What is MV (Manipulated Variable)?
MV stands for Manipulated Variable — the output signal of a controller, such as a PID controller, which actively influences the process. Using this signal, the controller drives an Actuator to bring the PV (Process Value) closer to the desired SP (Setpoint).
MV = what the controller does to steer the process.
🔁 How does MV work in a control loop?
- The controller compares the SP (desired) with the PV (measured)
- Based on that deviation, the controller calculates an MV
- The MV is sent as a control signal to an actuator
- The actuator influences the process → the PV changes → a new cycle begins
🔧 Examples of MV in industrial applications
| Application | MV = output signal to… | Purpose |
|---|---|---|
| Temperature control | Steam injection valve (0–100%) | Maintain tank temperature |
| Flow control | Pump variable frequency drive (Hz) | Regulate flow rate |
| Pressure control | Electronic pressure control valve (0–10 V) | Maintain constant pressure |
| Level control | Adjust pump speed via VFD | Stabilise tank level |
| pH control | Drive a dosing pump (flow rate) | Correct the pH value |
📊 MV in the control loop
- SP = 3.0 bar (setpoint)
- PV = 2.7 bar (measured value)
- MV = 65% valve opening → The controller opens the valve further to raise the pressure
⚙️ MV in OT systems
| System | Role of MV |
|---|---|
| PLC | Calculates the MV based on the PID controller or logic |
| SCADA | Visualises the MV and allows manual override |
| DCS | Coordinates hundreds of MVs and optimises process dynamics |
| Historian | Logs MV values for tuning, analysis and audit |
📌 In summary
MV is the output signal by which a controller influences a process to reach the desired state. It is essential for stable, efficient and automated process control.