We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
560 BERKLEY AND MANSBERG November
MOTION PICTURES OF OSCILLOGRAMS
It is sometimes desired to obtain motion pictures of an oscillograph trace for instructional purposes. If a conventional intermittent camera is used, difficulties frequently are encountered with a beating between the camera speed and the pattern repetition rate resulting in blank underexposed frames. The beat frequency is seen in the projected image. This effect may be reduced by using a long-delay phosphor such as the P7, and suppressing the initial blue flash with an amber filter. Where a drifting phenomenon is being recorded, the image tends to smear because of phosphorescence. In this case, the image may be recorded with a continuous motion camera adjusted in speed so that one frame on the film corresponds to an integral number of cycles
(a) (b)
(a) Recording fogged by cathode glow.
(b) Cathode glow removed with blue filter.
Fig. 12
of the phenomenon. If the resultant recording is then projected under standard intermittent conditions, the persistence of vision will give the same visual effect as the cathode-ray-tube image.
Another source of stray fog on the oscillograms is that of the glow from the cathodes of various tubes used in the oscillograph or from the cathode-ray tube itself. (See Fig. 12.) The cathode-ray-tube shield should be designed so as not only to shield for stray magnetic fields, but also for stray light beams. Cathode-ray-tube cathode-glow can best be minimized by using cathode-ray tubes in which special attention has been paid to stray light from such sources and in which a suitable screen application has been made so as to render the screen more or less opaque to the amount of light emitted by the cathode. Where very long exposures are required, as for example, where the cathoderay tube and camera perform monitoring or anticipatory functions, some stray light cannot be avoided readily when exposures run over