Answer to Question #219317 in Mechanics | Relativity for Emmanuel

Question

Discuss the working principle of a linear variable differential transformer LVDT.

Answer 1

Answer: The term LVDT stands for Linear Variable Differential Transformer. This is the most widely used inductive converter, which blocks the linear motion into an electrical signal.

The output through the secondary of this transformer is differential so it is called so. This is a very accurate inductive converter compared to other inductive converters.

LVDT construction

The main features of construction

The transformer consists of a primary winding P and two secondary windings S1 and S2 are wound on a cylindrical former (which is hollow in nature and contains a core).

Both secondary windings have the same number of turns, and we place them on both sides of the primary winding

The primary winding is connected to an alternating current source, which creates a flow in the air gap, and voltages are induced in the secondary windings.

The movable soft iron core is placed inside the first and the movement to be measured is connected to the iron core.

The iron core usually has a high permeability, which reduces harmonics and high sensitivity of LVDT.

The LVDT is housed inside a stainless steel housing as it provides electrostatic and electromagnetic shielding.

Both secondary windings are connected so that the output voltage difference between the two windings.

The principle of work and work

Since the primary is connected to an AC source, both AC and voltage are produced on the secondary LVDT. The output in the secondary S1 e1 and in the secondary S2 e2. Therefore, the differential output,

$e_{out}=e_1-e_2$

This equation explains the principle of operation of LVDT.

Currently, three cases arise according to the location of the kernel, which explains the operation of LVDT, discussed below as

I. When the nucleus is in the zero position (for no displacement)

When the core is in the zero position, the binding of the flow to both secondary windings is equal, so that the induced EMF is equal in both windings. Therefore, for the absence of bias, the value of the output ec is zero for e1 and e2 are both levels. Therefore, it shows that there was no relocation.

II. When the core moves up from the zero position (to move up from the reference point)

In this case, the binding of the flux to the secondary winding S1 is greater than the binding of the flux to S2. This will make e1 bigger than e2. Due to this, the output voltage is positive.

III. When the core moves down to the zero position (to move down to the reference point). In this case, the value of e2 will be greater than that of e1. Due to this output ez will be negative and shows the output to the reference point down.