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Diminishing Flux ??

Discussion in 'Electronic Basics' started by Randy Gross, Aug 29, 2005.

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  1. Randy Gross

    Randy Gross Guest

    I read a couple of postings wherein reference was made to magnets
    demagnetizing though the type of magnet was not revealed.

    What circumstance(s) is(are) involved?

    Is this a failing common to an alloy or manufacturing process?

    What consideration can I implement in projects that require them, good
    magnets don't come cheap?

  2. Jasen Betts

    Jasen Betts Guest

    extreme heat a the big killer, prolonged harsh vibration is another.
    I think mostly to the old steel magnets of 20+ years ago,
    if you use new magnets you should be fine unless you're targeting an
    unusually harsh environment...

  3. ncstateboy81

    ncstateboy81 Guest

    All magnets can be demagnetized, but some are much less sensitive than
    others. There are demagnetization curves for them. The following
    website shows a couple:
    Pay more attention to the curve with the knee in it. One axis has the
    flux density (B) and the other axis is the applied magnetic field (H).
    When designing magnetic systems it is important to stay in the linear
    region. When the applied magnetic field goes into the knee of the
    curve, and the field is removed, instead of following the original
    curve, the new magnetization (the flux density) can be found by tracing
    a line parallel to the original linear line from the point in the knee.

    As Betts pointed out heat has a huge affect. In the demagnetization
    curves there are lines for different temperatures. As the temperature
    increases the linear portion drops off at smaller applied fields.
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