The sensor requires no electrical contact between itself and the moving part it measures the position of. Instead, the sensor relies upon electromagnetic coupling. Find out more at http://brainrack.co/what-is-a-lvdt/
Basic Benefits of LVDT Sensors For Industries
What are some of the main benefits of using LVDT sensors? Some LVDT sensors can measure movements that are as tiny as a few millionths of an inch. They last a long time, don't produce friction to operate, and can withstand all sorts of tough conditions. They can also respond very quickly to changes and respond to these changes. They do all of these without needed electrical connections too.