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At the end of my light sensing instructable where I played with the measurement of reducing sun light levels as well as making it into a laser game , I mentioned that I wanted to have a go at making a full spectrometer. This instructable is a step closer.
In the instructable I said I wanted to add a diode array, unfortunately I have not been able to get hold of one, so this will be a scanning spectrometer.
Diode array spectrometers
These work generally by having no moving parts. The light passes through the sample and is split into its separate spectral components using a prism or similar device. The separate wavelengths then fall onto the detector where each absorbance value is measured at the same time.
These work slightly differently in that the light is first split by the prism, it the passes through a narrow slit which helps to reduce the number of wavelengths of light that can fall on the sensor after it has passed through the sample.
In this type of system there is a single detector that has to measure each value in turn and because of this the light splitting device has to rotate to direct the sequence of wavelengths onto the sample and so onto the detector.
The spectrometer in this guide will use a diffraction grating a hologram printed onto a price of glass, I got this from work (a spare from a service visit).
If you don't have access to a gratting, you can make one by cutting a piece of a DVD.
HOW Usefull is this instrument
The usefullness of this instrument is limited only by your imagination examples are as follows:
- Analysis of the light spectrum (measuring the amount and colour of available light
- Measurement of spectral reflectance transmitance and absorbance of materials
- Food colourants analysis
- Environmental analysis - pollution in water - its inexpensive and connect to a laptop and not a big issue if it gets field damaged
- Training tool (educational) A great way to get your children into progamming and developing imaginative solutions.
The above and many more would of course all require calibration of the equipment