
The Pre-CRT Oscilloscope - zdw
https://hackaday.com/2018/09/11/the-pre-crt-oscilloscope/
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kevin_thibedeau
The same basic principle is still used by better digital scopes to sample
periodic waveforms faster than their ADCs can support. This can get you into
the TS/s regime on the high end models.

[http://cdn.teledynelecroy.com/files/whitepapers/wp_ris_10220...](http://cdn.teledynelecroy.com/files/whitepapers/wp_ris_102203.pdf)

[https://www.tek.com/document/application-note/real-time-
vers...](https://www.tek.com/document/application-note/real-time-versus-
equivalent-time-sampling)

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timpattinson
Hijacking this to post an excellent video, with input from the designer, on
how this is done:

[https://www.youtube.com/watch?v=U3w_EWgGQuk](https://www.youtube.com/watch?v=U3w_EWgGQuk)

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saundby
So the "pre-CRT Oscilloscope" is an oscillograph.

When I came in the door in instrumentation work, they'd moved to self-
developing photo paper, so we got to use the former darkrooms as additional
storage space. CRTs came into use on oscillographs, with the physical
galvonometers being replaced by a CRT about half a centimeter tall and 200mm
wide displaying dots that were recorded on the photographic paper. They were
better at high frequencies, since they didn't have to deal with the physical
mass of the galvonometer's rotor (the shaft, coil, and a very small mirror),
but since there were a few beams in the CRT multiplexed between signal
channels there were compromises in what you could record on one record with a
CRT oscillograph, too. Typical galvo o-graphs recorded up to 48 channels on
30cm wide paper, CRTs up to 16 or 32 channels on 20cm paper.

Galvos took a lot of time to set up and calibrate. Adjustments to each one's
amplifier, travel range and optical focus, then testing & calibration on each
day of use.

