Advantage of LVDT

Question

Advantage of LVDT

Examoogle · Accepted Answer

Option D: All of above

Explanation & Concepts:
The Linear Variable Differential Transformer (LVDT) is an inductive transducer used to convert mechanical displacement into an electrical signal. It is widely favored in instrumentation due to its high accuracy, robust design, and excellent resolution.

Working Principle: An LVDT consists of a primary coil energized by an AC source and two secondary coils connected in series opposition. As the ferromagnetic core moves, the mutual inductance between the primary and each secondary coil changes, resulting in a differential output voltage proportional to the core displacement. When the core is in the central null position, the induced voltages in the secondary coils cancel out, yielding zero output.

Key Formulas: $V_{out} = V_{s1} - V_{s2}$ — Differential output voltage where $V_{s1}$ and $V_{s2}$ are secondary coil voltages.; $V_{out} \propto \Delta x$ — Output voltage is directly proportional to the displacement $x$ within the linear range.

Key Points: Operates on the principle of mutual induction.; Provides an AC output voltage proportional to the core position.; The core is non-contacting, which minimizes mechanical wear.

Advantages: High linearity (often within 0.05% of full scale); Infinite resolution due to lack of friction/steps; High sensitivity and high output voltage; Rugged construction capable of withstanding shock and vibration

Disadvantages: Sensitive to stray magnetic fields; Requires high displacement for full output compared to other sensors; Dynamic response is limited by the mass of the core

Applications: Measuring small displacements in material testing; Used as a secondary transducer in pressure and force sensors; Automated industrial inspection and position control

Additional Info: The core is typically made of high-permeability nickel-iron alloy.. The 'null' position corresponds to the core being perfectly centered between the secondary windings.

Answer: D is correct — The LVDT is characterized by high linearity, excellent resolution, high sensitivity, and a rugged, low-friction mechanical design.

Exam Tip: Always remember that LVDT output is AC; it requires a phase-sensitive demodulator if a DC output is needed for a controller.

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Option A: 0.05% linearity and finite resolution

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Option B: High output and high sensitivity

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Option C: Rugged and less friction

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