If you’ve used a scope before you probably noticed that the sample rate and the voltage resolution changes as you zoom in and out.
If a scope didn’t suffer from a limited buffer how would you want to zoom in and out on your data?
- I would like to have a fixed sample rate (x-axis) and voltage resolution (y-axis) for each capture that don’t change based on my zoom settings.
- I would like to zoom in and out and have the scope change the sample rate (x-axis) and voltage resolution (y-axis) to maximize the sample rate and voltage based on my zoom level.
- I would like the option to do both, by fixing the sample rate (x-axis) and voltage resolution (y-axis) using zoom (or some other method) and then locking those settings (maybe with a button) to zoom and pan around with the fixed settings.
- Something else - I’ll comment below
Thanks for your help!
With Logic2 we are used to setting a sampling rate appropriate to the job at hand which stays the same regardless of zoom. That is pretty understandable and unsurprising. I don’t think the reasons for setting the sampling rate change much for a scope measuring analog data compared to a logic analyzer measuring logic signals - set the rate to show the information you need.
If there were no constraints (like storage and processing time) there would never be a need to use other than the highest available sampling rate.
With Logic2’s analog data display I do miss not knowing where the actual samples were taken. At high zoom it is impossible to know how much of the signal shown is real. Showing a blob on the trace fixes that.
For a scope at low zoom it is important to show the “envelope” of the signal. An average of the data represented by each point can be highly misleading. For signals with narrow intermittent spikes the signal envelope can be misleading too. A really smart way of showing compressed (more than one sample per display point) signals is to bin the samples in each display point by amplitude and generate a “histogram” showing the bin counts as brightness. That gets you a vertical line of pixels mapped onto the bins that show the count of samples in each bin by pixel brightness. If you were looking at a high frequency square wave that would look like two horizontal lines for the top and bottom of the square wave. If you were looking at a high frequency sine wave you would see a band that was bright at the top and bottom and faded out toward the middle.
Thanks Peter for your feedback. The histogram is definitely a great way to show those types of varying signals in a clear and concise way.
I was curious if you had thoughts about the dynamic range of the voltage at each sample (volts per adc bit or voltage resolution) with regard to zooming as well?
At high vertical zoom the “what is real” problem is just the same as with high horizontal zoom and the answer is just the same: blobs at the quantization points. Faint lines in both cases help your eye “join the dots”, but it can help to have a “dots only” mode, especially for noisy signals. And of course the histogram mode is still useful with high vertical zoom and low horizontal zoom.
I agree with Peter.
Idealy, you’d have infinite resolution and just be able to zoom in and out seamlessly, but on a normal scope (espcially the cheap ones with just a few K of sample memory) this is not possible. On a Logic device, the really great option is to be able to make a long sample at the needed speed to see the details. Go wide to find the particular point that’s interesting and then zoom in to get to the details.
As for the histogram idea, I’d add the eye diagram/persistence option for repeating signals (with brightness of pixels showing the histogram level). Even my cheap Chinese Hantek scope can do this.
Thanks for your feedback Kai. This helps us make sure we are building the right stuff for our next product.
Regarding vertical resolution, does the hardware actually have the capability of changing this? So we could increase sensitivity, equivalent to using a preamp? I don’t think anything in the current UI exposes this. Just curious because this would be a nice feature. If so, what is the greatest sensitivity supported?
We are working on a new hardware platform that will have this functionality. Have a good weekend!