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Help with Scope & Function Generator Snafu

Discussion in 'Electronic Basics' started by [email protected], Jul 14, 2008.

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  1. Guest

    I am trying to do a simple experiment involving an ocilliscope and a
    function generator in the same circuit. My plane is to have the
    function generator set to produce a 10V (no load) sine wave an vary
    the freq from 100-2700 Hz.

    A .1 uf capactictor and a 1K resistor are connected in series across
    the output leads of the function generator. I want to connect the
    ocilliscope leads across the resistor to measure the voltage drop
    across the resistor. I calculate that the voltage drops should range
    between .6V and 8.6V using the above frequencies.


    Scope: Tektronix D10 5103
    Function Generator: MCP SG1639A

    The problem that I am having is that I think that the scope and
    function generator share a common ground because as soon as I connect
    the positive leads of the scope and function generator together
    (without connecting the ground leads together) I get a wavefrom on the
    scope that represent the 10V sine wave. If I connect both leads of
    the scope probe across the resistor I get the same 10V sine wave
    signal not the .6V AC signal. Why are the gound test leads of the
    scope anf freq generator common. I can't see any switch on the
    function generator to control this.

    Is my assumption about the common ground correct? Do I need to
    connect the scope or function generator to an isolation transformer?

    Also, is it safe to short the output leads of the function generator
    together.

    Any help would be greatly appreciated. Thanks
     
  2. Jamie

    Jamie Guest

    You need a scope with floating commons for the probes.

    I got a hand held that does just that even if its running off the
    wellwart.!
    It was cheap but it works!

    http://www.saelig.com/miva/merchant.mvc?Screen=PROD&Product_Code=PSSA017&Category_Code=PSSA

    P.S.
    They have a 60 mhz version that isn't much more..
    http://www.saelig.com/miva/merchant.mvc?Screen=PROD&Product_Code=PSSA006&Category_Code=





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