Absolute displacement measurements in hydraulic cylinders
The induSENSOR EDS product line for displacement measurements on or in hydraulic cylinders has been available for many years. The probe sensor is based on the eddy current principle and consists of a measuring coil and a coil for temperature compensation, which are installed in a pressure-sealed stainless steel tube. An aluminium tube, which fits over the probe sensor in a non-contact manner, is used as the measurement object. An important advantage of this measurement technique is its robustness.
For OEM applications, such a sensor was integrated into a miniature hydraulic actuator. The sensor weighs 13g and is 56mm long with a flange diameter of 7.7mm and a probe diameter of 2.5mm. The linear measurement range is 28mm, customised adjustments of similar sized versions enable ranges up to 100mm. Electronics for signal processing and power supply to the sensor can easily be mounted externally. Separating the electronics makes the sensor suitable for continuous use at temperatures up to 165°C.
The oil in the cylinder also acts as a mechanical absorber of shock and vibrations. The integration in the cylinder provides protection against mechanical damage and external influences. By using appropriate connection methods and materials, the probe sensor can withstand up to 375 bar pressure, making it ideal for hydraulic systems.