Cheap LUX meter to calculate DLI and PAR

[BadGrandpa007]

Hi, i had the idea to buy a cheap LUX meter to calculate the aproximate DLI and PAR. I see people are doing that. Some guys alrady calibrated some meters from The apogee PRO devices. ChatGPT says he can calculate the data for me, it just needs the LEDs SPD data and i have it. My LED is Mars Hydro SP250W, perfect for 2x4space. The PAR meters are sooo expensive, i just cant afford them, so i thought this would be a solution, better that nothing at all.. Im wondering what would be the calculation error from LUX to PAR even if the Ai calculates it from the SPD data.. i thought if the error would be some 5-10% it not so important i could just adjust the height with lets say 10% reserve.. What do you think about this?

 

[Sativa1970]

LUX is a measure of all light on a surface and PAR is only the light useful to the plant is the short answer. Margin of error puts it closer to an educated guess at best. The best answer to all of your questions is to search you tube for MIGRO-Mars Hydro sp250 PAR test and review. MIGRO is a source you can trust.

 

[BadGrandpa007]

LUX is a measure of all light on a surface and PAR is only the light useful to the plant is the short answer. Margin of error puts it closer to an educated guess at best. The best answer to all of your questions is to search you tube for MIGRO-Mars Hydro sp250 PAR test and review. MIGRO is a source you can trust.

thanks, that video helped a little bit

 

[Sativa1970]

I'm not sure what your question was then. Were you looking for a formula you could use on other lights? Calculating PAR at different distances?

 

[OGpapa]

Photon app for your phone.

 

[Delps8]

Hi, i had the idea to buy a cheap LUX meter to calculate the aproximate DLI and PAR. I see people are doing that. Some guys alrady calibrated some meters from The apogee PRO devices. ChatGPT says he can calculate the data for me, it just needs the LEDs SPD data and i have it. My LED is Mars Hydro SP250W, perfect for 2x4space. The PAR meters are sooo expensive, i just cant afford them, so i thought this would be a solution, better that nothing at all.. Im wondering what would be the calculation error from LUX to PAR even if the Ai calculates it from the SPD data.. i thought if the error would be some 5-10% it not so important i could just adjust the height with lets say 10% reserve.. What do you think about this?

When I started growing in 2021, I tried Photone, which was called "Korona" at the time, and it could not provide a result even though I was using a diffuser and a blurple setting. I contacted the programmer (I've been a software engineer for 30+ years) and, after a few emails, decided it was best to go with an Apogee.

At the time, I wasn't convinced that a lux meter was a valid substitute for a PAR meter. I was wrong.

There are some situations where the accuracy of a PAR meter can be of value. If you've got the $$ and/or are slightly obsessive about getting the most out of your plants, I would say, yes, get a PAR meter.

On the other hand, using a lux meter + the conversion values in the document I've written, is in practical terms, as (in)accurate as using a PAR meter.

All instruments are "wrong". My Apogee is calibrated to 5%±. When I take a series of light readings on my grow, the results will never be the same because I cannot put the sensor in the same exact location as I did in my previous set of readings. Of course, if I'm taking one reading on the top of the reservoir, the location will be the same so the reading will be the same.

That's not a valid argument because it has no bearing on the real world.

If I lower the sensor of the meter, the PPFD changes by about 50µmol. That's > the inaccuracy of the meter

If I move the sensor from one side of a small bud to the other, the PPFD may change by 50 or 100 or 0µmol.

The best that I can hope for with my Apogee, is to get an indication of what the light levels are but it's wrong to think that those numbers are "correct". Instead, they're a guide as to what to do to get the results I want from the plant.

My take - get an Apogee if you've got the resources. Second, in the attached paper I used a Uni-T lux meter. The sources for the conversion factors are as cited. The 0.015 factor has no cite because it's the factor that's was floating around when I first looked into this thee years ago.

The newer model of the lux meter has Bluetooth connectivity and I was hopeful that the meter would allow me to push a button on the meter and have it record the reading. Unfortunately, that's not the case. Instead, you can set a sample frequency and the data will be captured on the phone. I set mine to take a sample very two seconds and that worked out OK. I understand why Uni did it that way (it's cheaper than modifying the meter to allow it to capture by pushing) but, for me it was a disappointment.

Instead of that, I create a note in my iPhone, put the phone next to me, and put it into dictation mode and the read out the values.

Interestingly, Bugbee has been asked about using a lux meter and he pooh pooh's it. It seems that the left hand and the right hand aren't talking at Apogee because if you go to the iOS App Store, you can download "Clear Sky Calculator" which is used to take readings from the sun and generate a PPFD value so that you can check it against your PAR meter. That's exactly the same technique that the lux meter + conversion factor does except it is less accurate because of the inherent problems I using a tiny phone sensor to try to capture light that's not coming directly into the sensor (that's why a lux meter has a conical diffuser and you've got to kludge it on the I phone with a strip of paper).

 

[Sativa1970]

@Delps8 I carefully walked around that rabbits hole. You did an elegant swan dive like bugs bunny. ​

 

[Trump]

When I started growing in 2021, I tried Photone, which was called "Korona" at the time, and it could not provide a result even though I was using a diffuser and a blurple setting. I contacted the programmer (I've been a software engineer for 30+ years) and, after a few emails, decided it was best to go with an Apogee.

At the time, I wasn't convinced that a lux meter was a valid substitute for a PAR meter. I was wrong.

There are some situations where the accuracy of a PAR meter can be of value. If you've got the $$ and/or are slightly obsessive about getting the most out of your plants, I would say, yes, get a PAR meter.

On the other hand, using a lux meter + the conversion values in the document I've written, is in practical terms, as (in)accurate as using a PAR meter.

All instruments are "wrong". My Apogee is calibrated to 5%±. When I take a series of light readings on my grow, the results will never be the same because I cannot put the sensor in the same exact location as I did in my previous set of readings. Of course, if I'm taking one reading on the top of the reservoir, the location will be the same so the reading will be the same.

That's not a valid argument because it has no bearing on the real world.

If I lower the sensor of the meter, the PPFD changes by about 50µmol. That's > the inaccuracy of the meter

If I move the sensor from one side of a small bud to the other, the PPFD may change by 50 or 100 or 0µmol.

The best that I can hope for with my Apogee, is to get an indication of what the light levels are but it's wrong to think that those numbers are "correct". Instead, they're a guide as to what to do to get the results I want from the plant.

My take - get an Apogee if you've got the resources. Second, in the attached paper I used a Uni-T lux meter. The sources for the conversion factors are as cited. The 0.015 factor has no cite because it's the factor that's was floating around when I first looked into this thee years ago.

The newer model of the lux meter has Bluetooth connectivity and I was hopeful that the meter would allow me to push a button on the meter and have it record the reading. Unfortunately, that's not the case. Instead, you can set a sample frequency and the data will be captured on the phone. I set mine to take a sample very two seconds and that worked out OK. I understand why Uni did it that way (it's cheaper than modifying the meter to allow it to capture by pushing) but, for me it was a disappointment.

Instead of that, I create a note in my iPhone, put the phone next to me, and put it into dictation mode and the read out the values.

Interestingly, Bugbee has been asked about using a lux meter and he pooh pooh's it. It seems that the left hand and the right hand aren't talking at Apogee because if you go to the iOS App Store, you can download "Clear Sky Calculator" which is used to take readings from the sun and generate a PPFD value so that you can check it against your PAR meter. That's exactly the same technique that the lux meter + conversion factor does except it is less accurate because of the inherent problems I using a tiny phone sensor to try to capture light that's not coming directly into the sensor (that's why a lux meter has a conical diffuser and you've got to kludge it on the I phone with a strip of paper).

I've been looking into this for a friend that can't seem to get his phone app working correctly. He's a first time grower so, for now, he doesn't need anything as accurate as an Apogee meter but he has an Iphone. I know the Photone app needs a filter of some sort to get it to work on the phone. Are there any other apps that he can download for now that will get him in the ballpark?

I agree that any meter reading is relative to the point in time and location that you are taking it. I use Tent Buddy but I take readings from all over the canopy and average them out. I realize that it's probably not the true reading but, as you mentioned, it doesn't have to be pin point. As long as I'm in range then I'm good,

 

[Sativa1970]

I've been looking into this for a friend that can't seem to get his phone app working correctly. He's a first time grower so, for now, he doesn't need anything as accurate as an Apogee meter but he has an Iphone. I know the Photone app needs a filter of some sort to get it to work on the phone. Are there any other apps that he can download for now that will get him in the ballpark?

I agree that any meter reading is relative to the point in time and location that you are taking it. I use Tent Buddy but I take readings from all over the canopy and average them out. I realize that it's probably not the true reading but, as you mentioned, it doesn't have to be pin point. As long as I'm in range then I'm good,

On my android I had to place a 1 inch tall cylinder out typing paper around the lens to get a "useful" reading. If you are using a light from a reputable company the values are listed and reasonably accurate. Is he using an off brand or alternative lighting? Just wanting to verify and geek out on numbers is an acceptable reason too.

 

[Trump]

SF1000

 

[Sativa1970]

This what you are looking for?

 

[bluter]

Hi, i had the idea to buy a cheap LUX meter to calculate the aproximate DLI and PAR. I see people are doing that. Some guys alrady calibrated some meters from The apogee PRO devices. ChatGPT says he can calculate the data for me, it just needs the LEDs SPD data and i have it. My LED is Mars Hydro SP250W, perfect for 2x4space. The PAR meters are sooo expensive, i just cant afford them, so i thought this would be a solution, better that nothing at all.. Im wondering what would be the calculation error from LUX to PAR even if the Ai calculates it from the SPD data.. i thought if the error would be some 5-10% it not so important i could just adjust the height with lets say 10% reserve.. What do you think about this?

you can find the algorithms online to calculate it for yourself. it's a bit of an exercise, but you can use them to check the online calculator.

Photon app for your phone.

this. i'd only spend that amount on it. you can buy par/lux/ppfd meters. they range pretty wild in both cost and quality.

When I started growing in 2021, I tried Photone, which was called "Korona" at the time, and it could not provide a result even though I was using a diffuser and a blurple setting. I contacted the programmer (I've been a software engineer for 30+ years) and, after a few emails, decided it was best to go with an Apogee.

have been told the app has gotten much better, but i wouldn't bother with burple still even now. par meters have never measured burple correct. for white light apogee and fluke are two good brands. fluke is the industrial go to.

Interestingly, Bugbee has been asked about using a lux meter and he pooh pooh's it. I

was not aware of that. would have assumed he'd be all over dli, par maps, etc. that's kinda curious.

i've never followed his stuff all that closely. he's a great way to make things super complicated if you go down that rabbit hole. new growers can get hung up and obsess over something when they either have a non issue or a different one.

if you are technical oriented he delves deep into the science which a lot of growers find interesting.

I've been looking into this for a friend that can't seem to get his phone app working correctly. He's a first time grower so, for now, he doesn't need anything as accurate as an Apogee meter but he has an Iphone. I know the Photone app needs a filter of some sort to get it to work on the phone. Are there any other apps that he can download for now that will get him in the ballpark?

the photone app should work.

as you mentioned, it doesn't have to be pin point. As long as I'm in range then I'm good,

you guys are right. it's the range that is important. it doesn't always have to be perfect in every variable.

On my android I had to place a 1 inch tall cylinder out typing paper around the lens to get a "useful" reading.

you are measuring more of the bounce light than the true in that circumstance. it's why lux/par meters have a convex top to measure 180 in all directions.

If you are using a light from a reputable company the values are listed and reasonably accurate. Is he using an off brand or alternative lighting? Just wanting to verify and geek out on numbers is an acceptable reason too.

was wondering if anyone would bring this up. good point @Sativa1970

this is important. you can have fantastic lux/par readings and a great ppfd map and still have crappy light depending on the level of quality the led mfgr has built the rig too.

 

[Delps8]

@Delps8 I carefully walked around that rabbits hole. You did an elegant swan dive like bugs bunny. ​

Just found your reply…

Great graphic and thanks for the chuckle!

My hope is that I've done the "heavy lifting" and can boil things down to a couple of paragraphs. Since I started growing in 2021, I've tried to cut a clearing through a lot of conventional wisdom. Much of it simply has no basis in reality and, for a variety of reasons, the community will move on from "the old way" to "the new way". Of course, as is the nature of all things, what is the new way today will, eventually, become the old way.

 

[Trump]

This what you are looking for?

I don't like using manufacturer suggested readings.

In your experience, is this map close in actual readings to what they claim? If so then I will instruct him to use the PAR map for now until he's able to figure out his phone app issue.

EDIT - Sorry! Wrong Newb. This one is using an ACI S22 Ionboard light.

 

[Sativa1970]

In your experience, is this map close in actual readings to what they claim?

It depends.. If the light has a manufactured name like HUNCHOW MAXLIGHT I would say there numbers are most likely "embellished", to say the least. On the other hand if you are looking at SPIDER FARMS, VIPARSPECTRA, MARS HYDRO or any other reputable brand you can trust it to be close. MIGRO channel on you tube has a lot of independent testing. Just checked, they have a review and light readings for the sf1000. Luck of the parts bin and grow room setup will have some minor effect on the actual readings as well.

I've tried to cut a clearing through a lot of conventional wisdom. Much of it simply has no basis in reality and, for a variety of reasons, the community will move on from "the old way" to "the new way".

Flawed experiments and misinterpreting results have created a lot of myths over the years and new ones will be made today. There is always some scientific truth buried in the myth that yielded results. It's often psychological not botanical science. Without that one truth the myth would have never started. Key is to separate the true science behind the myth. Never grow out of the "why" stage of life if you truly want to learn.