How can I modify the High Speed Data Reader VI to show correct time information in x-axis?

[Chunrok]

I am just a beginner learning the LabVIEW programming currently.
I have a PXI 6115 DAQ card and have to make a hardware timed acquisition VI for maximum performance. Thus I use the High Speed Data Logger VI for data acquisition.
However, when I read my data by using the High Speed Data Reader VI, it doesn't show its correct time information in the graph.
How can I modify the High Speed Data Reader VI to show correct time information in x-axis?
I hope you can explain easily because I am a beginner.

[SarahM]

Hey Chunrok,

I've modified the High Speed Data Reader VI slightly so that it now uses the scan rate of the data (as determined from the file) to set the scaling for the data points. If you wanted the start time to be a specific time you could use the start time obtained from your file to set the xscale offset as well.

I hope this helps!

Sarah Miracle
National Instruments

[Chunrok]

Thanks much, Sarah!
In fact, I found some answer by myself some time ago.
Basically, your example also works fine. However, it doesn't show the whole data in x-axis when the data measured with high scan rate. It shows somehow about 1024 points of the data at maximum.
What is wrong with this? Could you let me know how to fix this up?

[SarahM]

Hey Chunrok,

I think what is happening is that the chart history is too short. If you right click on the chart and select Chart History Length you'll see that it's set to 1023. This means that the chart only retains the last 1023 points that were charted. Increase this number to however many points you want the chart to retain.

I hope this helps!

Sarah Miracle
National Instruments

[Chunrok]

Hi, Sarah!
I know in LabVIEW Help says "The number of data points in chart history buffer must be between 10 and 2,147,483,647. The default is 1,024."
However, it isn't working even though I change it to some 10,000 or more. It looks like my chart remembers somehow only 1,024 points. Why?
Thanks anyway for you help. Have a great day, Sarah!

[SarahM]

Hey Chunrok,

I'm not exactly sure what's happening with your chart. I set my chart history to 10,000 and I see as many points as I read in. If you're using the High Speed Data Reader example I would try changing the block size to read in more than 1,024 points. You may also want to try changing the x-axis to auto scale or manually changing the minimum and maximum to make sure you're viewing all the data.

I hope this helps!

Sarah Miracle
National Instruments