How to Plot PPF Chart with Quantum Sensors for LED light comparison

robincnn

robincnn

Well-Known Member
I see some compnies posting PPF Chart. But i am not sure if their charts can be compared to each other as their setups may have been diffrent.
Is there any standard to plot PPF Chart with Quantum Sensors for LED light comparison

Altough a single COB might be a point source of light and would have a circular pattern. More COB then pattern might be Oval, Square or any other shape. However since most gro spaces are Square or rectangle it makes sence to plot values on 2x2 feet or a 3x3 feet or similar grid.
Height is important but is usually listed so thats good.

Is it called a PAR chart of a PPF chart/plot ?


1) Should the measuring environment walls be reflective?
If think best to have an open area with no walls to walls at distance to minimize any reflections.
2) Should the base surface be reflective? Should the Quantum Sensor always point vertically up or angled towards the light source? If it is angled towards the light source it may add the reflections from base.
 
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Rahz

Rahz

Well-Known Member
I remember someone saying the standard was to have the sensor vertical. There may even be leveling devices to insure precision. Standards are good but I think the vertical measurement probably gets a penalty on the outer measurements... so if taking measurements for one's own purpose I would angle the sensor to get the highest reading since it will be the most true.
 
alesh

alesh

Well-Known Member
robincnn said:
I see some compnies posting PPF Chart. But i am not sure if their charts can be compared to each other as their setups may have been diffrent.
Is there any standard to plot PPF Chart with Quantum Sensors for LED light comparison

Altough a single COB might be a point source of light and would have a circular pattern. More COB then pattern might be Oval, Square or any other shape. However since most gro spaces are Square or rectangle it makes sence to plot values on 2x2 feet or a 3x3 feet or similar grid.
Height is important but is usually listed so thats good.

Is it called a PAR chart of a PPF chart/plot ?


1) Should the measuring environment walls be reflective?
If think best to have an open area with no walls to walls at distance to minimize any reflections.
2) Should the base surface be reflective? Should the Quantum Sensor always point vertically up or angled towards the light source? If it is angled towards the light source it may add the reflections from base.
Click to expand...
Different (usually not very precise) quantum sensors/meters, different methodology, different spectra, [...]
These charts can give you some general idea but I wouldn't take them too seriously unless they're done independently and by certified meters.
 
robincnn

robincnn

Well-Known Member
All measurements were taken using Apogee SQ-120: Electric Calibration Quantum Sensor
Since there is no standard way of measuring, I cannot assume accuracy of my results.
The center reading should be accurate. On the outer 2 ft box, measurements may be 10%-20% higher due to ground(A4 white papers) reflections. Open area nearest wall 5 feet away. No lens or reflector unless specified.
If you have 2 COB close together, just double the numbers.

UNO Vero 10 COB
Vero 10.png
 
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robincnn

robincnn

Well-Known Member
I was able to convince Khatod to share a sample of each for testing. Will post results in next 1-2 weeks.
PL1825SR 90 degree round pattern
PL1845SR 120 degree square pattern

KB 80 is good but I thought it would have sharper cutoffs. It's pattern is almost like the LEDIL reflector.

Things got complicated when tested in a small 2x2 reflective mylar tent without any plants. The gains with reflectors and lens were much less. Rahz suggested something similar in his 1st post of 'Going Commercial thread'. I saw may be just 5 to 10% gain with reflector and 10 to 15% with lens. Lens and reflector do seem to help a lot if one or more sides of grow area are not reflective.
 
P

PurpleBuz

Well-Known Member
robincnn said:
I was able to convince Khatod to share a sample of each for testing. Will post results in next 1-2 weeks.
PL1825SR 90 degree round pattern
PL1845SR 120 degree square pattern

KB 80 is good but I thought it would have sharper cutoffs. It's pattern is almost like the LEDIL reflector.

Things got complicated when tested in a small 2x2 reflective mylar tent without any plants. The gains with reflectors and lens were much less. Rahz suggested something similar in his 1st post of 'Going Commercial thread'. I saw may be just 5 to 10% gain with reflector and 10 to 15% with lens. Lens and reflector do seem to help a lot if one or more sides of grow area are not reflective.
Click to expand...
who sells the Khatod ?
 
Greengenes707

Greengenes707

Well-Known Member
I expected what we saw...a 80* lens vs a 90* reflector. If anything I would expect the lens to give much higher instantaneous readings than the reflector. It's the reason single die and small platform chips based lights use lenses over reflectors...to maximize their center numbers.
The light coming down/out isn't happening in the same manner. A lens has a collimation effect, focusing the light to a point. As where a reflector is more like a tightening of the dispersion, like a choke on a shotgun. Diffusion is beneficial for many things, penetration being one of them. A wide angle reflector or bare is closer to diffusion than a lens of any angle.

The end all test for this would be to put them in a sphere and see which is actually emitting the most total light. That is what I am curious, I have been looking for a sphere for lots of little test like such, no luck yet still.

Thanks robin for the variety of test.
 
Stephenj37826

Stephenj37826

Well-Known Member
Greengenes707 said:
I expected what we saw...a 80* lens vs a 90* reflector. If anything I would expect the lens to give much higher instantaneous readings than the reflector. It's the reason single die and small platform chips based lights use lenses over reflectors...to maximize their center numbers.
The light coming down/out isn't happening in the same manner. A lens has a collimation effect, focusing the light to a point. As where a reflector is more like a tightening of the dispersion, like a choke on a shotgun. Diffusion is beneficial for many things, penetration being one of them. A wide angle reflector or bare is closer to diffusion than a lens of any angle.

The end all test for this would be to put them in a sphere and see which is actually emitting the most total light. That is what I am curious, I have been looking for a sphere for lots of little test like such, no luck yet still.

Thanks robin for the variety of test.
Click to expand...
I suspect a really good reflector will of course have higher total ouput. A reflector that only corrects the stray light would be best for most photons to the canopy I suppose. Especially if it was 98% reflective German aluminium. Not sure on the percentage of light a 90° reflector actually reflects of the total output of the cob but I suspect it's not above 20%. SO if it did correct 20% of the light at 98% reflectivity you're looking at 99.6% efficiency? I think lenses can get close to that high with the proper coatings/glass but that is yet to be seen. Like supras said lenses would be great at that point. I'm leaning twords ordering my lenses coated. Upfront cost will be crazy but in the end it will be well worth it. Now to see if I can get them in low iron glass. That would be especially useful if the cobs had uv light in them.
 
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robincnn

robincnn

Well-Known Member
allow me to overthink this for a moment ...in a wide grow area even the photons emitted at angles grater than 45-60 degree may hit the canopy somewhere. In a small grow area the 45-60 degree photons may bounce off the walls and reach canopy .
Lens or reflector may have losses but may provide the light with a shorter path to canopy without need of reflections from wall. If Inverse square law is applicable then shorter path with Lens or reflector may provide more intensity despite their losses.

@Greengenes707 Would the Diffusion (as the name suggest) decrease the penetration over distance. Could use your perspective here. Not sure about your plan with the sphere.. if you plan to coat inside reflective and place sensor on end opposite on diameter to COB. Would a cube suffice.

Rahz said:
10-15% in a tent might not be extreme but not small potatoes either.
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It is tricky because with an open non reflective area the PAR meter can be aimed towards the light source for max value. With a reflective environment a lot of light comes bouncing off the walls so sensor reads highest when slightly more vertical and not aimed towards cob. So expect some small errors in my data.

@Stephenj37826 I saw your post . Anti reflective doubles the price of lens. I wouldn't bet on theoretical gain numbers unless i see it on my apogee. Would be nice to test a single lens with and without the Anti reflective coating.

Vero 29
vero29.png
 
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Growmau5

Growmau5

Well-Known Member
one of you math nerds needs to man up and buy a Spectrometer integrated sphere, they are only a quarter million dollars.

In the meantime, I wonder if purchasing a large beach ball and covering it with paper machet and painting the inside white would be a decent substitutebeach ball.png beach ball.png for our purposes of light measurement.
 
SupraSPL

SupraSPL

Well-Known Member
robincnn said:
KB 80 Degree lens, LEDIL Reflector and last one without lens or reflector.
Two black markers are 1 ft apart
Click to expand...
Great data thank you!

Another way we can try to level the playing field for testing is by attempting to match the size of the illuminated area and allowing the distance to canopy to vary, because in practice bare COBs can get closer to the canopy, unless they are very high powered in which case a lens or reflector is highly recommended.

Regarding the sharpness of the cutoff, with lenses it is affected by the size of the LES, the size of the lens and the distance between LES and lens. In this case I expect you would get a sharper cutoff by increasing the distance between LES and lens, but with a lens that much larger than the LES it might never have a sharp cutoff.

For reflectors, the sharpness of the cutoff is affected by the height of the reflectors sides. A tall reflector will have a sharper cutoff than a short reflector because it reduces lateral scatter. That is something that reflectors have over lenses, a lens is all or nothing but you can make "partial" short reflectors for lower powered COBs (~25W or less) or you can make reflectors specifically for COBs that are bordering a walkway with taller reflector height on that side.
 
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