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How do I Access Internal Channels on my DAQ Device using DAQmx?



Primary Software:
Primary Software Version: 1.0
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
How do I access the internal channels for my DAQ device using the DAQmx API?

Solution:
By default, DAQmx Physical Channel controls and constants filter out internal channels for DAQ devices, as well as things like invalid I/O types. Channels labeled "internal" are typically used for self-diagnostics and self-calibration, and thus are hidden by default to avoid overcomplicating DAQmx configuration for newer programmers and end-users.

Note: A list of internal channels for your device can be found in DAQmx Help: Internal Channels. Also note that for S Series devices, there are additional steps necessary to correctly access internal channels, which are listed in the DAQmx Help documentation mentioned above.

To view these hidden channels, you'll need to modify the default I/O Name Filtering options for that particular control or constant. Complete the following steps to Enable Internal Channels:

LabVIEW
LabWindows/CVI
.NET API

LabVIEW:
  1. Right-click the DAQmx Physical Channel control or constant on the front panel or block diagram and select I/O Name Filtering from the dropdown menu.
     
  2. Check the Internal Channels checkbox in the Filter Names dialog.

  3. Internal channels should now be listed in the Physical Channel dropdown menu.
Note: In addition to showing internal channels, you can also customize things such as I/O Type and even limit the options to a particular device to prevent users from inputting invalid channels for a control.

Note: The default filtering for a physical channel control or constant is determined when that control or constant is created. If the control or constant is copied from an existing control or constant, it will inherit the properties of the original control or constant. This includes constants or controls created by right-clicking on the input terminals of a DAQmx VI.

LabWindows/CVI:

  1. In a source (.c) file, type a DAQmx function and then right-click on the text, and select Recall Function Panel.

     
  2. In the function panel, click the ”…” button next to the text box beneath Physical Channel, and select Filter…

  3. In the Filter Settings dialog that pops up, select Internal Channels and click OK.

  4. Internal channels should now be listed in the Physical Channel dropdown menu.


.NET API:

In the .NET API, you are required to specify the access level of the GetPhysicalChannels method during configuration of the method. Specify Internal or All instead of External, and you will see the additional channels. See the example below:

DaqSystem.Local.GetPhysicalChannels(PhysicalChannelTypes.AI, PhysicalChannelAccess.Internal)


Related Links:
KnowledgeBase KB 35TGB1VM: NI-DAQmx Internal Channels for Self-Diagnostics and Self-Calibration
KnowledgeBase KB 3G0G2IZH: Enabling the Advanced Channels on a DAQmx Terminal Control/Constant
KnowledgeBase KB 533A1Q9N: Can I Create a Global Virtual Channel Out of an Internal NI-DAQmx Channel?
White Paper: Learn 10 Functions in NI-DAQmx and Handle 80 Percent of Your Data Acquisition Applications
KnowledgeBase KB 25S9MQED: Archived: Using Internal Analog Input Channels in Traditional NI-DAQ (Legacy)

Attachments:





Report Date: 02/04/2010
Last Updated: 01/25/2017
Document ID: 563B1D3A

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