SOLUTION

LINEAR VARIABLE DIFFERENTIAL TRANSFORMER (LVDT)

This is the most widely used inductive transducer for translating linear motion into an electrical signal. As we know that displacement is a vector quantity representing a change in position of a body or a point with respect to a reference. It can be linear or angular (rotational) motion. With the help of the displacement transducer, many other quantities, such as force, stress, pressure, velocity, and acceleration can be found. 

The main electrical displacement transducers work on the principle of

Variable resistance: transducer is a strain gauge.

Variable inductance: transducer is a linear variable differential transformer

Variable capacitance: transducer is a parallel plate capacitor with a variable gap

Synchros and resolvers: used to measure angular displacement

Advantages of LVDT:

1. Linearity: The output voltage of LVDT is almost linear for displacement up to 5mm.
2. High Output: The LVDT gives reasonably high output and hence requires less amplification.
3. High Sensitivity: The LVDT has a high sensitivity of about 300 mV/mm. i.e., 1mm displacement of the care produces an output voltage of 300 mV.
4. Ruggedness: The LVDT is mechanically rugged and can withstand mechanical shock and vibrations.
5. Less friction: Since there is no sliding contact, the friction is very less.
6. Low Hysteresis: The LVDT has low hysteresis, hence its repeatability is extremely good under all conditions.
7. Low Power Consumption: Most LVDTs consume Less than the watt of power. The LVDT transducers are small, simple, and light in weight. They are stable and easy to align and maintain.

Disadvantages of LVDT

1. Comparatively, large displacement is necessary for appreciable differential output.
2. They are sensitive to stray magnetic fields. However, this interference can be reduced by shielding.
3. The temperature affects transducers.
4. The dynamic response is limited.

Applications of LVDT

1. The LVDT can be used in all applications where displacement ranging from fractions of a few mm to a few cms have to be measured.

2. Acting as a secondary transducer, LVDT can be used as a device to measure force, weight & pressure, etc.