In order to test the OtterVIS LGL spectrophotometer and the new UART-Version, I prepared some crystal violet solutions: 0.001m, 0.002m and 0.003m. The lightsource was a halogen lamp connected with a very simple optical fibre to the kuvette. The baseline was taken with suitable integration parameter (nice feature). The scan of each solution was saved and plottet with octave.
I measured the solutions with my old but professional MN-NANOCOLOR UV/Vis.
The results of the OtterVIS is not bad! And there is a lot of room for improvement in the Soltware etc.
In order to test the OtterVIS I connected the output of it to the math software GNU Octave. This program has a lot of advantages:
- compatible to MATLAB
- good documentation
- a large community
- you can create scripts for repetitive tasks
- and its free
Find the Peak
There is an interesting web site about signal processing in scientific measurements. One sub section is concerned with peak finding in data. I adjusted the script to meet my needs. (findpeaks.m)
How to use the scripts
- Make a nice record by tweaking the SH und ICG-period.
- Save the record (no baseline | no Absorbtion (still under construction) | enable Save in[nm]). e. g. test.dat in the spectra directory.
- Open octave and navigate to the spectra directory. (e.g. ls shows you where you are)
- type ovis_peaks(„test.dat“,3900,1,1) and hit return.
The script ovis_peaks needs the filename, zero value, autoleveling on / off, display details and plot file on/off. It uses the findpeaks.m script to do the work. The output is a plot, a jpeg-file and a description of the peaks found.
Check repeated Measurements
To allow multiple exposures and keep the redraw functional I implemented a timer. The parameter of the timer can be configured by a dialog. The record are saved in the form name-no_of_exposure-seconds.dat.
How to check a repetative single peak
- Make a nice record of e.g. laser with a single peak by tweaking the SH und ICG-period. (no baseline, no absorbtion, enable save[nm]).
- Answer die multple exposure dialog. E. g. 10 exposures, after 30 sec the next record and filename starts with „532“.
- Press the red record button and wait until the measurements are done. This will generate a sequence of files: 532-0-0.dat, 532-1-30.dat, 532-2-60.dat etc.
- Open octave and navigate to the spectra directory.
- type repro(„532-*.dat“,3900,1) and hit return.
The pictures show the result of two collections of multiple exposures. I used two lasers with 405nm uns 650nm. The 405nm records showed always one peak at the nearly the same mark. The 650nm laser records sometimes displayed a second peak.
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