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detecting a magnet

Discussion in 'Electronic Design' started by Brian, Feb 3, 2005.

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  1. Guy Macon

    Guy Macon Guest

    _Good Vibrations_ by the Beach Boys.
     
  2. Rich Webb

    Rich Webb Guest

    [snip...snip...]
    A cow magnet? This would be a magnetized cow, possibly one that has a
    large uptake of iron from feeding on ferrous soils? Or a magnet used to
    stick a (small) cow to a (large) refrigerator?

    ....clickety... google ...clickety...

    Well, by the Wrinkled Sack of Zeus! I have lead a sheltered life.
     
  3. Brian

    Brian Guest

    For those of you without "hick" experience....
    Lotta metal aroud for cows to pick up and eat. Ya stuff a big magent down
    their gullet, catches the debris before it perforates something :)
     
  4. Brian

    Brian Guest

    I have played with the capacitance detection in the past. Range stinks.
     
  5. Active8

    Active8 Guest

    They're called metal detectors when you put them on the end of a
    stick. Beat it against a ref and listen to it click.
    Maybe as the cycle pulls up to the light, the coil senses the flux
    that wasn't there a split second ago (dphi/dt) and it gives the
    detector enough bump to make some noise. I've seen dumb detectors
    switch the lights after a right turn on red. Annoying little
    bastrds, they are.
     
  6. Mike Fields

    Mike Fields Guest

    Easy - just run a cat past the dog house to see if he is home ... (also
    counts
    as a "cat scan" )
     

  7. Or a GMR sensor - more sensitive. NVE and Philips make them.
    For ultimate sensitivity, try a fluxgate magnetometer.
     
  8. John Fields

    John Fields Guest

     
  9. I read in sci.electronics.design that John Fields <[email protected]
    At audio frequencies, you might find a difference, due to the differing
    incremental permeabilities of the magnet when demagnetized and
    magnetized. But the difference could well be quite small.
     
  10. Andrey

    Andrey Guest

    If you don't want to mess with coils, think about solid state sensors.

    They go, in order of increase of sensitivity:
    Hall Effect sensor - GMR sensor - Magnetoresistive sensor - Magnetometer.

    Solid State Magnetometer (like the one made by Honeywell) is made around
    Magnetoresistive sensor(s) but with well thought signal conditioning which
    increases it's range. It will give you 2 - 3 feet range for the magnet you
    describe.

    You should think in advance what you gonna do about stray targets and false
    triggering.

    Andrey


    Magnetometer.
     
  11. Ken Smith

    Ken Smith Guest

    No, for the ultimate try a low temperature SQUID. The have a noise of
    something like 10fT / sqrt(Hz).
     
  12. Ken Smith

    Ken Smith Guest

    The reaction depends on the dog. I think feeding the dog radioactive food
    and using automatic radiation detector would work better: That would be
    Radio-Acitve Dog Automatic Ranging (RADAR)
     
  13. Guy Macon

    Guy Macon Guest

    Those who have tried this have posted glowing reports.
     
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