A proportional control is defined as:

Proportional control is a fundamental concept in control systems where the output response of the system is directly related to the difference between a desired set point and the current state of the system. In this context, when there is a deviation from the set point, a proportional controller adjusts the actuating element—such as a valve or damper—in a way that corresponds to the magnitude of the deviation.

For instance, if the temperature in a room is lower than the set point, a proportional controller will adjust the heating system to increase the temperature by a certain amount. The adjustment of the actuator is not binary (on/off); rather, it allows for smooth variations in output based on the input error. This results in improved maintainability of the desired conditions (like temperature or pressure), as smaller deviations will produce smaller corrections, leading to fine-tuned control.

This definition is key because it highlights the essence of proportional control: the relationship between the input error and the actuator’s response is consistent and direct, ensuring that the system can operate efficiently and effectively within desired parameters.