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Techniques in High-Speed CathodeRay Oscillography*
BY C. BERKLEY AND H. P. MANSBERG
ALLEN B. DuMoNT LABORATORIES, INC., CLIFTON, NEW JERSEY
Summary — The shortest photographic exposures are made while taking pictures of cathode-ray oscillographic patterns. Because of the unique characterististics of cathode-ray-tube images, many specialized techniques are required to record them adequately and to overcome the problems encountered. These techniques are considered in detail. Their proper use will result in considerable improvement in cathode-ray oscillography.
rip HE USE OF PHOTOGRAPHY in connection with cathode-ray oscilloJ_ graphs and tubes considerably enhances the versatility and usefulness of such equipment. The permanency of the record and data obtained is sometimes an advantage in itself. For example, it is a common experience when working on a circuit to make some slight changes, seeking to effect an improvement in wave shape ; and to continue making slight changes over a period of days, at the end of which time, one can no longer tell by looking at the cathode-ray-tube pattern whether or not the end result is any better than the original one. If oscillograms are available though, comparison by superposition immediately gives the desired information.
Fig. 1 shows a typical example of the result of slight changes in the parameters controlling the clipping action of a circuit. The fact that clipping is taking place at three levels because of the changes can be clearly seen.
Perhaps the best way of quickly specifying the behavior of some complex electronic equipment such as a television set, for example, is to describe the wave shape at as many points in the circuit as desired. This can be done rapidly by making a series of oscillograms showing these wave shapes. Drawings are generally insufficient for showing the fine details which sometimes make considerable difference in the performance of the equipment. In addition, there is an inherent advantage in the use of a camera in gathering data from the face of an
* Presented October 12, 1949, at the SMPE Convention in Hollywood.
NOVEMBER, 1949 JOURNAL OF THE SMPE VOLUME 53 549