Data acq with AD2 to capture periodic events

[Bruce Boyes]

Hi, this sounds so simple, maybe I am missing something. I have an AD2 with WF. What I want to do is sample at say 10 KHz on two channels, and have a large buffer say 20 seconds worth, which will just overwrite with new data until I say stop.

I am trying to capture signals on railroad tracks when a train goes by. I can't know exactly when this will be, so I'd like to have the scope running and ready. Obviously when the train comes I can tell that... and stop the capture after it passes. Then we need to save that data file and look at it later with a spreadsheet and/or the WF viewer. We're looking for anomalous spikes in voltage. A train will pass one direction then about 5 minutes later another train in the opposite direction, then nothing for an hour. I have to also manage some other instrumentation at the same time. If I mess up, it's another hour... and people are standing around giving me access to these signals, so I want to get this right the first time.

I am trying the Scope in Record mode. I can set the scope to 10 KHz sample rate but max is 10M samples... still that should give me 1000 seconds, 17 minutes. At 100 KHz sample that is 100 seconds or 1.7 minutes. That should be enough.

Is there a way it can capture the most recent 10 M samples until I stop it? If I have to manually start it before the train arrives that gets tricky.

I've looked at the tutorials: not much there on Record mode that I could see. I found the WF ref manual at https://reference.digilentinc.com/reference/software/waveforms/waveforms-3/reference-manual and see logging settings on Page 18, and found that under the View menu.... If I set Execute to "Each acquisition" that autosaves whatever is collected every time I press Record and the acquisition completes? If I Stop it early then I have to manually Save Acquisition?

There seems to be only one Source option: a single channel? Can I record two channels at the same time? I don't see how to do that... I need to capture the signal on each rail if possible.

There is a little "Buffers" tab at the top left but nothing to view or change... I'll keep experimenting here but that's not always the best way to get to an optimal solution.

Ultimately I would like to have a Raspberry Pi 3B+ connected and logging, maybe for months or until a large SD card fills up. But in another forum area I see that doesn't work due to USB data problems from the AD2 to the RPi. Urk. I just posted there asking if any new progress on this.

Do I have the right tool for the job here? I did read the specs before I ordered.

Thanks

Bruce

[attila]

Hi @Bruce Boyes

You can set the trigger to Normal and select a source that won't be triggered like Manual. In this case the stop button will stop the capture or use External trigger to trigger, to stop.

The Logging in "each acquisition" mode is executed event when you Stop the capture.

Under Logging/Export/Source you have the same options-source as under File/Export. The Oscilloscope or Acquisition source saves data from all the enabled channels.

The Buffers store the last 10 captures, by default. The interested ones can be saved in tabs.

Use the Help tab of the application (or Help/Browse ) which is the latest version of doc, corresponding to the software version.

[Bruce Boyes]

Thanks, I have this working on a test signal, automatically logging each triggered acquisition to a file, auto-incrementing the filename, etc. I'm running both in Windows10 and Ubuntu 18.04. I'm using the online documentation which is mostly pretty good. Reading the design note about the AD2, it's a pretty amazing product. Am looking at buying another to sample electrical and magnetic fields, synching them all to a common trigger event, if I can figure out how to do that. Will be posting some new questions about all that... thanks for the support.