Motion Control & Drives


Position sensor detection for ­hydraulic cylinders

July 2018 Motion Control & Drives

Siko’s SGH wire-actuated encoders measure cylinder stroke as well as speed in hydraulic cylinders with impressive efficiency, flexibility and robustness.

The technology

SGH sensors use a wire draw mechanism that is integrated directly into the cylinder to measure the stroke. The wire is secured to the piston head. When the cylinder extends, the wire wound on a wire drum is pulled out. The resulting rotation of the drum is detected by the contactless sensor system and converted into a linear position. This means that precise and absolute position or speed tracking of the cylinder is possible at any time. The magnets used to measure the rotation are scanned by the contactless sensor system through the pressure resistant base plate of the SGH sensors. The electronic components are fully encapsulated and located on the non-pressurised side of the system. The entire measuring system is therefore incorporated into the cylinder and optimally protected against external environmental influences. The advantage is that in contrast to measuring systems mounted externally on the cylinder, the sensor system cannot be damaged, negatively affected or even destroyed by environmental conditions.

Developed for tough conditions in mobile hydraulic applications

The SGH sensors were designed and developed in line with the strict specifications of renowned hydraulic cylinder manufacturers. Market demands ensured that Siko met its requirements regarding robustness, durability and functionality. Siko worked closely with cylinder manufacturers to define and satisfy the specifications regarding service life, shock and vibration resistance, EMC and compatibility with various hydraulic media. All specifications were tested and confirmed in endurance tests at the facilities of cylinder manufacturers, or in external accredited laboratories.

Intelligent sensors for smart cylinders

The SGH technology transforms hydraulic and telescopic cylinders as well as piston accumulators into smart cylinders and hydraulic systems. A suitable sensor is available for all applications. With measuring lengths of up to 5000 mm, a wide selection of interfaces as well as high flexibility for integration of the sensors, the SGH family offers a wide range of possibilities. Redundant options and sensors for performance levels of up to PLd are available for safety critical applications.

Reliable position tracking

Smart sensors take mobile hydraulics to a new level of safety and efficiency. Functional safety is a term that is being widely discussed. Safety concepts for mobile machinery has been a topic of interest since the implementation of the new Machinery Directive EN 13849. Sensors in the Siko SGH range help implement intelligent safety concepts for mobile machinery and meet the requirements of the specific safety standards for different utility vehicles.

The safety versions of the SGH25 and SGH50 sensors meet the requirements for use in applications up to Performance Level d (PLd). Safe and redundant design in compliance with CAT3 as well as a safe mechanical design means Siko products are pre-destined for use in safety-critical applications, also under unusual conditions.

In addition, the sensors supply process data which not only serve to satisfy safety requirements, but also offer an added value for the machine. The process data can, therefore, provide insight into an impending seal maintenance interval. Flexible support tracking in crane and lifting applications extend the working ranges of the machine. Memory functions in industrial trucks save time and make work safer. All these are examples of how SGH sensors not only make machinery safer, but also more efficient.

Advantages of the SGH encoder include:

• Absolute detection of the cylinder position.

• Direct integration into the cylinder.

• Measuring range up to 5000 mm.

• Can be used in safety applications up to PLd.

• No drilling of the piston required.

• Can also be used in telescopic cylinders.

• Perfectly protected due to protection category IP69K.

• Durable and robust. – developed in line with mobile hydraulic requirements.

• High EMC.

For more information contact Instrotech, +27 (0)10 595 1831, sales@instrotech.co.za, www.instrotech.co.za



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