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oscilloscope input impedence?

Discussion in 'Electronic Basics' started by tom, Dec 6, 2004.

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  1. tom

    tom Guest

    I've got a real dumb newbie question so bear with. I'm running some
    interconnected amplifiers ect with the required 93 ohm coax for the
    modules but I want to monitor the signal on my scope which has a
    1megaohm input impedance. Now I know the scope is designed to not load
    the circuit being tested by having a high input impedance but doesn't
    that cause a big reflected voltage signal and thus a misread of the
    real voltage ? Or does the scope somehow compensate or do I have it
    wrong? Thanks. tom
  2. Andrew Holme

    Andrew Holme Guest

    Connect a 93 ohm dummy load across the last output and connect your x10
    'scope probe across that.

    For the ultimate in fidelity, twist some fine wire around the shield right
    at the end of the probe and use that as ground instead of the normal probe
    earthing lead. This makes a _big_ difference at high frequencies. When
    looking at a 1 MHz clock, for example, all the ringing, overshoot and
    undershoot disappears.
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