For best results, use a Vernier Emissions Fiber (VSP-EM-FIBER).
For better results when not using an optical fiber:
Align the aperture directly with the light source. Misalignment can shift the measured wavelengths of spectral lines by as much as three or four nanometers. This can be seen if you continuously collect data while slightly changing the alignment of the spectrometer as you are using it to look at a gas discharge tube. In general misalignment will cause the measured wavelengths to be smaller than the expected wavelengths.
If the light source is dim or if some spectral lines are not registering, you can increase the sample time. When using LabQuest App, increase the sample time from the Meter screen. In the Sensors menu, choose Data Collection…. You will be able to increase the sample time there. In Logger Pro, find Set Up Sensors in the Experiment menu. Select the spectrometer and you will be able to increase the sample time in the pop-up window.
If the light source is bright enough to cause the readings of the spectrometer to “max out” at 1.0 even with short sampling times, increase the distance between the light source and the spectrometer. Very good results can be obtained with the spectrometer 20 cm to 30 cm away from a gas spectrum tube. In cases where it is impractical to increase the distance between light source and spectrometer, as when measuring solar spectra, then slightly offset the alignment of the aperture with the light source.