Math behind

Rahz said:

The relative SPD values factored with the mole values.

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The specific problem is that column E formula is basically B2/ photon energy.
Then in cell F4 the formula E/B cancels out the B (B2) in column E formula. Which would negate the SPD value.

That hypothesis coincides with my original suspicions in this post https://www.rollitup.org/t/diy-leds-how-to-power-them.801554/page-169#post-13552734
From that post:

The 4.64 looked a lot like the factor for a lime green (555nm) conversion.

If the SPD is negated, that may explain the problem I am having with accepting the 4.64.

Until someone can explain the B2 and F4 equations I am at a loss. At this point I am still leaning towards an error in the spreadsheet.

There are those that say the SPD numbers are correct but no one is explaining the math.

I put over 30 hours of effort in to my post. Reverse engineering someone else's code is not easy. I am serious here. I sincerely want to know. In hindsight, I should have wrote my own, then compared.

Can anyone show me how they know the conversion numbers are correct? I have not seen the light yet.

My conversion numbers are sub one. For a 20,000 lumen CoB I measured 325 µMoles.

A value with the units µMole/J to convert a luminous figure to quantum makes zero sense.

The Emperor has no clothes?

Does anyone understand this math?

Does anyone have a scientifically sound method to prove this spreadsheet works?

alesh said:

Sorry this section doesn't make any sense.

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Being the one that created this spreadsheet which is a spectacular undertaking you should understand the simplicity of Inverse Square.

We can't allow everyone to willy nillly pick whatever height or distance to use when measuring µMoles. There must be a standard distance. Years ago I found that distance to be 1 meter. Today I can't find anyone that can confirm that. There are some LED grow light vendors that agree with me but I cannot use a vendor as a citation.

I made the measurements at 19" which is an arbitrary height. I used that height because it gave strong but not too strong (off the chart) values.

The height is not relevant to the acquired ratio between lumens and µMole but the proof to show the values are scientifically correct require some standardization.

alesh said:

Guess what. (3000 lm / 209.2 lm/W) * 4.59 µmol/J = wait for it = 65.82 µmol/s

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I really hate to burst your bubble. If your numbers match my measured 62 µMole, that only proves yours number are wrong.

The 62 µMole was measured at a willy nilly arbitrary 19". It is NOT the number you need to match.

But wait a second?? You have the SPD number for a Vero Decor 1750K 97 CRI???

If I had those numbers I could put an end to this in short order.

I have other measurements too. We just need one set of yours and one set of mine to compare and resolve this issue.

Please do not construe my effort as negative. I am working hard to get this right.

I could save a lot of money not having to purchase the CoB to measure the SPD.

I do know my measurements reflect the datasheet's SPD very accurately. I have superimposed my measurements against the datasheet SPD and they have been spot on.

NoFucks2Give said:

Can we agree that as the LED gets closer to the canopy the µMoles will increase?

So when someone states their fixture output 1000 µMoles do they just pick whatever distance they want. Or is there some sort of standard saying what the distance should be e.g. 1 meter?
.

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i appreciate all the calcs and this has probably been covered but there is a fundamental flaw in not distinguishing output ((umol/s), independent of space or distance) vs. par intensity (PPFD, umol/s/m^2). there is no distance you can use to take a PPFD measurement and convert it into PPF output. A spot measurement at any distance whether 1mm, 1m, or 1000 km, is still only measuring intensity at a point caused by a very small fraction of the light source and disregarding the gross output shining in all the other directions. This is why integrating spheres are used because they measure reflected not direct light and are able to be calibrated from NIST-traceable light sources of known output.

NoFucks2Give said:

We can't allow everyone to willy nillly pick whatever height or distance to use when measuring µMoles. There must be a standard distance.

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again there is no distance when measuring gross output. it is not part of the equation.

NoFucks2Give said:

The height is not relevant to the acquired ratio between lumens and µMole but the proof to show the values are scientifically correct require some standardization.

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i know of no way to accurately measure gross light output to caclulate umol/J other than a calibrated sphere and precise electrical input measurement

NoFucks2Give said:

The problem with do the conversion from lumens to PPFD is there is no simple way to know if your result is correct.

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What's so complicated. Just divide the lumens by PPF or lux by PPFD. It's THAT simple. Seriously.

NoFucks2Give said:

A value with the units µMole/J to convert a luminous figure to quantum makes zero sense.

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It's not µMole/J but µmol/J and it makes perfect sense.

You have the radiant watts in the PAR range (PAR watts) and you multiply that by the amount of photons generated per Joule to get photons per second.

So µmol/J * W = µmol/s. Makes perfect sense. Bonus tip W = J/s

Just try to understand instead of maintaining this state of cognitive dissonance.

NoFucks2Give said:

And that is why I'd never use a PAR meter. I have found my radiospectrometer to be very accurate within 1% of calculated parameters.

Johnson Grow Lights... I have been on your website. There is one minor thing that bugs me about your site.

You have a graph of McCree I do not remember if it was action or absorbance spectra, but which ever it is labeled, it's the other one.




How do you know the PAR multiplier is correct?
How do you know the digitized SPD is correct?
What if the PAR multiple was generated with the digitized SPD and they are both wrong?
How do you know?

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We test our products in a Goniophotometer and then a Sphere which uses a radiospectrometer. I trust a CSA certified lab over any testing I could do myself.

The discrepancy can be found in the fact that almost every led has a different light distribution. That's why good led companies supply .Ray files. You can't really take a spot measurements with any device and know total photonic output without capturing every single Photon with the sensor...... Sphere is the tool that is used to do this....

and even the sphere is an estimation of course. as weve seen people say "well gavitas dont do well in spheres" etc.

in our application the goniophotometer is critical as you mention- because it really demonstrates the throw of a light. efficiency is great but it has to get it to canopy uniformly at a reasonable distance to be useful

Stephenj37826 said:

We test our products in a Goniophotometer and then a Sphere which uses a radiospectrometer.

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And in my opinion PPF from a sphere is a useless number. I do not want the light that bounces off the ceiling, which will never reach the plant canopy, included in the flux measurement.

I do not want the total photonic output. I want to know only about what is reaching the leaf of the plant.

The integrated sphere is an isotropic measurement for isotropic light sources. Where a T5 LED may be considered isotropic a flat SMD cannot and the sphere is not a valid measurement.

Further more the sphere inflates the measurements. I prefer the flat earth measurement rather than the sphere.

What does the certified CSA lab have that makes you more comfortable? A piece of equipment that is calibrated to NIST standards? A spherical photonic sensor (one that measures photons from an angle other than just 90°)? I have that.

Stephenj37826 said:

You can't really take a spot measurements with any device and know total photonic output

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I want the spot measurement. Not the total useless photonic output. Only what reaches the leaf. aka PPFD. Fuck PPF.

NoFucks2Give said:

And in my opinion PPF from a sphere is a useless number. I do not want the light that bounces off the ceiling, which will never reach the plant canopy, included in the flux measurement.

I do not want the total photonic output. I want to know only about what is reaching the leaf of the plant.

The integrated sphere is an isotropic measurement for isotropic light sources. Where a T5 LED may be considered isotropic a flat SMD cannot and the sphere is not a valid measurement.

Further more the sphere inflates the measurements. I prefer the flat earth measurement rather than the sphere.

What does the certified CSA lab have that makes you more comfortable? A piece of equipment that is calibrated to NIST standards? A spherical photonic sensor (one that measures photons from an angle other than just 90°)? I have that.



I want the spot measurement. Not the total useless photonic output. Only what reaches the leaf. aka PPFD. Fuck PPF.

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We also measure with a Goniophotometer which gives us light distribution as well. The sphere is once again used to measure spectrum and give us the par multiplier.

wietefras said:

t's not µMole/J but µmol/J and it makes perfect sense.

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Do you know what I mean when I say µMole? I often tell people to listen to what I mean not what I say.
You really get hung up on the little piddly shit that does not matter. It's kind of annoying when you say this with such authority when you are wrong. It IS Mole. Mole is an SI unit of measure. mol is the unit symbol or abbreviation. microMole, milliMole, nanoMole do you like that? Those are SI units with SI prefixes. µMole is an acceptable common way to express a micromole.

Stephenj37826 said:

We also measure with a Goniophotometer which gives us light distribution as well.

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That's fine and dandy. But I do not want those numbers. I want the measurements from a PHOTOMETER not something made to measure a device (i.e. light bulb) invented in the 18th century with an obsolete antiquated piece of equipment being improperly used to inflate the figures. LEDs are NOT light bulbs. I want the single point measurement and the single point being the plant's leaf.

Goniophotometers for automotive and aircraft lighting, light signaling systems and similar test specimens
Retroreflectometer for vehicle retro-reflectors, road markings and other retroreflective materials
Photometer for the equipment of light labs, as a single measuring point or for on-line production control
- source http://www.optronik.de/

NoFucks2Give said:

That's fine and dandy. But I do not want those numbers. I want the measurements from a PHOTOMETER not something made to measure a device (i.e. light bulb) invented in the 18th century with an obsolete antiquated piece of equipment being improperly used to inflate the figures. LEDs are NOT light bulbs. I want the single point measurement and the single point being the plant's leaf.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://en.m.wikipedia.org/wiki/Goniophotometer&ved=0ahUKEwjWhs7x4LXUAhWIWSYKHcTKAzgQFgg0MAA&usg=AFQjCNEMLH3gSaAHtNZqzU0rWWWlL6wDpg&sig2=B8asfR067JNSJBYMy3MiRw

Goniophotometers for automotive and aircraft lighting, light signaling systems and similar test specimens
Retroreflectometer for vehicle retro-reflectors, road markings and other retroreflective materials
Photometer for the equipment of light labs, as a single measuring point or for on-line production control
- source http://www.optronik.de/

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Goniophotometer is used to measure light distribution by a single luminary. Once you have the data it is compiled into an .IES format that most lighting software uses to calculate light distribution in a facility/building.... I have a radiospectrometer and thus far the Goniophotometer measurements are spot on. This is a simulation of the HLG-550 pro.... When I do the simulation and also measure the same place under the fixture in real time the simulation is within 1-2% which is about as good as it gets.

I can get ppfd numbers anywhere on this simulation. Just point and click.

wietefras said:

What's so complicated. Just divide the lumens by PPF or lux by PPFD. It's THAT simple. Seriously.

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IF it's so fuckin' easy, show me the math on how to get the PPFD from the LED datasheet.
I'm still waiting for you to show me the math used in Alesh's spreadsheet. If it's so fuckin' easy WTF is your problem in producing the math?

Stephenj37826 said:

that most lighting software uses to calculate light distribution in a facility/building..

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I like that. A lot. What software did you use to create that image? How much does it cost?

I have been up on my soap box because it is a pet peeve of mine how the LED datasheet give distorted figures.

But the thing at issue here is @wietefras is saying there is no reason to account for the distance µMole in measurements. Do you agree that no distance requirement would make the measurement useless? For some reason I believe the standardized distance is 1 meter. That may be a defacto standard. PPFD and quantum measurements not being SI units kind of excludes them from standardization. I believe the CIE made 1 meter a standard but finding anything on their site is a nightmare or costs and arm and a leg and is nearly illegible. Your thoughts?

NoFucks2Give said:

I like that. A lot. What software did you use to create that image? How much does it cost?

I have been up on my soap box because it is a pet peeve of mine how the LED datasheet give distorted figures.

But the thing at issue here is @wietefras is saying there is no reason to account for the distance µMole in measurements. Do you agree that no distance requirement would make the measurement useless? For some reason I believe the standardized distance is 1 meter. That may be a defacto standard. PPFD and quantum measurements not being SI units kind of excludes them from standardization. I believe the CIE made 1 meter a standard but finding anything on their site is a nightmare or costs and arm and a leg and is nearly illegible. Your thoughts?

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I think there is merits to both. You need to know the efficacy of the led itself to start with.... Then you change light distribution through optics. A professionally built Horticulture led fixture will take both of these into account. So basically I'm saying pick the most efficient led you can (total photonic energy or watt umol/j then either use off the shelf optics or create your own custom optic to give you the desired light distribution. Both metrics are important. One without the other ends up with a less than satisfactory led luminary.


The software is free. It's called dialux.

NoFucks2Give said:

Do you know what I mean when I say µMole? I often tell people to listen to what I mean not what I say.
You really get hung up on the little piddly shit that does not matter. It's kind of annoying when you say this with such authority when you are wrong. It IS Mole. Mole is an SI unit of measure. mol is the unit symbol or abbreviation. microMole, milliMole, nanoMole do you like that? Those are SI units with SI prefixes. µMole is an acceptable common way to express a micromole.

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No, the SI symbol for Mole is mol. You are confusing the term/unit Mole and the symbol mol. It's ridiculous to insist on using the wrong word all the time.

Also it's not even µmol (or µMoles if you feel the need to be "different"), but you need to be specific as to whether you are referring to µmol/s or µmol/s/m2 instead of calling everything "µMoles".

Stephenj37826 said:

I think there is merits to both.

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The metrics have their place. It's me that does not find them useful in selecting LEDs or grow light fixtures.

How do you feel about the charlatan grow light vendors that publish the PPFD with a spectrometer or PAR meter when they did the measurements at six inches. Or are you on the same boat as @wietefras where the distance does not matter.