Question

If the amplitude is proportional to the core movement, then the output of a Differential Transformer (LVDT) is a:

• A. Sine-wave
• B. Square-wave
• C. Ramp-wave
• D. DC Voltage

Hint:

LVDT → AC excitation → Sine wave output proportional to displacement.

Answer 1

The Correct Option is A

A Linear Variable Differential Transformer (LVDT) is an electromechanical device used to measure linear displacement. The fundamental operation of an LVDT involves its core movement, which alters the magnetic field and generates an electrical output. Here's a concise explanation of how the output is determined:

1. Construction and Working of LVDT: An LVDT consists of a primary coil and two secondary coils wound on a cylindrical form. When an AC voltage is applied to the primary coil, it induces a current in the secondary coils.

2. Core Position and Amplitude Relationship: The ferromagnetic core, when moved linearly, affects the magnetic coupling between the primary and secondary coils. The output voltage from the secondary coils changes with the core's position.

3. Output Characteristics: The combined output from the secondary coils varies sinusoidally with the core position. As the core moves from the center position, the differential voltage changes in a manner that is proportional to the sine of the displacement angle.

4. Resulting Output: Given the proportional nature between the core movement and the induced voltage, and the sinusoidal characteristic of this relationship, the output of the LVDT when the amplitude changes due to core movement is indeed a sine-wave. This characteristic is because the differential transformer is excited by AC voltage, translating mechanical movement into a sinusoidal electrical output.

Thus, if the amplitude is proportional to the core movement in an LVDT, the output will be sinusoidal, confirming that the correct answer is: Sine-wave.