable: It is the demand variable measured and controlled.

Desired Variable: it is the demand signal (setpoint) to which the process variable is controlled.

Deviation: it is the error signal caused by the difference between the measurement and the demand signal.

Output: It is the corrective signal from the controller to the final control element.