Thanks for this Sir this was exactly what I was looking for. Also good to know that the tubes arnt specked for full screen width and true spec is a reduced graticule size.
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On 3/13/2020 10:33 AM, Chuck Harris wrote:
I think I know what you are asking, but not completely sure.
The scopes are generally specified to be in calibration only
in the center region of the CRT. For instance, the 2465 family
says between the second, and 10th graticule line horizontally,
and the second and 6th graticule line vertically.
The reason for this is there is some serious work done to fight
the electron beams natural desire to see a spherical screen,
rather than a flat screen.
Also, there is often confusion about what part of the lit phosphor
is the part from which to measure.
The trace is an embodiment of a probability "bell curve". The
center is where most of the electrons hit the phosphor screen, and
towards the outside is where some noise deflected electrons hit.
It is best practice to consider the brightest, most central part
of the width of the beam to be the "trace"... So, when making a
peak-to-peak measurement, it will be from brightest to brightest...
not from furthest most visible fuzz to furthest most visible fuzz.
As I have a backlog of plugins to calibrate, I have a questions I cant seem to find a good answer too. When calibrating a scope. Is the reference the center of the graticule line, the bottom edge, or the top edge. Common since tells me it should be the center of the graticule is the alignment point. But I am hoping to confirm. Or am I asking my analog scopes to be a little too accurate?