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Microwave oven temperature probe port grounding

Discussion in 'Electronic Repair' started by Tom Del Rosso, May 9, 2007.

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  1. Just wondering what would happen if a metal container was used in a
    microwave, but grounded to the phono jack for the temperature probe.
    Assuming the connection was good, of course.
     
  2. bz

    bz Guest

    The 'grounding' would not help.

    A 'good ground' at microwave frequencies would be much less than 1/4 wave.
    The wavelength is about 3 cm.

    A good ground would thus need to be much less than 1/2 cm.

    A metal container is probably going to arc to the inside of the oven in
    several places.

    It may detune the cavity badly enough to present a high SWR to the magnetron
    and damage or destroy the magnetron.

    --
    bz

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     

  3. The wavelength is too short for any effective grounding, and that is
    a 1/4" Phone jack, not a phono jack.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  4. Very interesting. I thought the wavelength was a few inches.

    So how does the probe get away with it?
     
  5. He meant to say 1/4 wavelength is around 3 cm. :) The wavelength is
    a few inches, like around 5 inches.

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  6. bz

    bz Guest

    Actually, I was thinking x-band radar was very close to the microwave oven
    frequency. I was wrong.

    The X band ranges from 7 to 12.5 GHz.
    The microwave ovens actually operate in the S band, the 10 cm radar band. The
    S band covers from 2 to 4 GHz.

    According to http://hypertextbook.com/facts/1998/HowardCheung.shtml
    most microwave ovens operate on 2.45 GHz which gives 11.8 cm wavelength, 4.6
    inches, for a quarter wave of a little over one inch or 2.95 cm

    In any case, it is still a bad idea to put any metal bowls into your
    microwave over, unless the metal object has been designed for use in a
    microwave oven.



    --
    bz 73 de N5BZ k
    I fixed radars for a living in the mid 70's. I had a 1st class radiotelephone
    license, second class radio telegraph license with ship radar endorsements.

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     
  7. Ok, but the probe is over 6 inches long without the plug, so why doesn't it
    collect a charge? I always assumed it was because of the grounded plug.
     
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