World's First Electronic AWG -The Photoformer

I did this when I was a teenager, early 60's, with a pmt and my Knight-Kit DC-coupled scope. In retrospect, it's surprising that the loop was stable.

Any idea when this was first done?

John

Are you telling us you conceived and built this independently?

It almost certainly goes back to the 40's, or whenever analog computers first were seriously relied upon to solve scientific analysis problems.

I remember this trick from way back (can't remember the source, but I didn't think of it myself)... it's really just the electronic analog of a mechanical cam follower, which would date back at least to sometime in the industrial revolution.

Best regards, Spehro Pefhany

Yup. I was building a light-beam radar (surplus military xenon flashtube, 931A pmt, crude optics) and just for grins aimed the pmt at the face of the scope. At the right distance and gain settings, it traced the curvature of the tube. So then I stuck my hand in the way...

It's cool, the way the beam will ride up the slope of your finger, then fall off. Lots of people must have done this by accident... once you've got a pmt connected to a scope, it's pretty obvious.

I invented the dual-slope integrating ADC about that same time, but forgot to patent it. I figured that as long as I used relays to do the analog switching (that's what I imagined) it wouldn't be very accurate.

John

Hey, this looks a lot like the famous 'flying spot scanner'. Put an object between a TV with a white raser and a phototube. It was used by TV technicians to generate a standard test pattern by using a transparent image in the middle. All in a box, you inserted a selection of transparencies for different test patterns.

Luhan

Just a nitpick, but I'd say that something as fundamental as a cam follower came WAY before the "industrial revolution"; people have been doing mechanical things since the Pharaohs - the "revolution" happened by steam power and the Jacquard loom, i.e., "Automation". ;-)

Cheers! Rich

"Fred Bloggs" schreef in bericht news: snipped-for-privacy@nospam.com...

I once picked up a *very* old TV-signal generator, made of a CRT driven in the same way as a normal TV (line scan and frame scan) with a choice of slides to put in front of the tube, and a photodetector placed in front of that. All inside a closed cabinet, with a lid on the top to be able to change the slides.

Its called a flying spot scanner. In the US one was made by B&K/Precision, model 1077 that also had a hroizontal drive for the fluback transforemer, and a tunable VHF modulator. One of the slides was a grid for convergence of early color TVs. I have one in storage. These were still being sold, into the '70s.