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Peak voltage measurement

Discussion in 'Electronic Basics' started by [email protected], Jan 22, 2007.

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  1. Guest

    I'm looking for a cheap way to test a system I have, The system works
    by starting at 0V. When it is triggered it will produce a peak voltage
    with a magnitude of less then 100V, the system then produces a voltage
    of the same or lower magnitude but with the opposite sign, and then go
    back to 0V. All of this will occur over about 1/2 a second. I'd like to
    come up with a way of measuring the voltage of the peaks without using
    an oscilloscope.

    My first thought was looking for a cheap voltage meter that could
    measure peak voltage, but as far as I can tell such a device doesn't
    exist. If someone knows of such a device, or another solution that
    would work for this I would be extreamly grateful.
  2. chuck

    chuck Guest

    Because your transient voltage changes so slowly (~1/2 second) you have
    several options available.

    You can construct an op-amp peak hold circuit for a couple of dollars
    and read peak voltages with your DMM. Do a google search on "peak hold
    op-amp" and you'll find several simple solutions.

    If the system you are testing has a reasonably low internal impedance,
    you can also charge a capacitor to the peak voltage and then measure
    that voltage with a high internal resistance DMM. 10 Megohms is typical
    for DMMs. If the capacitor is low-leakage, you can connect the DMM to
    the capacitor after charging and read the peak voltage. A diode in
    series with the capacitor will ensure that only the positive (or
    negative, if you prefer) peak will charge the capacitor. Without knowing
    how much loading your system can withstand, and the risetime of the
    voltage peak, it is really impossible to suggest values for components.

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