Top 6 Questions to Answer to Reduce Process Variability eBook
Top 6 Questions to Answer to Reduce Process Variability
There are times when a process variable (PV) shows an unacceptable level of variability around its setpoint (SP) while being regulated by a PID controller. In order to improve the quality of regulation of the process variable, there are six important questions to consider.
In this eBook we provide the six questions along with subsequent observations to help you in answering the questions.
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Tuning Rules for PI and PID
Tuning Rules for PI and PID
Determining Which Controller to Use
A key challenge in setting up a control system is determining what type of controller to use. The PID controller is generally accepted as the standard for process control, but the PI controller is sometimes a suitable alternative. A PI controller is the equivalent of a PID controller with its D (derivative) term set to zero.
It is important to understand how controllers interact with each different type of process. For details, see Table 1.
Table 1 – How PI and PID Controllers Interact with Different Kinds of Processes
| Controller | Pl Controller | PID Controller |
| Effective for These Processes | Fast processes, such as flow, pressure, and some temperature loops. | Slower processes, such as level and insulated temperature. |
| Tuning Parameters | P = Proportional I= IntegralPl controller is the equivalent of a PID controller with its D (derivative) term set to zero. |
P = Proportional I= Integral D = DerivativeThe derivative term is particularly important for integrating processes, such as level, position, & well-insulated temperature.In general, using a derivative term can significantly increase the speed of the response of a non-integrating process and suppresses overshoot. |
| Response Speed | Response is slower, thus enabling a smooth and accurate PV change. | Response is faster, thus enabling setpoint to be reached more quickly. |
| Overshoot | Overshoot will likely occur. | Reduced or no overshoot. |
