A controller that includes proportional, reset, and derivative functions is referred to as what type of controller?

A controller that incorporates proportional, reset, and derivative functions is recognized as a PID controller. The term "PID" stands for Proportional, Integral, and Derivative, which are the three fundamental components that define its operation.

The proportional aspect of the controller adjusts the output based on the current error, which is the difference between the desired setpoint and the actual process variable. The integral portion addresses the accumulation of past errors, effectively eliminating any persistent steady-state error that might exist. The derivative component predicts future error based on its rate of change and provides a dampening effect, helping to mitigate overshoot and enhance system stability.

This combination allows the PID controller to achieve precise control over a process by responding to current conditions, correcting past errors, and anticipating future trends. As a result, it's commonly utilized in various control applications where maintaining a desired output is critical.

Other types of controllers, like PI and PD controllers, each incorporate only two of the three elements of the PID controller. The "On-off controller," in contrast, simply toggles the control output on or off without any modulation based on error, which makes it less effective for applications requiring fine-tuned control.