The offset = 1 - 1 = 0, indicates that the integral control action eliminates any offset. It also indicates that the increase in controller gain and decrease in reset value reduce the value of natural period of oscillation and damping factor of closed loop response. Hence, we can improve the speed of the closed loop response at the expense of higher deviations and longer oscillations. In other words, high and low makes the closed loop response more sensitive and proportional action will be stronger. On the other hand, low and high makes system sluggish but integral action would be stronger (no offset, no overshoot).

IV.2.5 Effect of derivative control action on a process

We shall find closed loop response of first order and second order processes under the influence of a “derivative only” controller.

	(IV.33)
	(IV.34)

It indicates that the derivative control action does not change the order of the response. It also indicates that time constant of the first order process is increased by a positive quantity of , i.e ., the derivative control action makes a process sluggish. On the other hand, natural period of oscillation of second order process remains same. Damping factor increases with increase in and/or Increase in damping factor means less sensitivity of process response and more robustness in the process behavior.