EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: tom66 on March 14, 2014, 10:23:43 pm
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It seems DS1074Z will process I2C/RS232 accurately when zoomed in, but not when zoomed out. This appears to be down to the Dig.Sample rate in the options menu, I am guessing it is aliasing its internal sampling (separate from normal processing) when zoomed out. But, the option is greyed out. Any way this can be changed?
(Note the "?" on the bus when zoomed out, also, the data bits are usually corrupted on longer transfers.)
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This scope decodes from screen memory. I'm pretty sure that the full memory is only available for reading when the scope's run/stop button is red (stopped.) That's certainly true for SCPI, so I imagine there is an architectural reason.
If your scope is stopped for the screenshots, then this is probably just a limitation of the scopes. Now that I type that, I seem to recall reading that it's a common thing among Rigols - inability to decode from anything but the screen.
Someone else will likely pipe up and correct/confirm what I've written.
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Hi Tom66, I have an Agilent 2000x series, and it does exactly the same thing. When I go to 320 ms/div, I get red blocks that do not decode mixed in with blue blocks that do. I think it is more to do with the sweep speed, and not so much the sample rate. Mine goes down to 50 KSa/s at 210 ms/div, but it continues to decode until I get to 320 (still at 50 KSa/s).
Anyone else know if my hypothesis is correct?
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Try adjusting Horizontal position and Timebase to get all of the packet of data on screen. Then single shot. Then zoom with Timebase to area of interest.
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I can do that, and it'll decode fine when zoomed in - I guess it's just a limitation.
It would also explain why things like risetime/frequency cannot be measured when zoomed out.
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It would also explain why things like risetime/frequency cannot be measured when zoomed out.
Right. Measurements are made from data in Display memory, not Sample memory.