Hmm, Dave, it's odd, but it doesn't seem to me that you're seeing any fluorescence -- do you see any, visibly? Do you normally, with this setup and motor oil? For example, in this set, it seems like you are just seeing the LED itself, but no fluorescence:

Do you know why? I had hoped to see whether the variation in LEDs correlated with any systematic change in the emission/fluorescence light wavelengths.

Correction for graph number 2, it says :"data from March 9th" it should say:"data from March 10th"

sorry

Hey Jeff, unfortunately with refined oil the organic chemistry aspect gets changed dramatically, thats why when you shine a UV flashlight or laser thru it it will fluoresce but it will be a white-blueish color which is indicates mineralization. That's why I was suggesting a variable LED to control wavelength ie.,a 1w or 3w high output LED 350Ma 400-405nm range, it's all about that electronic transition state, ground state to a higher energy state.

Crude oil is a different story, it still has it's organic properties intact, there are double and triple carbon/hydrogen bonds, those bonds become rearranged during processing, so in order to "see" their respective fluorescent spectras you have to separate those bonds into their derivatives, like the benzo rings, naphthols. That is also why if you notice on the sets, there is a slight shoulder type "hump" at the drop off of each line, thats the aromatic hydro carbons, but they are too complex, so thats all your going to see is a hump, no info can be gleened from that.

I have been doing a lot of research and reading on this subject and am learning a lot. I also believe there is a limitation to this detector as far as the camera is concerned, but it still is effective as far as fluorescent compounds with emissions above 400nm, and there's plenty of them. It's just a matter of getting the right technique down.

dave stoft did a great analysis with different oils https://publiclab.org/notes/stoft/01-26-2016/otk-proto3-analysis

and to me it seems to concure with my results today, since 10w40 is a much lighter type oil you can see the same tell tale "hump" on the descending line, and then on the graph for the 308nm scan you see a more defined vertical drop point for the light refined oil which looks the same for the sets I did today and on the graph I posted.

@dhaffnersr - I'm curious, what do you mean by a "variable LED to control wavelength"?

Hey @ethanbass, more so, I mean modulating the intensity by means of PWM, although there is a temperature wave length correlation in LEDs, example: with increasing voltage obviously increases light intensity, thus increasing internal temperature of the semi-conducting material of the LED does have an effect on wave length fluctuation. This effect is more precise with increasing current rather than voltage, like with an LED drive that has dimmable control.