What is meant by "proportional band" in a control system?

Proportional band refers to the range of the process variable over which the controller's output changes in response to deviations from the setpoint. In a control system, when the process variable deviates from the desired setpoint, the controller calculates the error and adjusts the output to correct that error. The proportional band defines the limits of this adjustment; it indicates how much deviation in the process variable is necessary to produce a certain level of output change from the controller.

For example, if the proportional band is set wide, the controller may allow for larger deviations before making significant changes to the output. Conversely, a narrow proportional band means that even slight deviations from the setpoint can lead to larger changes in output. This characteristic allows for finer control of the process, making proportional band a vital parameter in tuning control loops.

Understanding this concept is crucial for control system technicians, as it directly impacts system responsiveness and stability. Therefore, it is vital for operators and technicians to accurately configure the proportional band for optimal performance in their control systems.