What is RVDT? Working, Construction, Formula, Applications

The Rotary Variable Differential Transformer (RVDT) is an electromechanical transducer that converts the angular displacement of a rotating shaft into an electrical signal. It is a dependable and precise device used in a variety of industrial applications. In this article, we will explore the working principle, construction, and applications of RVDT in detail.

Working Principle:

The RVDT operates based on the principle of mutual induction. It consists of a primary winding and two secondary windings wound on a cylindrical former. An AC voltage is applied to the primary winding, while the secondary windings are connected in opposite directions. As the shaft rotates, it alters the mutual inductance between the primary and secondary windings. This change induces a voltage in the secondary windings that is proportional to the angular displacement of the shaft. The output voltage of the RVDT is linearly related to the input displacement.

Rotary Variable Differential Transformer (RVDT)
Rotary Variable Differential Transformer (RVDT)


The RVDT is constructed using a cylindrical former made of non-magnetic materials like glass or ceramic. The primary winding is wound around the central part of the former, and the secondary windings are wound on both sides of the primary winding. The secondary windings are connected in opposite directions to eliminate common-mode noise. The former is then mounted on a shaft, which is linked to the rotating system whose displacement needs to be measured.

RVDT Formula:

The RVDT formula establishes the relationship between the input angular displacement (θ) and the corresponding output voltage (Vout) of the RVDT. The formula is expressed as:

Vout = Vmax * (θ / θmax)

In this formula:

– Vout represents the output voltage generated by the RVDT in response to the input angular displacement.

– Vmax is the maximum output voltage that the RVDT can produce, corresponding to the maximum angular displacement.

– θ represents the input angular displacement or position, indicating the rotation or movement of the object or system being measured.

– θmax represents the maximum angular displacement or position that corresponds to the maximum output voltage (Vmax), establishing the maximum limit of accurately measurable angles.

According to the formula, the output voltage (Vout) is directly proportional to the input angular displacement (θ). As the angle increases, the output voltage increases proportionally. The scaling factor is determined by the ratio of the input angular displacement (θ) to the maximum angular displacement (θmax), multiplied by the maximum output voltage (Vmax).


The RVDT finds extensive use in various industrial applications for measuring the angular displacement of rotating shafts. Some common applications include:

1. Aerospace: RVDTs are employed in aircraft and spacecraft to measure the angular displacement of control surfaces like flaps, ailerons, and rudders.

2. Robotics: RVDTs are used in robotics to measure the angular displacement of robotic arms and joints.

3. Power Generation: RVDTs are utilized in power generation plants to measure the angular displacement of turbine blades and generator rotors.

4. Automotive: RVDTs are employed in automotive applications to measure the angular displacement of steering systems and suspension systems.


The RVDT offers several advantages, including:

1. High Accuracy: RVDTs provide precise measurements and linearity across a wide range of angular displacements.

2. Reliability: RVDTs are highly reliable devices with no moving parts, making them suitable for harsh industrial environments.

3. Low Noise: RVDTs produce low noise output, making them suitable for high-precision applications.

4. Easy to Install: RVDTs are easy to install and require minimal maintenance.

The RVDT is a precise and reliable device used to measure the angular displacement of rotating shafts in various industrial applications. Its accuracy, reliability, and low noise output make it suitable for high-precision tasks. As technology

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