Oil testing kit Blog
shorter spectrometer geometry with two slits?
What I want to do
answer two questions: Can straylight be eliminated in a simple spectrometer setup through using a double slit? Can a double slit reduce the length of the spectrometer?
My attempt and results
I took the block that comes with the desktop spectrometry kit and cut two grooves in it cross-wise.
then i aligned two slits in the front and parallel groove in the block, and attached a DVD slice to the angle, and a webcam mounted on a block parallel to the DVD:
Then I put the whole thing in a small box for some light-proofing:
Questions and next steps
Waving it around there is definitely no stray light and it gives a clear spectrum. The .18mm slits are a little small for capturing much light from fluorescence spectra. I'm going to trade them out for some laser cut slits tomorrow and try again.
Why I'm interested
it would be easier to mount a spectrometer on a smartphone and other devices if it were smaller and more rigid.
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A Lil' Box for the Oil Testing Kit. (Incomplete)
Oil Testing Kit from a sheet of A4 Paper? (kind of...)
Sometime ago, @warren and @mathew were trying to make a container for the Oil Testing kit, from nothing but a piece of A4 paper.
This is what they came up with: http://publiclab.org/notes/warren/07-05-2014/oil-testing-spectrometry-workshop-at-fab-10
Since that time, I have been trying to develop a more efficient version. This is what I came up with so far.
It has a few minor issues/bugs, so I was hoping people here wouldn't mind giving their two cents on what can be done to make improvements.
The Lil' Box Itself.
This is what it looks like so far:
(Ignore the hole in the top. That shouldn't be there)
How it works.
This image shows how the Box works; superimposed over the Public Labs Spectrometer.
What You Will Need.
-A Standard Sheet of 80GSM, A4 Paper. (I didn't have any black A4 paper so used what I had to absorb extra light in my current model)
-An Old Toilet Roll Tube.
-An Oil Testing Kit.
-Shiny/Reflective Foil.
-Tape/Glue/Paperclips.
Step1: Folding.
Fold your sheet of A4 paper so that you have a grid of existing guidelines to use when the box is folded together.
Step2: Cutting.
Cleanly cut along the red lines (make sure your don't cut through the bit that attaches the lid to the rest of the box).
Punch holes through the dots at the center of the blue lines.
You should end up with something like this:
Step3: Sticking:
Stick shiny foil over the grey squares. The small flap should have shiny foil on both sides.
Also, stick the diffraction grating over the hole that is where the green dot is.
Step4: Assembling.
See the images here for information on assembling the box: https://plus.google.com/photos/108742728244628800104/albums/6064423192648884241?authkey=CJ-JiPXNkcWocQ
Spectral Workbench Test Images:
These are images that I have taken so far during the development process.
The latest of which uses my current model, which uses the curve of a toiler roll tube to deflect light towards the camera.
https://spectralworkbench.org/sets/show/1523
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Public Lab Launches a Kickstarter for a Homebrew Oil Testing Kit
NEWS RELEASE
FOR IMMEDIATE RELEASE
September 24, 2014
Public Lab Launches a Kickstarter for a Homebrew Oil Testing Kit
New Do-It-Yourself kit "fingerprints" oil contamination by type
NEW ORLEANS, LA -- The Public Laboratory for Open Technology and Science (Public Lab) has launched a Kickstarter campaign to introduce a new community science technique: the Homebrew Oil Testing Kit. Oil and gas contamination affects communities around the world, yet nearly all lack the basic tools to measure and identify crude, heating, or motor oil. Public Lab’s $50 kit will enable coastal residents, beachgoers and backyard scientists the world over to analyze oil pollution themselves using simple, open source hardware. The kit is constructed from easy-to-find materials like a Blu-Ray laser pen, a cardboard box, and a piece of a DVD.
Public Lab’s open source spectrometry project was originally begun to ground-truth the presence of oil in the wake of the BP oil disaster of 2010. A spectrometer can precisely measure the colors of light emitted by carefully prepared samples when they are illuminated with strong ultraviolet light. The Homebrew Oil Testing Kit will provide everything needed to collect and prepare samples, scan and analyze them, and share the results online.
Unusually, this campaign has only two main reward levels: the $50 Kit itself with a April 2015 ship date, and a $100 early-access beta tester program set to begin just one month after the October 23 campaign close. Public Lab is calling for beta testers to join the project through this campaign in order to solve key remaining challenges in the open source techniques, and participants will be asked to publish their own solutions and to improve the kit’s design.
“The collaborative approach is what makes this project special. We’re working together toward open solutions, built on the innovations of Public Lab members around the world.” -- Jeff Warren, Public Lab
Inspired by the Homebrew Computer Club of the 1970’s, a hobbyist group which set out to make computing more accessible, the Homebrew Oil Testing Kit aims at bringing the ability to identity oil and gas contamination into every home. The Homebrew Oil Testing Kit Kickstarter is an expansion of a $110,000 Kickstarter campaign in 2012 that shipped an early version of Public Lab’s DIY Spectrometry Kit to over 1,600 backers, and introduced the idea of everyday people using low-cost spectrometers to identify environmental contaminants on their own.
“Who can tell the stories of environmental contamination? Without accessible tools like the Homebrew Oil Testing Kit and communities that know how to use them, industry controls the narrative.” -- Shannon Dosemagen, Public Lab
Additional information on the Homebrew Oil Testing Kit Kickstarter can be found at: https://www.kickstarter.com/projects/publiclab/the-homebrew-oil-testing-kit
About the Public Laboratory for Open Technology and Science
The Public Laboratory for Open Technology and Science (Public Lab) is a community which develops and applies open-source tools to environmental exploration and investigation. By democratizing inexpensive and accessible “Do-It-Yourself” techniques, Public Laboratory creates a collaborative network of practitioners who actively re-imagine the human relationship with the environment.
The core Public Lab program is focused on “civic science” in which we research open source hardware and software tools and methods to generate knowledge and share data about community environmental health. Our goal is to increase the ability of underserved communities to identify, redress, remediate, and create awareness and accountability around environmental concerns. Public Lab achieves this by providing online and offline training, education and support, and by focusing on locally relevant outcomes that emphasize human capacity and understanding. For more information, please visit http://publiclab.org.
Contacts
Public Laboratory for Open Technology and Science: Shannon Dosemagen; phone: 504.239.4642; email: media@publiclab.org
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Oil fluorescence scanning on an Ocean Optics spectrometer
What I want to do
At LEAFFEST 2014, Mary, Luisa, and others reproduced the kind of fluorescence spectrometry scanning we've been doing with the Oil Testing Kit using a lab spectrometer, an Ocean Optics device. We used the same 405nm laser pointer and the same samples -- of suspected BP crude, fish oil, and mail-ordered crude from ONTA, all dissolved in mineral oil, and plain mineral oil. Here are the graph and the files, which Louisa emailed to me:
Update: Mary sent me specs on the device, below:
Spectra were measured with an OceanOptics SD2000 dual spectrometer (http://oceanoptics.com/wp-content/uploads/OEM-Data-Sheet-S2000.pdf), using the first spectrometer (wavelength range: 200-850nm; grating: 600 lines at 300nm; 25um slit).
Spectrometer is spectrally calibrated with a mercury/argon calibration source (http://oceanoptics.com/product/hg-1/). Values are relative DN, and are not radiometrically calibrated.
I had to add ".txt" to the end of each file to get them to upload, but that also makes them easier to open up.
BP_2014_256_15_59_12.fos.rdb.txt
Mineral_2014_256_16_01_28.fos.rdb.txt
Fish_2014_256_16_00_46.fos.rdb.txt
ONTA_2014_256_16_02_03.fos.rdb.txt
Questions and next steps
Presumably the calibration is OK? And the intensities are adjusted -- linear -- unlike our own spectrometer. So it's could be a basis for calibrating our device, if we assume that the setup is similar enough.
I'm especially interested in importing this data into Spectral Workbench, and am working on a way to upload this format. For now, you can view one of the files on Github too; they're just a column of wavelengths, a column of intensities, and an index column counting from 0 upwards:
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spectrometer vermont calibration leaffest
Graded oils using UV fluorescence
What we want to do
Me and @Warren are trying to replicate the heavy to light sorting of oils, as seen in "Laser Remote Sensing at Sea, A Quantitative Approach" byT. Hengstermann and R. Reuter and a bunch of other people's work.
Specifically, we're looking in a shift in the color of spectra emitted by fluorescing oils from red (heavy oil) to blue (lighter oil). look at Figures 1, 4a & b from Hengstermann & Reuter:
Our attempt and results
I tried to replicate this in spectral workbench, first on one spectrometer and then again with a bunch of spectrometers with different cameras in them. @warren has been working with the data and re-working spectral workbench to do cool things with the data. We've been talking on the phone too.
@warren tried smoothing the graphs, equalizing area, and equalizing height. The most legible and compelling, is to split the area of the graph and mark the exact middle. When that is performed, the progression of oil grades from light to dark (blue to red) is nice and clear.
OK, I added a couple more features -- one which bisects a graph with a vertical line where the area of the graph is equally divided -- what's that actually called? Anyhow I've just labelled it "Find graph 'centers'":
I also made a "Crop view" feature so you can zoom in a bit. It kind of sucks so maybe I'll add a real zoom feature and let people scroll back and forth. But it's too late tonight. But this makes it much easier to see the sequence of heavy/light oils:
https://spectralworkbench.org/sets/show/1482, of the SYBA cam:
https://spectralworkbench.org/sets/show/1484, of the filterless Infragram Webcam:
And https://spectralworkbench.org/sets/show/1481, of the filterless Infragram Webcam:
Questions and next steps
The order of oil grades is similar between the two different spectrometers. But each camera still produces different centers.
To make these spectra comparable between cameras, it looks like some sort of calibration samples will be needed. There are a lot of moving parts in these measurements such as concentration, or the path of the laser. We're still using a variable light path-- moving the laser around-- to give us spectra that aren't blown out.
Blowouts are a big problem we both noticed, and we're thinking some blowout warning in Spectral workbench might be useful. It might aso be possible to just watch one color channel:
Why do we want to do this?
we're looking to make an inexpensive means of identifying oil in the field that works between different cameras and devices.
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spectrometer oil fluorescence spectral-workbench
Better smoothing and equalizing graph height for comparison of oil spectra
What I want to do
Based on the difficulties @mathew highlighted in his research note yesterday, I spent today developing a smoothing system (using the Spectral Workbench API: https://spectralworkbench.org/macro/warren/smooth_save) which:
- saves its "smoothed" version of the data, so it can be compared in sets
- tags the spectra with "smoothed:1+10" where the sampling row is 1 and we average in 10 additional rows below it
I also created, at @mathew's suggestion, a "equalize height" comparison tool (https://spectralworkbench.org/macro/warren/equalize-height) for sets, since in some cases that may be more useful than the existing "equalize area" (https://spectralworkbench.org/macro/warren/equalize_area).
My attempt and results
I've worked solely with the data @mathew collected in his note, so far. I'm writing this as I work, but a simple initial comparison of unsmoothed vs. smoothed data can be seen with these two sets:
- unsmoothed: https://spectralworkbench.org/sets/show/1475
- smoothed: https://spectralworkbench.org/sets/show/1483
I've also run "equalize height" from the "More tools" menu to ease the comparison.
Next, I'm going to try it with a larger set, which includes samples of North Dakota crude oil and a variety of motor oils @mathew tested with the same webcam we use for the Infragram Webcam -- albeit without the blue or red filter: https://spectralworkbench.org/sets/show/1481
For each spectrum in that set, I:
- made a copy
- checked for overexposure or clipping by looking for a flat-topped peak in RGB mode
- if overexposed, selected a new cross section that was not
- copied the calibration from this CFL spectrum
- ran the new "Auto smooth 10 rows below" tool which just runs my macro (link above)
I then added all of them into a new set:
Compare this with this collection, which is also height-equalized, but not smoothed:
The unsmoothed set has too much noise to infer much, although one does make out two "humps" -- one in the 520-580nm range and another in the 580-600nm range. But the smoothed version not only shows those much more clearly, it also shows how closely the two North Dakota crude samples align.
I think we can also see the 20W-50s aligning, and with them the 5W-30 until it diverges above 500nm. The 80W-90s also seem to be reasonably aligned.
The highest points of each type also seem to be occasionally different, although the 80W-90 and the crude are probably not distinguishable just on peak position -- but the secondary "hump" at 575 seems to make the crude stand out quite a bit.
Questions and next steps
What are these "humps"? I theorize that although they're reproducible with a single camera/device, the actual hump shape is from the recombining of the RGB data from the camera's 3 color channels. You can see that the crude spectra's RGB data, when separated out, show matching peaks -- when combined, you get humps:
The motor oils don't show that as much:
However, although the humps themselves may be artifacts, they may be a consistent way to compare oils -- for the time being just on the same camera/spectrometer. I could imagine shipping heavier and lighter oils to "bracket" an unknown sample. Or, we could focus on peak position -- I do wonder if we don't mix channels at all, if the blue channel alone could be a more reliable measure of peak position.
Finally, we really need to help people watch out for clipping/overexposure. I think there should be an automatic indicator of where clipping is occurring on ANY saved spectrum. Maybe it could offer to help you identify a dimmer row where clipping isn't happening. Data like the below is not useful for comparison since the brightness is too high for the camera, flattening the top of the graph, but it's not very apparent until you go to RGB mode:
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