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Inductive Proximity Sensors

Inductive Proximity Sensors. Brett Anderson ECE 5230 Assignment #1. Outline. 1. To Explore Further 2. Major Applications 3. Theory of Operation 4. Possible Measurements 5. Sensor Outputs 6. Applications 7. Conclusions. References. www.bently.com www.allenbradley.com

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Inductive Proximity Sensors

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  1. Inductive Proximity Sensors • Brett Anderson • ECE 5230 • Assignment #1

  2. Outline • 1. To Explore Further • 2. Major Applications • 3. Theory of Operation • 4. Possible Measurements • 5. Sensor Outputs • 6. Applications • 7. Conclusions

  3. References • www.bently.com • www.allenbradley.com • http://www.ndt-ed.org/EducationResources/CommunityCollege/EddyCurrents/Physics/mutualinductance.htm • www.davidson.com/au

  4. To Explore Further • An interesting paper on applications: www.bently.com/articles/apnotes/an047.asp • Here is a great presentation on monitoring industrial systems: www.vibration.org/Meeting/0903/ Gearbox%20Spectral%20Components%20Presentation%20V2.ppt

  5. Major Applications • The Eddy Current probe has many applications in industry • These applications are varied, but all require reliable, accurate results • These sensors are robust, and can typically handle extreme environments • These applications are discussed in greater detail in later slides

  6. Theory of Operation • These sensors use mutual inductance between a known inductor and a conductive material • Commonly referred to as “eddy current” probes • Mutual inductance is a function of the distance between the inductor and the material

  7. How “Eddy Currents” Work • An inductive coil is placed near a conductive surface • An AC voltage (typically around 2Mhz) is applied to the coil • Mutual inductance begins to occur Source: http://www.ndt-ed.org/EducationResources/CommunityCollege/EddyCurrents/

  8. How “Eddy Currents” Work • The coil generates a magnetic field • Circular or “Eddy Currents” begin to flow in the conductive material • These currents resemble an eddy in a stream of water http://www.ndt-ed.org/EducationResources/CommunityCollege/EddyCurrents/

  9. 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 http://www.ndt-ed.org/EducationResources/CommunityCollege/EddyCurrents/

  10. 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

  11. What is Lift-Off? • Lift-Off is a very important measurement that can be made by Eddy Current Sensors • It represents the distance from the coil to the test material • This leads to a great number of industrial, manufacturing, and other important applications

  12. Sensor Output in Proximity Applications • A demodulator demodulates the signal from the sensor, and outputs a DC voltage which is proportional to the distance from the sensor to the conductive target • This output voltage is linear over the specified range of the specific sensor

  13. Typical Sensor Output • Provides very high resolution output over ranges on the order of millimeters • The range an be increased depending on the application, but typically not more that several inches

  14. Calibration • From the factory, most proximity probes are calibrated to measure 4140 steel • Because different materials have different conductivity 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

  15. Applications • Can be used as an encoder that monitors rotation • Can measure thing like speed and acceleration Source: AllenBradly.com

  16. 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 from this output data Source: AllenBradly.com

  17. Applications(Cont) • Used in Automated Assembly lines • Sensor detects each part as it passes • Provides Accurate, Real-Time information about quantity and quality in manufacturing processes Source: AllenBradly.com

  18. Another Application • Inductive sensors monitor automated machinery • They can detect anything out of the ordinary and serve as a fail safe shutoff, which can save millions of dollars in preventing damage to malfunctioning machinery. Source: AllenBradly.com

  19. Power Systems Applications • High Power turbines often operate in high temperature, strenuous environments • Inductive Sensors and be linked to a data system 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

  20. Turbine Shaft Orbit Monitoring • Two inductive sensors can be used to monitor the health of a turbine • When placed 90 degrees apart, they can monitor the X and Y position of the shaft as it rotates • 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 serious damage occurs

  21. Illustration of Orbit Monitoring

  22. 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 is shut down to prevent serious damage

  23. General Applications • Good for many short distance, high resolution applications • Can be used to detect the presence or absence of conductive material • Good for long distance monitoring of machinery and industrial devices • Usually works well in extreme environments

  24. Other Applications • Quality Control • Autonomous removal of bad parts on an assembly line • Reliable and consistent results

  25. Other Applications(Cont) • Real-Time information on the position of railroad track switches • Reliable due to resistance to changing conditions

  26. 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

  27. 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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