Rotary Variable Differential Transformer-RVDT

Principle of RVDT:

RVDT is used where precise angular movement is to be measured. RVDT uses the same principle as the LVDT except that, LVDT is for linear measurement while RVDT is for Angular one.

Construction and Working of RVDT:

RVDT is almost identical in the construction with LVDT. The ferrite core in LVDT is replaced by heart or cardiode shaped core. This core is mounted on the shaft or plunger which is capable of rotating. This rotational movement of the shaft creates the imbalance in the external circuit and this imbalance signal is used to measure the angular displacement of the shaft. RVDT give linear output up to displacement of +-40 degree. Then output starts becoming nonlinear.

Applications:

1. RVDT in the signal conditioning as RVDT Conditioner.
2. RVDT as the position sensor.

Examples:

1. Quarter Turn Valve.
2. Mail Sorters.
3. Fractional Shaft measurements.
4. Actuator position sensing in the Aircraft.
5. Marine, Constructional and Agricultural vehicles.

Advantages of RVDT:

1. Low cost.
2. Solid and Robust construction makes it to work in different environments.
3. No frictional resistance, so high accuracy over long time duration.
4. Negligible hysteresis.
5. Excellent reproducibility.

Disadvantages of RVDT:

1. Contact between plunger and measuring surface is always not possible.
2. RVDT provide linear output for about +-40 degree which limits its usability.