What is an LVDT and how does it measure displacement?

LVDT (Linear Variable Differential Transformer) measures linear displacement using electromagnetic induction. It has a primary coil and two secondary coils wound on a cylindrical former with a movable magnetic core. AC excitation in the primary induces voltages in secondary coils; core position determines voltage difference. LVDT provides infinite resolution, excellent linearity (0.1%), frictionless operation (no contact between core and coils), and rugged construction. Used in position sensing, thickness measurement, and valve position feedback.