Making A Functioning Spectrometer

Amelia Settembre
Jan 25, 2020 · 8 min read

Light can be used to measure so many aspects of the known world: elements, color, galactic shift… and more! Not only that, but light is almost everywhere, which makes our job about a thousand times easier. So, how exactly to we start measuring this light?

Well, we’re going to need a spectrometer (above is a summary on how spectrometers actually work), but for right now we’re going to focus on the components and construction! There are actually two different types of spectrometer:

  1. The homemade spectrometer, usually without a computer program. This spectrometer can’t really measure in-depth the same way a scientific one can. Instead, it’s entirely based on what you can see with your eyes, meaning it’s also significantly less accurate. If you’re using a homemade spectrometer, you’re likely only going to be able to tell different types of light from one another — like fluorescent v.s. LED light bulbs. This aside, the homemade spectrometer is still excellent for a comprehensible demonstration on how spectrometry works.
  2. The scientific, computer-based spectrometer. Instead of a more basic device, this spectrometer can go much deeper in terms of what it’s able to measure. Because the perimeters are way more refined, defining elements and — if you’re working on the large scale — measuring the movement of galaxies. Sadly, if you’re hoping to score one of these yourself, they’re pretty expensive.

Those are the two types of spectrometers, mostly labeled by cost and measurement capabilities. For a project I was doing, I looked deeper into making homemade spectrometers, which are generally much more affordable. Here’s a little about how that went, and how you can make your own.

Building A Functioning Spectrometer At Home

When I first started looking up how I could make my own spectrometer, I hit a bunch of dead ends. That’s because all the best spectrometers I could make cost upwards of 150 USD, which seemed kind of outrageous for a broke teen like myself. I started to ask around at my school to see if anyone actually had any spectrometers I could use and study with, and as it turned out, one of the teachers actually had experience in spectrometry!

Between him and research I did at home, I found there are two main ways to make your own spectrometer without ever having to hook it up to a computer:

  1. From scratch. This method includes using diffraction grating (which is very difficult to get your hands on, so a good alternative is a CD) and a basic wooden box.
  2. With a kit. I ended up using one of the kits from my teacher while also studying the way computer programs worked (although I didn’t get to use any myself).

Either of these options only cost around 10 USD, which is much simpler than one of the more complex computer versions. The spectrometer kit I was fortunate enough to use had three parts: the entrance slit, the diffraction grating, and the plastic midpiece that prevented extra light from entering.

These pieces assembled pretty easily, turning into a final product which was easy to use and interesting to conduct experiments with. The light is a little bit hard to discern in the finished product (in the far right image above, you can see what a “reading” looks like), but there are distinctions between the different results (i.e. ultraviolet readings will be different than LED ones).

However, if you’re not interested in making a spectrometer with an actual kit, there’s plenty you can do. Before I used the kit, I did have blueprints for a spectrometer which didn’t end up getting created because it became too expensive.

In this spectrometer, I did include a webcam which could upload for a visual connection to the computer which wouldn’t be analyzed. This just meant that instead of looking through a specific slit, I’d be able to see the results up on the computer. Although this initially seemed successful, it included many more components that the kit did:

  • Diffraction grating. As it turns out, hardly anyone sells this anywhere, and even after emailing multiple scientific supply companies I came up empty-handed. That’s when I learned you can actually repurpose an old blank CD, which works the same!
  • Collimator. This is just a curved mirror which bounces the light for measurement around inside the spectrometer so it can have the right angle when it enters the final place for the reading.
  • A camera/mirror lense. This focuses the light before it actually enters the detector. It helps to get a clearer and more accurate reading.
  • Detector. This scans the light beam and puts it on the computer screen. I had intended to use a webcam for this, but ultimately I couldn’t find one which would work as well as I wanted it to.

Over all, if you used this particular format, the readings would end up looking something like this image below, falling on the emission spectra of the elements. However, this format is usually used more for professional spectrometers.

Using Professional Spectrometers/Software

Professional spectrometers work similarly to regular spectrometers, the biggest differences between them being the way light is taken in (spoiler: professional spectrometers let off light first) and the way the information is processed.

The information for professional spectrometers is usually taken into a computer program where it’s analyzed and determined exactly what scientists are looking at. Sometimes this comes from a more accurate reading without actual computer analysis, and other times it comes from a total analysis and result with little manual interaction.

In this particular software, the height of the color spikes shows the concentration in the result. So where did the rest of the light go? Well, when the spectrometer directs white light at a particular object, it absorbs some portion of it. For example, if you’re looking at a red table, it’s red because that table absorbs all light except for red. It’s the same with any object of color: it only appears one color because all light except for that one color is absorbed.

By then using the emission spectra of the elements (basically looking at all elements and their special “signatures”, patterns of light) you can determine what type of element you’re looking at. This can be pretty helpful, especially for scientist examining other planets and trying to determine their concentration. Another good demonstration of a different software is in the image below, picturing another way of registering the concentration of light that’s not absorbed.

However, there’s another use of spectrometers which I haven’t quite talked about yet, and that’s mass spectrometry in the biotech field. Readings here look quite different, especially since they’re taken by measuring the densities of different molecules within a sample. Here, light isn’t really involved to the same extent as it is when applied to the space tech field, but there’s still a lot of value in this application.

In the image above, the amounts of molecules of certain densities are weighed. In this particular case, there are the most molecules with a 43 m/z reading. It’s amazing that depending on what type of version of the same machine you use, you’ll have completely different outcomes.

Summing All This Up

Spectrometry is wild, and it has dozens of applications which are still going strong into the future. If you want to cash in on the future by making or buying one of these devices, you do have a couple options.

  1. You can make one with a kit, from scratch, or even buy it. If none of these are applicable, see if you can work in a lab — many labs are home to spectrometers and would more than likely let you have temporary access to one for a research assignment. Spectrometer kits and certain designs from scratch aren’t super expensive, but you can easily get bogged down in the world of hundred dollar lenses and detectors if you’re not careful.
  2. Now that you have a spectrometer, check out the readings. There are different levels of how in-depth the end result will be, usually ones which affect the amount of projects you can do with it. Manual spectrometers are entirely visual based, meaning you have to tell on your own by looking at the emission — but with a more professional option you can have computerized analysis that helps determine what you’re looking at.
  3. If you’re into biotech, check out mass spectrometry. This isn’t exactly the same as the galactic shape measurements nor the element determiner, but it will 100% help you figure out concentrations of certain molecules in a certain test sample. The output looks pretty different too, so you likely won’t be seeing rainbow bars — prepare for more of a bar chart. Side note: these are much harder to make at home; I haven’t attempted it.

Remember, you don’t need fancy lab instruments or tons of money to have a spectrometer to explore the wonders of light with. Spectrometers aren’t the most common, nor the easiest to come by, but even building a little one with a kit is an amazing demonstration of light measurement. All you really need to know is where to look.

Thank you for reading this article, I hope you learned a little something about building spectrometers and observing readings from professional ones! If you’d like to talk more or learn more about my work, email me at amesett@gmail.com or find me on LinkedIn!

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Amelia Settembre

Written by

A young woman who loves studying aerospace and philosophy! I’d love to talk, you can find me at amesett@gmail.com or on LinkedIn!

The Startup

Get smarter at building your thing. Follow to join The Startup’s +8 million monthly readers & +788K followers.

Amelia Settembre

Written by

A young woman who loves studying aerospace and philosophy! I’d love to talk, you can find me at amesett@gmail.com or on LinkedIn!

The Startup

Get smarter at building your thing. Follow to join The Startup’s +8 million monthly readers & +788K followers.

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