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Pulsed electromagnetic field indicator

  1. Sep 2, 2015 #1
    I just found this forum and would love some help on creating an indicator that lights up when placed next to a pulsed electromagnetic field. I'm thinking a small LED that lights up when placed near a pulsed electromagnetic field to confirm the electromagnetic field is active.

    How would I design this? I would like to use the housing of a small key ring flashlight with an LED in it.
    My question is what internals would I need to create the LED to turn on simply by placing the unit near a pulsed electromagnetic field?

    Thanks for the help guys
  2. jcsd
  3. Sep 2, 2015 #2


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    Staff: Mentor

    Welcome to the PF.

    What is the source of the field? How strong is it, and what is the center frequency? How often is it pulsed? If you hold an AM radio next to it, can you tune the radio to hear the pulses? Or maybe an FM radio?
  4. Sep 2, 2015 #3
    It is a medical application for use as a bone growth stimulator to promote healing of bone fractures.
    My interest is in proving that the unit is actually functioning and emitting a pulse. If I can show this visually by lighting an LED then I'm happy.

    To answer your questions:
    The pulsed electromagnetic field strength is 790 milligauss
    The pulses are 3.8 kHz per pulse and 350 pulses per second

    I havn't tried the radio experiment but that's a good idea and something I will try.

    Let me know what you think
  5. Sep 3, 2015 #4


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    Gold Member

  6. Sep 4, 2015 #5
    Thanks for the help guys. I'm now considering buying a gauss meter. I noticed that most of them have a peak sensitivity in hertz- my device is putting out 3.8khz per pulse. Does this mean I'm going to need to purchase one of the more expensive units that reads kHz or will the $13 Elf Zone reader with LED's suffice?
  7. Sep 4, 2015 #6


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    Gold Member

    Elf Zone reader: I have no idea what this will do. It could pick up stray fields in your environment or any local ghosts you may have (???? :nb)). Or it may work fine.
    It seems sensitive and wideband (to 10KHz)
  8. Sep 6, 2015 #7
    I tried the radio experiment both AM and FM and there was no interference with either frequency. I suppose that's understandable since the frequency is 3.8khz
    I guess I will buy the cheapest gauss meter (elf zone) and see if that picks up anything from the device
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