In a proportional controller, the output is directly proportional to the controller input. As the input changes, the output will change proportionally within the proportional band. Outside the proportional band, the output will remain unchanged.
The width of the proportional band can be adjusted to set the sensitivity of the controller's response. A narrow proportional band implies a high controller gain, making the controller more sensitive to changes in the input signal. This can result in faster response but can also lead to instability if the system is not properly tuned.
Conversely, a wide proportional band implies a lower controller gain, making the controller less sensitive to changes in the input signal. This may lead to slower response, but it can improve stability and reduce oscillations.
The optimal width of the proportional band depends on the specific process characteristics and desired performance. Often, the proportional band is initially set wide to ensure stability and then gradually narrowed to improve the controller's response and performance.
In summary, the proportional band of a PID controller determines the range of input signal deviations within which the output will change proportionally in a linear relationship to the input signal. Adjusting the width of the proportional band can modify the controller's sensitivity and the overall dynamic response of the system.