What is a Feedback Loop?
A Feedback Loop is a control mechanism in which a system continuously measures its output and compares it to the desired value (Setpoint), in order to apply corrective action based on that comparison.
Feedback loops ensure that a process operates in a stable, accurate and self-correcting manner.
They are essential in automation, process control and Motion Control applications such as temperature control, speed regulation and level monitoring.
🔁 How does a feedback loop work?
- Setpoint (SP): the desired value (e.g. 100°C)
- Process Value (PV): the measured value (e.g. 96.3°C)
- Comparison: the difference (error signal) between SP and PV
- Controller: determines the appropriate action based on the error signal
- Actuator (MV): adjusts the system (e.g. opens a gas control valve)
- Sensor: measures again → the loop repeats
🔧 Key terms
| Term | Description |
|---|---|
| PV | Process Value – measured value |
| SP | Setpoint – target value of the system |
| MV | Manipulated Variable – output signal sent to the actuator |
| Controller | Adjusts the output based on the difference between SP and PV |
| PID | Commonly used feedback controller in industry |
🧠 Example: temperature control
- SP = 100°C
- PV = 95°C (sensor measures this)
- Controller = increases gas valve opening via MV
- Result: temperature rises → PV approaches SP
🏭 Practical applications
- PID-controlled temperature or pressure regulation
- Motion Control: position and speed control of motors
- Tank filling/dosing based on weight or flow
- Synchronisation of multiple PLC-controlled axes
- Automatic balancing of heating/cooling systems
✅ Benefits of feedback loops
- Automatic correction without manual intervention
- Higher accuracy and stability
- Self-correcting behaviour in the face of disturbances
- Essential for safe and efficient process control
📌 In summary
A feedback loop ensures that systems self-correct based on measurements, and as such forms the core of modern industrial automation.