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7J20: Difference between revisions
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Rapid scan means that it can capture the spectrum quickly enough | Rapid scan means that it can capture the spectrum quickly enough | ||
to show spectral changes at temporal resolution of a few milliseconds. | to show spectral changes at temporal resolution of a few milliseconds. | ||
The spectrometer is packaged in two enclosures linked by an umbilical cable. | |||
The 7J20 is a 2-wide plug-in for [[7000-series scopes]] containing the sweep timing and mainframe interface circuits. | |||
The external enclosure is labeled "J20". | |||
It has controls for the optical components (grating, filters etc.) on one side and an input aperture on the other. | |||
==Internals== | |||
The instrument is based on a [https://en.wikipedia.org/wiki/Monochromator Czerny-Turner Monochromator], | The instrument is based on a [https://en.wikipedia.org/wiki/Monochromator Czerny-Turner Monochromator], | ||
in essence a narrow slit followed by a [https://en.wikipedia.org/wiki/Diffraction_grating diffraction grating]. | in essence a narrow slit followed by a [https://en.wikipedia.org/wiki/Diffraction_grating diffraction grating]. | ||
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and produces a periodic electric signal which is then displayed by the scope mainframe. | and produces a periodic electric signal which is then displayed by the scope mainframe. | ||
[[File:7J20-principle.jpg | thumb | 400px | center | Operating principle (click to enlarge) ]] | [[File:7J20-principle.jpg | thumb | 400px | center | Operating principle (click to enlarge) ]] | ||
The internal vidicon horizontal scan voltage corresponds to wavelength, | The internal vidicon horizontal scan voltage corresponds to wavelength, | ||
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Inside the 7J20, there are 40 trimmer potentiometers that allow the lookup function to be tweaked | Inside the 7J20, there are 40 trimmer potentiometers that allow the lookup function to be tweaked | ||
so that the horizontal scale of the system is accurate. | so that the horizontal scale of the system is accurate. | ||
[[File:Tek_j20_interim_normalizer2.png | thumb | 400px | center | Normalizer (click to enlarge) ]] | |||
The 7J20 is very rare. According to Dennis Tillman, ''Best estimate is ~40 were actually built.'' | The 7J20 is very rare. According to Dennis Tillman, ''Best estimate is ~40 were actually built.'' | ||