Expo convertors with tubes ?

[harrybissell at prodigy.net]

In the "slightly after the Heroic Age" Tektronix announced a product intended for one of their digitizing oscilloscopes that used magnetic deflection of an e-beam to "illuminate" photosensors which generated a 8 bit binary code based on the deflection amount. A primitve but VERY high speed, almost FLASH 8 bit converter...
I don't know if it was ever used in a commercial product.

Maybe this might be an approach... One of those "Magic Eye" tubes focused on a masked photoconductor ???

(or maybe we should swallow a reality pill and use <gasp> solid state devices)

:^) Harry.

PS isn't a CdS cell "solid state" (and thus forbidden)???


 ---- On Dec  5 Paul Perry <pfperry at melbpc.org.au> wrote: 
> At 01:16 AM 6/12/99 +0100, Rene Schmitz  wrote:
> 
> >I don't see how this tube could be used to build an expo convertor. 
> >The QK329 has a square law. 
> >
> >However I could imagine that an exp (or log) law tube could be made using
> >the same deflection principle. Replaceing that parabolic shape with an
> >exponential one.
> >
> During the Heroic Age, people had oscilloscopes with a cardboard screen
> stuck to the tube, cut in the shape of what transfer function they wanted
> (log, square, Macdonalds arches, you name it).
> They had a photocell looking at this, in a sealed box.
> As the cro trace moved across, a feedback arrangement moved the spot up
> and down so it rode on the edge of the screen.
> And, looking at the Y signal, gave you the required.
> 
> paul perry melbourne australia 
>