What is a Linear Variable Differential Transformer(LVDT)?

An LVDT (Linear Variable Differential Transformer) is an electromechanical device that converts mechanical motion or vibrations—specifically rectilinear motion—into variable electrical currents, voltages, or signals, and vice versa. It is primarily used in automatic control systems and as a mechanical motion sensor in measurement technologies. Electromechanical transducers are classified based on their conversion principles or output signal types.

In essence, a linear transducer outputs a voltage that correlates with the measured parameters, such as force, allowing for straightforward signal conditioning. LVDT sensors are sensitive to electromagnetic interference, and using shorter connection cables can help reduce electrical resistance and minimize errors. Typically, a linear displacement transducer requires three to four wires for power supply and signal output.

The physical structure of an LVDT consists of a hollow metallic cylinder in which a smaller-diameter shaft moves freely along the cylinder's axis. This shaft, or pushrod, has a magnetically conductive core that must remain inside the cylinder's coil assembly during operation.

In practical use, the pushrod is connected to the movable object whose position is being measured (the measurand), while the coil assembly is fixed to a reference point. As the measurand moves, the core shifts within the coil assembly, and this motion is captured electrically.