# measure peak to peak voltage?? how

Discussion in 'Electronic Design' started by 5hinka, Sep 21, 2004.

1. ### 5hinkaGuest

Hi
I have sinusoidal or triangle signal.
I need to measure peak to peak voltage.
How Can i do it?? I know that i should
use some op amps, resistor, diods,
but cannot find any design.
Could You help me??
Greetings
5hinka

2. ### John FieldsGuest

---
1. Oscilloscope

2. True RMS voltmeter.
For an infinitely repeating sinusoidal signal multiply what your
meter says by 2.828. For an infinitely repeating triangle, 3.464.

3. ### 5hinkaGuest

Hi

Ehh
I need to include it into my project.
Oscilloscope is too big ;-))

4. ### RolavineGuest

Subject: Re: measure peak to peak voltage?? how
You could use peak detectors made from op amps, positive and negative, and then
measure the dc voltage between them with a volt meter. There are circuits that
work in the 'Op amp Cookbook'.

Or, how about the previous suggestion to just multiply the AC rms measured on a
meter?

Rocky

5. ### Tam/WB2TTGuest

A clamping circuit, followed by a rectifier. However you will have to take
into account the two diode drops.

Tam

7. ### Ken SmithGuest

Whats the frequency?
You didn't say how exact you want the measurement. I'll assume you want
it fairly good and that the frequency is fairly low.

I think you may want a fast comparitor or two. If you are after the
peak-peak, you basically want the circuit to measure the voltage that is
there for a very short time.

The purpose of the comparitor is to compare the output with the input. If
the input ever exceeds the output, you need to raise the output. If not,
you need to lower it.

You may need a pair of comparitors, because you need to find the pos.
and neg. peaks to subtract for the p-p measurement.

8. ### Ken SmithGuest

Or, make an recifier with no drop.

9. ### Jim ThompsonGuest

See "FullWaveRectifier.pdf" on the SED/Schematics page of my website
for a starting point (note, there are four pages).

ISTR that I posted a version that was peak-to-peak on a.b.s.e, but I
can't locate it right now.

...Jim Thompson

10. ### Jim ThompsonGuest

On Tue, 21 Sep 2004 17:48:37 -0700, Jim Thompson

[snip]
See......

Newsgroups: alt.binaries.schematics.electronic
Subject: Peak-to-Peak Detector (S.E.D) - Peak-to-Peak-Detector.pdf
Message-ID: <>

...Jim Thompson

11. ### BanGuest

Below is a nice peak detector circuit, it is fast enough for audio and quite
precise. The negative half wave is done by another one with the diodes
inverted. the final result is done by subtracting the 2 values. The
pushbutton switch is to reset, can maybe replaced by a resistor for

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view\font\fixed

12. ### John WoodgateGuest

You missed off the output terminals.

13. ### Spehro PefhanyGuest

If you know the waveform in advance, just measure the average voltage
(precision rectifier- easy up to a few kHz anyway) and low-pass filter
and scale the output voltage correspondingly.

Best regards,
Spehro Pefhany

14. ### Steve RobertsGuest

Ad633 low cost multiplier with one input fed DC scaled to Jim's above
mentioned constants, the other input fed with your input wave
followed by a normal cheap AC panel voltmeter?

AD633 has transfer function of (x1-x2) * (y1-y2)/10 +z
where x and y are the differential inputs.

Just a goofy idea that would drive professors who have never seen a
Gilbert multiplier batty.

Steve Roberts

15. ### BobGardnerGuest

They always told me 'there is no such thing as peak to peak voltage'. At one
instant, there is a positive peak voltage, and at some other instant, there is
a negative peak voltage, but the voltage is a function, and only has one value
at an instant in time. Now lets argue about whether the product of rms voltage
and rms current is rms power or average power.....

16. ### Jim ThompsonGuest

Track down, on a.b.s.e, the following post....

Peak-to-Peak Detector (S.E.D) - Peak-to-Peak-Detector.pdf
From: Jim Thompson Date: Tue, 21 Sep 2004 18:18:54 -0700 Size: 30.9k

...Jim Thompson

17. ### Rich GriseGuest

I get a feeling that bobgardner just wants to start a discussion over
whether the term "peak-to-peak" voltage even has meaning in the context of
a time-variant function.

In the interim, I've found the answer to the angels on a head of a pin
dilemma - an infinite number can dance on the head of a pin, since they're
imaginary and don't take up any space. ;-)

Cheers!
Rich

18. ### Ken SmithGuest

Who are they and why do they always say these things.

Peak to peak voltage:

(a) The most positive voltage minus the most negitive voltage seen within
the measurement time. This is what is normally meant by peak to peak.

(b) The most positive minus the most negitive voltage that will ever be
seen. This is what you use when designing for overvoltages etc.

(c) The range of voltage that the signal spends 90% or 99% of its time
between. This is used when refering to noise.

(d) The same as any of the above with after the removal of some low
frequency components. This is used when measuring the fur on a waveform.

RMS voltage:

You the the voltage at each instant or time square it, find the average of
the squared value and the take the squareroot. This is very hand for
rating things like lightbulbs that don't react quickly to the input
voltage.

Peak to peak current:

(the same as the above with s/voltage/current/ )

RMS current:

(See RMS voltage )

Peak to peak power:

(a) Peak to peak voltage times the peak to peak current. This is used to
get a number that impresses the uninformed.

(b) In audio amplifiers this is the power produced when the pull up
transistor first shorts, then blows open and then the pull donw transistor
does the same. This is how many audio amplifiers are rated.

(c) The peak power caused by the positive swing plus the peak power caused
by the negitive swing. This is an almost honest measure of the pulsed
output handling ability of a circuit, so it is never used.

RMS power:

(a) Take the instantanious power square it, average the squares and then
squareroot the average. This is the RMS power but no-one ever means this
when they say RMS power.

(b) Average power misnamed RMS power. This is what most people mean if
they say RMS power.

(c) A completely fictional number created in the marketing department.

19. ### leggGuest

non sequitur

Look it up the definition.

Also check "peak and random deviation" (PARD).

RL