Color Simplifies Chart (Jan, 1948)

Color Simplifies Chart

If you think the colorful maze of wavy lines on this seven-element oscillogram is complex, just try to unscramble the same lines on the one without color (inset). Westinghouse oscillographers, having the same trouble, collaborated with Ansco film experts on a method of photographing the wavy-line readings in color. By placing a filter of a different color in the path of each light beam before it strikes the moving film, as many as seven readings can be produced in separate colors at the same time. Then, to record the colored lines, color film is substituted for the usual black-and-white.

  1. Stephen Edwards says: January 16, 20111:18 pm

    Or you could just halve the vertical gain on each (or double their vertical spacing) so they don’t overlap.

  2. Andrew L. Ayers says: January 16, 20112:05 pm

    Something I find interesting is that they were still using electromagnetic optical oscillograph instruments at such a late time; oscilloscopes existed at that time – so what was the reason that they were still using the older technology? The only explanation I can think of would be the increased number of channels available for the same timebase; I would imagine that the tube and CRT-based oscilloscopes of the period probably only had a max of 2 “native” channels available, and to increase the number of (virtual) channels in such a system you’d reduce your timebase and increase flicker at the same time (and at a certain number of channels, the reduced speed and flicker would be so bad, even with long-decay phospher CRTs, that it wouldn’t be readable)…

  3. MikeBurdoo says: January 16, 20117:02 pm

    That’s correct. Oscillographs were very useful because oscilloscopes of the period had no way of storing and presenting data for further analysis. I used them when I was an engineer at G.E. in the 60’s to look back a few minutes along the timeline and see the relationships of five or six parameters (usually looking for the anomaly that caused the system to go unstable). They also gave a permanent record of the data so you could paste it in the test report.

  4. Andrew L. Ayers says: January 17, 20117:28 pm

    MikeBurdoo: Did they ever try something like “multiplexing” multiple oscilloscopes optically (thru prisms and/or split mirror systems) to enable more than 1-2 traces displayed at once (then filming the output using something like a tele-cine camera)?

  5. MikeBurdoo says: January 17, 201111:32 pm

    Andrew, I don’t believe I ever saw anything like what you are describing. I did use a scope with a four trace plugin but the main advantage of the oscillograph was that you didn’t have to sync it to a trigger and you got a time axis that was basically the entire length of paper on the roll instead of 5 inches on a CRT. Some of those oscillographs could really rip out the paper when they got moving (you could easily see individual 400 hz sine waves), and then you could stretch the paper out on the bench, get a cup of coffee, and look at your signal relationships until you found whatever caused the system to go nuts. We did have polaroid scope cameras, but they didn’t solve the problem of the compressed time base on the scope screen.

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