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Thread: Help doing calculations szed

  1. #1
    Join Date
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    Default Help doing calculations szed

    Ok guys, I need some help.

    I don't have access to any magical programs (skyzan), so I got my information from laserpointersafety.com to do the actual calculation.
    I love math, and I'm missing something here, I think its the order of operations.

    This is for a 1000 mwatt green 532nm laser with an mrand of 1.5

    (32.8 / mrand) * (Square root of (12.7 * mwatts * VCF))

    (32.8 / 1.5) * (Square root of (12.7*1000*.088016)) = (21.8667) * (Square root of (1117.803)) = 21.8667 * 33.40
    = 730.34 <----THIS IS WHAT I GOT.

    http://www.laserpointersafety.com/calculator.html
    gets 2,311.9 feet <-- THIS IS WHAT THEY GOT.

    HELP!
    Last edited by darkrider; 03-27-2017 at 14:50.

  2. #2
    Join Date
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    Charleston, SC
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    Default

    Your visual correction factor is off by an order of magnitude.

    For 532 nm green, the VCF is .8802. Your calculation below uses .08802. So, yeah, after you take the square root of a 10-fold error, you're going to be off by a factor of ~3.16. And sure enough, if you multiply your wrong answer (730) by 3.16, you get the correct answer (2307, which is close enough to 2311. Rounding takes up the rest).

    Adam


    Quote Originally Posted by darkrider View Post
    Ok guys, I need some help.

    I don't have access to any magical programs (skyzan), so I got my information from laserpointersafety.com to do the actual calculation.
    I love math, and I'm missing something here, I think its the order of operations.

    This is for a 1000 mwatt green 532nm laser with an mrand of 1.5

    (32.8 / mrand) * (Square root of (12.7 * mwatts * VCF))

    (32.8 / 1.5) * (Square root of (12.7*1000*.088016)) = (21.8667) * (Square root of (1117.803)) = 21.8667 * 33.40
    = 730.34 <----THIS IS WHAT I GOT.

    http://www.laserpointersafety.com/calculator.html
    gets 2,311.9 feet <-- THIS IS WHAT THEY GOT.

    HELP!

  3. #3
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    Feb 2017
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    Edmonton Alberta
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    Dam, thats a whole decimal place!

    This is one of the reasons I love doing the math by hand, then checking against a few sources.
    Now I have gone out of the way to educate myself and learn. I LOVE LEARNING, thanks Adam.

  4. #4
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    Default

    There's also Maurice's MPE calculator here:

    http://mpe.laserextreme.nl/

    No VCF in the MPE calulator (irrelevant for retina safety as opposed to flash blindness effects).

    However, it appears the Laser Pointer Safety Calculator assumes beam diameter which IS essential for safety.

    Also, assuming the stated power = the actual power is the mother of all fckups, and would put my projector out by a full 30% under it's actual value. ie. Quoted power - 2.1W, measured power = 2,8W.
    Last edited by White-Light; 03-29-2017 at 06:32.

  5. #5
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    How did you do the measurement for "Actual power"

    -------------------------------------

    I am now trying to calculate slant range dam government paperwork!

    Its another level of learning.

  6. #6
    Join Date
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    If you have an iPhone check out James Stewart's 'Laser NOHD' and 'Laser Safety', both available in the App Store. Both are great apps for quick and easy calculations.
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

  7. #7
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    Jem, I have them both, I like to learn the math though. Its easy to use a calculator, better for me to understand what all this stuff means. SAFETY first.
    Especially when it comes to other peoples visions, or pilots crashing planes

  8. #8
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    No problem with you wanting to learn the math. However, once you've done that, use the app
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

  9. #9
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    Default

    I created a spread sheet to do all the calculations in the future hehe, verified against skyzan

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