Ⅰ、 Overview

Servo cylinders are widely used in many industrial automation fields, such as machine tools, metallurgical equipment, construction machinery, etc., which require high precision position control. Magnetostrictive displacement sensor as a key supporting components of servo cylinder, bear the real-time monitoring cylinder piston rod expansion and contraction displacement of the important task, for the operation of the whole system to provide feedback signals, to ensure that the action is accurate in place.

Ⅱ、The working principle

There are various types of common displacement sensors, such as magnetostrictive displacement sensors, which utilize the magnetostrictive effect, when a current pulse passes through the waveguide filament, it generates a toroidal magnetic field, which interacts with the magnetic field of the movable magnetic ring outside the waveguide filament to generate strain pulses in the waveguide filament, and the position of the magnetic ring, i.e., the displacement of the piston rod is determined through the measurement of the pulse propagation time; and the Linear Variable Differential Transformer (LVDT) The LVDT is based on the principle of mutual inductance, where the primary coil inputs an AC excitation voltage and the secondary coil induces a voltage difference related to the position of the piston rod, which is processed and converted to obtain a displacement signal.

Ⅲ、The key performance indicators

Precision: high precision is the core requirement, generally up to micron or even nanometer level, like precision machine tools supporting the sensor accuracy is often better than ± 0.01mm, in order to protect the degree of precision processing.

Resolution: reflecting the small displacement changes that can be detected, for the fine operation of the equipment, the requirements of high resolution, such as electronic chip manufacturing equipment associated with the sensor resolution of up to 0.1μm.

Linearity: refers to the degree of linear deviation between the sensor output and the actual displacement, good linearity to ensure that the displacement measurement is accurate and reliable in the full range, the product linearity up to ±0.05% FS (full scale).

Repeatability: the consistency of the results of multiple measurements of the same displacement, high repeatability to ensure stable operation of the system, repeatability error is usually controlled within a small range, such as ± 0.005mm.

                                                         
                                                                                                 Servo Cylinder Displacement Sensor

Ⅳ、Installation points

To ensure the coaxiality of the magnetostrictive displacement sensor and the cylinder piston rod, the installation deviation will lead to an increase in the measurement error, the general coaxial deviation needs to be controlled within 0.1mm, with the help of professional fixtures to assist in the installation and calibration. The sensor must be fixed firmly and reliably, to prevent the cylinder from frequent action in the process of loosening displacement, the use of high-strength bolts and reasonable design of the mounting bracket structure, can effectively protect its stability. For the protection requirements of the environment, such as humidity, dust, strong electromagnetic interference places, do a good job of sensor protection package, choose the appropriate sealing materials, shielding shell, to ensure its normal working life.

Ⅴ、Selection considerations

Cylinder stroke: according to the servo oil large and small stroke range selected sensor appropriate range, to ensure that the whole process can be accurately measured, generally recommended that the sensor range is slightly larger than the cylinder stroke, leaving a margin of 10% - 20%.

Working environment: high-temperature environment to choose a high-temperature sensor, its materials, electronic components can adapt to high temperatures; in corrosive environments, such as chemical equipment, the sensor shell, contact parts need to have corrosion resistance.

Compatibility with the control system: the sensor output signal type (analog, such as 4-20mA, 0-10V, digital, such as SSI, CANopen, etc.) should be adapted to the back-end control system, to facilitate seamless and rapid data processing.

Ⅵ、Maintenance

Regularly clean the magnetostrictive displacement sensor surface dust, oil and other pollutants, to avoid its impact on the measurement accuracy, available mild detergent wipe, pay attention to do not damage the sensitive parts.

Check the installation parts of the fastening situation, if loose in time to fasten; at the same time to see whether the connection cable is broken, aging, to ensure stable signal transmission, and timely replacement of the problematic cable.

Calibrate the sensor regularly according to the requirements of the product specification, especially when the equipment has been running for a long time or when the accuracy shows signs of deviation, use the standard displacement calibration device to recalibrate its zero point, range and other parameters to ensure the accuracy of the measurement.