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Archived: Using Internal Analog Input Channels in Traditional NI-DAQ (Legacy)

This document has been archived and is no longer updated by National Instruments

Note: This page is about NI-DAQ also known as Traditional NI-DAQ (Legacy). NI-DAQmx replaced Traditional NI-DAQ (Legacy) in 2003. NI strongly recommends using NI-DAQmx for new designs and migrating existing Traditional NI-DAQ (Legacy) applications to NI-DAQmx. Please review the Getting Started with NI-DAQmx guide for more information on migration.

Hardware: Multifunction DAQ (MIO)

I would like to test my E Series Multifunction (MIO) data acquisition device to verify that the analog outputs and analog inputs are working. Are there any special Virtual Channels I could use for diagnostics?

I would like to monitor the voltage at the analog output pins (DAC0OUT, DAC1OUT) of my E Series data acquisition device. Can I internally acquire the analog output voltage without external wiring?

This KnowledgeBase describes the use of internal analog input channels in Traditional NI-DAQ (Legacy). These special channels require no external connections and provide an easy way to test the analog inputs and outputs of an E Series measurement device. They can also be used to monitor analog output voltage without the need to wire the output back to an input pin.

Note: For information on performing this type of operation in NI-DAQmx please refer to KnowledgeBase 3L9G7246: Read the Value of Analog or Digital Output Channels.

There are several internal analog input Virtual Channels that can be used to run diagnostics on the analog output and analog input capabilities of any E Series multifunction (MIO) measurement device. They are also useful as a means to acquire the voltage at the analog outputs without using any analog inputs.

Internal analog input channels are routed using an internal switching matrix, so no wiring or cabling is required. The table below lists the most commonly used internal analog input channels. Not all devices support these internal analog inputs. For a more detailed list of the channels your device supports, see the Hardware Capabilities section of the LabVIEW Help file. If you are programming with NI-DAQ function calls, refer to the DAQ Device Internal Analog Input Channels section of the NI-DAQ Help file.

Virtual Channel Strings NI-DAQ Constants Numeric Channels Description
_AO0vsAOGnd ND_INT_AO_CH_0 21230 Internally routes Analog Output Channel 0 to the Analog to Digital Converter
_AO1vsAOGnd ND_INT_AO_CH_1 21240 Internally routes Analog Output Channel 1 the Analog to Digital Converter
_AIGnd ND_INT_AI_GND 21210 Internally routes Analog Input Ground to the Analog to Digital Converter
_Ref5V ND_INT_REF_5V 21290 Internally routes Analog Input 5 Volt Reference to the Analog to Digital Converter

Note: When programming with NI-DAQ function calls, you should use the NI-DAQ Constants in your programs; do not use the Numeric Channels. These constants are defined in the NI-DAQ constants include file (

Analog Input/Output Self-Diagnostics Example

Because no external connections are required, internal analog inputs provide a convenient means to verify the operation of your E Series measurement device. In this example, we test a PCI-MIO-16E-1 device by generating a sine wave on the analog output and then use an internal analog input to verify the sine wave.
  1. Launch the Measurement & Automation Explorer (MAX). Double-click the Device and Interfaces heading to display all National Instruments devices installed in your computer. If you don’t see your device listed, go to the View menu and select Refresh. Right-click on the E Series device you would like to test and select Properties, as shown below.

  2. Next test communication with your device by clicking on the Properties, and then the Test Resources button. If the device is properly installed and registered by the operating system, you should see a message indicating that the device has passed the test. If the device does not pass the resource test, refer to the Hardware Installation/Configuration Troubleshooter for assistance. Click the OK button to close the message box.


  3. Now open the Test Panel by clicking on the Test Panels... button. Click on the Analog Output tab and select Sine Generator as the Output Mode. Click the Start Sine Generator button to start output on analog output channel 0. The analog output controls are grayed out while waveform generation is in progress.

  4. Now that the sine wave is running, you are ready to view it. Click on the Analog Input tab and enter 21230 or _AO0vsAOGnd in the analog input channel control.
  5. Congratulations, you have successfully tested your measurement device using internal analog input channels! To test the other analog output, start sine wave generation on analog output channel 1 and enter 21240 or _AO1vsAOGnd in the analog input channel control.

Related Links:
KnowledgeBase 3L9G7246: Read the Value of Analog or Digital Output Channels
DAQ Support: Online E Series Diagnostic Utility (Legacy)
Data Acquisition Support
KnowledgeBase KB 563B1D3A: How do I Access Internal Channels on my DAQ Device using DAQmx?



Report Date: 01/29/2001
Last Updated: 01/31/2017
Document ID: 25S9MQED

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