Algorithm for simulating phosphor persistence of analog oscilloscopes | Hacker News Reader

Algorithm for simulating phosphor persistence of analog oscilloscopes

richardandersson.net

31 pointspillars11 comments

That looks very cool. I have fond memories of working with analog oscilloscopes.

I started college in 2007, and they handled us newbies in EE analog oscilloscopes for learning, as it does not have the (in)famous auto-scale button.

Working with other engineers, I’m still the one that can handle an oscilloscope the best.

We can derive many parallels in education challenges arising from introduction of new automated functions in tech.

As a grad student in 1986, I was a TA for freshman physics lab, and an obligatory rite of passage was the notorious "oscilloscope lab." The other TA, and the professor, were both theoreticians. I was the only grad student with any electronics experience, because it was my hobby. Still is.

We had a large lab room full of about 30 scopes and signal generators, most of which had flaky controls. No explanation was given beforehand (that any of the students read, at least), and there wasn't time to explain things like how or why the scope shows a stable display of a time-varying waveform.

And because of the behavior of the controls, no explanation was believable.

It was a debacle.

As for phosphor-like digital displays, I wonder how many patents Tektronix has on the concept. Many of them are probably expired by now.

There were analog scopes with auto scale, though. My Tek 2465A has the AUTO button prominently featured. Analog scopes and computerized/automated scopes overlapped in history. The 2465A even had firmware updates.

Auto setup was introduced on the 2465B. A-series has the updated buttons and unlabeled timebase knobs.

My 2465A clearly has auto-scaling. I would know since I've owned it for thirty years. I believe the differences to the B are 350 vs. 400MHz, and the Sony CRT.

You can get the 2465A operator manual online to see for yourself.

You could approximate this on <canvas> by drawing on multiple overlapping canvases: on every frame 1) clear the primary canvas and draw the waveform on it, 2) clear the secondaries with rgb(0,0,0,0.3) as the fill color (decrease the alpha for bigger blurs), 3) draw the primary on the secondaries. Apply additive blend mode and blur filters in CSS to the secondaries.

It’s not the most elegant solution, but more simple than drawing on one canvas.

In my secondary school, we had two contiguous rooms with computers. One has the modern one, color screen with Windows 3.1 or something.

The other room had the old computers, a monochrome white monitor, perhaps an orange Hercules monitor and also the old green one. In the green monitor the phosphorus took a looong time to fade away. When you turn it off, you can still read the content of the screen for like five seconds.

Cool! I tried to put it into my experimental tetris-like game here https://www.susmel.com/stacky/ - you can press R to have it rendered as such, toggle R once again for amber on black more and R again to normal render mode.

Is the phosphor supposed to take an entire second to fade from solid?

It depends on multiple factors from substrate to the strength of the beam. I've seen older age oscilloscopes that took even more. The beauty of those machines, no two alike.

Don't forget the "Youscope" scene demo, another XY mode signal made to be displayed on oscilloscopes.

https://www.pouet.net/prod.php?which=31592

Unlike the "Oscillofun" song though, the scope signal is not the same as the audio signal.

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