Rotary variable differential transformer

The transformer acts as an electromechanical transducer that outputs an alternating current (AC) voltage proportional to the angular displacement of its rotor shaft.

In operation, an alternating current (AC) voltage is applied to the transformer primary to energize the RVDT.

RVDTs employ contactless, electromagnetic coupling, which provides long life and reliable, repeatable position sensing with high resolution, even under extreme operating conditions.

Putting the above mathematical equations in some theoretical form, the working of RVDT can be explained as below.

Basic RVDT construction and operation is provided by rotating an iron-core bearing supported within a housed stator assembly.

When the rotor is in a position that directs the available flux equally in both the in-phase and out-of-phase coils, the output voltages cancel and result in a zero value signal.

When the rotor shaft is displaced from E.Z., the resulting output signals have a magnitude and phase relationship proportional to the direction of rotation.

Since most RVDT signal conditioning systems measure signal as a function of the transformation ratio (TR), excitation voltage drift beyond 7.5% typically has no effect on sensor accuracy and strict voltage regulation is not typically necessary.