Spectroscopy

Gas discharge tubes

Spectrum Tubes

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A UV-Visible-IR Spectrometer

The i-Phos HD spectrometeter, by Chris Wesley, is a ready-made version of the Theremino spectrometer, with the option of a single 1mm slit, or a set of interchangeable slits. 3D-printed PLA slits are available in widths of 0.5, 1, 2, 3, 4 and 5 mm. Metal slits in PLA frames are also now available in widths of 50, 100, 200 and 500 μm. The wavelength range is from about 360 nm (near UV) to 1150 nn (IR), with some fall-off at the extremes. Resolution achievable with a 1mm slit is around 1 nm.
      The diffraction grating in the i-Phos is a piece taken from an unused 4.7 GiB DVD-R disc. The rulings in that case have a spacing of 0.74 μm, gving about 1350 lines/mm.
     Here we adapt the i-Phos by removing the supplied 1 mm slit and attaching a Frederiksen symmetrically-adjustable slit assembly. As supplied, the Frederiksen slit gives a continuous adjustment range from about 100 μm to 6 mm, and the minimum aperture can be reduced by careful adjustment of the slit-blade holder. The exact setting is easily determined by measuring across the outside of the blade holder (using a dial caliper) and subtracting a fixed amount.


[Article under construction].




Fusion 360 CAD rendering of a 3D-printable mount, for attachment of a Frederiksen symmetric adjustable slit assembly to the i-Phos spectrometer. Orange colour is for visualisation only. Final print, in ABS, is black.

Design by Stephen Knight.

Links

i-Phos HD Spectrometer (Chris Wesley)
Chris building a standard definition version.
Standard 640 × 480 manual-exposure webcam is no longer available, so a dedicated 1920 × 1080 full HD camera module is now used.

Making a DIY Spectrometer [Creative Lab] YouTube Video.

Theremino website (please support this open-source facility).
Theremino Spectrometer Technology.
Theremino Spectrometer Construction.
 Theremino Spectrometer, Sample Spectra.
 Software download.  Help file (instructions) is in the zip file.

Frederiksen Adjustable Spectrometer Slit:
I finally obtained a Frederiksen adjustable slit from Timstar (WF Education Group) but it took 4 months on back order before I got it. Still, I suspect that Timstar deserves praise for getting it for me at all, because when I went back to the Frederiksen Scientific site to give a link to it, the item seemed to have disappeared from their catalogue.
     It is a beautiful piece of precision engineering. Making something similar is not beyond the capability of a good engineering workshop, but certainly not a trivial undertaking.

Ovio Instruments - Frederiksen slit.

Public Lab, spectrometer FAQ

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DWK 2021 July 4^th