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potential sensor (copier)

Discussion in 'Electronic Repair' started by [email protected], Nov 9, 2007.

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  1. Guest

    I'm looking for a used (new if cheap) TDk or MuRATA (or anyone elses
    for that mater) potential sensor used for looking at the electrostatic
    field on the photosensitive drum. I work in a electrostatics lab and
    we need a tiny field mill, so if anybody has one floating around, or
    knows where to order them in the US please let me know.



    Steve Roberts
    Research Associate
    The University of Akron,
    Akron, Ohio
  2. msg

    msg Guest

    How tiny? We used to build field mills as small as four inch diameter
    for experiments but the ones deployed outdoors were always the big,
    rugged, 10 inch diameter variety. Do you have machine shop access?
    Field mill mechanical construction is straight-forward and well


  3. Sjouke Burry

    Sjouke Burry Guest

    Whats wrong with a floating gate FET like used in small microphones?
    They are cheap enough to cannibalize one, and even the circuit behind
    such a microphone can be copied to read the voltages on the drum.
    The Fets are small, and you can use a few millimeters gatewire as a
    sense electrode. Put the rest of the Fet in a grounded shield, with only
    the gate wire poking outside. And the smaller the hole the wire is peeking
    through, the smaller the sense area becomes, altough the sensitivity
    will then be much smaller.
    Keep us posted.
  4. msg

    msg Guest

    A general reference for the casual reader of this thread of an overview
    of electric field measuring techniques may be read here:

    This is by no means comprehensive but it is a useful description of some
    common techniques.

    We also used to build radioactive probes (also described in the above
    document) which is a cheap alternative; look to ionization smoke detectors
    for the sources ;-)


  5. Guest

    we have a couple of the floating fet ones, but the boss wants
    better and distance insensitive, so we need the rotary chopper type.
    I found a surplus one out of a electrostatic coater,and got it
    working, but its housing is too big. My target is a electrospun
    nanofiber jet, and the whole assembly is only 6" from top to bottom,
    so I need a very tiny probe. Since the fiber is made electrostaticly
    and in cross section looks like the Tasmanian Devil from Bugs Bunny
    Cartoons, I need a meter that measures independant of target size and
    location. The rotary chopper or tuning fork ones will do that. I dont
    want to measure voltage on a surface, I want to see the space charge
    field in volts per meter.
    Plus it would be nice to have a off the shelf unit so each grad
    student could have their own. Commercial instrument grade ones are
    too big.

    Thanks, Steve
  6. Guest

    Thanks for the paper, very interesting. Whats the geometry of the RA
    probe? That looks promising and I dont mind hacking the smoke detector
    sources. The campus rad safety officer's gonna have nightmares, but he
    can be delt with. We have a world class machinist, fabrication is not
    a problem. If I could shrink it to pager motor size,. it would be

    Thanks, Steve
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