I. Overview
Servo cylinders are widely used in many industrial automation fields, such as machine tools, metallurgical equipment, construction machinery, etc. They have high requirements for precise position control. As a key accessory component of the servo cylinder, the magnetostrictive displacement sensor is responsible for real-time monitoring of the extension and retraction displacement of the cylinder piston rod, providing feedback signals for the operation of the entire system to ensure precise and accurate actions.
II. Working Principle
There are various common types of displacement sensors, such as magnetostrictive displacement sensors. They utilize the magnetostrictive effect. When a current pulse passes through the waveguide wire, a ring-shaped magnetic field is generated, which interacts with the magnetic field of the movable magnetic ring placed outside the waveguide wire, causing strain pulses in the waveguide wire. The position of the magnetic ring, that is, the displacement of the piston rod, is determined by measuring the pulse propagation time. There is also a linear variable differential transformer (LVDT), based on the principle of mutual inductance. The primary coil inputs an AC excitation voltage, and the secondary coil induces a voltage difference related to the position of the piston rod. After processing and conversion, a displacement signal is obtained.
III. Key Performance Indicators
Precision: High precision is the core requirement, generally reaching the micrometer or even nanometer level. For instance, the precision of sensors used in precision machine tools is often better than ±0.01mm to ensure the precision of processing.
Resolution: It reflects the small displacement change that can be detected. For equipment with fine operations, high resolution is required. For example, the resolution of sensors associated with electronic chip manufacturing equipment can reach 0.1μm.
Linearity: It refers to the degree of linear deviation between the sensor output and the actual displacement. Good linearity ensures that the displacement measurement is accurate and reliable throughout the full range. The linearity of the product can reach ± 0.05%FS (full scale).
Repeatability: The consistency of results when measuring the same displacement multiple times. High repeatability ensures the stable operation of the system, and the repeatability error is usually controlled within a small range, such as ±0.005mm.
Servo cylinder displacement sensor
IV. Key Points for Installation
To ensure the coaxiality of the magnetostrictive displacement sensor and the cylinder piston rod, excessive installation deviation will lead to an increase in measurement error. Generally, the coaxiality deviation should be controlled within 0.1mm, and professional tooling fixtures can be used to assist in installation and calibration.
The sensor must be firmly and reliably fixed to prevent loosening and displacement during the frequent operation of the cylinder. The use of high-strength bolts and the reasonable design of the installation bracket structure can effectively ensure its stability.
For environments with protective requirements, such as damp, dusty, and strong electromagnetic interference sites, it is necessary to properly encapsulate the sensors, select appropriate sealing materials and shielding housings, and ensure their normal working life.
V. Considerations for Selection
Cylinder stroke: Select the appropriate range of the sensor based on the large and small stroke ranges of the servo oil to ensure precise measurement throughout the process. Generally, it is recommended that the sensor range be slightly larger than the cylinder stroke, with a margin of 10% to 20% reserved.
Working environment: In high-temperature environments, high-temperature resistant sensors should be selected, whose materials and electronic components can adapt to high temperatures. In corrosive environments, such as chemical equipment, the sensor housing and contact components need to have anti-corrosion properties.
Compatibility with control systems: The output signal types of sensors (analog quantities such as 4-20mA, 0-10V, digital quantities such as SSI, CANopen, etc.) should be compatible with the back-end control system to facilitate seamless integration and rapid data processing.
VI. Maintenance and Care
Regularly clean the dust, oil stains and other contaminants on the surface of the magnetostrictive displacement sensor to avoid affecting the measurement accuracy. You can wipe it with a mild cleaner, but be careful not to damage the sensitive components.
Check the tightness of the installation parts. If any are loose, tighten them in time. At the same time, check if the connecting cables are damaged or aged to ensure stable signal transmission and replace the faulty cables in a timely manner.
In accordance with the requirements of the product manual, calibrate the sensor regularly. Especially when the equipment has been running for a long time or there are signs of accuracy deviation, use the standard displacement calibration device to readjust its zero point, range and other parameters to ensure measurement accuracy.
Shenzhen Miran Technology Co., LTD
June 30, 2025