# 1V p-2-p

Discussion in 'Security Alarms' started by Roger Tegard, Apr 16, 2004.

1. ### Roger TegardGuest

Hi All,

Trying to bring a new Pelco cam online. Part of the setup procedure
detailed under "Direct Drive Auto Iris Lens" is as follows:

"Slowly adjust the pot counterclockwise until the optimum picture in
obtained (video output level of 1V peak-to-peak)."

The only way I know how to read peak-to-peak voltages is with a 'scope.
Any of you old timers know how to accurately read peak-to-peak voltages
with something other than a scope?

Roger

3. ### Roger TegardGuest

Naw.... too obvious!

The goal was to keep all system adjustments to objective, repeatable
standards wherever possible.

Roger

4. ### Roger TegardGuest

Both of those are very sweet. After reading this, I did a search on
Ebay (portable oscilloscope) and found this:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=45014&
item=3809183802&rd=1&ssPageName=WDVW

Anybody used one of these or heard any reviews??

Roger

6. ### Warren PieceGuest

These guys do a nice job with this sort of thing, Bob Lalonde posted it here
once.. very useful

http://tinyurl.com/2e7e4

8. ### roryGuest

you can use a regular meter to test video signal also.

9. ### AegisGuest

Explain that.

[/QUOTE]

11. ### AegisGuest

Still waiting to see how you get a peak-to-peak measurement from a meter.

12. ### G. MorganGuest

RMS voltage x 1.414 x 2

13. ### AegisGuest

Huh? So if the RMS voltage is 2v, then 2 x 1.414 x 2 ?

14. ### G. MorganGuest

Someone named "Aegis" <> Proclaimed on Tue, 20 Apr
2004 21:15:01 GMT,

yes
If RMS= 2V then PP~5.656V

1.414 is rounded sqrt of 2

you multiply by 2 because RMS times 1.414 is Peak

15. ### AegisGuest

..707 is the inverse of 1.414... I know the formula, but yours didn't have an
equal sign and didn't make sense at the time.

Vrms = Vpeak (or Vp-p/2) x .707 and Vp-p = Vrms x 1.414 x 2

However, that's all fine and dandy if your meter is sensitive enough... A
Fluke 72, for instance, is not... It puts a load on the circuit and will
throw off your adjustments (at least at the 1Vp-p level). Most techs don't
have an RMS meter that won't augment the readings with its own built-in load
assuming they have an RMS meter at all. Have you actually tried this in
practice?

Then again, most techs don't have o-scopes either (or would know what to do
with one if they did).

16. ### G. MorganGuest

Nope.. Never had to. I have installed many auto-iris lenses and never
heard of measuring 1Vp-p !!

Also I wouldn't rely on a RMS meter and that formula to calculate a
p-p voltage in the 1V level at all! :0

I know what you were really saying to the guy who wanted to use his
meter for "measuring video signal" I concur - can't be done. It's
p-p voltage with a meter " when I chimed in.
It's been 10 years since I used a scope - I wouldn't know how to use
it now either!

-Graham

P.S.
(ironically it's been over 10 years since Bass used Scope or any other
brand mouthwash)

17. ### roryGuest

you wont get peak to peak, but you can tell if it is getting a good signal.

18. ### AegisGuest

Tell me what exactly you are looking for... Are you measuring AC voltage
with an RMS meter?
I really am curious to see how this is done... seriously.

19. ### DavidGuest

For very-low-frequencies, if you're looking for 1Vp-p, in a pinch you
*could* use a really good, accurate RMS AC meter and adjust it for a reading
of .353 volts.
That's cause: Vrms = Vpp x .353 (and Vpp = Vrms x 2.83)

But then you have to wonder, if that RMS AC meter will give an accurate
Most Rms meters are real accurate at 60 hz, I think. Forget about accuracy
at video frequencies...

For an accurate reading, I think you're hosed without a scope.

-Dave

20. ### AegisGuest

I agree, but he insisted... If he is correct, I must know his technique...
Frankly, I don't see it happening.