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How to Display SignalExpress Data with History

Primary Software: LabVIEW Signal Express>>Development System
Primary Software Version: N/A
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
Data from a multipoint acquisition is displayed without a history in LabVIEW SignalExpress. How can the history of the acquisition be displayed instead?

Solution:
There are two general types of displays in the LabVIEW environment: Graphs and Charts. Every time data is sent to a Graph, the Graph erases its history and overwrites it with the new data (see Note below).  When data is sent to a Chart, the Chart appends the new data to the old, and it removes as much old data as necessary to accommodate the new.

The Chart display is not a feature of SignalExpress 1.x, but you can achieve its behavior by creating a user-defined step. Inside the step, store the data in an uninitialized shift register from previous runs. (See the attached SignalExpress project for an example.)

LabVIEW SignalExpress 2.0 takes many considerations into account when displaying data. To conserve memory utilization and make sure that the display can keep up with the acquisition, the program displays single-point updates with a chart and multi-point updates with a graph. So if you run your DAQmx acquisition in Continuous Samples or N Samples acquisition modes, it will display the data updates with a graph. If you run in 1 Sample (On Demand) mode, the data is displayed on a chart.

You can adjust the length of the chart's history (in number of samples). From the menu bar, select Tools»Options.... The dialog box below will appear. Under the Data View category, change the Chart History Length.



Note: When writing one value at a time to the display, the chart history length setting applies for the XY Graph as well as the Waveform Chart.


Related Links: KnowledgeBase 4GHB0B2Z: How can I create an X-Y plot in Signal Express?
Example Code: User Defined Step to Create XY Graph in SignalExpress
Product Manuals: Display Formats - LabVIEW SignalExpress Help

Attachments:


cont acq and chart.zip - cont acq and chart.zip

Report Date: 02/08/2007
Last Updated: 10/31/2008
Document ID: 467BQDSF

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