Lux to Par to PPFD Conversion Charts

Sxott · Sep 7, 2015

I just bought a Hydrofarm Active air Lux meter. I didnt have the money to go with a new PAR meter and just wanted to know how my COB builds compared to my 1000 HPS (lux wise) and checking out uniformity..

I was completely blown away.....

24" from the HPS, I was reading 25,000 lux in the center and 15,000 lux on the edge of 4 ft. ( w/large adjustawing and open sides warmed up 15 min)

I measured my COB builds designed to put out around 12500 PPFD (according to the spreadsheets here)
I was reading 58,000 - 62,000 lux across the whole canopy at 12" ! (in tent)

I did not expect to see that large of a difference !

I was wondering if any charts exist to figure out the PAR from these lux numbers for the given Cree and Vero xxxxk COBS???

FranJan · Sep 7, 2015

http://www.photometrictesting.co.uk/File/blog_scotopic_photometry.php

Abiqua · Sep 7, 2015

There are multipliers for light source and hence dividers[ opposite number .9xxx for example]

Its probably easier to use a source multiplier or narrow it down for LED using either two of the same Lux Meters or measured against a Par Meter....

either way, more of a spot checker, than an accurate modeler......

------[I have used a multiplier of .0100 to calibrate my Lux meter [[Arduino]] to the datasheet output......3k Cree]

Google for more Lux to PPF source multipliers....... :peace:

Source Multiplier
Sunlight 0.0185
Fluorescent (Grolux) 0.029
Metal Halide 0.0141
Fluorescent (865/840) 0.0135
High Pressure Sodium 0.0122

alesh · Sep 8, 2015

Abiqua said:
There are multipliers for light source and hence dividers[ opposite number .9xxx for example]

Its probably easier to use a source multiplier or narrow it down for LED using either two of the same Lux Meters or measured against a Par Meter....

either way, more of a spot checker, than an accurate modeler......

------[I have used a multiplier of .0100 to calibrate my Lux meter [[Arduino]] to the datasheet output......3k Cree]

Google for more Lux to PPF source multipliers.......

Source Multiplier
Sunlight 0.0185
Fluorescent (Grolux) 0.029
Metal Halide 0.0141
Fluorescent (865/840) 0.0135
High Pressure Sodium 0.0122

It's a quite simple formula:
QER/LER

Sxott · Sep 8, 2015

alesh · Sep 8, 2015

Sxott said:
QER?

The amount of photons each joule of a radiation carries. I'm not sure how is this quantity officially called but I think it should be quantum efficiency of radiation, at least it is here. The unit is definitely µmol(of photons)/J .

Greengenes707 · Sep 8, 2015

alesh said:
It's a quite simple formula:
QER/LER

I never really knew where/how exactly those where obtained...never really thought about it either. Thanks for the lesson.

So @Sxott,the conversion factor for a 3k Cree would be 4.86/325=0.014953846153846

Sxott · Sep 8, 2015

Greengenes707 said:
I never really knew where/how exactly those where obtained...never really thought about it either. Thanks for the lesson.

So @Sxott,the conversion factor for a 3k Cree would be 4.86/325=0.014953846153846

Thank you but, I, not sure what to do with this number?

alesh · Sep 8, 2015

Sxott said:
Thank you but, I, not sure what to do with this number?

If your meter measures illuminance (lux) correctly (it probably doesn't), then you can use this factor (valid for Cree 3000K/80CRI spectrum) to get PPFD in the point where you performed the measurement.

TimeToBurn · Sep 8, 2015

Sxott said:
I just bought a Hydrofarm Active air Lux meter. I didnt have the money to go with a new PAR meter and just wanted to know how my COB builds compared to my 1000 HPS (lux wise) and checking out uniformity..

I was completely blown away.....

24" from the HPS, I was reading 25,000 lux in the center and 15,000 lux on the edge of 4 ft. ( w/large adjustawing and open sides warmed up 15 min)

I measured my COB builds designed to put out around 12500 PPFD (according to the spreadsheets here)
I was reading 58,000 - 62,000 lux across the whole canopy at 12" ! (in tent)

I did not expect to see that large of a difference !

I was wondering if any charts exist to figure out the PAR from these lux numbers for the given Cree and Vero xxxxk COBS???

Why did you measure the HPS at 24" and COB's at 12"? What's the COB measurement at 24"? Was the HPS measured in tent?

Stephenj37826 · Jan 2, 2016

TimeToBurn said:
Why did you measure the HPS at 24" and COB's at 12"? What's the COB measurement at 24"? Was the HPS measured in tent?

Im guessing for 2 reasons. His diy ficture is probably rather large and at 12" he is hitting the footprint he desires. HPS is a single point light source so 24" is probably optimum for spread and unlike the cobs heat is a problem closer than 24".

PurpleBuz · Jan 2, 2016

TimeToBurn said:
Why did you measure the HPS at 24" and COB's at 12"? What's the COB measurement at 24"? Was the HPS measured in tent?

you missed the key comment ....

"I was reading 58,000 - 62,000 lux across the whole canopy at 12"

ttystikk · Jan 2, 2016

PurpleBuz said:
you missed the key comment ....

"I was reading 58,000 - 62,000 lux across the whole canopy at 12"

I'm looking forward to seeing this for myself.

BuddyColas · Jan 8, 2016

Sxott said:
I just bought a Hydrofarm Active air Lux meter. I didnt have the money to go with a new PAR meter and just wanted to know how my COB builds compared to my 1000 HPS (lux wise) and checking out uniformity..

I was completely blown away.....

24" from the HPS, I was reading 25,000 lux in the center and 15,000 lux on the edge of 4 ft. ( w/large adjustawing and open sides warmed up 15 min)

I measured my COB builds designed to put out around 12500 PPFD (according to the spreadsheets here)
I was reading 58,000 - 62,000 lux across the whole canopy at 12" ! (in tent)

I did not expect to see that large of a difference !

I was wondering if any charts exist to figure out the PAR from these lux numbers for the given Cree and Vero xxxxk COBS???

I'll wade into the fray. Take a look at this thread, very educational.
https://www.rollitup.org/t/diy-led-cree-cxa3070.789575/page-147

Post #1083 from Mr Flux
"For the CXA 3000K, divide the number of lux by 67.3"

That will give you an approximate umol reading. Also, that is a very even spread on your canopy. Pictures? :mrgreen:

wietefras · Jan 9, 2016

Indeed, just check SupaSPLs sheets and divide the lm/W by the umol/s/W figures. Every light color will have a different conversion, but they way he calculates the PAR values is a fixed formula always resulting in the same conversion factor.

Apogee report a list of lumen/PAR conversions: http://www.apogeeinstruments.co.uk/conversion-ppf-to-lux/
Sunlight 54
Cool White Fluorescent Lamps 74
Mogul Base High Pressure Sodium Lamps 82
Dual-Ended High Pressure Sodium (DEHPS): ePapillion 1000 W 77
Ceramic Metal Halide (CMH942): standard 4200 K color temperature 65

So divide the lux reading from sunlight by 54 and you get an indication of PAR. For HPS is somewhere between the 82 and 77.

planti · Apr 25, 2016

wietefras said:
Indeed, just check SupaSPLs sheets and divide the lm/W by the umol/s/W figures. Every light color will have a different conversion, but they way he calculates the PAR values is a fixed formula always resulting in the same conversion factor.

Apogee report a list of lumen/PAR conversions: http://www.apogeeinstruments.co.uk/conversion-ppf-to-lux/
Sunlight 54
Cool White Fluorescent Lamps 74
Mogul Base High Pressure Sodium Lamps 82
Dual-Ended High Pressure Sodium (DEHPS): ePapillion 1000 W 77
Ceramic Metal Halide (CMH942): standard 4200 K color temperature 65

So divide the lux reading from sunlight by 54 and you get an indication of PAR. For HPS is somewhere between the 82 and 77.

Hey!! Where did you find the "SupaSPLs sheets"

Thanks

wietefras · Apr 26, 2016

Not sure. These get posted around here quite a lot. Ledbuilders.org also has some drive documents with them

Uberknot · Sep 9, 2016

TimeToBurn said:
Why did you measure the HPS at 24" and COB's at 12"? What's the COB measurement at 24"? Was the HPS measured in tent?

Approx. with tablet meter....I have a better meter on the way to test a bit.

These numbers are pretty much equally spread through out the 2x2 area from the light bouncing off walls etc..

32" in a 2x2 tent at 875 mA 4 x cob light = 20k lux.

24" in a 2x2 tent at 875 mA 4 x cob light = 38k lux

24" in a 2x2 tent at 1750 mA 4 x cob light = 77k lux

You can see double the mA and double the flux I would say at 32" 1750 mA it will be around 40000 lux.

salmonetin · Sep 9, 2016

https://www.rollitup.org/t/spectral-lightmeter-gigahertz-optik-msc15.913239/page-10#post-12895236

....there are info on the pdf...

Principles of Radiation Measurement

...on the web of apogee.... and awesome knowledge base...

http://www.apogeeinstruments.com/knowledge-base/

http://www.apogeeinstruments.com/conversion-ppf-to-lux/...

...and i saw info on an pdf called ....Photmetric Radiometric and Quantum Light Units...

:peace:

Saludos

Lux to Par to PPFD Conversion Charts

Sxott

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FranJan

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Abiqua

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alesh

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Sxott

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alesh

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Greengenes707

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Sxott

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alesh

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TimeToBurn

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Stephenj37826

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PurpleBuz

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ttystikk

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BuddyColas

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wietefras

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planti

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wietefras

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Uberknot

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salmonetin

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