As in any field, process control has its own set of common terms that you should be familiar with and that you will use when talking about control technology.
1. Setpoint (SP):
The target value we aim forβwhether itβs pressure, temperature, flow, or level. Itβs the destination.
2. Process Variable (PV):
The actual value measured in the system. Itβs the GPS of your process, always telling you where you are.
3. Error:
The difference between Setpoint and Process Variable (SP β PV). Itβs the gap weβre always trying to close.
4. Controller Output (CO):
The signal generated by the controller in response to the error. It tells the final control element (like a valve or motor) how to respond.
5. Manipulated Variable (MV):
The variable the controller adjusts to influence the processβoften the position of a control valve, pump speed, or heater power. This is how the controller drives the process toward the setpoint.
6. Load Disturbance:
Any external influence that disrupts the processβlike ambient temperature changes, feed variations, or upstream pressure shifts. A good control system anticipates and compensates for these.
7. Dead Time & Lag:
Delays are part of every process. Dead time is the delay before any response is seen, and lag is the slow response afterward. Both affect loop performance and require skilled tuning.
8. Offset
Offset is a sustained deviation of the process variable from the setpoint.
Control loops arenβt just academicβtheyβre the invisible hands that keep plants running safely, smoothly, and efficiently. Mastering them means mastering performance
