Gather PAR data to build community database? - The Planted Tank Forum
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post #1 of 38 (permalink) Old 07-01-2011, 12:56 PM Thread Starter
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Gather PAR data to build community database?

I ordered an Apogee MQ-200 last night and would like to help Hoppy and the other LED-heads fill out the fledgling database to give everybody an idea of what to make/buy.

Once it gets here, I want to make sure my data is as consistent as possible with the data already collected.

Can somebody put together a procedure or set of guidelines/conditions under which I should take these measurements?

Unfortunately, my tank is so heavily hardscaped and planted that getting a broad set of measurements from surface to substrate under water will be limited to just a square foot or so near the front of the tank.

I'll be adding a new color and some optics to the fixture before I take any measurements, so I can easily get a full battery of free-air measurements while I have the fixture off the tank.

I will have Neutral White, Cool White, 660nm Deep Red, and 505nm Cyan on the fixture. The Apogee sensor isn't very sensitive to the reds that for up the spectrum, but I couldn't find a quantum meter I could afford that was that capable.

I also have a selection of other colors I can measure if there is any interest: 400nm, 450nm, 490nm, maybe a few others, and some 735nm that wont even register on the meter, I'm sure.
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post #2 of 38 (permalink) Old 07-01-2011, 01:25 PM
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scouring the forums for the info is going to a bit heinous, but i've been wanting to do it myself too lately..

Generally from what i've seen, you want to take readings throughout the tank and directly under the light at different distances, usually 3" from the light, 12" from the light, 18" from the light, 21" ' ', 24" basically as deep as you can go. And you also want a reading from the sides of the tank at those distances so you know what kinda spread the light is getting.

The best way to take the readings that i've seen, is to attach the sensor to a stick or some sort so you can stick it in the tank with your arm not in the way and get a good level reading. Hoppy has shown pics of it in a couple threads, and DaveH and plantbrain have as well, those are the big 3 lately that have a lot of the PAR info on multiple fixtures and bulbs so far here in the forums.

I think i'm going to start scouring and make an excel spreadsheet..

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post #3 of 38 (permalink) Old 07-01-2011, 02:40 PM
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When you measure PAR in planted tanks full of water there is almost no way to standardize the readings. Some tanks have lots of plants shading parts of the tanks, others don't. Some tanks have very clean glass, inside and outside, and others don't. Some tanks have tannin stained water and others don't, etc. That's why I only use data taken in air. It is then fairly easy to correct those PAR readings for various sets of tank conditions, and you then have PAR numbers that are specific for the light only.

If you get PAR readings for 3 distances from the light, say 6 inches, 12 inches and 24 inches, it is easy to determine the PAR at any other distance. A reading at each end of the light and at a few distances off the center of the light, front to back, will complete the characterization of that light.

One thing I just discovered, accidentally, is that you need to measure PAR in an area with no white walls nearby. I used a hallway for my last measurements, because it was dark there, but the white walls distorted the readings by reflecting a lot of light.

Where ever you take the measurements it is best to start with measurements with the light turned off, then subtract that PAR from the readings with the light on. Generally that will be about 1-5 mms of PAR to be subtracted - important for low readings and irrelevant for high readings.

With LEDs, you need to include the LED current with the readings, since PAR varies with current. And, to be really useful, you need to include the LED spacings in the readings.

Of course, all of this is relevant only if you are seeking data about the light. If you are seeking data about the tank and the plants in it, you just measure PAR in the filled tank at various locations of interest.

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post #4 of 38 (permalink) Old 07-01-2011, 02:43 PM
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You cannot see 735nm, that's inflared spectra and plants cannot use it




Quote:
Originally Posted by cggorman View Post
I ordered an Apogee MQ-200 last night and would like to help Hoppy and the other LED-heads fill out the fledgling database to give everybody an idea of what to make/buy.

Once it gets here, I want to make sure my data is as consistent as possible with the data already collected.

Can somebody put together a procedure or set of guidelines/conditions under which I should take these measurements?

Unfortunately, my tank is so heavily hardscaped and planted that getting a broad set of measurements from surface to substrate under water will be limited to just a square foot or so near the front of the tank.

I'll be adding a new color and some optics to the fixture before I take any measurements, so I can easily get a full battery of free-air measurements while I have the fixture off the tank.

I will have Neutral White, Cool White, 660nm Deep Red, and 505nm Cyan on the fixture. The Apogee sensor isn't very sensitive to the reds that for up the spectrum, but I couldn't find a quantum meter I could afford that was that capable.

I also have a selection of other colors I can measure if there is any interest: 400nm, 450nm, 490nm, maybe a few others, and some 735nm that wont even register on the meter, I'm sure.



Regards,
Tom Barr
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post #5 of 38 (permalink) Old 07-01-2011, 02:49 PM
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Ok, this is everything I could find on TPT compiled into 1 spreadsheet. No data was changed/edited in the making, straight replication from posts made on this forum using a PAR meter. Credits go out mainly to Hoppy, DaveH, and Rockhoe14er, as I borrowed you're data to make this. Anyone else I missed, sorry, let me know :/



And a link to download the actual excel spreadsheet I made thats a tadbit easier to read.
http://dl.dropbox.com/u/7150123/Comm...%20Results.xls

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Last edited by HolyAngel; 07-01-2011 at 06:58 PM.
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post #6 of 38 (permalink) Old 07-01-2011, 03:10 PM
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Obviously I only compiled the Linear Strip data and no LED's or anything else..

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post #7 of 38 (permalink) Old 07-01-2011, 05:52 PM
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it would be cool if someone would test the par for a cfl!


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post #8 of 38 (permalink) Old 07-01-2011, 06:10 PM
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haha that's my par data for the zoomed fixture.

I also have some par data from my LED fixture when it was run at 1300 ma if you're interested.

I also can make a new correlation between par and current running on my 12 Cree XPG LED's. Right now i raised the fixture to where the current correlates with the par readings. For example 1 amp means 100 par at the substrate and .5 amps means 50 par at the substrate. The fixture is 21 inches above the tank and about 37 inches above the substrate.


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post #9 of 38 (permalink) Old 07-01-2011, 06:54 PM
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Sanjay has been testing metal halide gear for 10+ years. I believe it would make sense to align with his methodology where applicable rather than reinvent the wheel.

Sanjay's Reef Lighting Guide


Not directly related, but a good primer:
PatI: What is Light?
Part II: Photons
Part III: Making Sense of Light Measures
Part IV: Color Temperature
PArt V: Everything You Need to Know About Metal Halide Lamps and Ballasts
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post #10 of 38 (permalink) Old 07-01-2011, 07:00 PM
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Quote:
Originally Posted by Rockhoe14er View Post
haha that's my par data for the zoomed fixture.
I edited my post so you're on there now ^^

--

For the LED/CFL PAR data, think that should be separate spreadsheets for each?

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post #11 of 38 (permalink) Old 07-01-2011, 11:17 PM Thread Starter
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Quote:
Originally Posted by plantbrain View Post
You cannot see 735nm, that's inflared spectra and plants cannot use it
I can definitely see mine. Mfg spec indicates +/- 10nm with a 735 nominal. Maybe mine are 725.

As far as plants are concerned, it was my understanding that the red (660) /far red(735) balance affected plant elongation to help compete in high density or sub-canopy evnironments. More far red means more stretch. However, the papers I read were about terrestrial plants. Perhaps aquatics are different?
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post #12 of 38 (permalink) Old 07-01-2011, 11:24 PM Thread Starter
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Quote:
Originally Posted by Hoppy View Post
Of course, all of this is relevant only if you are seeking data about the light. If you are seeking data about the tank and the plants in it, you just measure PAR in the filled tank at various locations of interest.
I'm not terribly concerned about the tank. The plants have already told me they are happy.

Ill measure it just have a data point and satisfy my curiosity, but I mostly want to contribute to the cause and play with a new toy.
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post #13 of 38 (permalink) Old 07-29-2011, 01:05 PM
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Quote:
Originally Posted by orchidman View Post
it would be cool if someone would test the par for a cfl!

agreed!


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post #14 of 38 (permalink) Old 07-29-2011, 01:11 PM Thread Starter
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I've got the PAR meter and some CFL spirals laying around, but no reflectors. What kind of reflectors do you CFL guys use?
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post #15 of 38 (permalink) Old 07-29-2011, 02:08 PM
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5" and 8" clip on worklights from Lowes, they have silver metal reflectors.

There are pictures of them in my Journals.


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