Voltage Drop in PXI Digital Pattern Instrument Loopback Test

Updated May 8, 2024

Reported In

Hardware

  • PXI Digital Pattern Instrument
  • PXIe-6570
  • PXIe-6571
  • Astronics PXIe-6943

Issue Details

I am using Digital Pattern Editor software to generate a pattern of 3.3 V through pin1. The digital pattern is looping back to the pin2, measuring with the Digital Oscilloscope in Digital Pattern Editor. My digital pattern is as follows: 
2024-04-30_14h29_34.png

However, I observe a voltage drop of around 1.4V in my input channel.
Digiscope with loopback (1).png

What is the possible root cause for the voltage drop?
 
 
 

Solution

For non-drive pins, you should assign the pin state data as L or H (which indicating Compare low and Compare high.) instead of 0 and 1 (which indicating Drive zero and Drive one).

If the pin1 is generating digital pattern and pin2 is reading the pattern, you should set the pin state data as follows:
2024-04-30_14h31_28.png

You should also ensure that you are using High Z as termination mode.
Digilevel with High Z termination mode 1.png
 
 

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