A Tektronix TDS 684B Oscilloscope Uses CCD Analog Memory

Re:A Tektronix TDS 684B Oscilloscope Uses CCD Analog Memory by crote on Monday May 05, 2025 @02:35PM (#43898023)

Could it be some kind of fixed per-bucket offset?

I wouldn't be surprised if the CCD has all sorts of funky analog stuff going on internally which has different impacts on different samples, which would be incredibly hard to deal with on its own.

However, if this behaviour is merely a fixed offset, it would be fairly easy to compensate for this on the digital side: just do a calibration with a known signal, and the measured offset can be used to reverse its effect in future sampling.

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Re:A Tektronix TDS 684B Oscilloscope Uses CCD Analog Memory by tverbeure on Monday May 05, 2025 @02:51PM (#43898194)

Could be. I've already measured with sawtooth and square waveforms to get a better idea about the interleaving and noise, but not yet with a pure DC input.

Another possibility is that there's some charge decay which you could calibrate for.

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Re:A Tektronix TDS 684B Oscilloscope Uses CCD Analog Memory by Retr0id on Monday May 05, 2025 @03:17PM (#43898454)

I mentioned in another comment, but I started writing an emulator for my TDS 684A's firmware. If I can get it a bit further along (most of the business logic seems to be implemented in smalltalk) then maybe we can answer some of these unknowns by looking at what the calibration routines do.

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Re:A Tektronix TDS 684B Oscilloscope Uses CCD Analog Memory by tverbeure on Monday May 05, 2025 @04:04PM (#43898900)

Having an emulator for that is really interesting.

Is the smalltalk program stored? Some kind of byte code or the original source code?

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Re:A Tektronix TDS 684B Oscilloscope Uses CCD Analog Memory by Retr0id on Monday May 05, 2025 @04:13PM (#43898981)

It's something bytecode-y, I haven't been able to make sense of it yet.

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