Lux to Par to PPFD Conversion Charts

Sxott

Sxott

Well-Known Member
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???
 
Abiqua

Abiqua

Well-Known Member
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

alesh

Well-Known Member
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.......:peace:

Source Multiplier
Sunlight 0.0185
Fluorescent (Grolux) 0.029
Metal Halide 0.0141
Fluorescent (865/840) 0.0135
High Pressure Sodium 0.0122
Click to expand...
It's a quite simple formula:
QER/LER
 
Sxott

Sxott

Well-Known Member
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
Click to expand...

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

TimeToBurn

Well-Known Member
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???
Click to expand...
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

Stephenj37826

Well-Known Member
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?
Click to expand...

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".
 
BuddyColas

BuddyColas

Well-Known Member
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???
Click to expand...

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

wietefras

Well-Known Member
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.
 
P

planti

Member
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.
Click to expand...

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

Thanks
 
wietefras

wietefras

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

Uberknot

Well-Known Member
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?
Click to expand...
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.
 
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