Glossary · Control theory and process control
Derivative controller
Also known as: D controller, Derivative action
German: D-Regler
In control engineering, a derivative controller (derivative action) produces an output proportional to the rate of change of the control error or of the measured value; it is used in combination with proportional action, never alone.
- Control theory
In one sentence
Derivative action responds to the rate of change of the error or measurement; it dampens loops and is used with P action, not alone.
Example
In a temperature loop with a slow heater, derivative action reduces the heating output as the temperature rises quickly toward the setpoint, limiting overshoot.
How it applies
- Engineering: A pure derivative controller has no output at constant error, so it cannot hold a setpoint; that is why derivative action appears only in PD controller and PID controller structures. Derivative action amplifies measurement noise, so it is usually filtered and often applied to the measurement rather than the error to avoid spikes on setpoint changes.
- Commissioning: Noisy signals such as flow measurements usually run without derivative action. Check the signal quality before enabling it.
- Documentation: State whether derivative action acts on error or measurement and which filter time is used. Parameter names differ between vendors (derivative time, rate, Td), so glossaries and manuals should map them.
Derivative controller vs. PD controller
"Derivative controller" names the D component in isolation, as in the German D-Regler of control theory textbooks. A PD controller is the practical combination of proportional and derivative action.