In my last entry, I talked about using a magnetostrictive linear position sensor in a hydraulic cylinder. I received a few questions about that application, and I wanted to take this opportunity to answer one of them.
Q. Why is it necessary to use a non-ferrous spacer to attach the magnet ring to the face of the hydraulic cylinder’s piston?
Magnetism, much like electricity, follows the path of least resistance. And the large, flat surface of a steel hydraulic cylinder piston provides an irresistible path for magnetic lines of flux. And, since the magnet ring can only provide so much “power”, the shunting of a large portion of the magnetic field strength through the piston face can ultimately result in there not being enough magnetic energy at the position transducer to ensure proper operation.
For more information on linear position transducers, click here.
A magnetostrictive position transducer relies on a magnet to act as a position marker. In a hydraulic cylinder, the magnet usually takes the form of a doughnut-shaped ring which is attached to the face of the piston. Since the piston is almost always made of ferrous metal (i.e., steel), it is important to use a non-ferrous material to act as a spacer so that the magnet does not directly contact the piston face.