UV-B & UV-A: Lamp ouptut and goal umol

Beta Test Team · Mar 10, 2015

This thread is not about UV-B and THC production as is so often discussed, even though such effect from UV-B in the context of this thread is very possible.

Instead, this thread is about providing a goal UV-B irradiance that has positive effects on plant physiology and growth, which is:
0.1 to 5 umol/s/area2

UV-A and blue range should be at least about 10x greater than UV-B irradiance. And this isn't an issue with any lamps I've seen.

This thread is meant more to try and collect UV-B and UV-A values for various lamps. This study by Dr. Bugbee and student has collected many lamps spectral irradiance for UV-B and UV-A, as a percentage as compared to umol/s within PAR range:
http://cpl.usu.edu/files/publications/poster/pub__6740181.pdf

It's clear T12 VHO fluorescent have a good amount of UV-B and UV-A, in fact, about as much (and slightly more more) than is commonly found in sunlight at solar noon.

As an example, the Philips MasterColor Elite 942 T12 CMH emits about 0.03% UV-B and 1.9% UV-A as compared to umol/s within PAR range. And the Philips MasterColor Elite Agro 930 T12 (now called "Green Power") emits about 0.01% UV-B and 0.4% UV-A as compared to umol/s within PAR range.

So, assuming a canopy irradiance of 800 umol/s/area2 (which is what we suggest), the MasterColor Elite 942 T12 CMH provides about 0.24 umol/s/area2 UV-B, well within the target range for beneficial plant response.

And assuming the same canopy irradaince (800 umol/s/area2) for the Green Power (Elite Agro 930), the UV-B is only about 0.08 umol/s/area2, below the target range.

So the MasterColor Elite 942 CMH lamp emits about 300% more UV-B and about 475% more UV-A than the Green Power (MasterColor Elite Agro 930). And that also means the sun emits about 1,666% more UV-B than the 942 at solar noon, and about 5,000% more UV-B than the Green Power at solar noon; at least for the location of the sunlight measurements (and date) from the above study.

The thing to remember when comparing UV-B and UV-A of lamps to the sun, is we have to account for the changing UV-B and UV-A throughout the day from the sun, which means the total UV-B and UV-A per day between the sun and lamps is reduced vs. per second.

Ericos · Mar 10, 2015

It wouldve been nice to see them get the data on the mogul base 315. I know in the design specs s the UV A and B are considerably higher than the pg base, iirc. So possibly its UV emittance compare to plant health is even more effective with that lamp?

Beta Test Team · Mar 10, 2015

Yea, could be. Though, too much UV-B isn't good for plant growth.

I think you're referring to this lamp?
http://www.usa.ecat.lighting.philip...928601175501_na/#photometrics_diagrams_anchor

It does show a good amount of UV-B and UV-A, but I don't have data for those wavebands like in the first post. The spec sheet lists those wavebands as irradiance.

vostok · Mar 10, 2015

Not too good for a growers eye balls either ...good luck with your studies

Beta Test Team · Mar 10, 2015

Yup, good point. Although neither are most well lit grow rooms. And that's much less UV-B you'd get by looking at the lamp vs. looking at the sun. I think wearing polarized sun glasses in grow rooms is a must, or some type of safety sun glasses.

UV-C is the real danger.

ghostmade · Mar 29, 2015

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Beta Test Team · May 10, 2015

I thought I would post something here I wrote to someone last night. This is about how to measure UV-B, and the goals one would want to reach (in terms of UV-B irradiance).

The meter suggested is decent, and is what I use, because a better UV-B meter (one that is considerably more accurate) is a couple thousand dollars, and even then it's not accurate enough to justify the price. The best way to measure UV-B would be a spectroradiometer, which are greater than around $5K for a good model.

For the meter listed below, the master meter's NIST traceable calibration was done with two typical tanning lamps, which have UV-B and UV-A spectra similar to that of noon-day tropical sun's radiation, so it's pretty close to the spectrum used in the attached study on UV-B and Cannabis. That means using the listed meter is a good choice for measuring UV-B for Cannabis growth.

For the UV meter, I would suggest model 6.2, which is the the UV-B version, rather than the 5.7, which is the UV-B + UV-A. The reason is it's more important to know the UV-B irradiance, and there will be more than enough UV-A if there's sufficient UV-B: https://www.solarmeter.com/model62.html

Goal UV-B irradiance values as measured with SolarMeter 6.2:

VEG @ 18 hour photoperiod:
(min) 8 μW/cm2
(max) 20 μW/cm2

VEG @ 20 hour photoperiod:
(min) 7 μW/cm2
(max) 18 μW/cm2

VEG @ 22 hour photoperiod:
(min) 6 μW/cm2
(max) 16 μW/cm2

FLOWERING @ 12 hour photoperiod:
(min) 11 μW/cm2
(max) 30 μW/cm2

NOTES:

(1) Watt implicitly means per second, which is how the SolarMeter shows measurements.

(2) The minimum value isn't the absolute minimum, just the goal minimum, so e.g. if you're using 18 hour photoperiod for veg, 2 μW/cm2 or 4 μW/cm2 is okay, but 8 μW/cm2 would be better.

(3) The maximum value equates to the max natural UV-B (weighed with UV-B plant growth inhibition functions) found over a whole day under clear sky conditions and minimum solar zenith in Columbia, South America at 0' latitude, 3 km elevation, June, 1980.

(4) The neat thing about the SolarMeter 6.2 is its relative radiation response curve is a pretty close match to the weighting function used to find the values listed above. This means the SoloarMeter 6.2 is pretty accurate for use to measure UV-B for Cannabis to increase THC (and coloring), according to the seminal UV-B study on Cannabis I attached to this post. (See the two screenshots at the bottom of this POST to see what I mean.)

(5) The accuracy of model 6.2 is +/- 10%.

(6) The minimum values listed equate to about 5 kJ/m2/6 hours and the max equates to about 13.4 kJ/m2/6 hours; those min and max values I converted from the min and max tested values in the attached study on UV-B and cannabis. These values showed considerable increase in THC in all UV-B studies on Cannabis (drug type), and are the values I use, was well. And again, as pointed out in #3 above, the maxium values I listed equate the same total daily dosage of UV-B found in Colombia, South America at noon on clear day in June at about 10,000 feet elevation.

UV growth inhibition action spectrum:

SolarMeter model 6.2 relative radiation response curve (from 280-322 nm, disregard the graph below 280 nm and above 322 nm):

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UV-B & UV-A: Lamp ouptut and goal umol

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