A _______________ only controller will have an offset from the desired set point.

A proportional-only controller is characterized by its reliance on the proportional term of a control algorithm to adjust outputs in response to error signals. This means it adjusts the output in direct proportion to the error between the desired set point and the process variable.

However, one of the limitations of a proportional-only controller is that it typically cannot eliminate the steady-state error, leading to an offset between the actual process variable and the desired setpoint. This offset occurs because as the process variable approaches the set point, the proportional action decreases, reducing the output adjustment to a point where it may no longer reach the exact set point.

Other types of controllers, such as integral controllers, can eliminate this steady-state error over time by continuously adjusting the output based on the accumulated error. Derivative controllers focus on the rate of change of the error, and pneumatic controllers refer to the type of actuation rather than the control strategy itself. Thus, a proportional-only controller inherently results in a steady-state offset as it cannot compensate indefinitely for persistent errors.