AN AUTOMATIC SLIT CONTROL SYSTEM
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Date
1962
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Publisher
Ohio State University
Abstract
Every operator of single-beam spectrometer equipped only with a manual slit control is familiar with the annoying routine of repeatedly stopping the scan, opening the slits, and starting the scan again, as the source energy progressively decreases at longer wavelengths. To eliminate this problem, an inexpensive electro-mechanical slit servo system has been designed, which automatically opens the monochromator slits as the spectrum is scanned, thus maintaining the background energy approximately constant throughout the scan. This system follows a pre-assigned non-linear schedule designed to match the dispersion curve of the prism and the fall-off in black-body radiation of the source. The nonlinear circuit contains simple resistors and two linear ten-turn helipots. Voltages generated in the wavelength drum helipot circuit and the slit helipot circuit are combined to produce a difference signal, which is then amplified by a standard servo amplifier to drive a servo motor, which in turn drives the slit drum through a simple gear train. Specific circuits which have been used with KBr and CsI prisms in a Perkin-Elmer Model 12-C spectrometer will be presented, together with background spectra obtained with each prism.
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Author Institution: Flint College of the University of Michigan