PAR Measure

Discussion in 'Resources' started by Schmitty, Nov 27, 2017.

  1. Schmitty

    Schmitty Supporting Member

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    hey so I’m reaching out to see if someone has a way to test PAR and would be willing to come by and test mine or rent it to me for a day?
     
  2. kinetic

    kinetic Webmaster

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  3. ashburn2k

    ashburn2k Webmaster

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    @Schmitty is a member and I currently have the par meter, where are you located?


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  4. Bruce Spiegelman

    Bruce Spiegelman BOD

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    Just looked at your build thread and it looks like you're running a Kessil 360 on your tank. Awesome light, but a PAR meter won't do you much good. Measuring PAR on an LED light isn't particularly accurate, but on a Kessil a PAR meter doesn't work at all. On Kessil's website they indicate the only way to properly measure is with a PUR meter which almost no one has.
     
    Last edited: Nov 28, 2017
  5. Ibn

    Ibn Supporting Member

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    Wonder if anyone has tried the Seneye for PUR measurements.
     
  6. Bruce Spiegelman

    Bruce Spiegelman BOD

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    Let's get one!
     
  7. Ibn

    Ibn Supporting Member

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    Can't swing it myself and don't really use Kessils, so it won't apply to me. I've been considering picking up the Apogee µCache and using it on one of their SQ 510/520 sensors, since that does account for the wider spectrum, but that's an arm and a leg. Can't swing it for now.
     
  8. RandyC

    RandyC Supporting Member

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    Ryan at BRS would probably disagree that kessils can't be measured: https://www.bulkreefsupply.com/vide...-led-light-a-great-option-for-sps-reef-tanks/.

    I've never actually understood this argument. Light is light, measuring light is measuring light. I think this misunderstanding may come from not fully understanding the results you get. I can agree that just taking a PAR number and not measuring the spectrum output of the light may yield less than desired results. I'm no light expert, so someone please correct me if I'm wrong. PUR is actually just a subset of PAR. PAR measures the amount of light available in the sensor's range (in the case of our club meter 410-692nm). PUR represents the same spectrum wavelength range, but only includes the wavelengths that are usable by chlorophyll. So, for example, while a super bright green LED may have a big PAR number, it may not help much with growing coral since chlorophyll doesn't use much, if any, of the green spectrum.

    What could be debated is whether or not wavelengths below 410nm are usable and significant. If you're wanting to have that included the Apogee MQ-510 measures wavelengths from 389-692nm.

    I have a seneye.

    Seneye actually doesn't measure PUR. It measures PAR and measures the spectrum. It then produces a percentage for PUR that represents the percentage of light that is known to be photosynthetically usable by chlorophyll of the PAR it measured. In the case of my Radion xw15r Pro G4 and AI Prime HD, that percentage was always somewhere between 76-82%. Seneye measures light between 400-700nm.

    See: http://answers.seneye.com/index.php?title=en/Aquarium_help/What_is_PAR_&_PUR_?

    The one thing that seneye does not do is cosine correction. Which means it doesn't compensate for the angle you're holding the meter and it's reported value can vary drastically depending on how you're holding it.
     
    Last edited: Nov 29, 2017
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  9. Ibn

    Ibn Supporting Member

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    Good info!
     
  10. RandyC

    RandyC Supporting Member

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    Oh and to be clear my PUR measurements are based on my light settings, not what the light unit can or can't output. My settings are based on the Coral Labs/EcoTech AB+ profile which sets out to mimic 18,500K and 20,000K throughout the day.

    Obviously, your PUR values will vary based on the spectrum you choose to run.
     
    Last edited: Nov 28, 2017
  11. Vhuang168

    Vhuang168 Supporting Member

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    The issue that the sensor is not as sensitive in all wavelengths. So it will measure some wavelengths better than others.




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  12. RandyC

    RandyC Supporting Member

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    Apogee has correction factors that can be applied post-measuring to obtain the correct PAR value for various light sources. The Apogee MQ-210 sensor is not as good as the MQ-510 for LED unit's using a lot of blues. Interesting enough, the correction factor for metal halides is almost equal to most LEDs colors for the MQ-510. I can see why Kessil may be complaining over this as the blue range (peaking at 448nm) has a fairly high correction factor on MQ-210. However, light output from LEDs can still be measured.

    * PPFD = PAR

    Apogee MQ-210 Spectral Correction Factors:
    spectral correction factor - MQ-210.PNG

    Apogee MQ-510 Spectral Correction Factors (ignore the comparison from SQ-100):

    spectral correction factor - MQ-510.PNG

    Source:
    https://www.apogeeinstruments.com/content/MQ-210-manual.pdf
    https://www.apogeeinstruments.com/content/MQ-510-manual.pdf
     
    Last edited: Nov 29, 2017
  13. Schmitty

    Schmitty Supporting Member

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    San Francisco in Potrero Hill

    San Francisco
     
  14. ashburn2k

    ashburn2k Webmaster

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    god damn it i was there yesterday lol ok when do you need it?


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  15. rygh

    rygh Supporting Member

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    I really think Kessil is over simplifying the issue for marketing purposes.

    The PAR on Kessils can be measured fairly well. From all I can find, probably within 15% using the clubs PAR meter.
    Light is light. Although as the spectrum diverges from "normal", error is introduced in sensor.
    So not perfect, but hardly completely wrong.

    BUT: The real point is that simple PAR numbers are imperfect for comparing different LED lights in reef tanks.
    You technically want to just measure the exact spectra that Coral want.
    Some argue that is PUR, others argue it is even more complex.
    PAR may work for comparing different lights that all have roughly normal spectra.
    But if some have very different spectra, like Kessil, it is hard to compare.

    So instead of saying all that, Kessil simply says you cannot measure it.
     
  16. Vhuang168

    Vhuang168 Supporting Member

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    Those correction factors are over simplified for the end users.

    Even with a $3k Licor system, the numbers are off.

    Doesn’t really matter to me, the corals tell me what I need to know.


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  17. Bruce Spiegelman

    Bruce Spiegelman BOD

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    I keep track of my PAR on the tanks with T5s simply to watch how much they degrade over time. Plus having the PAR reading constantly displayed on my apex screen is just cool. :)
     
  18. RandyC

    RandyC Supporting Member

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    In the end that's all that matters, but no harm in people trying to better understand our little ocean in a box.
     
  19. Wlachnit

    Wlachnit Vice President

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    Do you have the apex sensor?
     
  20. BAYMAC

    BAYMAC Guest

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    Given the kessil matrix has quite a few colors, you'd have to apply numerous corrections on it with the Apogee. I think that is what they're getting at.
     

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