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LVDT: Basic Principle, Theory, Working, Explanation & Diagram | Linear

Variable Dierential Trans!ormer

A very basic transducer which is always useful in the eld of instrumentation, I havestudied about this in my college days. Now let me explain about the LV! with its

"rinciple of #peration and I will explain how it is constructed for its well $nown

operation and you can understand the wor$ing of LV!.

Principle o! LVDT:

LV! wor$s under the principle of mutual induction, and the displacement which is a

non%electrical energy is converted into an electrical energy. And the way how the

energy is getting converted is described in wor$ing of LV! in a detailed manner.

LV! consists of a cylindrical former where it is surrounded by one primary winding

in the centre of the former and the two secondary windings at the sides. !he

number of turns in both the secondary windings are e&ual, but they are opposite to

each other, i.e., if the left secondary windings is in the cloc$wise direction, the right

secondary windings will be in the anti%cloc$wise direction, hence the net output

voltages will be the di'erence in voltages between the two secondary coil. !he two

secondary coil is represented as () and (*. +steem iron core is placed in the centre

of the cylindrical former which can move in to and fro motion as shown in the gure.

!he A excitation voltage is - to )*V and the operating fre&uency is given by - to

/ 01.

Working o! LVDT:

Let2s study the wor$ing of LV! by splitting the cases into 3 based on the iron core

position inside the insulated former.

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"ase #:#n applying an external force which is the displacement, if the core reminds

in the null position itself without providing any movement then the voltage induced

in both the secondary windings are e&ual which results in net output is e&ual to 4ero

i.e., +sec)%+sec*5

"ase $:6hen an external force is appilied and if the steel iron core tends to move

in the left hand side direction then the emf voltage induced in the secondary coil is

greater when compared to the emf induced in the secondary coil *.

!herefore the net output will be +sec)%+sec*

"ase %76hen an external force is applied and if the steel iron core moves in the

right hand side direction then the emf induced in the secondary coil * is greater

when compared to the emf voltage induced in the secondary coil ). therefore the

net output voltage will be +sec*%+sec)

'(antages o! LVDT:

8 Innite resolution is present in LV!8 0igh output8 LV! gives 0igh sensitivity8

Very good linearity8 9uggedness8 LV! "rovides Less friction8 Low hysteresis8 LV!

gives Low power consumption.

Disa'(antages o! LVDT:

8 Very high displacement is re&uired for generating high voltages.8 (hielding is

re&uired since it is sensitive to magnetic eld.8 !he performance of the transducer

gets a'ected by vibrations8 Its is greatly a'ected by temperature changes.

pplications o! LVDT:

5: LV! is used to measure displacement ranging from fraction millimeter to

centimeter.5: Acting as a secondary transducer, LV! can be used as a device to

measure force, weight and pressure, etc..

0alf cell7

A half-cellis a structure that contains a conductive electrodeand a surrounding

conductive electrolyteseparated by a naturally occurringHelmholtz double layer. Chemical reactions

within this layer momentarily pump electric chargesbetween the electrode and the electrolyte,resulting in apotential differencebetween the electrode and the electrolyte. The typical anode

reaction involves a metal atom in the electrode dissolved and transported as a positive ion across

the double layer, causing the electrolyte to acquire a net positive charge while the electrode acquires

a net negative charge. The growing potential difference creates an intense electric fieldwithin the

double layer, and the potential rises in value until the field halts the net charge-pumping reactions.

https://en.wikipedia.org/wiki/Electrodehttps://en.wikipedia.org/wiki/Electrolytehttps://en.wikipedia.org/wiki/Helmholtz_double_layerhttps://en.wikipedia.org/wiki/Helmholtz_double_layerhttps://en.wikipedia.org/wiki/Electric_chargehttps://en.wikipedia.org/wiki/Potential_differencehttps://en.wikipedia.org/wiki/Potential_differencehttps://en.wikipedia.org/wiki/Electric_fieldhttps://en.wikipedia.org/wiki/Electric_fieldhttps://en.wikipedia.org/wiki/Electric_fieldhttps://en.wikipedia.org/wiki/Electrolytehttps://en.wikipedia.org/wiki/Helmholtz_double_layerhttps://en.wikipedia.org/wiki/Electric_chargehttps://en.wikipedia.org/wiki/Potential_differencehttps://en.wikipedia.org/wiki/Electric_fieldhttps://en.wikipedia.org/wiki/Electrode

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This self-limiting action occurs almost instantly in an isolated half-cell in applications two dissimilar

half-cells are appropriately connected to constitute a !alvanic cell.

A standard half-cell, used inelectrochemistry, consists of a metal electrode in a

" molar#" mol$%& aqueous solutionof the metal's salt, at ()*+elvin#( C&.

"/

The electrochemicalseries, which consists ofstandard electrode potentialsand is closely related to the reactivity series,

was generated by measuring the difference in potential between the metal half-cell in a circuit with

a standard hydrogen half-cell, connected by asalt bridge.

The standard hydrogen half-cell0

(H1#aq& 1 (e23 H(#g&

The half-cells of a 4aniell cell0

5riginal equation

6n 1 Cu(13 6n(11 Cu

Half-cell #anode& of 6n

6n 3 6n(11 (e2

Half-cell #cathode& of Cu

Cu(11 (e23 Cu

https://en.wikipedia.org/wiki/Galvanic_cellhttps://en.wikipedia.org/wiki/Galvanic_cellhttps://en.wikipedia.org/wiki/Electrochemistryhttps://en.wikipedia.org/wiki/Electrochemistryhttps://en.wikipedia.org/wiki/Concentrationhttps://en.wikipedia.org/wiki/Aqueous_solutionhttps://en.wikipedia.org/wiki/Aqueous_solutionhttps://en.wikipedia.org/wiki/Kelvinhttps://en.wikipedia.org/wiki/Kelvinhttps://en.wikipedia.org/wiki/Half-cell#cite_note-1https://en.wikipedia.org/wiki/Electrochemical_serieshttps://en.wikipedia.org/wiki/Electrochemical_serieshttps://en.wikipedia.org/wiki/Standard_reduction_potentialhttps://en.wikipedia.org/wiki/Standard_reduction_potentialhttps://en.wikipedia.org/wiki/Reactivity_serieshttps://en.wikipedia.org/wiki/Standard_hydrogen_electrodehttps://en.wikipedia.org/wiki/Salt_bridgehttps://en.wikipedia.org/wiki/Salt_bridgehttps://en.wikipedia.org/wiki/Daniell_cellhttps://en.wikipedia.org/wiki/Anodehttps://en.wikipedia.org/wiki/Cathodehttps://en.wikipedia.org/wiki/Galvanic_cellhttps://en.wikipedia.org/wiki/Electrochemistryhttps://en.wikipedia.org/wiki/Concentrationhttps://en.wikipedia.org/wiki/Aqueous_solutionhttps://en.wikipedia.org/wiki/Kelvinhttps://en.wikipedia.org/wiki/Half-cell#cite_note-1https://en.wikipedia.org/wiki/Electrochemical_serieshttps://en.wikipedia.org/wiki/Electrochemical_serieshttps://en.wikipedia.org/wiki/Standard_reduction_potentialhttps://en.wikipedia.org/wiki/Reactivity_serieshttps://en.wikipedia.org/wiki/Standard_hydrogen_electrodehttps://en.wikipedia.org/wiki/Salt_bridgehttps://en.wikipedia.org/wiki/Daniell_cellhttps://en.wikipedia.org/wiki/Anodehttps://en.wikipedia.org/wiki/Cathode