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Effect of Coiled cord on 30KHz Square wave signal??

Discussion in 'Electronic Basics' started by royalmp2001, Aug 16, 2005.

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  1. royalmp2001

    royalmp2001 Guest

    Can anyone tell me what effect a coiled cord, like that of a headphone
    cord, would have on a 30KHz square wave signal (waveform or otherwise)?
    Thanks
    Marius
     
  2. Is the signal passing only one way through the coiled cable, or also
    returning back through a second conductor?
     
  3. Ban

    Ban Guest

    It would have no effect if the length is in normal proportions. Otherwise it
    would attenuate the signal resistivly depending on the load impedance and
    the DC resistance of that cable. There wouldn't be any frequency depending
    phenomena because the effect of the coil is cancelled by the return current.
     
  4. royalmp2001

    royalmp2001 Guest

    Hello again, John...
    You have answered so many of my questions in the past..thanks for
    looking.

    Well, the application consists of passing a 30KHz square wave signal to
    an anti-static wrist-strap through its single-conductor coiled cable.
    The strap is worn on one wrist with the signal passing through the
    human body and then out to another wrist-strap and coiled cable which
    go back to the oscillator's ground connection.
    I know that the effect of the human body tends to round off the
    squareness of the waveform, but I wonder what effect the coiled cables
    are having. Obviously the load current is going to be quite
    small...like less than 1mA.
    I cannot find a source of straight-cable anti-static wriststraps.
    Thanks
    Marius
     
  5. At this current, the resistance of the wire is insignificant, compared
    to the skin and body resistance. The only effect that may show up is
    the inductance of the two coils. You can roughly approximate this
    with the common formulas used to approximate the inductance of spaced,
    single layer solenoidal coils. The more you space the turns, the
    lower the inductance. So the worst case would be when the two cables
    are not extended at all.

    http://www.qsl.net/in3otd/indcalc.html

    Once you have a rough idea of the coil inductance, you can use the
    normal inductive impedance formula, 2*pi*f*L=ZL multiplied times the
    current, to estimate the voltage drop across these coils.
     
  6. mike

    mike Guest

    Obviously??? that's my favorite technical word...
    Why not just figger out what parameter is interesting to you and measure
    it?
    mike

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