DIY Spectro II

There is a more philosophically focussed companion article over at ArkFab.

At long last, second generation DIY spectro has arrived!

The spectrophotometer. Yes, that is an invisibility cloak. You can't see the stuff that's under it can you? Then that stuff is invisible!

If you recall, when last we left our humble spectrophotometer, it was a shambling mess of stone-age technology. Now, its a shambling mess of information-age technology!

Let’s take a closer look…

hax0r hijinx: fading fast

A Detective Story

About to run the Final Qualifying Round for some second generation DIY Spectro, I placed the first blank into the cuvette holder, and pressed start (or rather ran python tryna.py; I’m tryna measure a spectrum, gosh!). The machine hummed into action, now that the motor control wire was plugged into slot 9, which the computer was communicating with rather than slot 2, which the computer was not.

A few minutes later I got the results: Nothing. The machine was not seeing any light. At all.

See, normally when I scan a blank sample, the detector (which has different sensitivities at different colors) shows a characteristic hill shape:

Some typical blank sample runs. Horizontal axis is motor position in degrees (0-180) and vertical axis is detector response. Black is the mean of the time series coming from the detector at a given motor position (1 sec data per degree); green is the standard deviation of the time series, and red denotes the maxima/minima. Time series were preprocessed to remove annoying serial communications glitches.

But when I ran this blank: