Download - Proximity_Sensor EI 44
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Inductive Proximity SensorsSwarndeep Kushari
AEIE 1044Seminar#1
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Outline
1. Major Applications
2. Theory ofO
peration 3. Possible Measurements
4. SensorOutputs
5. Applications 6. Conclusions
7. To Explore Further
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Major Applications The Eddy Current probe has many
applications in industry
These applications are varied, but allrequire reliable, accurate results
These sensors are robust, and can
typically handle extreme environments These applications are discussed in
greater detail in later slides
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Theory ofO
peration These sensors use mutual inductance
between a known inductor and a
conductive materialCommonly referred to as eddy current
probes
Mutual inductance is a function of thedistance between the inductor and thematerial
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How Eddy Currents Work
An inductive coil is
placed near a
conductive surfaceAn AC voltage
(typically around
2Mhz) is applied to
the coil
Mutual inductance
begins to occur
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How Eddy Currents Work
The coil generates a
magnetic field
Circular or EddyCurrents begin to
flow in the
conductive material
These currents
resemble an eddy in
a stream of water
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How Eddy Currents Work
The Eddy Currents
generate their own
magnetic field These fields have
interaction with the
coil through mutual
inductance
This leads to a
measurable result
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What can be measured?Electrical conductivity and magnetic
permeability of the target material
The amount of material cutting through
the coils of the magnetic field
The condition of the material(whether it
contains cracks or defects
Lift-Off
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Typical SensorO
utput Provides very high
resolution output
over ranges on theorder of millimeters
The range can beincreased
depending on theapplication, buttypically not morethat several inches
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Calibration From the factory, most proximity probes are
calibrated to measure 4140 steel
Because different materials have differentconductivity and permeability, special
calibration is needed to ensure accurate
measurement of each specific material
This usually involves some alteration of the
signal conditioning and demodulation process
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Applications Can be used as an
encoder that
monitors rotation Can measure thing
like speed and
acceleration
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EncoderO
utput This is what the output
looks like when being
used as an encoder The peaks represent
the teeth on the
sprocket
Speed and acceleration
can be determined from
this output data
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Applications(Cont) Used in Automated
Assembly lines
Sensor detects eachpart as it passes
Provides Accurate,Real-Time
information aboutquantity and qualityin manufacturingprocesses
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Power Systems Applications High Power turbines often operate in high
temperature, strenuous environments
Inductive Sensors and be linked to a datasystem through a robust cable allowing for
the monitoring of these systems
Information gathered by these sensors can
greatly add to the life and health of high
power turbines and generators
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Turbine ShaftO
rbit Monitoring Two inductive sensors can be used to
monitor the health of a turbine
When placed 90 degrees apart, they canmonitor the X and Y position of the shaft as itrotates
When bearing start to go out, the movement
in the X and Y direction begins to increase This is detected by the sensors, and the
bearings can be replaced before seriousdamage occurs
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Illustration ofO
rbit Monitoring
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Vibration Monitoring
An inductive sensor can
monitor the vibration of
a turbine shaft
Typically, there is
maximum limit that the
shaft is allowed to
vibrate, once that point
is passed, the system isshut down to prevent
serious damage
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General Applications
Good for many short distance, highresolution applications
Can be used to detect the presence orabsence of conductive material
Good for long distance monitoring of
machinery and industrial devicesUsually works well in extreme
environments
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Other Applications
Quality Control
Autonomous
removal of bad partson an assembly line
Reliable and
consistent results
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Other Applications(Cont)
Real-Time
information on the
position of railroadtrack switches
Reliable due to
resistance to
changing conditions
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LimitationsVery short range of measurement
Material being measured must be
conductive
Target must be larger than the sensor
tip
Can only measure displacement in
relation to the sensor
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Conclusion Inductive sensors operate on the
principle of mutual induction
They are useful in a wide variety of
applications
They provide high-resolution, reliable
outputs
Can be used in varied conditions
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Referenceswww.bently.com
www.allenbradley.com
http://www.ndt-
ed.org/EducationResources/Community
College/EddyCurrents/Physics/mutualin
ductance.htm
www.wikipedia.org
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To Explore FurtherAn interesting paper on applications:
www.bently.com/articles/apnotes/an04
7.asp
Here is a great presentation on
monitoring industrial systems:
www.vibration.org/Meeting/0903/Gearbox%20Spectral%20Components
%20Presentation%20V2.ppt
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