LVDT - Linear Variable Differential Transformers - (all MESSOTRON types Dxx)
LVDTs consist of primary and secondary coils (beside each other or over and under, depending on the model) which are not connected electrically and which are coupled according to the transformer principle via a ferromagnetic core. The secondary coil consists of two coils (halves) which are wired inversely, the overall signal of which thus forms a “difference”.
The primary coil of the LVDT, supplied with an AC voltage, induces a voltage in the secondary coil. Because of the inverse wiring, in the center position of these coils (immersion core)the voltage is equal to zero. If the immersion core is shifted, the measurement voltage at the differential inductor changes proportional to the displacement.
A LVDT permits more favorable displacement-construction length relationships than, for example, LVITs and is less sensitive to external interference factors (e.g. greater temperature differences within the sensor range or changes in resistance in the measuring cable). The more elaborate construction leads to somewhat higher manufacturing costs.