Lvdt

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LINEAR VARIABLE DIFFERENTIAL

TRANSFORMER (LVDT)

PRESENT BY:KAUSIK DAS.(0215)Student of (ECE) The Assam Kaziranga University .

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CONTENTS: Transducer:

Its Classification Active and Passive Transducers Advantages of Electrical Transducers Application of Transducers

LVDT: Construction Principle Operation Advantages and Disadvantages Uses

References

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A Transducer is a device which converts mechanical force into an electrical signal

Many physical parameters such as heat, intensity of light, flow rate, liquid level, humidity and pH level etc. are converted to electrical form by means of transducers

TRANSDUCER:

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CLASSIFICATION

Transducers can be classified as:1) On the basis of principle of transduction as Capacitive Reactive Inductive etc

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2)As Primary and Secondary Transducers “Primary Transducer”- Bourdon Tube “Secondary Transducer” - Linear Variable

Differential Transducer(L.V.D.T)

3)As Passive and Active Transducers

4)As Analog and Digital Transducers, and,

5)As Transducers and Inverse Transducers

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• ACTIVE TRANSDUCERS

Active Transducers are those which do not require an auxiliary power source to produce their output.

They are also known as “self generating type” since they develop their own voltage or current output.

Eg: Velocity, temperature, light intensity and force can be transduced with the help of active transducers.

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• PASSIVE TRANSDUCERS Passive transducers derive the power

required for transduction from an auxiliary power source.

They are also known as “externally powered transducers”.

Eg:- Resistive, inductive and capacitive transducers.

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ADVANTAGES OF ELECTRICAL TRANSDUCERSThe advantages of converting physical quantities into analogous electrical quantities are :- Electrical amplification and attenuation

can be done easily and that to with static devices.

The electrical or electronic system can be controlled with a very small power level.

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The electrical output can be easily used, transmitted and processed for the purpose of measurement.

Due to the integrated circuit technology, the electrical systems are compact.

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APPLICATIONS OF TRANSDUCERS In Electroacoustic,Ex:

loudspeaker,microphone,hydrophone,piezoelectric crystel etc.

Transducers are used in medical instruments, such as in sonograph machines.

Electro-optical(photoelectricity),Ex: fluorescent lamp,incandescent lamp etc.

Transducers are used in music engineering and recording.

They are used in complex mechanical systems and even in safety systems like train brakes.

Electromagnetic,Ex: Antena,magnetic cartidge etc.

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LINEAR VARIABLE-DIFFERENTIAL TRANSFORMER(LVDT)

The linear variable-differential transformer(LVDT) is the most widely used inductive transducer to translate linear motion into electrical signal

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Linear Variable Differential Transformer (LVDT)

CONSTRUCTION:

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A differential transformer consists of a primary winding and two secondary windings. The windings are arranged concentrically and next to each other.

A ferro-magnetic core(armature) in the shape of a rod or cylinder is attached to the transducer sensing shaft.

The core slides freely within the hollow portion of the bobbin.

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An a.c. excitation is applied across the primary winding and the movable core varies the coupling between it and the two secondary windings.

As the core moves away from the centre position, the coupling to one secondary becomes more and hence its output voltage increases, while the coupling and the output voltage of the other secondary decreases.

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PRINCIPLE: Any physical displacement of the core

causes the voltage of one secondary winding to increase while simultaneously, reducing the voltage in the other secondary winding.

The difference of the two voltages appears across the output terminals of the transducers and gives a measure of the physical position of the core and hence the displacement.

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OPERATION: When the core is in the neutral or zero

position, voltages induced in the secondary windings are equal and opposite and the net output is negligible.

By comparing the magnitude and phase of output with input source, the amount and direction of movement of core and hence displacement may be determined.

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ADVANTAGES OF LVDT The transducers possess a high

sensitivity. The transducers have low hysteresis

and hence repeatability is excellent under all conditions.

They have infinite resolution. They are simple,light in weight and easy

to maintain.

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DISADVANTAGES OF LVDT They are sensitive to stray magnetic

fields but shielding is possible. They are inherently low in power output. Temperature affects the perfomance of

transducer.

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USES: The LVDT can be used in all applications

where displacements ranging from fraction of a mm to a few cm have to be measured.

Acting as a secondary transducer it can be used as a device to measure force, weight and pressure.

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Thank You !