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| Scope with fast waveform averaging (can your scope go faster?) |
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| maxwell3e10:
I played a bit more with Rigol DS6104. It's trigger out rate also has no direct relation to the number of averages, it does not change when averaging is turned on. The trigger out rate maxes out at about 180 kHz when the horizontal scale is 10 nsec/div and memory depth is set to auto, giving 700 waveform points. For shorter horizontal scale the trigger out rate goes down again. Under these conditions it can average 8192 points without significant drop in amplitude for 1 Hz sine wave. I can't increase the number of average points any more, but I can increase the input frequency to 3 Hz before the amplitude goes down to 1/2. |
| maxwell3e10:
Could someone run the 1 Hz sinewave test on a Keysight DSOX3000 series scopes? I am hoping they might be faster based on 1 M waveforms/sec update speed and the fact that my puny EDUX1002A with 50,000 waveforms/s update can still do fairly close to a top Rigol. |
| Someone:
--- Quote from: maxwell3e10 on August 10, 2022, 01:02:56 am ---Could someone run the 1 Hz sinewave test on a Keysight DSOX3000 series scopes? I am hoping they might be faster based on 1 M waveforms/sec update speed and the fact that my puny EDUX1002A with 50,000 waveforms/s update can still do fairly close to a top Rigol. --- End quote --- No, because it is a poorly designed test that doesn't measure what you think it does. We already have people posting/reporting the averaging rate in wfms/s |
| maxwell3e10:
No, it gives you exactly what you want, which is how fast the scope completes a given number of averages. So if you are playing with your DUT, it tells you how quickly the scope will respond to a signal change while doing the averages. Or if you want to save the data, it tells you how long to wait until you can hit the stop button. The waveforms per second (if the scope has a trigger out and one has another scope nearby to measure it) do not necessarily correspond to the number of waveforms averaged, as seen in a couple of examples above. Now, there was a test done earlier on another thread with 3000T scope: --- Quote from: 2N3055 on April 19, 2020, 12:03:51 am ---I made a test with my 3000T. 3 ns pulse with 10 kHz repetition rate. at 20 ns/div, normal ACQ mode, on trig out full 10 kHz. BUT, if I set average ACQ mode, it is STILL 10 kHz.... It seems to be doing running average. Meaning, there is no slowdown in acq rate, but latency in result after change. Latency will be proportional to number of averages and timebase, of course. At 200 ns/div normal ACQ, trigger rate is still 10kHz, but average ACQ drops to 1.7 kHz (at 1024 averages) So there is a slowdown here. It is highly dependent on settings. If OP would give exact settings, I have no problem running scenario to verify exactly how fast 3000T would be. --- End quote --- But all it says that the scope can average at more than 10 kHz, assuming the trigger out equals to waveforms averaged. Increasing the ns/div scale will necessarily slow it down, both because of longer acquisition time and possibly because there are more points in the waveform. Increasing the trigger rate until it is much higher than waveform/sec speed would tell what is the maximum speed. |
| Someone:
--- Quote from: maxwell3e10 on August 10, 2022, 03:17:31 am ---The waveforms per second (if the scope even has a trigger out) do not necessarily correspond to the number of waveforms averaged, as seen in a couple of examples above. Now, there was a test done earlier on another thread with 3000T scope: --- Quote from: 2N3055 on April 19, 2020, 12:03:51 am ---I made a test with my 3000T. 3 ns pulse with 10 kHz repetition rate. at 20 ns/div, normal ACQ mode, on trig out full 10 kHz. BUT, if I set average ACQ mode, it is STILL 10 kHz.... It seems to be doing running average. Meaning, there is no slowdown in acq rate, but latency in result after change. Latency will be proportional to number of averages and timebase, of course. At 200 ns/div normal ACQ, trigger rate is still 10kHz, but average ACQ drops to 1.7 kHz (at 1024 averages) So there is a slowdown here. It is highly dependent on settings. If OP would give exact settings, I have no problem running scenario to verify exactly how fast 3000T would be. --- End quote --- But all it says that the scope can average at more than 10 kHz, assuming the trigger out equals to waveforms averaged. Increasing the ns/div scale will necessarily slow it down, but increasing the trigger rate until it is much higher than waveform/sec speed would tell what is the maximum speed. --- End quote --- Keysight 3000, measuring averaging speed, and that thread has posts carefully checking that the trigger output rate was an accurate representation of acquisitions (not just raw triggers as in some other scopes). The post you quoted explicitly shows how the rate on the trigger output dropped when enabling averaging compared to the "normal" acquisition mode. Averaging speed is not some constant or even a ratio of the normal speed, it will have its own characteristics and limitations, which is why it has to be tested in isolation (and for the specific use case since fast in one situation will not always be fast in others). Averaging on that particular scope is slower than "normal" acquisitions, but you only notice it when the trigger rate approaches the limit. Which is why "testing" with trigger set to auto and estimating averaging rate by adjusting the ??? number??? of averages is many layers of misdirection. An (unintentionally) correlated trigger could make that average to 0 very quickly and provide extremely misleading results. |
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