Using Digital Output or +5 Volt Lines on the NI 6514/6515

Updated Aug 13, 2019

Reported In


  • PXI-6515
  • PXI-6514
  • PCI-6514/6515

Issue Details

I am using either the +5 Volt line or Digital output lines on my NI 6514/6515 to perform a digital output task. I'm not seeing any response when measuring the terminals though. Why is this happening, do I need to provide an external power supply?


Yes, according to page 3-3 of the 651X manual, you need to provide a +5V - +30V power supply to the card in order to use the 5 volt lines, or perform digital outputs.
"The output lines on the NI 6515 consist of photocouplers and Darlington
arrays. To connect to these signals, connect a 5 V to 30 V power supply to
COM, connect GND to ground, and cross a load between digital output
and COM."
Schematic drawings on how to provide this external power supply can be found below (sourced from page 4-6 of user manual).

Additional Information

The 651X family uses 24V logic. This means a low signal will output 0V-4V, while the high signal will output 11V - 30V. 


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