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Original question:

LDC2114: About the latest version of LDC_Tools (slyc137e)

LDC2114: Problem of Excel_FEMM_vlp28.xlsmProblem at Magnetic Material Simulation

user5203911
Intellectual 560 points
Part Number: LDC2114


Hello,

Problem　
Although there seems to be no problem with non-magnetic materials, there are doubts about the simulation results with magnetic materials.
For non-magnetic materials (Aluminum, 1100 and Copper, SUS304)   d: Target distance
Compared to the frequency when there is no target (Air), the frequency increases when the target is present (ⅾ = 0.5㎜). This is a correct result from the principle of operation of the inductive sensor.
For magnetic materials (Mu Metal, 1006 steel)
Compared with the frequency when there is no target (Air), the frequency decreases when the target is present (ⅾ = 0.5㎜). This seems to be an incorrect result due to the operating principle of the inductive sensor.

For example, in the case of 1006 steel, the result at Air (no target) is about f = 3.0740 MHz, but the frequency at the 0.5 mm position is 2.8971 MHz .   Even though the frequency should increase as the target approaches
Why does this result in the case of magnetic materials?  Is there something wrong with my way?

Please refer to the attached file for details.Excel_FEMM Sim problem at Magnetic Material.docx

Best regards

  • 0
    TI__Genius 17440 points

    Hello,

    This is actually normal behavior for magnetic materials. Permeable materials allow the sensor's magnetic field to pass through them and increase the sensor's inductance, which decreases the sensor frequency. At high frequencies (like the frequency you are using), typically this effect is not visible, and the eddy currents form on the target and decrease the sensor inductance. It's possible that with some especially permeable materials even high frequency AC magnetic fields will pass through the target. You can try different types of steel and different frequencies to find one that behaves like the non-magnetic materials.

    Best Regards,

  • 0 in reply to Kristin Jones93
    Intellectual 560 points

    Hello, Ms.Jones

    I received your explanations about the behavior of magnetic materials, I'm not a little convinced about this.

    The frequency is as high as about 4.5MHz, and the thickness of the target conductor is as thick as 1mm, so I think that 3SkinDepth is sufficient.

    Please refer to.http://www.tij.co.jp/jp/lit/an/snoa957a/snoa957a.pdf


    As far as Fig. 12 of SNOA957A LDC Target Design is concerned, both magnetic and non-magnetic materials have the same behavior as targets. The frequency increases as the target approaches.
    Similar results have been obtained in our experiments.


    Here, Nickel N200, Steel_C10101, SS430L are considered to be magnetic materials, but they have the same characteristics as other non-magnetic materials. Naturally, the magnitude of the frequency change tends to be greater for non-magnetic materials. What is surprising is that the frequency change of magnetic nickel is larger than that of non-magnetic SS304.

    Sorry to bother you, can you explain this again?

    Refer to

    Magnetic and non-magnetic materials as targets.docx

    Best regards

  • 0 in reply to user5203911
    TI__Genius 17440 points

    Hello,

    My apologies for the delayed reply; I am still looking into this. I'll have a response for you next week.

    Best Regards,

  • 0 in reply to Kristin Jones93
    TI__Genius 17440 points

    Hello,

    We are still investigating this issue to see whether or not it is an issue with the Excel FEMM tool or part of FEMM itself. 

    Best Regards,