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Vpp different from signal generator and scope

Discussion in 'Electronic Basics' started by [email protected], Jun 16, 2007.

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  1. Guest

    I have something simple but I can't seem to find an answer to it.

    I am getting a different Vpp measurement on the scope from the signal
    generator. When put in a 1Vpp 200KHz square wave from my signal
    generator, while the frequency is dead on at 200KHz, I got a reading
    of 2 Vpp on the scope. I made sure the signal generator is outputting
    Vpp, not RMS. My scope is on DC Coupling.

    Does anyone know why my Vpp reading on the scope is doubled?

    Many thanks.
     
  2. Are you using a divide by 10 probe?
    If so, have you tuned the probe compensation capacitor to
    produce a flat frequency response?

    Another possibility is that your vertical gain knob has
    slipped on the shaft, since the gain ranges normally have
    1-2-5 volts per cm jumps.

    Does your scope have a reference output to check both the
    frequency response and gain?
     
  3. JeffM

    JeffM Guest


  4. It sounds like the rated output is into a fixed impedance, and you
    don't have a load on the generator. You can get two or more times the
    rated output when the equipment is used, this way.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  5. bg

    bg Guest

    wrote in message
    The generator needs to be terminated.
    bg
     
  6. Jamie

    Jamie Guest

    do you have a 50 ohm load on the generator?
     
  7. The signal generator is set to 50ohm output termination. So unless you
    add 50ohms to the output, the output voltage will be double what you
    expect.

    Many generators will allow you to switch the output to "high
    impedance" mode and then you will get the output value as indicated on
    the generator.

    Dave.
     
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