LVDT Transducer: Advantages and Disadvantages

What is LVDT? Introduction

• LVDT stands for Linear Variable Differential Transformer or Transducer.
• 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.

… about construction … Working of LVDT …

• 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

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Benefits or Advantages of LVDT Transducer

The following are the benefits or advantages of an LVDT Transducer:

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

Drawbacks or Disadvantages of LVDT Transducer

The following are the disadvantages of an LVDT Transducer:

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