What type of controller has output proportional to the amount of deviation?

A controller that has output proportional to the amount of deviation is known as a proportional controller. This type of controller produces an output that is directly related to the difference between a desired setpoint and the actual process variable, referred to as the error or deviation. For instance, if the temperature in a boiler is below the setpoint, the controller increases the output to the heating element proportionally to how far the temperature is from the desired level. This means that the greater the deviation, the larger the output response from the controller.

Proportional control is widely used because it is simple and effective for many applications. It allows for continuous adjustment based on real-time data, helping to maintain processes within desired limits without overly complex systems. This characteristic is what distinguishes it from other types of controllers, such as integral controllers, which accumulate the error over time, or two-position controllers, which switch outputs on and off without proportional response.