What is an LVDT?
A Linear Variable Differential Transformer (LVDT) is an electromechanical sensor used to measure linear displacement with exceptional precision. It converts small linear movements into an electrical signal, making it invaluable in industries where high accuracy is required.
LVDTs are widely used in industrial automation, aerospace, automotive, and medical applications. Their non-contact, frictionless operation makes them superior to other position sensors in terms of longevity and reliability.
How LVDTs Work
An LVDT consists of:
- A primary coil (excitation coil)
- Two secondary coils (output coils)
- A movable ferromagnetic core
When an AC voltage is applied to the primary coil, it induces a voltage in the secondary coils. As the core moves, the voltage output shifts, allowing for precise measurement of displacement. The difference between the two secondary voltages determines the position of the core.
Advantages of LVDTs
- High Precision and Resolution
- Capable of measuring minute displacements with exceptional accuracy.
- Resolution is theoretically infinite since the output signal is continuous.
- Frictionless Operation
- No mechanical contact with the core, ensuring long life and minimal wear.
- Rugged and Durable
- Can withstand harsh environments, including extreme temperatures and vibrations.
- Excellent Linearity
- Provides a near-perfect linear response over a wide range of motion.
- Reliable Over Long Distances
- LVDTs are commonly used in applications requiring measurement over extended travel ranges.
Common Applications of LVDTs
- Aerospace and Defense
- Aircraft control surfaces, landing gear positioning.
- Missile guidance and navigation systems.
- Industrial Automation
- Machine tool positioning.
- Quality control and precision measurements.
- Automotive Industry
- Suspension and chassis monitoring.
- Brake system testing.
- Medical Equipment
- MRI and CT scanners for precise movement control.
- Prosthetics and robotic-assisted surgery devices.
- Energy and Power Generation
- Monitoring steam turbine valve positions.
- Controlling nuclear reactor control rods.
LVDTs are often chosen over potentiometers and optical encoders in environments where durability and reliability matter most. Unlike potentiometers, which suffer from wear over time, LVDTs maintain their accuracy for years.
Factors to Consider When Choosing an LVDT
- Stroke Length: Choose a sensor that matches the range of displacement in your application.
- Excitation Voltage & Frequency: Ensure compatibility with your system’s power source.
- Environmental Protection: If operating in harsh conditions, opt for rugged, sealed LVDTs.
- Mounting Configuration: Consider whether a captive-core or free-core LVDT is best for your setup.
LVDTs are among the most reliable and accurate displacement sensors available today. Their contactless operation, durability, and exceptional linearity make them an industry standard for precision measurement. Whether in aerospace, industrial automation, or medical applications, LVDTs provide the performance needed for critical motion sensing tasks.
