brett anderson sensor
TRANSCRIPT
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Inductive Proximity Sensors
Brett Anderson
ECE 5230
Assignment #1
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Outline
1. To Explore Further
2. Major Applications
3. Theory of Operation
4. Possible Measurements
5. Sensor Outputs 6. Applications
7. Conclusions
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References
www.bently.com
www.allenbradley.com
http://www.ndt-
ed.org/EducationResources/Community
College/EddyCurrents/Physics/mutualin
ductance.htm
www.davidson.com/au
http://www.bently.com/http://www.allenbradley.com/http://www.allenbradley.com/http://www.bently.com/ -
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To Explore Further
An interesting paper on applications:
www.bently.com/articles/apnotes/an04
7.aspHere is a great presentation on
monitoring industrial systems:
www.vibration.org/Meeting/0903/Gearbox%20Spectral%20Components
%20Presentation%20V2.ppt
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Major Applications
The Eddy Current probe has manyapplications 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 of Operation
These sensors use mutual inductancebetween 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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Source: http://www.ndt-
ed.org/EducationResources/CommunityCollege/EddyCurrents/
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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http://www.ndt-
ed.org/EducationResources/CommunityCollege/EddyCurrents/
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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http://www.ndt-
ed.org/EducationResources/CommunityCollege/EddyCurrents/
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 throughthe coils of the magnetic field
The condition of the material(whether it
contains cracks or defects
Lift-Off
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What is Lift-Off?
Lift-Off is a very important measurementthat can be made by Eddy Current
Sensors It represents the distance from the coil
to the test material
This leads to a great number ofindustrial, manufacturing, and otherimportant applications
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Sensor Output in Proximity
ApplicationsA demodulator demodulates the signal
from the sensor, and outputs a DC
voltage which is proportional to thedistance from the sensor to the
conductive target
This output voltage is linear over thespecified range of the specific sensor
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Typical Sensor Output
Provides very highresolution outputover ranges on theorder of millimeters
The range an beincreaseddepending 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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Source: AllenBradly.com
Applications
Can be used as an
encoder that
monitors rotation Can measure thing
like speed and
acceleration
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Source: AllenBradly.com
Encoder Output
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 fromthis output data
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Source: AllenBradly.com
Applications(Cont)
Used in AutomatedAssembly lines
Sensor detects eachpart as it passes
Provides Accurate,Real-Time
information aboutquantity and qualityin manufacturingprocesses
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Source: AllenBradly.com
Another Application
Inductive sensorsmonitor automatedmachinery
They can detectanything out of theordinary and serve as afail safe shutoff, whichcan save millions of
dollars in preventingdamage tomalfunctioningmachinery.
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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 Shaft Orbit Monitoring
Two inductive sensors can be used tomonitor 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 of Orbit 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 ofmachinery and industrial devices
Usually works well in extremeenvironments
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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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Limitations
Very 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 ofapplications
They provide high-resolution, reliable
outputsCan be used in varied conditions