Linear Variable Displacement Transformer
The linear variable differential transformer (LVDT) is a type of transducer used to accurately measure displacement. It is composed of a primary coil centered between two secondary coils (identically wound and spaced) which are wrapped around a cylindrical tube. A ferromagnetic core is then passed through this tube. LVDTs work in a similar manner to transformers. A central primary coil A induces a magnetic field using AC current. This establishes a field in a magnetic core of permeable material. Depending on where the core lays between the outside secondary coils B and C, a voltage differential between the two is created. This differential voltage is used to measure the distance the core has moved relative to the center, or Null Point. As the core moves further away from the null point in either direction, the voltage difference between B and C increases. Below are a couple videos I took during the testing phase of the LVDT.