Gaps in Sweep Chart

[AstroMed_Glen]

Hello,

I am capturing multiple channels of data and displaying them to the screen via sweep chart. The chart takes in an average of 20 new samples (per channel) per update/iteration. The problem that I am having is the that the sweep chart sometimes shows gaps inbetween chuncks of new data, like it does not always connect the new dots. The other types of charts (scroll and scope) do not have this problem. Just the sweep. Is there some work around that anybody knows about? I attached a picture for visual reference.

Thanks,
Glen

[mhaag]

Glen -

Thank you for contacting National Instruments. It sounds like the issue may deal with the resolution/size of the chart and the fact that the sweep chart has the vertical bar scrolling across. From the image you attached, it looks like the sweeping vertical bar may be causing certain points in the chart GUI to be cleared out.

What version of LabVIEW are you running this on? If you use the zoom features of the chart, can you see the portions of the plot that appear to be missing in your default view? Try this, and if the areas are indeed there, then you may look into resizing the chart or changing the scale to see if that helps correct the problem. Also, if you reduce the rate and number of points you are updating onto the chart, does that seem to mak
e a difference?

In LabVIEW there is a charts.vi shipping example. Do you see the artifact on the sweep charts in that example? I did not see the result in any of the tests I ran.

Let us know what else you see and if any of the above suggestions and questions provide any more insight into what might be happening.

Regards,
Michael Haag
Applications Engineer
National Instruments

[AstroMed_Glen]

Michael,

Thanks for your comments. I am running LV 6.1. Yes, I do believe that the data will look correct when the chart is resized or zoomed in on. I beleive all the data is there in the plot array. No NaN's or zeros in the array or anything like that.
I could not detect any discontinuities in the charts.vi. That runs normally.
If ths is a problem that is inherit in a sweep chart then I would somehow like to make my own, perhaps by overlaying two scope charts or something creative like that. Any ideas?

Thanks,
Glen

[AstroMed_Glen]

Also, data is acquired in a loop with a "wait till next ms" set to 100. If I bump this up to 500 ms I do get 5 times fewer gaps but my scroll bar takes a 5 times bigger step. This is not the look I am going for. I'd like a fast sweep step, as if it is an analog viewer.
If the wait is removed, I get something that is less that 100 ms, has a very small step, but has lots of gaps and discontinuities.

[AstroMed_Glen]

Can I make the red update bar turn off? Perhaps the chart would not be so confused as what to display underneath it after it passes. I looked for this property node but could be find the option.