Knowledgeiskey
Well-Known Member
going with a cob diy build frim what i seen 16" from canopy to light seems good but i def want some numbers/data to back it amd tips would be great
what light meters should i get
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- light meter lux ppfd
Underground Scientist
Well-Known Member
I got the Dr. Meter 0-100,000 lux off Amazon, $19.99. I've found it useful, and have done conversions for lumens and umols on a recent thread. I measured 2" increments from my lights and recorded the results. Awesome data to have for 20 bucks
Underground Scientist
Well-Known Member
Oh crap, you're using LED's huh? I think a PPFD meter is pricey and the only way to measure.
algebraist
Well-Known Member
Please excuse my ignorance -- why wouldn't you use the $20 Dr. Meter lux meter with LEDs? Thanks.
Underground Scientist
Well-Known Member
I haven't read extensively, but when a lot of us talk about lumens, we refer to HID and CFL which have particular light spectrums. Only a portion of this light emits as Photosynthetic Active Radiation, which is particular spectrums plants need to complete photosynthesis. A portion of these lights intensity are in the visible spectrum and are not useful for photosynthesis, but will show up on a lux meter. Many LED's contain tailored spectrums for PAR and although could give a lower lux value, actually could contain more light energy(lumens) that are devoted to plant growth. It may be able to be done with conversion factors, but that may depend on the manufacturer's spectrum choice, and the quality and ratios of that spectrum.
PAR meter is always the most accurate. So basically, if my own understanding is correct, the LED would register lower than another source because it has more PAR spectrum than the other sources if designed properly, and less wasted energy on non PAR light, so that less is more. The general issue with LED is penetration, initial investment, and burning out diodes and the process of fixing those burnt diodes.
algebraist
Well-Known Member
Makes sense @Underground Scientist; thanks very much.
sanjuan
Well-Known Member
A decent PAR meter costs hundreds of dollars. You pay for accurate measurement starting at about 600nm (for the deeper reds).
I've been fully satisfied using a digital footcandles (lux) meter to set up the COBs in my grow room. Accurately comparing different brands of luminaires on a test bench would require a good PAR meter and an integrating sphere but that's beyond my pay grade.
I've got the previous version of this but a generic ebay item might be just as good:
https://www.hydrofarm.com/p/LG17010
I've been fully satisfied using a digital footcandles (lux) meter to set up the COBs in my grow room. Accurately comparing different brands of luminaires on a test bench would require a good PAR meter and an integrating sphere but that's beyond my pay grade.
I've got the previous version of this but a generic ebay item might be just as good:
https://www.hydrofarm.com/p/LG17010