graph or chart with time date

[johnnyt]

I just can't seem to figure out how to graph current time and date on the x axis.  I'll be getting data from a serial port and parsing out to an array for logging.  Attached you will see a simple example in Labview 8.  I tried the property nodes but could not get the year past 1904.  Any help would be appreciated.  Thanks Much.

[Dennis_Knutson]

It would have been nice if you had attached the code with the property nodes to see what you were doing wrong.

There's a very old example that explains what you should be doing. Look up Real-Time Chart.

[johnnyt]

Hi Dennis,

Attached is how I was doing the property node.  Notice time is correct, but I just can't get the date and year.  Thanks.

[Dennis_Knutson]

Sorry, I didn't notice that you also wanted the date. You've have to enable absolute time I believe. The easiest way may be to create a waveform data type with the build Waveform function and wire the waveform to the chart.

[johnnyt]

"build Waveform function "

I tried that too, it only works with a single plot, not four, as in my example.  I have a feeling that Labview simply can't do what I want it to do: plot four sets of data on one chart with real date and time.   I've been working on this for almost two days now and I see no solution in site.

[Dennis_Knutson · Accepted solution]

Sure it can do it. You need to build the correct data type for the chart, of course.

Try this.

[johnnyt]

Thanks, Dennis, that did the trick!

[johnjt]

Hello Again,

I realize this is an old thread, but just recently I found that the technique we settled on to display time/date is causing a memory leak in my Labview application.  It just reared it's ugly head recently, and it takes weeks to show up.  I discovered with the help of Labview's VI analyzer that the build arrays were the culprit.  If I take them out of our example, then I will not be able to build the waveform.  So I am now, still looking for a solution to the original problem of getting the DATE into my graph.

To see the memory leak manifest itself, change the time of the loop to 1 millisecond or look at my attached examples.

[johnjt]

attached is a LV version 8.0

[Dennis_Knutson]

Yes, using the build array will cause memory problems if used for a long enough time. It's not at all a memory leak. You would need to implement a buffer to keep the arrays from growing past a certain size. There is an example called XY Chart.