The Tribune, Chandigarh, India - Science Tribune

In conventional electronic control systems, the output of the process under control is converted into an electrical signal output which is compared to a reference input signal. The difference or error signal actuates the controller to generate a control action signal. When the control signal is proportional to the error signal at a given moment, the output can take on any value between zero and one (fully off and fully on). If the control signal varies as the cumulative value of the error signals up to that moment, the control action is integral. It is also possible to have a control signal that depends upon the rate of change of error giving a derivative controller.