LVDT (Linear Variable Differential Transformer)

LVDTs consist of electrically unconnected primary and secondary coils which, depending on the design, are wound next to or on top of each other and coupled via a ferromagnetic core according to the transformer principle.

The primary coil supplied with an AC voltage induces a voltage via the magnetic coupling in the opposite coil halves of the secondary side, which is symmetrically zero in the centre position of the core or armature.

If the plunger is moved, the impedances of the two coil halves change in opposite directions to each other, so that a measuring voltage proportional to the distance travelled is present at the output of the secondary side.

Compared to differential chokes, a differential transformer enables shorter overall lengths and is also less sensitive to external interference such as electromagnetic interference or resistance changes in the measuring lines due to the galvanic separation of the primary and secondary windings. However, the more complex design leads to higher manufacturing costs.

LVIT (Linear Variable Inductive Transducer)

LVITs are based on the differential choke principle. They consist of a continuous coil with a centre tap or of two identical coils that lie next to each other and are connected in series.

A ferromagnetic core inside the coil system causes the impedances of both coil halves to change during movement. If the core is moved from its centre position, the impedances of the two measuring coils change in opposite directions, which is evaluated by the connected electronics and output as a signal proportional to the displacement.

Inductive displacement transducers as differential chokes are characterised by their cost-effective design, high accuracy classes and very low temperature drift.