Linear Variable Differential Transducer
LVDT (Linear Variable Differential Transformer), is an absolute position/displacement transducer that converts a position or linear displacement from a mechanical reference (zero, or null position) into a proportional electrical signal containing phase (for direction) and amplitude (for distance) information. The LVDT operation does not require an electrical contact between the moving part (probe or core assembly) and the coil assembly, but instead relies on electromagnetic coupling; this and the fact that LVDTs can operate without any built-in electronic circuitry are the primary reasons why they have been widely used in applications where long life and high reliability under very severe environments are a required, such as in Military/Aerospace, process controls, automation, robotics, nuclear, chemical plants, hydraulics, power turbines, and many others.
LVDT’s come in two different varieties, either DC or AC output. DC versions in general have integral electronics or there is limited need for complex signal conditioning, or AC variants which will require signal conditioning.
Considerations when choosing should be on size as AC versions are much smaller body length than DC, and also temperature.