APP007.TXT  TestPoint Application Note


APP007.TST  Associated Source File 


(c) Capital Equipment Corporation 1995





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Extracting Data From Lists


Examples include multiple A/D channels and instrument data.


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Whenever TestPoint returns a list of data, you typically want to 


get at the individual items that make up that list.  How  do you 


know when you have a list of data?  The easiest way to determine 


what type of data TestPoint is providing is to click on View > Data 


in the main menu. The name of the data type followed by the data 


values will then be displayed next to the object when the 


application runs. 





A common example occurs when sampling multiple A/D channels. 


TestPoint will return each channel as part of a list.  To 


separate that list into its component channels,  double click on 


the A/D reference in the center column of the action list.  This 


opens up the data reference dialog box for the A/D object.  Click 


on the data type drop-down list and select LIST as the data 


type, then click on ADD.  Provide a name for the first channel 


and continue to click on ADD until all channels have been named.   


Click on OK to close the data reference dialog box.  Drag in a 


display and then drag the A/D object to the display.  Double 


click on the A/D parameter in the display action line.  This will 


open up the data reference dialog box.  Click on the A/D channel 


you want to display ( a small arrow will appear on the line 


youâve selected) and then click on select.  The single 


A/D channel will now be selected and displayed.  This is much 


easier to do than it is to describe.  Try it once on A/D demo 


data with multiple channels selected as shown in the 


accompanying TestPoint listing. 





The same technique can be used for instrument data.  Data from an 


instrument  is often returned in the form of a complex header 


followed by the data of interest.  TestPoint lets you pick apart the 


header simply by naming each of its components. 





The same process is shown using the math object sublist function.  


This method may be preferable, even though it uses more objects, 


since it will return a correct result even if the returned value is a 


vector rather than a list.