A wide or full-spectrum light source really is key to a versatile spectro(photo)meter. A relatively cheap halogen lamp can be used for longer
wavelength. For the UV and near UV spectrum more expensive deuterium lamps may be added. Some single light sources like xenon lamps or ultra-high
pressure mercury lamps perform very good over almost the entire UV-Vis spectrum.
DIY photometers often use webcams as detectors, and this seems to work quite nicely. If you have standards you can use any sensor (which is actually
physically able to detect the photons you want to measure) to quantify the intensity of reflected, transmitted etc. light. This quantification is
actually the whole point of a spectroMETER. If you only want to qualitatively determine if certain spectral lines are present, you could instead use
a spectroscope.
Additionally, you usually want to decompose the light before sending it to the detector or even before letting it interact with the sample (or maybe
both). This is best done by utilizing a diffraction grating. In a simple setup, the complete spectrum is measured simultaneously. This has multiple
advantages, but mainly its simplicity is pivotal.
A classic and more robust and accurate setup is a monochromator before the sample. This way the sample only interacts with light of one wavelength at
a time and the detector measures only the light resulting from this interaction. The monochromator setup works by selectively blocking the light of
all but one wavelength leaving a diffraction grating.
[Edited on 23-7-2021 by zinc finger] |
