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1V p-2-p

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

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  1. Roger Tegard

    Roger Tegard Guest

    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
     
  2. Aegis

    Aegis Guest

  3. Roger Tegard

    Roger Tegard Guest


    Naw.... too obvious! :)

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

    Roger
     
  4. Roger Tegard

    Roger Tegard Guest


    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
     
  5. Aegis

    Aegis Guest

  6. Warren Piece

    Warren Piece Guest

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

    http://tinyurl.com/2e7e4
     
  7. Warren Piece

    Warren Piece Guest

  8. rory

    rory Guest

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

    Aegis Guest

    Explain that.

    [/QUOTE]
     
  10. G. Morgan

    G. Morgan Guest

  11. Aegis

    Aegis Guest

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

    G. Morgan Guest


    RMS voltage x 1.414 x 2
     
  13. Aegis

    Aegis Guest

    Huh? So if the RMS voltage is 2v, then 2 x 1.414 x 2 ?
     
  14. G. Morgan

    G. Morgan Guest

    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. Aegis

    Aegis Guest

    ..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. Morgan

    G. Morgan Guest

    Sorry about that.. :)
    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
    just the way you worded your second reply about "how can you measure
    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. rory

    rory Guest

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

    Aegis Guest

    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. David

    David Guest

    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
    reading at whatever *frequency* it's reading.
    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. Aegis

    Aegis Guest

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