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What Is a Virtual Channel and How Do I Create One?



Hardware: PXI/CompactPCI>>Controllers

Problem:
I am performing data acquisition and need to create a virtual channel. How can this be accomplished and what is the purpose of a virtual channel?

Solution:
Virtual channels allow you to configure data acquisition settings and use them in multiple VIs.  This saves you from doing the setup multiple times in the different VIs.  In the virtual channel you can define the scaling or conversion to do to your signal.  For example, a data acquisition (DAQ) board connected to a thermocouple will acquire data as a voltage. However, this voltage actually corresponds to a real-world temperature value, which would normally require you to add a separate conversion routine to your VI. You can use your existing data acquisition program to measure temperature using the virtual channels with no modification to the program.

You create virtual channels by using the DAQ Channel Wizard (see the related links, below). NI-DAQmx 7.4 or higher, and Traditional NI-DAQ 6.5 (Legacy) or higher use Measurement & Automation Explorer (MAX) to create virtual channels. Traditional NI-DAQ 6.1 (Legacy) or earlier uses the Traditional NI-DAQ (Legacy) Configuration Utility instead of MAX. The functionality is the same in the Traditional NI-DAQ (Legacy) Configuration Utility, but the interface has a different look and feel.

In MAX you can right-click on Data Neighborhood and select Create New.

 
 
Then, select NI-DAQmx Global Virtual Channel and click Next.

 
Follow the rest of the wizard to create the virtual channel. Once created, it will appear in MAX under Data Neighborhood»NI-DAQmx Global Virtual Channels. You can drag the virtual channel onto a LabVIEW block diagram to use it in your VI. 

Note: Not all DAQ hardware supports the use of virtual channels, so refer to KnowledgeBase 1A4DD2Z1 (linked below) for device-specific information regarding virtual channels.


Related Links:
KnowledgeBase 1A4DD2Z1: What DAQ Hardware Is Supported by the DAQ Channel Wizard?
KnowledgeBase 10OA65BB: DAQ Channel Wizard FAQ 

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Report Date: 10/27/2000
Last Updated: 01/30/2017
Document ID: 22QD2THE

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