# Peak to Peak

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

1. ### WAZGuest

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

2. ### BobGGuest

=======================
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. ### chuckGuest

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

No.

It's RMS.

Graham

5. ### EeyoreGuest

Yes there is.

Graham

6. ### Bob MyersGuest

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
discussions.

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
equal.

Bob M.

7. ### BobGGuest

===========================
I bet you can't measure it instantaneously.

8. ### DanneGuest

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

Danne

9. ### PeteSGuest

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

[ok, that's cheating]

Cheers

PeteS

10. ### Don BoweyGuest

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

Don

11. ### EeyoreGuest

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

Graham

12. ### BobGGuest

==========================================
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. ### EeyoreGuest

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

Graham

14. ### Michael A. TerrellGuest

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. ### Michael A. TerrellGuest

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. ### BobGGuest

=================================
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 AllisonGuest

** 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. ### ehsjrGuest

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

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.
http://www.facstaff.bucknell.edu/mastascu/eLessonsHTML/Signal/Signal2.htm#PeakToPeak
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.

Ed

19. ### BobGGuest

==========================================================
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 AllisonGuest

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

** **** off - ASD freak.

....... Phil