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E-field sensor

  1. Oct 29, 2009 #1
    Hello everyone,

    My name is Fred and I'm a newcomer to the forum. I'm designing a very simple E-field sensor. So all I did was I got two styrofoam balls, wrapped them around with a few layers of aluminum foil to serve as charge collecting surfaces. Put both "sensors" on the ends of a thin wood rod about 1m long. Hooked it up to my oscope and measured nothing. Expected, since the potential should be very small anyways. So I connected a 100GOhm resistor in series and then connected to the oscilloscope. Now I should be reading a decent (and somewhat steady) potential.

    But that's not happening. Any suggestions or comments?

    Thanks a lot,
  2. jcsd
  3. Oct 29, 2009 #2


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    Staff: Mentor

    Welcome to the PF, Fred. What is the frequency range fjor the E-field that you would like to measure?

    If DC, then if you can put some known amount of static charge on an object, you could devise a way to measure the force F=qE to give you the E field info. If AC, you can use some capacitive pickup techniques...

    What forms of E-field measurement have you found by searching the web or in books?
  4. Oct 30, 2009 #3


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    Science Advisor

    There is no reason that such an arrangement would give you a reading on an oscilloscope.

    Why do you think it would?

    It is very similar to a demonstration device used to show repulsion of electrostatic charges.
    You touch both balls with a charged rod (possibly ebonite or plastic that has been rubbed with cat's fur). They both acquire the same charge if they are touching and then tend to repel each other by flying apart. Gold leaf and moving vane electroscopes work on the same principle.

    But, they do not generate any voltage themselves just by being in an electric field.
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