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Question:What light sources might I use to calibrate my spectrometer if I don’t have a CFL available?

mimiss is asking a question about spectrometer: Follow this topic

by mimiss | May 05, 2020 13:14 | #23548


I'm interested in working with the LEGO spectrometer but I don't have a CFL at this time. Short of ordering one, what are some other ways that I could get started?

This figure from an unrelated paper has some details on the emission spectra of different light sources: https://www.researchgate.net/figure/Emission-spectra-of-different-light-sources-a-incandescent-tungsten-light-bulb-b_fig1_312320039



8 Comments

Could you use a laser pointer and still go through the same workflow with @cfastie's reference image? I'm not sure if the peaks would line up, they would presumably need to be the same wavelengths. But it seems like in theory you should be able to match anything that gives you a discrete peak at a known wavelength.

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Thank you for this idea! I have laser pointers in a few colors in my house that I can try out.

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kgradow1 wrote:


Could you use a laser pointer and still go through the same workflow with @cfastie's reference image? I'm not sure if the peaks would line up, they would presumably need to be the same wavelengths. But it seems like in theory you should be able to match anything that gives you a discrete peak at a known wavelength.


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Found something.It's a YouTube post by chem_talk on neodymium. It's a long way from complete, but according to the post, this rare earth isn't rare. And it shows a spectrum ( it's in the early part of the post)on absorbance, and florescence, both of which show good bands. The post is titled "neodymium compound, colors, and magnets". Still a lot of distance to go... But the video is a start. And neodymium magnets are relatively easy to find.


Of you take a look at commercial instruments, they will usually use holmium oxide or other holmium salts for calibration. Great. These salts are quite expensive. The neodymium salts look like they show many of the same bands and they are not expensive. But neodymium salts will take some development.


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I think I used a red laser and a green laser to get the calibration to work at some point...

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https://youtu.be/u5tUmdWALn0

Hopefully, this link works to the video

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There is a closely related chemical recently added to the USP for uv/vis standardization. It is a solution of didymium. Some places also use a glass with didymium in it. Didymium contains a large amount of neodymium.

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If a source like the sun or an incandescent lamp is used, then maybe using a photographic bg20 filter as a standard would do. The spectrum they attach for the bg20 is similar to the USP ( because they use an didymium filter in the bg20). The cost of the filters on ebay is about $25.

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