DAQ Time Chart

[AeroDesign]

Using LabView 7.0 and DAQ card 6062E, when I run my .vi to acquire and chart data, the time scale on the chart,which is set at min of 0 and a max of 3 min. changes to values that are not in that range. I get: 878276:14:14.60, for example at the beginning and end of the scale. What can I do to correct this?

[Shea C]

Hello AeroDesign,

Thank you for your question regarding waveform charts.
You mentioned that you were acquiring data to be plotted in a chart from time 0 to 3 min. One possible solution may be to set the chart to update in relative time. To do this right-click the chart, go to properties, click on the Format and Precision tab. With the x-axis selected choose Relative Time. Also make sure that AutoScale x is disabled by right clicking the x-axis on the chart and unchecking this feature. In some circumstances a waveform graph placed in a loop might be more appropriate. It�s hard to tell without knowing exactly what your application is or without seeing some simple code. An example of using a waveform graph called Cont Acq&Graph Voltage-Ext Clk.vi can be found in the
shipping examples of LabVIEW 7. The following links also provide some information on this issue.

http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RNAME=ViewQuestion&HOID=5065000000080000008C7D0000&ECategory=LabVIEW.LabVIEW+General

http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RNAME=ViewQuestion&HOID=506500000008000000617B0000&ECategory=LabVIEW.LabVIEW+General

Other resources can be found on the ni.com website by clicking the support tab at the top of the home page. Then search from Technical Resources at the top of the page for your topic. I hope these resources help! Let me know if you need any other support with this issue.

Shea C.
Applications Engineering

[AeroDesign]

"Auto Scale X" is unchecked and "Relative Time" is selected im my program. I'll attach the file. Thanks for your help.

[Shea C]

Hello AeroDesign,

Sorry for the delayed response. I had to refresh my memory on some of the data types you were using. The problem that you are having is becasue the data comming from the AI Read.vi is waveform data and has a system time attached to each data point. You can strip the data points of this system time by using the Convert from Dynamic Data function and selecting 1D array of scalars from the pop-up window. This will create an array of your data that will display on the chart without reverting the x-scale to system time. I hope this helps you out! Let me know how this works. You can find this function by searching in the functions palette for Dynamic Data.

Regards,

Shea C.
Applications Engineering