PAR measurement thread

[PhotonFUD]

Hey guys - with more and more people getting cheap PAR meters it would be great to have a place to share measurement results. The common units I have seen on the forums so far are:

Apogee - MQ-200, MQ-500, sensors SQ-500,SQ-520
Licor - Li-250A, sensors Li-190R
Hydrofarm - LGBQM Quantum PAR Meter
Spectral lightmeter - Gigahertz-Optik MSC15

The technology is getting cheaper and hopefully there will be more affordable products.

Anyhow, I will get it started with some box store bulbs that I used to set up my measuring station. I have selected three heights, 8", 12" and 18" with center, center + 9", and center +18" measurements taken using the Hydrofarm meter. Sure it is only 9 measurements per bulb but hey, it is a start. No reflectors used, the measuring station is in a darkroom and the bulbs were hung and measured at each height.




So CFLs are terrible.

Flood lamps aren't bad, the 40 degree sure makes a difference. Effective radius is about 3" however.

The big surprise was the EcoSmart outperforming the Philips. For a value bulb from a box store, it is good knowledge to know.

 

[Airwalker16]

Hey guys - with more and more people getting cheap PAR meters it would be great to have a place to share measurement results. The common units I have seen on the forums so far are:

Apogee - MQ-200, MQ-500, sensors SQ-500,SQ-520
Licor - Li-250A, sensors Li-190R
Hydrofarm - LGBQM Quantum PAR Meter
Spectral lightmeter - Gigahertz-Optik MSC15

The technology is getting cheaper and hopefully there will be more affordable products.

Anyhow, I will get it started with some box store bulbs that I used to set up my measuring station. I have selected three heights, 8", 12" and 18" with center, center + 9", and center +18" measurements taken using the Hydrofarm meter. Sure it is only 9 measurements per bulb but hey, it is a start. No reflectors used, the measuring station is in a darkroom and the bulbs were hung and measured at each height.

View attachment 3785139


So CFLs are terrible.

Flood lamps aren't bad, the 40 degree sure makes a difference. Effective radius is about 3" however.

The big surprise was the EcoSmart outperforming the Philips. For a value bulb from a box store, it is good knowledge to know.

I dont understand the "#" + "#" from center. How dis par go from 651 to... 4?

 

[PhotonFUD]

I dont understand the "#" + "#" from center. How dis par go from 651 to... 4?

Center is directly under the bulb. Center + 9" is 9" from the center. Center + 18" is 18" from the center. So 0, 9" and 18" for radius.

And that is what a 40 degree lens will do for focusing

8" height 9" from center there isn't much light. It pretty much dies after about 3" from center, so a circle roughly 6" dia.

 

[wietefras]

To compare lights, you need PPF measurements. PPFD is completely useless for that.

Especially if you don't use some form of reflectivity to equalize differences in spread.

 

[MeGaKiLlErMaN]

To compare lights, you need PPF measurements. PPFD is completely useless for that.

Especially if you don't use some form of reflectivity to equalize differences in spread.

What??? That's not true. PPFD is all that matters, but to make it mean something you need the same square footage... The reason being is that PPF is usually the middle measured... But when your light is the size of a space it is kinda pointless. PPDF tells you how much light is landing in the area..

 

[PSUAGRO.]

What??? That's not true. PPFD is all that matters, but to make it mean something you need the same square footage... The reason being is that PPF is usually the middle measured... But when your light is the size of a space it is kinda pointless. PPDF tells you how much light is landing in the area..

no, he's right................when comparing light sources====ppf/w

 

[MeGaKiLlErMaN]

no, he's right................when comparing light sources====ppf/w

Close, PPFD/W is more important and also works. You can do it over multiple areas, 3x3, 4x4, 5x5. You compare the numbers and you then have the most efficient setup for any given area. Check the signature and divide to see what's the best option... The DEHPS at .62PPFD/W or the 1.41PPFD/W 850W led? It's an easy choice when you look at the options.

 

[PhotonFUD]

To compare lights, you need PPF measurements. PPFD is completely useless for that.

Especially if you don't use some form of reflectivity to equalize differences in spread.

Sure you could use PPF and no doubt it would be much easier to compare. One easy to understand number that all manufacturers should be required to provide. We should be the ones to decide how much area to spray photons on.

But if height and an average over area are provided then it is much more accurate since you don't have to account for random losses that are typically set at 10% or 20% in many spreadsheet equations. Field measurement is always preferable but all data is valuable for planning. The goal is to improve planning accuracy.

Of course larger sample sizes are better but I am not willing to relearn statistics that I forgot a long time ago approximately 30 mins after the final exam. +/- 10% with 2 significant digits of resolution is fine for me.

And correct, no reflectivity. They were just spot measurements at those points to provide a frame of reference. Intentionally avoided reflection so that others can compare.

I am looking forward to seeing how much reflectivity does help though.

 

[Abiqua]

Build your own for around $25. The Fresnel lens is the hardest to source for a good clip around 395/735..... The sensor is around $5.

 

[wietefras]

Close, PPFD/W is more important and also works. You can do it over multiple areas, 3x3, 4x4, 5x5. You compare the numbers and you then have the most efficient setup for any given area.

That's comparing light distribution. The opening post is talking about light source comparisons and for that you need PPF.

Sure you could use PPFD to compare complete set ups including light sources, but then they would need to compare actual setups. With reflective walls and reflectors on the lights.

Check the signature and divide to see what's the best option... The DEHPS at .62PPFD/W or the 1.41PPFD/W 850W led? It's an easy choice when you look at the options.

This is exactly why you should not be using these PPFD measurements to compare lights.

Gavita Pro DE gives you 1600umol/s on the plants over 2m2 (800uml/s/m2 average). Which is around 1.6umol/s/W. COBs give you around 2.2umol/s/W after wall losses. So that's around 35 to 40% increase in light from the same wattage. Not the more than twice as much you see when using inaccurate dark room PPFD matrix measurements of only a portionof the light.

 

[JorgeGonzales]

What??? That's not true. PPFD is all that matters, but to make it mean something you need the same square footage... The reason being is that PPF is usually the middle measured... But when your light is the size of a space it is kinda pointless. PPDF tells you how much light is landing in the area..

OK, I think you are misunderstanding what PPF is, and you keep talking about PPFD/W and keeping the area the same so you can compare, and nobody has corrected you for some reason in your thread about it, and now we have this.

PPFD = PPF divided by area in meters squared. PPF is expressed in umol/J or umol/s/W (same thing), it's a photon count per second per watt between 400 and 700nm.

PPF is what matters, it's not a "middle measurement", it's not affected by distance, and PPFD/W is goofy so we can forget about that now.

 

[MeGaKiLlErMaN]

OK, I think you are misunderstanding what PPF is, and you keep talking about PPFD/W and keeping the area the same so you can compare, and nobody has corrected you for some reason in your thread about it, and now we have this.

PPFD = PPF divided by area in meters squared. PPF is expressed in umol/J or umol/s/W (same thing), it's a photon count per second per watt between 400 and 700nm.

PPF is what matters, it's not a "middle measurement", it's not affected by distance, and PPFD/W is goofy so we can forget about that now.

I understand what both are, however if you look at the PPF for a DIY led it will be poor, but it will have a higher PPDF. This is what I plan to test in my side by side so that people will understand that the amount that gets to a plan in the area is more important than over all light output.. Because falloff is a bitch.

I understand that this might seem to people that I'm using it wrong but one we have the results behind it it will make more sense.

The reason it's not being corrected is because most think the same way.. Yes uMol/W is important.. But you can only get so close so it could end up being wasted after a certain distance.. Which is what I'm attempting to demonstrate.

I may be wrong but I would rather test it out before saying so and have proof that I'm wrong... Mathematically it makes more sense to use PPFD/W but like I said we will see if I'm wrong... And if I am them I'll own up to it.

 

[JorgeGonzales]

I understand what both are...

If you understood, I wouldn't have typed all that, and you wouldn't be saying shit like:

Im not seeing anything for PPFD at all, only PPF at center, Any chance you have a PAR meter?

PPFD/W is goofy. I could explain further, but you'd be better served understanding what PPF actually is, and the rest is self-explanatory at that point. Trust me, you really don't understand, and I can talk about distance, and optics, and wall reflectivity and room size until the cows come home, but all of that should be obvious to you if you understand what these terms mean.

 

[MeGaKiLlErMaN]

That's comparing light distribution. The opening post is talking about light source comparisons and for that you need PPF.

Sure you could use PPFD to compare complete set ups including light sources, but then they would need to compare actual setups. With reflective walls and reflectors on the lights.



This is exactly why you should not be using these PPFD measurements to compare lights.

Gavita Pro DE gives you 1600umol/s on the plants over 2m2 (800uml/s/m2 average). Which is around 1.6umol/s/W. COBs give you around 2.2umol/s/W after wall losses. So that's around 35 to 40% increase in light from the same wattage. Not the more than twice as much you see when using inaccurate dark room PPFD matrix measurements of only a portionof the light.

Not according to my measurements that are unbiased. Look at the PPFD measurements at the same distances. Time will tell

 

[MeGaKiLlErMaN]

If you understood, I wouldn't have typed all that, and you wouldn't be saying shit like:



PPFD/W is goofy. I could explain further, but you'd be better served understanding what PPF actually is, and the rest is self-explanatory at that point. Trust me, you really don't understand, and I can talk about distance, and optics, and wall reflectivity and room size until the cows come home, but all of that should be obvious to you if you understand what these terms mean.

I'll remember this, take a look at the calculator first.

I would say it's new... And yes a bit goofy, but any new concept is.

PPFD is the average PPF for a given area right? PPF is the "total" light output correct?

So if you could spread out the light to be perfect over an area... Say 1500umols(PPFD not the PPF) since you are closer and have perfect coverage the total light output would not be the same if measured from a distance. Because it's not meant to be.

To me if you measure what the all the plants see average for each light... at the same distance... Then that would be a fair comparison right?

It's because the average that actually hits the plants is more important than the total output which doesn't assume that it ever gets there.

 

[MeGaKiLlErMaN]

Here is my point:

CXB3590DB36V4000K 16 COBS @1.05A ON 1.813 PROFILE HEATSINK
16 SQ.FT. CANOPY 92% EFFICIENT DRIVER @10 CENTS PER KWH
Total power watts at the wall: 618.48
Cobs power watts: 569
Total voltage forward: 542
Total lumens: 121891
Total PAR watts assuming 10% loss: 340
Total PPF: 1540.2
PPFD based on canopy area: 1036.16
PAR watts per sq.ft.: 21.25
Cob efficiency: 66.32%
Power watts per sq.ft.: 35.56
Voltage forward per cob: 33.85
Lumens per watt: 214.22
Heatsink riser thickness / number of fins / fin's length: 0.3in/6/0.95in
Heatsink area per inch: 100.94 cm^2
Total heat watts: 192
umol/s/W / CRI: 4.53 / 70CRI
Heatsink length passive cooling @120cm^2/heatwatt: 228 inches
Heatsink length active cooling @40cm^2/heatwatt: 76 inches
COB cost dollar per PAR watt: $2.36
Electric cost @12/12 in 30 days: $22.77
Electric cost @18/6 in 30 days: $33.9
Cost per cob: $50.17
Heatsink cost per inch cut: $0.66
Total cobs cost: $803
Total heatsink passive cooling cost: $150
Total heatsink active cooling cost: $50

There are multiple light sources compared to a singl point, so this is an attempt to make it fair across the board.

 

[JorgeGonzales]

I'll remember this, take a look at the calculator first.

I would say it's new... And yes a bit goofy, but any new concept is.

It's not goofy because it's new, it's goofy because it makes no sense. You are literally saying "I've invented this awesome new thing called PPFD/W, and we just need to keep the area and the distance the same to compare lights!" Anyway, you'll figure it out, or you won't.

And no offense, but I don't know how else to say this: I don't need to look at the calculator, because I don't need a calculator. Every time you paste Citizen numbers from the calculator, who do you think provided them to @bggrass?

As a matter of fact, there is an error in what you just pasted: umol/s/W: 4.53. That appears to be the QER, not PPF. The Citizen stuff you've been pasting looked correct, and that's the number you should care about.

 

[MeGaKiLlErMaN]

It's not goofy because it's new, it's goofy because it makes no sense. You are literally saying "I've invented this awesome new thing called PPFD/W, and we just need to keep the area and the distance the same to compare lights!" Anyway, you'll figure it out, or you won't.

And no offense, but I don't know how else to say this: I don't need to look at the calculator, because I don't need a calculator. Every time you paste Citizen numbers from the calculator, who do you think provided them to @bggrass?

As a matter of fact, there is an error in what you just pasted: umol/s/W: 4.53. That appears to be the QER, not PPF. The Citizen stuff you've been pasting looked correct, and that's the number you should care about.

Just look at the PPF compared to the PPFD and thats all you need to do to see the point.

 

[Shugglet]

Just look at the PPF compared to the PPFD and thats all you need to do to see the point.

How much of an impact does an individuals environment have on PPF vs PPFD?

 

[MeGaKiLlErMaN]

How much of an impact does an individuals environment have on PPF vs PPFD?

Zero but of all other aspects of the environment are the same then the last thing to consider is how to optimize light for your given area.