APPLICATION OF SERVOS TO SPECTROSCOPY
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Date
1952
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Publisher
Ohio State University
Abstract
Servomechanisms are now being used widely in the instrumentation for spectroscopy. The advantages of such designs are well recognized. However, these advantages are best realized only if great care is taken in the design, and if the user employs the resulting design to best advantage. It is also very important that the user recognize certain limitations which may arise. Inevitably, noise, or undesired signal, is present along with the true spectral data. Someplace in the system an effort is made to attenuate the noise without appreciably affecting the spectral data. Often this is done with a filter. Also, elements in the servo can be used to attenuate the noise, and this action is discussed. The effort to reduce the noise to an acceptable level results, even in the optimum condition, in some loss of spectral data, and can significantly affect resolution either by attenuating certain portions of the spectra where it is rapidly varying, or by accentuating certain characteristics of the spectra. Another effect which is encountered arises from friction, backlash, or other nonlinearities. Commonly this is called ``deadspot'' and is characterized by the system not following small inputs. For spectral lines which have steep sides, or for any spectra which is scanned rapidly, one can reach a condition in which the recording mechanism cannot travel at the required velocities. This can, of course, result in serious falsity of the spectra at and near regions of this excessive velocity. Design techniques aimed at minimizing such difficulties as listed above are discussed. Examples are given of the effect of such difficulties and considerations for optimum usage are suggested.
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Author Institution: The Perkin-Elmer Corporation