PAR meter

[DavidCampen]

Originally Posted by naoki

With a related note, this is interesting:
LED GROW LIGHTS | Cree LED Grow Lights | American Made LED Grow Lights | Best LED Grow Lights
White+Red LED seems to be getting more PAR than B+R (per watt). Even if white contains fair amount of green, the 5W white diodes may be more efficient for plants?

I doubt that they are measuring PAR correctly. Moles per second implies that this is the total flux from the source while I would guess that they are measuring intensity at only a single point. If so, then a large part of the difference between sources is likely due to different beam spread.

"Photosynthetically Active Radiation (PAR) represents the fraction of sunlight with a spectral range from 400 to 700 nm, usually expressed in µmol (photons) m-2 s-1"

Photosynthetically Active Radiation Measurement Application Page | LI-COR Environmental

Emphasis added is mine.

[naoki]

Good point, you are probably right that the difference is more to do with the coverage area. I don't know if this is intentional or not, but all companies try to use a bit of misleading info. Or I should say that most of customers, including me, aren't well educated about light, so we don't interpret the info correctly. Thanks.

[naoki]

There is a new relatively cheap USB PAR meter:

Biotek Marine BTM3000
BioTek Marine BTM3000 PAR Sensor | BioTek Marine
It came out with PC software at first, but now they have released Mac version, too. It is $195 from here.

It is using the Apogee sensor, so it does have the issue which David pointed out (low sensitivity near 700nm). Bare sensor + multimeter is still a bit cheaper, but it could be more convenient. And logging to the computer could be interesting to get the cumulative PPFD over a day (in greenhouse).

[RonaldJanson]

Thanks for sharing this post with us. Best Gorilla Grow tent Foolish grower... lumens are for people! That lumens are an applicable approach to measure gentle produced by a develop gentle is the all-time number-one indoor gardening fable. Measuring gentle supposed for photosynthesis in lumens is simply plain silly.

[estación seca]

Originally Posted by RonaldJanson

Thanks for sharing this post with us. Best Gorilla Grow tent Foolish grower... lumens are for people! That lumens are an applicable approach to measure gentle produced by a develop gentle is the all-time number-one indoor gardening fable. Measuring gentle supposed for photosynthesis in lumens is simply plain silly.

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