Labview chart with long history buffer

[sean m]

Hi All,

My next GUI has a requirement that we be able to display present measurements in a strip chart, and be able to scroll back and view many days worth of history.  I will be logging values to the database using Labview DSC.  Does anyone know if the standard Labview components are capable of scrolling back to display values from days ago?  Also I may need interactive zooming.

Thanks,

Sean

[Harold_Timmis]

you can right click the chart and make the scroll bar visible whether it goes for days or not I do not know.

[Joseph_Loo]

I depends on how big your buffer. I have one that goes back at least 10 days with the data being updated every minute.

[DianeS]

To set the buffer size for your chart, right-click on the chart and select "Chart history length...".  The default is set to 1024 points.  I don't know the maximum number of points the chart buffer will hold, but I'm sure someone does and hopefully he/she will share that information with us!

For the interactive zooming, you can use property nodes to do that.  (specifically, the X-scale max and min property nodes...I believe you will need to uncheck "Autoscale X", otherwise the chart will just autoscale again when you write your next data point to it)  There are undoubtedly other ways as well.

[DianeS]

Such as -- duh -- the "zoom" function on the graph palette.  You'll need to uncheck "Autoscale" for it to work, though.  There's a lot more information in the LabVIEW help, I suggest you start there.

Also, keep in mind that if you make your chart history very long, it will be a memory hog.

[A_Person]

The maximum value you can set for the chart history length is 2,147,483,647.   I would calculate the number of points you actually need to hold rather than trying to use any kind of maximum because of memory requirements as mentioned above.

[data logging]

i am using labview 2010. it automatically store values about 1024... waht is the max size in it

[RavensFan]

As big of a number you can fit in there without the program crashing.

There may be an ultimate limit of something like 2^31 or 2^32.  But, the RAM limits on your PC would probably put it much much lower than that.

[Beck45]

I find that when using very large Chart History Length, it starts slowing down the rest of the application.  I think I tried 70,000 or so and the slowdown started before that was full, however I have ~16 plots on one chart too.  I'm not sure why simply shifting a large number of data points is very CPU-intensive, but if it really has to be, then it's time LV starts using GPU acceleration! 

[data logging]

i am taking data from data acquistion card PCI-6025E .. that data acquistion takes about seven hours and i am logging data after every second... can you suggest me a number to allocate to its size