LVDT vs RVDT: Difference and Comparison

LVDTs are used to measure linear displacement or position and are commonly used in industrial applications. RVDTs are a type of sensor used to measure angular displacement or rotation, similar to an LVDT, but with a rotor that rotates as the angle changes.

Key Takeaways

  1. LVDTs (Linear Variable Differential Transformers) measure linear displacement, while RVDTs (Rotary Differential Transformers) measure angular displacement.
  2. LVDTs have a higher sensitivity than RVDTs, making them more suitable for high-precision applications.
  3. RVDTs offer better stability and repeatability for angular measurements than LVDTs, making them ideal for applications like shaft rotation.

What is LVDT?

LVDT (Linear Variable Differential Transformer) is a type of sensor used to measure displacement or position. It is a non-contact device, meaning it does not require physical contact between the estimated object and the sensor. It uses an electromagnetic field to measure changes in the position of a conductive core. The core is made of a ferromagnetic material such as iron or steel and is connected to a coil of wire. When an alternating current is applied to the coil, a magnetic field is created, which is proportional to the current in the coil. This magnetic field induces a voltage across the core, and the magnitude of the voltage is proportional to the displacement of the core.

The LVDT consists of three winding coils: the primary winding, the secondary winding, and the tertiary winding. The primary winding is connected to the AC power source, and the secondary and tertiary windings are connected in series. The secondary and tertiary windings and the primary winding are electrically isolated from each other.

The LVDT is a reliable and cost-effective way to measure displacement and is widely used in industrial applications such as machine tool monitoring, automotive testing, and electronic instrumentation. It is also used in medical applications measuring heart or respiration rates. The LVDT is reliable and accurate and is a widely used sensing device.


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What is RVDT?

RVDT (Rotary Variable Differential Transformer) is an electrical transducer that converts rotary motion into a proportional electrical signal. It consists of two winding coils, a movable core, and a stationary core. The movable core is connected to a shaft that is driven by a motor. As the motor turns the post, the movable core rotates within the stationary core, which generates a differential voltage between the two windings. This differential voltage is proportional to the angular displacement of the movable core.

RVDTs are used in various applications, including automotive, aerospace, and industrial control systems. They are often used to measure a rotating shaft’s angular displacement, position, velocity, and acceleration. They are also used in position and speed control systems, such as servo and stepper motors.

RVDTs are highly reliable and durable, with long operating life and low maintenance requirements. Additionally, they are resistant to vibration, shock, and temperature fluctuations. RVDTs are relatively inexpensive and easy to install, making them popular for many applications. However, they are limited in their dynamic range, so they are not suitable for applications requiring high precision levels or large angular displacements.

Difference Between LVDT and RVDT

  1. LVDT has a low-frequency response, while RVDT has a higher-frequency response. 
  2. LVDT is suitable for low-medium speed applications, while RVDT is suitable for high-speed applications.
  3. LVDT has three separate electrical connections, whereas RVDT has four electrical connections.
  4. LVDT is based on the electromagnetic induction principle, whereas RVDT is based on the reluctance principle.
  5. LVDT is used to measure displacement, whereas RVDT is used to measure angular displacement.

Comparison Between LVDT and RVDT

Parameters of ComparisonLVDTRVDT
Winding typeLVDT uses a primary winding to induce a magnetic field.RVDT uses a secondary winding to detect a magnetic field.
OutputLVDT has a linear output.RVDT has a rotary output.
Power consumptionLVDT has a low power consumption.RVDT has a higher power consumption.
ConstructionLVDT has a single-coil construction.RVDT has a two-coil construction.
SensingLVDT is used for displacement sensing.RVDT is used for angular sensing.
  1. A multichannel digital demodulator for LVDT/RVDT position sensors | IEEE Journals & Magazine | IEEE Xplore

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