Comparing position sensor technologies for hydraulic cylinder feedback: Page 4 of 4

September 18, 2018 //By Edward E. Herceg
Comparing position sensor technologies for hydraulic cylinder feedback
As the demand for increased control and functionality has increased over the years, sensor- instrumented cylinders are becoming more important in the heavy industry, subsea, and mobile equipment worlds.  Position feedback sensors for hydraulic or pneumatic cylinders have most commonly used one of three technologies:  Magnetostrictive (MLDTs), Variable Resistance (Pots), and Variable Inductance (LVITs) sensors.

The MHPE Series LVIT position sensor.

Remote field calibration is a standard feature offered on many variable inductance sensors. This feature permits a user to scale the output of the sensor after it is installed on the cylinder. With a simple process to set the zero and the full scale output points, the sensor will give the desired full scale output over its newly set range, so it is no longer necessary to scale the unit in the associated control system.

In a related fluid power application, though not involving hydraulic cylinders, spool position feedback sensing in two-stage hydraulic valves is often done with a pressure sealed LVDT.  A short range LVIT sensor with its simple inductive probe inserted into a blind hole in the end of the main spool is often an easier installation than the LVDT that requires an isolation tube to seal off the its core from the valve’s pilot pressure, and external electronics to operate the LVDT.

Where there are still many fluid power applications where resistance potentiometers and magnetostrictive sensors are a good solution, these applications tend to fall to either side of a bell curve. Recent electronic advancements and the flexibility of package designs make LVIT variable inductance sensors very cost effective for mainstream in-cylinder applications, especially those that tend to be near the peak of that bell curve.

 

About the author:

Edward E. Herceg is Chief Technology Officer at Alliance Sensors Group - www.alliancesensors.com

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