Figure. RVDT
In the previous article, we have learned about Linear variable differential transformer (LVDT). Rotary Variable Differential Transformer (RVDT) is a variation of LVDT and used to sense angular displacement. It is a passive transducer.
 
In short, RVDT provides a variable alternating current (AC) output voltage that is linearly proportional to the angular displacement of its input shaft. 
 
RVDT is very much similar to LVDT in construction except core. RVDT has a rotating core which rotates between the windings by means of a shaft. It has one primary and two secondary windings.
 
The primary winding is excited with alternating current source. The output pair(secondary windings) is structured so that one winding is in-phase with the excitation winding, and the second is 180° out-of-phase with the excitation winding.

 

 

 
The secondary windings are connected in series opposition. At the null position, output voltages of secondary windings S1 and S2 are equal. Hence the net output of RVDT is zero. When there is a clockwise rotation, it produces an increasing voltage of a secondary winding of one phase. When there is an anti-clockwise rotation, it produces an increasing voltage of a secondary winding of opposite phase.

Applications of RVDT

1. Hydraulic pump control
2. Valve position
3. Rotary actuator feedback
4. Dancer arm position
5. Throttle lever position feedback
6. Reeler / Dereeler

Excercise

Q. Describe the working of RVDT with the help of neat circuit diagram.

Rotary Variable Differential Transformer (RVDT) Working Principle & Applications

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