Public Lab Research note

Oil Testing Kit -- Assembly & Calibration!

by _mahsa_ | November 09, 2015 00:54 09 Nov 00:54 | #12379 | #12379

Hi, I'm Mahsa a member of the Oil Testing Kit beta program and below you'll find my experience assembling the oil testing kit.


Here are the contents to make the spectrometer and the cuvette frame:

IMG_20151012_211406069.jpg IMG_20151012_224916886.jpg

Spectrometer Assembly

I found @Cindy_ExCites post on the spectrometer assembly incredibly helpful, as are the online public lab directions (it was really hard to tell what was going on in the black and white photos that came with the kit -- I wish I had realized earlier that the directions were online with color photos!).

Since there are already comprehensive steps online, I won't go into step by step directions and instead share a couple photos I snapped during the process.

Attaching the camera to the block:

I would definitely recommend using 2 pieces of tape when attaching the camera, I didn't initially do this but ran into issues of the camera moving sideways when I started using the spectrometer. I got the idea from @Cindy_ExCites and here's their photo of it:


Making the diffraction grating from a DVD:

Putting all the pieces together and placing it into the frame:



Extra pieces, one looks important but I couldn't figure out where it should go...


Cuvette Frame Assembly

This part was a bit more complicated and time consuming. A glossary would've been helpful -- it took me an embarrassingly long time to realize what a 'cuvette' was! Again the black and white pictures in the directions that came with the kit were very hard to see and figure out where the folds were. If the pieces were light colored on one side and dark colored on the the other the contrast might have helped in figuring out where the folds were.

Again, @Cindy_ExCites post was incredibly helpful and even with their directions I struggles with "the M-folded sheet" piece. I made the same extra cuts @Cindy_ExCites did in it -- this is their photo of it:


Slits I cut into my piece:


Even after reading about @Cindy_ExCites placing the v-folded strip in the wrong way, I made the same mistake and it was a pain to get out. Here are some notes that might help others in figuring out the placement of the v-strip in relation to the m-piece:


The first time I assembled the cuvette holder, I had the little square in the middle popped up the wrong way, which resulted in the cuvette standing too high up. Here I'm pointing to the little square popped out the WRONG WAY:


and here it is popped out the CORRECT WAY:


Here you can see it popped out the right way and holding the cuvette:


Attaching the cuvette holder to the rest of the frame was a bit tricky. It was hard to tell where the flaps should go. @Cindy_ExCites has some good photos. One thing that wasn't apparent at first was that the long flap should be inserted into the crease of the holder (pink arrow) and then back thru a slit into itself (blue arrow). Hard to describe, but maybe this picture helps:




@Cindy_ExCites post was really helpful. Similar to them, I had to adjust the DVD. I also realized that the camera had shifted at this point and that's when I decided to apply a second layer of tape to stabilize it.

As for calibrating, I haven't been successful at getting it to work. My first couple tries I got an error that the spectrum is overexposed. For example: cfl.png

I tried using a warm compact florescence bulb, a cool bulb, a plastic bag over the spectrometer, and pointing it at different distances and still couldn't get it to work. Whenever the red and green levels were not overexposed, the blue didn't have peaks, like this:


Here are all my attempts: calibration 1, calibration 2, calibration 3, calibration 4, and calibration 5

I'll give it another try and update soon...


Cool. You've got some really nice pictures of the cuvette frame assembly. For calibration, have you tried capturing the light reflected from a piece of white printer paper? I've gotten the best results using this technique. If you hold the printer paper right up the bulb (you could tape it to the lamp) and then hold the spectrometer close to the paper, you should be able to get a good spectrum.

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Also, you should know that the blue peaks are always going to be weaker. Were any of the spectra you posted captured through the plastic bag? I noticed that 4 and 5 have decent size blue peaks but there is a big smeared out hump in between them that I am not getting in my CFL spectra.

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Thanks @ethanbass ! I can't remember which of my tries was with the plastic bag, maybe 4 and 5. I also tried the paper but set it up with the light shining onto the paper and the spectrometer also pointing at the same side of the paper (kinda in a triangle). Not sure why but it didn't occur to me to put the paper between to the light and spectrometer -- I'll give it a try and hopefully that works!

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