Re: Automatic Brightness Control : was it ever implemented ??

Ted Rook

The 2213 that I had for a short while included automatic brightness. On my machine it
seemed to not work very well, perhaps it was defective (forty year old machine) so I wasn't
disappointed that the 2213A which replaced it had dropped auto-brightness in favor of
manually adjusted brightness.


On 13 May 2018 at 13:56, Vincent Trouilliez wrote:

[Sorry for the previous message, got sent inadvertently while I was in the middle of writing it !
:-/ Discard it]

Hi group,

Sometimes I wonder about this... maybe the experts on here have some view on this ??

I mean, the brightness of the trace varies considérably depending on sweep speed, ranging
from blinding at slow speed, to barely visible when at full speed + x10 mag turned on, so one
has to constantly adjust the brightness control whilst working.

So, seeing as Tek was the leader in the scope world for decades, always finding ways to
improve performance or usability, going to great effort to make nice user interfaces..... did
they ever implement some kind of automatic brightness control, so that a use can just adjust
the brightness level, and the scope would maintain that setting regardless of the sweep
speed ??

I mean OK, would be a bit of a stretch for tube/valve scopes in the 50's/60's, but in the '80s
where there were micro-controllers running the state of the art 2400 analog scopes back in
the day, it might have been technically possible ?
I don't know... for example, Tek could determine experimentally, how much to vary the
voltage on the CRT's grid that's responsible for brightness adjustement, to get a constant
brightness, for every time base setting/sweep speed, for a given desired brightness level.
then they could put that data in a little look up table.

Then, when the user rotates the brightness control on the front panel, instead of the knob
driving directly a pot connected the CRT grid, it could instead
go to an ADC, the scope could look that up in the table, and do some basic linear
interpolation between two points, when need be, then vary the grid voltage as needed.

I only have a 2232 scope, so I don't know about the 24 series. I understand the 24 series was
the state of the art of Tek's analog scope, I think they could have easily implemented
something like this, from a technical point of view ?

Anyway, I was just curious to know if Tek did it at some point, maybe as one-shot on some
particular scope model then abandoned it, or maybe some other scope manufacturer did it ??


Vincent Trouilliez

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