Glossary · Pneumatics and hydraulics
Servo valve
Also known as: Electrohydraulic servo valve, Servovalve
German: Servoventil
In hydraulics, a servo valve is a high-response, continuously operating control valve that converts a low-power electrical signal into a precisely proportional hydraulic flow or pressure, typically using a torque motor and a pilot stage, for closed-loop control.
- Fluid power
In one sentence
A servo valve converts a small electrical signal into precisely proportional hydraulic flow for dynamic closed-loop control.
Example
A test rig uses servo valves to drive hydraulic actuators that simulate road loads on a vehicle axle.
How it applies
- Engineering: Servo valves are used where high dynamics and accuracy are needed, such as test systems, presses and flight simulators. They require very clean fluid and filters matched to the valve.
- Commissioning: Null adjustment, loop tuning and filter conditioning (flushing) are done before operation.
- Maintenance: Contamination is the main failure cause; oil analysis and filter changes are critical.
- Documentation: State required fluid cleanliness (for example as an ISO 4406 code), filter intervals and the flushing procedure. Describe behavior on loss of signal, which depends on the valve's failsafe design.
Servo valve vs. proportional valve
A servo valve typically has higher bandwidth and near-zero overlap. A Proportional valve is more robust against contamination and used where dynamics are less demanding.