Hydraulic Cylinder Position Sensor Technology

Ensuring precision movement in robotic assemblies.

As the demand for greater control and functionality increases, position-sensor-instrumented hydraulic cylinders are becoming more important in the heavy industry, mobile equipment, and subsea worlds. Position sensors for feedback in hydraulic or pneumatic cylinders have typically used one of three technologies: Linear Variable Inductance Transducers (LVITs), variable resistance potentiometers (Pots), or magnetostrictive transducers (MLDTs). While other sensor technologies have occasionally been used in these applications, the focus of this article is a comparison among these three popular technologies. Ultimately, a user or systems integrator must determine the exact requirements of the application and which technology best satisfies them on a total installed cost versus performance basis. The strengths and weaknesses of linear variable inductance, variable resistance pots, and magnetostrictive sensors are all examined below, together with a feature-by-feature comparison chart.

First, a point to be noted is that all three of these common sensing technologies utilize a long probe that extends into a deep, small diameter blind hole gun-drilled into the internal end of the cylinder rod.