When a cylinder must stop at intermediate positions or keep pace with another axis, the controller needs a trustworthy measurement of motion. A basic end-of-stroke switch confirms only that a point was reached. Continuous position feedback reports where the actuator is throughout the stroke. The sensor choice should follow the required control accuracy, stroke, environment and maintenance plan.
What should the sensor actually measure?
A sensor built into the cylinder can measure piston position relative to the cylinder body. An external device may instead measure the moving machine member relative to its frame. These are not always identical: pin clearance, structural deflection and backlash can change the relationship between cylinder stroke and the position that matters to the process. State the control point on the machine drawing before asking for a sensor.
Common feedback options
| Option | Useful feature | Integration check |
|---|---|---|
| Internal magnetostrictive transducer | Non-contact continuous piston position; available as a cylinder-integrated option | Stroke length, dead zone, connector location, output format and service access |
| LVDT | Continuous linear displacement measurement with established control-system use | Excitation or signal conditioning, protected installation and usable measuring range |
| External linear sensor or cable encoder | Can observe a machine member directly and may be easier to replace | Guarding, alignment, cable travel, exposure and the effect of frame movement |
Parker documents magnetostrictive probes, LVDTs, linear potentiometers and string potentiometers as possible feedback devices for servo control. This list does not mean that any sensor can be substituted without checking the controller’s electrical input and the cylinder’s mechanical design.
Specify performance at system level
Resolution, repeatability and accuracy describe different properties. Also ask about update time, temperature effects, electrical noise and what happens after power is restored. Position accuracy at the load depends on the sensor, valve, hydraulic stiffness, friction and mechanical linkage. A precise transducer alone cannot remove backlash or a poorly tuned valve response.
RFQ checklist
- Required stroke, speed, stopping tolerance and repeatability at the load.
- Sensor mounting location, environmental rating, connector orientation and cable route.
- Controller supply voltage, signal protocol, fault detection and safe response to lost feedback.
- Calibration method, replacement access and FAT measurement points.
For multiple actuators, pair this selection with our cylinder synchronization guide. Discuss an integrated sensor when requesting a custom press cylinder.
References: Parker electrohydraulic actuator and LDT guidance; Parker position servo control bulletin. Cover: original schematic illustration.