waveform chart continuous acquitstion x scale display time (s)

[RJP]

Hi,
I am acquiring continous data (Type 1D array of Waveform (DBL) ) from 4 channels from a DAQ (NI 9211) and displaying it on a Waveform  Chart.
I am not being able to display the time in seconds (Starting with 0 and ending whenever the user stops the acquisition) on the X Axis.
Any help would be greatly appeciated.
Thanks you

R

[Brooks_C]

Hello RJP,

You can change the scale of the x-axis by right clicking on your x-axis and selecting formatting.  In the Graph Properties window that pops up you can change the format to either relative time or floating point.  I believe that one of these two will be the one that you want, and if not you can take a look at the others available as well.

Cheers,

[RJP]

Hi,
That doesn't actually resolve my problem because it's not the actual time that I want.
I want to have it start at 0 seconds and so on...

R
LV 8.2

[GerdW]

Hi rjp,

show relative time instead of absolute time in the axis?

[Dennis_Knutson]

Have you looked at the example called Real-Time Chart? To start at 00:00:00, you just have to set the XScale.Offset to 0.

[RJP]

Well. when I run the VI everything looks fine, but whenever I start acquiring data it's as if the time on the x axis is overwriten and shows the actual time instead of starting at 0.
I did set the XScale Offset to 0 but it didn't help.

[Dennis_Knutson]

I don't often work with charts but I seem to remember a problem with waveform data types. With a graph, you can select to ignore timestamp but the chart does not have that option. You can use the Get Waveform Components to just get the Y array and wire that to the chart. Or, use a graph and set the ignore option.

[RJP]

Actually the Chart and the Graph both have the "Ignore Waveform time stamp on x-axes" option.
But after I checked it and then clicked Ok on the Properties window, when I go back to the chart properties the option is always uncheked.
Do you any idea why is this happening? (Both with a chart or a graph)
Thanks

[RJP]

It seems to be a bug in LV 8.2

http://zone.ni.com/devzone/cda/tut/p/id/6210
444876NK " Ignore waveform time stamp on x-axes does not take effect "

Am I right?

[Dennis_Knutson]

I don't have 8.2 to check. with 8.5, it works by just setting using the relative time.