enelson

Thanks @attila!

Hi @attila, Correct me if I'm wrong, but the x-y plot on the right should present the same measurement(s) shown in (or by) the two y-t traces on the left. So even if there was a ground loop issue, the ground loop should affect both plots equally, meaning for example the CH2 max on the left should match the y (CH2) max on the right. So I think this is a subtle issue with the waveforms software, how it is displaying the x-y plot. Having said that, I do have a 5VDC power supply on order to use with my AD2. Perhaps you are psychic! :-) the WaveForms software I'm using is version 3.16.3 64-bit for Windows 10, in case that helps. Regarding ground loops, this two-terminal current source circuit is only attached to the AD2. W1 and 1+ connect to the positive terminal of the current source, 2+ connects to the positive end of the shunt resistor = negative terminal of the current source, and 1-, 2- and GND connect to the negative end of the shunt resistor. There are no other connections to any other power or any other device. So that means no ground loop, yes? Let me know if I've misunderstood. Perhaps I can reproduce this behavior using 1+ to measure W1 and 2+ to measure W2. No circuit involved. Thanks for engaging me on this topic! And have a great day.

Hi, while measuring the I-V characteristic of a two-terminal current source with my Analog Discovery 2, I noticed the vertical position of the trace in the x-y plot is not quite correct. In the following screen capture, CH1 (yellow) is the voltage across the source plus a current measurement (shunt) resistor, and CH2 (blue) is the voltage across the shunt resistor. The x-y plot on the right looks fine on this vertical scale. For example, the CH2 peak is 300 mV in both plots. When I zoom CH2's vertical scale to more closely examine the difference between the rising and falling halves of the triangle wave, the trace in the x-y plot appears to be too low relative to the x-y plot's graticule. For example, CH2 peaks around 299 mV in the normal y-t trace on the left, but in the x-y plot on the right that peak is low by about 0.3 mV. Exported data and the cursor suggest the zoomed y-t plot is good, so I'm thinking the calculation for where points go on a vertically zoomed x-y plot is not quite right. Is this something you can look into? Note this concern is not about the two vertical graticules on the left and right being slightly misaligned. While it would be nice if the two graticules were aligned, my concern is that reading CH2 values off the x-y plot on the right gives me some (slightly) wrong numbers. Thanks! I'm still having a blast with the AD2. Have a great day.

Thanks @attila! Have a great day.

Hi @attila, thanks for responding. I'm not referring to the noise band, although that is a nice feature so thanks for having it. Perhaps some screen snapshots will suffice to illustrate. I'm measuring the voltage across a diode (channel 1) that is driven by a 2.5 V peak 1 kHz triangle wave (channel 2) through a 17.8k resistor. I've zoomed the trace on one of the channel 1 peaks, where I see about a mV of noise in this channel 1 trace, taken with no averaging. This noise is presumably due to the relatively noisy environment in my "lab". Now if I average 100 traces, I expect the noise to be substantially reduced, perhaps by a factor of 10. However, when I set averaging to 100 and press 'single' for a single acquisition, waveform counts 100 triggers and I get a trace like the following (after zooming again). The noise is still there, contrary to my expectations for what averaging should do. However, if I press 'run' instead of 'single', and then 'stop' some time after the 100 triggers, the zoomed trace below now looks very nice, with very little noise, in line with what I expect averaging should do. So it looks to me like averaging is not really working when one requests a single acquisition. It might be showing just the first (or last) of the 100 traces I requested waveforms to collect and average. Thanks for looking at this again!

I'm not sure if this is the right place to report what I think is a bug in waveforms. I'm using version 3.16.3 64-bit on windows 10. I was having difficulty using averaging in the scope timebase controls to eliminate some noise. When I click on 'single' acquisition, the scope appears to trigger the appropriate number of times (e.g., 100) before displaying a new trace. But the noise is not reduced, as if the scope is showing me just the trace from the first (or maybe the last) trigger. Clicking on 'run' similarly counts the appropriate number of triggers and then displays a new trace, but with the expected noise reduction from averaging. I can then click on 'stop' to export the averaged traces, so I'm not stuck. Hopefully this is easy to fix in subsequent versions of waveforms, so that a 'single' acquisition does the requested averaging. I am otherwise having a great time so far with waveforms and my analog discovery 2. Thanks!