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Peak to Peak

Discussion in 'Electronic Basics' started by WAZ, Aug 22, 2006.

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  1. WAZ

    WAZ Guest

    When we say there is 110V AC, is that peak to peak?
  2. BobG

    BobG Guest

    There is no such thing as 'peak to peak'... the voltage is a
    function.... is only has one value at any instant in time... it goes up
    to 110 V average or rms in 1/120th of a sec, then goes nagative the
    next half cycle. The peak is about 170V (rms x sqrt(2))
  3. chuck

    chuck Guest

    The 110 VAC (or 125 VAC) is the rms
    value of the 60 Hz sine wave.
  4. Eeyore

    Eeyore Guest


    It's RMS.

  5. Eeyore

    Eeyore Guest

    Yes there is.

  6. Bob Myers

    Bob Myers Guest

    Of course there's such a thing as "peak to peak" voltage; it's
    very often used to describe the maximum expected total
    "envelope" or "swing" of a given AC voltage or signal. It's
    generally not much of a concern, though, in electrical power

    The "110 VAC" (or 117 VAC or 230 or whatever number
    you encounter), though, is an "RMS" (root-mean-square)
    value, which is 0.707 of the peak voltage for a sinusoid.
    This is the voltage definition most commonly encountered in the
    electrical power field, as it is the "effective" voltage (i.e., the
    one you would use in power calculations for resistive loads -
    for instance, a 100 V (RMS) AC supply results in the same
    power consumed (and heating provided) by a given resistive
    heating element as would a 100 V DC supply, all else being

    Bob M.
  7. BobG

    BobG Guest

    I bet you can't measure it instantaneously.
  8. Danne

    Danne Guest

    Yes, 110V AC is in RMS (110 Vrms). 110V AC is about 311 Vpp (peak to

  9. PeteS

    PeteS Guest

    Sure I can - just wait for 2 adjacent separate dv/dt = 0 instantaneous
    events and take the difference ;)

    [ok, that's cheating]


  10. Don Bowey

    Don Bowey Guest

    I bet you I can. Now, put your money where your mouth is. Make it worth
    while, but affordable by you.

  11. Eeyore

    Eeyore Guest

    I'd like to see you measure anything truly "instantaneously" !

  12. BobG

    BobG Guest

    You sound like a betting man. I'll give you one reading. You agree that
    the voltage has only one voltage at any instant? So you can't do it
    unless you find the positive peak over a whole cycle, and the negative
    peak over a whole cycle. Sort of a job for some signal processing, or a
    couple of diodes and caps, or something that will average over 1/60th
    of a sec. That aint instantaneous is it?
  13. Eeyore

    Eeyore Guest

    Have you heard of something called the second derivative ? As in d2V/dt2 ?


  14. Sure I can, with an oscilloscope.

    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

  15. 110 VAC RMS = 311.08 V P-P

    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
  16. BobG

    BobG Guest

    Nah. If its digital, and I give you one measurement, you get a dot. If
    its analog, and I give you one sweep, an instantaneous measurement is
    any height of the trace from zero to the trace. So you could measure
    the positive or negative peak at that instant, and hope or guess that
    the other peak would be symmetrical, but you've lost the bet because it
    would take you two measurements at two instants in time to measure two
    peak voltages. I win.
  17. Phil Allison

    Phil Allison Guest

    ** Groper MENACE ALERT !!

    ** Says a complete fool demonstrating his MASSIVE ignorance.

    ** Yawn - just like ANY varying quantity.

    Ascribing magnitude to a steady AC voltage IS the issue - fuckhead.

    There are 4 ways:

    1. Average rectified value.

    2. RMS value.

    3. Peak value.

    4. Peak to peak value.

    The last is useful where the wave is asymmetrical or remains one polarity -
    ie the ripple voltage on a filter cap.

    ........ Phil
  18. ehsjr

    ehsjr Guest

    I don't think so. First it was you who stuffed
    instantaneous into the discussion. Peak to peak
    is obviously not instantaneous. Still, lets go
    with your "instantaneous", and your single measurement.

    Install a peak detector circuit, then take a single
    measurement. At the instant you take the measurement,
    the cap holding the detected peaks ( + and - ) will
    hold the peak to peak value. You lose - not that that
    is important. What's important is below.

    Peak to peak is understood to be the difference between
    the highest peak and the lowest peak.
    Lets not confuse the issue by saying peak to peak doesn't
    exist and specifying bullshit "instantaneous" measurements
    where a scope shows one dot or a DMM or analog meter wouldn't
    have sufficient time to respond, let alone show a true reading.

  19. BobG

    BobG Guest

    You should win a prize for being an ambassador of goodwill from down
    under. Have you ever been told that your brusk obscene language and
    outbursts at strangers makes you seem deranged? No one has ever told
    you that? I bet your coworkers are terrified that you might explode in
    an apoplectic spasm of tourettes tics if someone says 'Good morning Mr
    Allison'. I think the manual of personality disorders might have a
    chapter on Phil Allison syndrome. Pop a cork Phil!
  20. Phil Allison

    Phil Allison Guest

    "BobG" = a complete fool demonstrating his MASSIVE ignorance.

    ** **** off - ASD freak.

    ....... Phil
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