Waveform Chart or Graph from Dynamic Data Not Updating (Timestamp issues?)

[wdenny3885]

I am still a noob, and banging my head against the wall here. I am pretty sure I have timestamp issues, but have not been able to figure this out, and it seems so simple.

High Level Goal

• I am collecting a numeric value from a VISA command in a loop. (I.e.  1.9) (complete)
• Log it to a file, with a timestamp (I.e. - 1/1/1999 12:12:12:12  - 1.9 ) (complete)
• Graph it on a chart while it's looping and collecting. (can't get it to work).

A sample view of what is going on. Yes, someone is going to say "post the VI" but there is a ton of other stuff in there with the hardware connectors,  so I am not sure if it would even run w/o all the connection.  I wasn't sure it would be helpful for this specific issue.

What is happening:

• The waveform chart (or graph) moves as if the magnitude is updating, but never plots. The time stays at 0 plus or minus a few seconds. (pictured below)
• Using a probe on the dynamic data, one of two things happens. 
  • The t0 in the waveform always updates to the current timestamp, and dt stays at 1
  • the t0 in the waveform stays at 0, and the dt stays at 1.
• This makes it look like In the loop, it is always sending the "first" point, and updating as such. I have tried everything I can think of short of manipulating the waveform data points in the loop w/ "Update Waveform" VI.
• Note: There are two shown here to illustrate the two changes I have found, there are ultimately 4 signals i want to plot, but assuming the same issue will fix them all.

Issue 1 - probe display and Set Dynamic Data Attributes Config

Or Issue 2 - Probe display and Set Dynamic Data Attributes Config

[altenbach]

Your graph seem to only have one point, so make sure to use a plot style with points and not just connecting lines.

I cannot see the chart you mentioned.

Are the points spaced equally in time?

(We don't debug images with express VIs and dynamic data because there is no way to tell what inside them)

[wdenny3885]

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@altenbach wrote:

Your graph seem to only have one point, so make sure o use a plot style with points and not just connecting lines.

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Yes, I can see that, I actually turned that on so that I could verify the probe data was making into the Waveform VI. It is just graphing 1 point over and over again. I am trying to see why, and wondering if it is a timestamp issue.

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(We don't debug images with express VIs and dynamic data because there is no way to tell what inside them)

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Thanks, I knew that was coming. I actually said it at the top, so thanks for reading that. As soon as I post that, the next comment will be "hey, that is too new of a version, post another on a compatible version" and so on. I was looking for actual conceptual ideas and feedback on things to try. I did post what is inside them, that is what the configuration screenshots were for.

[altenbach]

So try this:

replace the graph with a chart (do you know the difference?) and wire it to the same wire as the "measure 1" indicator. I am not sure what units you want as time axis, but you can set t0 and dt at the start of the program.

[wdenny3885]

Yes, setting that up as a chart, from the DBL indicator works. Pictures below.

   

The issue I had with this, (and why I tried to move to the dynamic data, was that I could not get the chart to "accumulate" data for a period, and then move. These are long running experiments, so a rolling minute of data isn't helpful, but a 3 inch chart with 5 hours in itis unreadable. I was hoping to "accumulate" about an hour, and then start rolling. That would be the X axis would not from from 9AM to 10AM in data collection, then start scrolling along as new data came in at 10:00:01. I couldn't get a chart do do this. (yes I used chart history data point length). But the start and end times don't match up with reality and I couldn't make that work? No matter what i put in number of points, the times are not correct on the x axis.

Example: this is 5000 points saved, at 10:30 in the morning, on a 500 ms loop. (not only is it not 6pm, this suggests 1M 40S of data, about 200 points before it starts scrolling)

[altenbach]

You can do a ptbypt n point average and only update the chart every n'th iteration.