Question: How do I make sure the "YELLOW LINE" threshold is the same for each measurement with the spectormeter (trying to maintain consistent conditions for experiments across multiple days)

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Dr_Z asked on March 08, 2018 19:40
133 | 1 answers | #15896


I am running a series of spectrometer experiments and I have noticed variability in the peaks of my spectra from day to day. I am using the same light source, positioning, and spectrometer positioning for each run, but each time I boot up my laptop and camera interface I have to set the "yellow line" threshold for the spectrometer camera. Is there a way to fix the position from day to day so I have consistent measurements?



2 Comments

I suspect there are two issues here: 1) the software interface and 2) mechanical instability. On #1, I believe the web-based software always needs to 're-zero' where to take the single-line of image data within the video frame. On #2, assuming you are using the paper-and-velcro PLab spectrometer, there simply is not sufficient mechanical rigidity in the design to provide the repeatability you require. (Might be helpful: https://publiclab.org/notes/stoft/03-02-2015/plab-3-spectrometer-upgrade-prototype )


@Ag8n true, calibrating before a measurement (or series of) helps assure the measurement data is referenced. As per wavelength references, while there are better standards, the bandwidth of web-cam / DVD spectrometers is, at best, about 1nm (while the 'typical' paper/velcro build might be no better than 5nm repeatability) so using 3 spectral lines from the simple CFL is generally sufficient.


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1 Answers

I think stoft (see above) has some good suggestions.

Calibrating more often is also a good idea.

Better standards, Holmium oxide for example, would be ideal. They just aren't affordable. The cfl lamps have to do as a std.


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