Algorithm for simulating phosphor persistence of analog oscilloscopes
10 comments
·July 24, 2025jwrallie
analog31
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.
jeffbee
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.
kevin_thibedeau
Auto setup was introduced on the 2465B. A-series has the updated buttons and unlabeled timebase knobs.
jeffbee
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.
Keyframe
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.
gus_massa
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.
Dwedit
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.
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.