What type of controller provides a proportional output based on the error between process variable and setpoint?

A proportional controller is specifically designed to produce an output that is directly proportional to the error measured between the process variable (the current value of the variable being controlled) and the setpoint (the desired value). The output of the controller varies in direct relation to the magnitude of this error.

For example, if the process variable is significantly below the setpoint, the proportional controller will generate a larger output to correct the error. Conversely, if the process variable is very close to the setpoint, the output will be smaller. This principle allows the controller to adjust the control variable dynamically based on how much deviation exists from the setpoint.

In contrast, other types of controllers, such as integral and derivative controllers, serve different functions. An integral controller focuses on accumulating the past errors to eliminate steady-state error, while a derivative controller predicts future error based on the rate of change. A PID controller combines all three elements: proportional, integral, and derivative, but the question specifically asks for the type of controller that operates solely based on proportional output related to the current error. Therefore, the proportional controller is the correct answer.