Randomblame
Well-Known Member
Hi Vehlor!Hello
I read that if you multiply your radiant watts by 4.66 and then divide the resulting number by the area of your plant (in square meters) , you get a rough estimate of your PPFD.
Now the problem is that to calculate the radiant watts I need to kmow if the led is 50%, or 45%, or 60% efficient. I have been reding a lot and analyzing data sheets but can find a way to calculate radiant watts and heat watts. Can you (or anyone reading this) help me with this?
Also, how far does the light need to be from the plants for this formula (radiant watts * 4.66 / m^2 ) to work? 18 inches?
Thanks.
You need more than a simple multiplier to calculate the radiant power, at least you need some lux readings to use a multiplier. But there are other ways...
Either you need LER and QER values of the LED* you want to calculate or you use a tool like the one below. Here you only have to enter the total lumen/lux output of the fixture, the spectrum in °k/color in nm, distance and length(if it's not a point source) and you get a fairly accurate calculation of the expected radiation values.
http://dev.edman007.com/~edman007/pub/par-dli-cal.html
*) there is a thread created by @alesh if I remember correctly. It's about how to calculate these values by only using the datasheet.
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