electromagnetic displacement sensors

8/10/2019 Electromagnetic Displacement Sensors

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ELECTROMAGNETICDISPLACEMENT SENSORS

Ananya 08M104Ashwathi 08M106

Harshvardhan Gupta 08M119

Sharath Yale 08M141


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Linear Variable Differential Transformers

The linear variable differential transformer (LVDT)

is a type of electrical transformer used for

measuring linear displacement.

The transformer has three solenoidal coils placed

end-to-end around a tube.

The center coil is the primary, and the two outer

coils are the secondaries.

A cylindrical ferromagnetic core, attached to the

object whose position is to be measured, slides

along the axis of the tube.


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Schematic of an LVDT


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Working of an LVDT

When the core is displaced in one direction, the

voltage in one coil increases as the other decreases,

causing the output voltage to increase from zero to

a maximum. This voltage is in phase with the

primary voltage.

When the core moves in the other direction, the

output voltage also increases from zero to amaximum, but its phase is opposite to that of the

primary.


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Characteristic of LVDT


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Characteristic of LVDT


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Rotary Variable Differential Transformer


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A rotary variable differential

transformer (RVDT) is a type of

electrical transformer used for

measuring angulardisplacement.


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More precisely, a Rotary Variable DifferentialTransformer (RVDT) is an electromechanical transducerthat provides a variable alternating current (AC) outputvoltage that is linearly proportional to the angular

displacement of its input shaft. When energized with afixed AC source, the output signal is linear within aspecified range over the angular displacement.

RVDTs utilize brushless, non-contacting technology toensure long-life and reliable, repeatable position sensingwith infinite resolution. Such reliable and repeatableperformance assures accurate position sensing under themost extreme operating conditions.


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ADVANTAGES OF RVDT

Low sensitivity to temperature, primary voltage & frequency

variations

Sturdiness

Low cost

Simple control electronics

Small size


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RVDT

Contact between plunger and measuring surface is always

not possible.

RVDT provide linear output for about +-40 degree whichlimits its usability.

LVDT

Internally non contact but externally has to be connected

where the measurement has to be made

Not feasible for very long range measurements

Disadvantages


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Brain Probe

Device addresses the

clinicians need for precise placement

of electrodes for functional

neurosurgery

unique push/pull cable drivemechanism

The LVDT accurately monitors

the position of the probe

Data is collected to map

surface features of the brain.


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LVDTs are used to measure

spring deformation in

weighing systems

Once the system isconstructed, the output of the

transducer is mechanically or

electrically zeroed value

then read.

LVDTs offer severaladvantages over these

technologies, including

ruggedness, life expectancy,

and temperature stability

Weighing System


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Typical RVDTs are linear

over a range of about40

Sensitivity is 2 to 3mV per

volt per degree of rotation

Input voltages in the rangeof 3V RMS at frequencies

between 400Hz and 20kHz.

Measurement ranges are

100m to 25cm Sensitivity is 2.4mv per

volt per degree of rotation Input voltages are from 1V

to 24V RMS, withfrequencies 50Hz

LVDT & RVDT Comparison

LVDT RVDT

electromagnetic displacement sensors

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