Genuinely curious, did the LED's you tested before have a precise wavelength they produced? I was under the impression that pretty much all LED's had a 10-15nm spread.
Trying out a new spectrometer
- Thread starter AKReefing
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OP
OP
There's pretty much always a peak wavelength. Yes, they do have a spread. That's generally measured at half height, and is called full width half maximum (FWHM).
It's a good thing they aren't a single wavelength. I don't think it would make the corals fluoresce much.
Nonya
Valuable Member
I guess as long as the meter is consistent, you can piece together a fixture with equally spaced wavelengths if you're trying to cover an area of the spectrum. Still, with +/- 5nm leeway, a 400nm LED and a 390nm LED could both be 395nm. Unless the seller guarantees a certain wavelength, it's still a crap shoot. I'm speaking from a DIY perspective. The retail fixtures generally space the wavelengths far apart.
OP
OP
I meant a single peak for a single-color LED.
OP
OP
Ever so slightly off-topic, but I Googled "average FWHM LED" and came across a really great article by Zeiss Campus (Fundamentals of Light-Emitting Diodes (LEDs)). It's a long but informative read, but it covered quite a bit of information relevant to reefers, including FWHM, fluorescence, and evenLED vs. Arc Lamp (i.e., MH and mercury) stability. I knew MH intensity degraded fairly quickly, but if the article is to be believed--wow.
zeiss-campus.magnet.fsu.edu
ZEISS Microscopy Online Campus | Light-Emitting Diodes
High-power LEDs generate sufficient intensity to provide a useful illumination source for a wide spectrum of applications in fluorescence microscopy.
OP
OP
Probably not. Aquarium UV sterilizers typically use wavelengths below 300nm, which would be out of range of my spectrometer. Amazon labels this UV-c.
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luxdium
Community Member
Mercury vapor-based UV sterilizers have deterministic UV-Vis spectral distribution with very narrow spectral peaks. Even if your meter doesn't read the UV-C range, it should show representation in the following bands:
(I)
| Band 1 | 365.0153 |
| Band 2 | 404.6563 |
| Band 3 | 435.8328 |
| Band 4 | 546.0735 |
| Band 5 | 576.9598 |
These were measured by NIST and can be used as a reference to compare measurements.
Unlike LEDs and other lights, UV lamps are governed purely by quantum theory and won't vary as much between bulbs. As the lamp is energized, the electrons in the mercury atoms get excited and begin to oscillate between lower and higher energy levels producing light in the UV-VIS spectrum with narrow bands corresponding to unique emission lines of mercury.
Owing to the simple electronic shell configuration of Mercury, Hg-Ne lamps are used in academia to calibrate instruments before they're used in experiments. Mercury-based UV sterilizers operate under the same principles so they can be used as an accessible substitute if certified traceability is not required.
In the 350-800nm band, you can expect to see a spectral signature that looks like the below:
(I) Source:
K. Burns, K. B. Adams, and J. Longwell, J. Opt. Soc. Am. 40, 339 (1950). The lines of natural Hg I are broadened by hyperfine and isotopic structures. As a result, the line shapes can vary according to spectrometer resolution, observation time, etc. Mainly because such effects can affect the measured wavelengths, we have given no more than three decimal places for the lines of Hg I. Using a low-pressure electrodeless lamp source, Sansonetti et al. [SSR96] have made high-accuracy measurements of 26 of the Hg I wavelengths measured by Burns et al. in the 2536-5791 Å region; the resulting standard deviation of 0.003 Å between the two sets of measurements may be at least partly due to line-shape effects. We also note that the wavelengths given here should not be used for calibrations based on lines from pencil-type lamps if uncertainties smaller than 0.01 Å are desired; measurements by Sansonetti et al. [SSR96] in the region 2536-5791 Å show the pencil-lamp Hg wavelengths to be systematically longer than the values of Burns et al. by an average of 0.0068(32) Å.
OP
OP
That's interesting. I'll consider it. Thank you.
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OP
OP
So here's the graph you provided of a UV bulb overlaid on the graph my inexpensive spectrometer produced of a spiral fluorescent bulb. A lot of the peaks seem to match very well across the entire visible spectrum. Mine didn't pick up the one at 365nm, so I wonder just where the range of mine ends. Anyway, this is just one more data point confirming whether I have a decent tool to measure my individual LEDs. If it doesn't detect UV, it really doesn't matter to me. UV LEDs would only be used for fluorescence. They haven't really been proven to be essential for anything else yet.
luxdium
Community Member
So here's the graph you provided of a UV bulb overlaid on the graph my inexpensive spectrometer produced of a spiral fluorescent bulb. A lot of the peaks seem to match very well across the entire visible spectrum. Mine didn't pick up the one at 365nm, so I wonder just where the range of mine ends. Anyway, this is just one more data point confirming whether I have a decent tool to measure my individual LEDs. If it doesn't detect UV, it really doesn't matter to me. UV LEDs would only be used for fluorescence. They haven't really been proven to be essential for anything else yet.
A mercury vapor UV lamp is a fluorescent bulb without phosphors. Phosphors can block some UV.
I am surprised by how wide those green peaks are under your meter. They're wide for a fluorescent bulb.
Test with a UV lamp. They're not very expensive.
OP
OP
Considering how inexpensive it was, it's not an issue to me. The green-yellow region is of little importance to me as a reefer. I'm just glad everything aligns well across the visible range.
telegraham
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I'm Team Green around these parts, as I like what it does for my human eyeballs. I run a relatively white-looking tank. And oddly, green seems to be the only spectrum the PARwise nails.
Regarding the $15 bulb, it's a great reference lamp when comparing data.
OP
OP
It's on order. Thanks
OP
OP
So here's a new capture of a fluorescent ceiling light that I overlaid with the fluorescent spectrum from Wikimedia.com. I offset them vertically to help distinguish between the two. There's more definition with the new capture, probably because I held the fiber several feet from the light. I think the one above may have over-driven the sensor a bit. Peak #1 from the Wikimedia graph may be there on mine, but very weak. Peaks 2 through 22 are all represented, but 6 through 11 appear somewhat merged. Still, that's the green/yellow/orange part of the spectrum I don't concern myself with.
I suspect that it probably won't detect anything below 400nm, but I really don't need it to at this point.
In general, I'm very pleased with my super-inexpensive Spectryx spectrometer.
I suspect that it probably won't detect anything below 400nm, but I really don't need it to at this point.
In general, I'm very pleased with my super-inexpensive Spectryx spectrometer.
OP
OP
Reference #27 above:
So the Spectryx seems to drop off just below 400nm, but peaks 2 through 5 from the UV light are absolutely dead on.
| Band 1 | 365.0153 |
| Band 2 | 404.6563 |
| Band 3 | 435.8328 |
| Band 4 | 546.0735 |
| Band 5 | 576.9598 |
luxdium
Community Member
Mercury-vapor UV lamps emit wavelengths that photolyze oxygen molecules and create valent atoms that reattach to form ozone. In fact, some ozone generators use similar lamps.
OP
OP
So what do you think about my UV measurements above?
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