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07-21-2008, 10:20 PM
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Member
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Join Date: Jun 2008
Posts: 34
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Reality check: 4 T8s=6000 fc?
I just got a light meter today and at six inches under my bank of 4 T8s it gives a reading of 6000fc--or at least I think it does. Is that even remotely possible?
Unless I am missing something (and I do that from time to time), the meter has two levels, one for sun and HID (or just higher levels) and one for fluorescents, (or just lower levels). One takes up where the other leaves off. The fluorescent (lower) gauge is calibrated up to 10 X 100. I put it six inches beneath my bank of lights and the needle springs off the chart--but there is no way to read whether it is 1500 fc, 2000 fc, 2500 fc--just more than 1000 fc. If I flick the switch from fluorescent to sun/HID it reads 1000 x 6, or 6000 fc--an unbelievable reading for a bank of 4 T8s, right? They are on for 16 hrs a day and my phals would be dust by now at those levels, wouldn't they?
So which is more wrong here, me or the meter? The meter is supposed to be accurate with 2%. Is it really possible my 4 T8s really are giving off 6000 fc of light? I might think 2000-2500 max. Or is the meter likely incorrect and I have grounds to return the meter and buy another one. What test can I use?
I notice in the highly recommended Hydrofarm meter you have a similar setup, two scales calibrated for low end and high end light. I suppose I could buy one of those at $25 or so and compare and still not be out a load of money...
I don't know what to do...
Maybe my meter is giving a perfectly good reading (hard to believe as it is), but how can I tell? And if I got the Hydrofarm meter (or any other meter for that matter) and the readings differed, how would I know which one was correct? I guess I'm asking "What is truth?" or at least "Where can I find it?"
Frustrated Charlie
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07-22-2008, 08:58 AM
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Roots are good
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Join Date: Sep 2006
Zone: 5a
Location: Cadillac, Michigan, USA
Posts: 7,426
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Not possible. My t5's read 1800 FCs at 10". I think you are not using the light meter correctly. Just my 2 cents. I had one of those $30 wonders and threw it away because it never did give me a reading I trusted. Your intuition is correct that it is either defective or something. It just isn't possible to get that much light from t8s or we'd all be using them.
__________________
Ross
http://orchids-ross.blogspot.com/
I don't do most Dendros or large, "floofy orchids". For me it's minis (like Angraecoides), Paphs, and others that crept in somewhere along the line. See my orchid list for complete collection (usually not current.)
Last edited by Ross : 07-22-2008 at 09:01 AM.
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07-22-2008, 09:27 AM
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Member
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Join Date: Jun 2008
Posts: 34
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There's not much to do wrong, though I probably could do it. The instructions say to point the sensor directly at the light source and then it is just a matter of reading what the needle indicates. If it surpasses 500 on the lower graph, you flick a switch and take the reading on the upper graph.
I have great HO T8s, and they are VERY bright for what they are--
# Wattage: 32 watts
# CRI: 91
# Kelvin: 5000
# Lumens: 3300
# Hour Rating: 34,000 hours--
but I knew these readings were just too good to be true.
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07-22-2008, 10:20 AM
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Senior Member
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Join Date: Jan 2008
Zone: 8a
Location: East Texas
Age: 30
Posts: 994
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Good question. I bought a cheap-o light meter and I wasn't sure how much to trust it either. I know what you mean about just reading the needle, but it will jump around depending on the distance and angle of the probe/sensor. Not much to add here, except I'm happy to see this topic being discussed.
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~Royal
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07-22-2008, 02:25 PM
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Member
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Join Date: Jun 2008
Posts: 34
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Charley's Greenhouse was true to its word and gave me a full refund--and didn't ask me to return the meter if I believed it was defective, which I do.
Now I back in the dark again about the light.  |
07-22-2008, 02:32 PM
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Roots are good
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Join Date: Sep 2006
Zone: 5a
Location: Cadillac, Michigan, USA
Posts: 7,426
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I use this one (the 840020 - only because I need both measurements at times.) It's been flawless, if a bit pricey.
__________________
Ross
http://orchids-ross.blogspot.com/
I don't do most Dendros or large, "floofy orchids". For me it's minis (like Angraecoides), Paphs, and others that crept in somewhere along the line. See my orchid list for complete collection (usually not current.)
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07-22-2008, 11:24 PM
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Member
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Join Date: Jun 2008
Posts: 34
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Ross, did you leave out a link or something to the meter you use? I can't track it with a number and not even a brand name. I checked the blog link, but if there is anything there I missed it. Sorry if I'm being dense.
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07-23-2008, 09:08 AM
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Roots are good
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Join Date: Sep 2006
Zone: 5a
Location: Cadillac, Michigan, USA
Posts: 7,426
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__________________
Ross
http://orchids-ross.blogspot.com/
I don't do most Dendros or large, "floofy orchids". For me it's minis (like Angraecoides), Paphs, and others that crept in somewhere along the line. See my orchid list for complete collection (usually not current.)
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