Glossary · Control theory and process control
PI controller
Also known as: Proportional-integral controller
German: PI-Regler
In control engineering, a PI controller combines proportional and integral action: the proportional part reacts to the current control error and the integral part removes steady-state error over time.
- Control theory
In one sentence
A PI controller combines proportional and integral action; it is the most common controller for flow, pressure and level loops.
Example
The flow loop of a dosing pump uses a PI controller with a gain of 0.5 and an integral time of 3 seconds.
How it applies
- Engineering: Most process loops, such as flow, pressure and level, run as PI because derivative action would amplify noise. A PI controller with saturation needs Anti-windup.
- Commissioning: Tune the gain for response speed and the integral time for how fast offset disappears. Record both, with units, because vendors express integral action differently.
- Documentation: Control narratives often say "PID" when the loop actually runs as PI. State the active terms, so later changes and troubleshooting start from the right assumption.
- Maintenance: Keep the tuned values in the configuration backup, so a replaced controller or restored project starts with the verified parameters.
PI controller vs. PID controller
The PID controller adds derivative action for more damping on slow processes such as temperature. For fast or noisy loops, PI is usually the better choice.