Kategorie: Uncategorized

Absorbance and quantitative Spectroscopy

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.

OtterVIS LGL meets OCTAVE

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
  1. Make a nice record by tweaking the SH und ICG-period.
  2. Save the record (no baseline | no Absorbtion (still under construction) | enable Save in[nm]). e. g. test.dat in the spectra directory.
  3. Open octave and navigate to the spectra directory. (e.g. ls shows you where you are)
  4. 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 
  1. 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]). 
  2. Answer die multple exposure dialog. E. g. 10 exposures, after 30 sec the next record and filename starts with „532“. 
  3. 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.
  4. Open octave and navigate to the spectra directory. 
  5. 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.