Question

-Would the LVDT have been effective for measuring the vibrations of the thicker
beam? Justify your answer.

- What might be some of the challenge in utilizing this instrument in a real-world
application?

Answer 1

LVDT stands for Linear Variable Differential Transformer or Transducer.

• It is passive transducer which measures linear displacement. It produces variable AC voltage which represents physical position of object connected to it.

• In simple form, it uses one primary energized by AC voltage and two secondary coils (having equal number of turns) wound around hollow tube. Movable soft iron core is placed between primary and secondary coils.

When alternating current is connected to primary coil, magnetic field expands and contracts around the coil.

• When the field is strong and large enough it cuts the secondary coil and induces voltage. Induced Voltage at secondary is in phase with applied voltage at primary coil. • Each secondary coil produces separate voltage.

The LVDT will not be effective for measuring the vibration of the thicker beam, because the vibrations will be very less pronounced with the stiffer beam. This would lead to a much smaller amplitude which will be difficult to detect, and with the bias error the accuracy will be reduced.

In real world applications the LVDT will be less accurate at measuring the damping ratio and natural frequency because outside forces such as wind have an effect on the vibrations being measured that could cause large errors in the data.

Some other limitations are-

Large displacement is needed for small output.

It is affected due to external magnetic field and hence the entire LVDT circuit need to be shielded to achieve desired accuracy.

Vibrations due to displacement can affect the performance of the LVDT device.

The performance of LVDT is affected due to increase in temperature.

In order to get DC output, external demodulator is required.

It has limited dynamic response.