10 Advantages and 5 Disadvantages of lvdt transducer

Introduction : A Linear Variable Differential Transformer (LVDT) is an electromechanical transducer used to convert linear displacement into an electrical signal. It is known for its high accuracy, infinite resolution and frictionless operation. LVDT is widely used in industrial automation, aerospace and structural monitoring. However, like any device, it has both benefits and drawbacks that must be evaluated based on application requirements.

LVDT Features & working:

• It is a passive transducer which measures linear displacement.
• It produces a variable AC voltage which represents the physical position of an object connected to it.
• In its simplest form, it uses one primary coil energized by an AC voltage and two secondary coils (having an equal number of turns) wound around a hollow tube.
• A movable soft iron core is placed between the primary and secondary coils. This is shown in Figure 1.

• When an alternating current is connected to the primary coil, a magnetic field expands and contracts around the coil.
• When the field is strong and large enough, it cuts the secondary coil and induces voltage. The induced voltage at the secondary is in phase with the applied voltage at the primary coil.
• Each secondary coil produces a separate voltage.

Uses of LVDT

LVDTs are preferred in these applications due to their high accuracy, long service life, and ability to operate in harsh environments.

• Industrial Automation: Used for precise position feedback in actuators, valves, and robotic arms.
• Aerospace Applications: Measures the movement of control surfaces, landing gears, and actuators.
• Civil Engineering: Monitors structural displacement in bridges, dams, and buildings under stress.
• Automotive Testing: Used in crash testing and suspension system development to measure displacement.
• Power Generation: Detects valve positions and turbine movement in nuclear and thermal power plants.
• Material Testing Machines: Measures elongation, compression, or deformation of materials under load.
• Medical Equipment: Used in devices like MRI-compatible instruments and patient movement monitoring systems.
• Geotechnical Monitoring: Helps track earth movement, tunnel displacement, or ground settlement over time.

Advantages of LVDT Transducer

Following are some of the benefits of LVDT Transducer:

1. It has a high measurement range, from 1.25 mm to 250 mm.
2. It has low power consumption, less than about 1 Watt.
3. It is a frictionless device.
4. It offers high resolution, greater than 10 mm.
5. Higher sensitivity of greater than 40 V/mm can be achieved.
6. It is smaller in size.
7. It is less in weight.
8. It has lower hysteresis.
9. It is solid and robust in construction. Hence, it is tolerant to shocks and vibrations.
10. It has excellent repeatability.
11. It has very low output impedance.

Disadvantages of LVDT Transducer

Following are some of the drawbacks of LVDT Transducer:

1. Large displacement is needed for a small output.
2. It is affected by external magnetic fields, and hence the entire LVDT circuit needs to be shielded to achieve desired accuracy.
3. Vibrations due to displacement can affect the performance of the LVDT device.
4. The performance of the LVDT is affected due to an increase in temperature.
5. In order to get a DC output, an external demodulator is required.
6. It has limited dynamic response.

Conclusion: LVDT transducers provide excellent precision, durability and long term reliability, making them ideal for accurate displacement measurement in demanding environments. Despite their high cost, sensitivity to electromagnetic interference, and requirement for signal conditioning, their non-contact nature and high resolution often outweigh the drawbacks. Ultimately, LVDTs are a robust solution when precise and continuous linear measurement is essential.