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Low noise measurement cable question

Discussion in 'General Electronics' started by qu1nn, Jul 15, 2004.

  1. qu1nn

    qu1nn Guest

    Hello.
    I am using a Agilent 34401A & 34902A instrument (6.5 digit multimeter)
    and I am trying to get the best possible connection for precision uV
    measurements.

    I was going to go for shielded, twisted pair (for example Alpha Wire
    #86701CY)
    however I was advised by a wiser engineer that we should use coax.

    Does anyone have any suggestions?
    In Particular I am looking for small diameter wire (Agilent Suggests
    AWG20) the problem lies in the fact that the Agilent 34902A only has a
    opening of 0.8"x0.5" and for 16 channels of possible connecitons, it
    kinda makes life difficult.

    Thanks for your suggestions
    qu1nn
     
  2. This rather depends on the multimeter.

    Usually the inputs are truly differential with no connection with the
    ground. If you are certain that yours signal pair input is truly isolated
    from ground then I would suggest using the best screened twisted poir cable
    you can get. Attach the screen to a good ground reference at one end only.

    If, on the other hand, the multimeter has one signal terminal grounded
    anyway then go with the coaxial.

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  3. I use Thermax RGU-404 low noise cable.
    0.075" OD. Teflon inner & outer insulation.
    Dielectric is coated with a black semiconductive coating.
    Used a lot in military applications.
    You'd be able to fit about 70 cables through that hole.
    It's probably hard to find, though.


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