Can Inductance Proximity Sensors Detect Magnets Encased in Metal?

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SUMMARY

Inductance proximity sensors can potentially detect magnets encased in metal, but the effectiveness largely depends on the type of metal casing used. Eddy currents induced by current-carrying inductors are utilized for detecting metal, but the shielding effect of the casing may hinder magnetic field detection. Non-ferrous casings, such as copper or aluminum, allow for the use of reed switches, Hall sensors, or GMR sensors to sense the magnetic field created by the magnet. This method is also applicable for measuring fluid levels in containers.

PREREQUISITES
  • Understanding of eddy currents and their application in metal detection
  • Familiarity with inductance proximity sensors and their operating principles
  • Knowledge of non-ferrous materials and their effects on magnetic fields
  • Experience with reed switches, Hall sensors, and GMR sensors
NEXT STEPS
  • Research the principles of eddy current testing and its applications
  • Learn about the operation and sensitivity of Hall effect sensors
  • Explore the differences between ferrous and non-ferrous materials in magnetic detection
  • Investigate the use of GMR sensors in industrial applications
USEFUL FOR

Engineers, sensor developers, and anyone involved in metal detection or magnetic field applications will benefit from this discussion.

sensor
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Hi

To detect position of a metal we can use the eddy currents induced by a current carrying inductor. It is described in this link.

http://www.marktec.co.jp/e/product/ndt/ect/principle.html Would this still work if the target is a magnet enclosed in a metal casing. Basically I need to detect the position of a magnet that is enclosed in a metal casing.

Thanks in advance
 
Last edited by a moderator:
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Hi sensor

welcome to PF :)

The metal case is likely to shield the magnetic field. It would probably depend on the sensitivity of the sensor used to if it could detect
any magnetic field that may or may not be outside the metal casing

Others may have more ideas :)

Dave
 
sensor said:
Hi

To detect position of a metal we can use the eddy currents induced by a current carrying inductor. It is described in this link.

http://www.marktec.co.jp/e/product/ndt/ect/principle.html Would this still work if the target is a magnet enclosed in a metal casing. Basically I need to detect the position of a magnet that is enclosed in a metal casing.

Thanks in advance
The system will detect metal casing.
Modern metal detectors (like those on airports) usually use method of resonance coils.
 
Last edited by a moderator:
If you place the magnet in a non-ferrous casing, such as copper, aluminum, titanium etc... Then, you can sense the field created by the magnet by using reed switches, Hall sensors, or GMR sensors.
This is a simple enough trick for measuring fluid levels in a container.
 
Most likely this can only be answered by an "old timer". I am making measurements on an uA709 op amp (metal can). I would like to calculate the frequency rolloff curves (I can measure them). I assume the compensation is via the miller effect. To do the calculations I would need to know the gain of the transistors and the effective resistance seen at the compensation terminals, not including the values I put there. Anyone know those values?

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