I came across a problem when measuring multiple spectra in one sequencer. Originally I wanted to use a switch board to switch between different pixels of my sample, however spectra and resulting performance metrics were not consistent.
We simplified the sequencer and could replicate the issue within a simple loop. The first recorded spectrum has a lower intensity than the following spectra. We tried adding a hold and delay at various positions but could not really detect a difference. Attached are some screenshots. Do you have an idea what the issue could be and how to go about debugging it?
Best,
Jörn
I observed similar behaviour with such USB-Spectrometers during my time as researcher. It need some repetitions until the spectras settle in a steady state which becomes more obvious the lower the integration time is.
I don’t think that it is related to SweepMe! or the driver. The code just calls the last spectrum and returns it.
If this is an artefact of the spectrometer, changing Hold or Delay in SwepeMe! will not make a difference. Only Hold could make a difference if the time between initializing the spectrometer and measuring is important.
I would test the outcome, when increasing the integration time of the spectrometer. I guess it will be stepwise reduced.
Further, you could check the programming commands of your spectrometer whether there is any command to acquire a fully fresh spectrum. Some spectrometer might run in some internal endless acquiring mode and the get_intensities command just returns the last acquired one. This could be partially effected when there was no light at the beginning of taking the spectrum.
At the same time, this could also mean that the spectrum of other samples might be partially affected from the previous one which is hardly visible if all spectra are merely similar.
Better would be to change the triggering to acquire a completely new spectrum when the acquisition is initiated.
Let us know if you need professional support with this or if you can figure something out.
If there is a real problem with the spectrometer and adapting the used communication commands does not help, one could test whether it helps to retrieve an early spectrum during the ‘initialize’ phase each driver has that is discarded and not further used.
Another origin for such an observation could be that it takes time until your sample lights up. However, a Hold time typically solves this as it adds a time between applying the set values and measuring/acquiring the data.
