NI USB-8502 Loses Connection Randomly

Issue Details

I am using NI XNET database editor with NI USB-8502 and want to read data from a CAN Bus device. System cables are twisted pair type and buses are terminated on each end with 120 Ohm resistors. Everything should work properly but my NI USB-8502 loses connection with the computer thus making me unable to continue the testing.
What can be the reason for this issue? How can I fix it?

Solution

The NI USB-8502 High-Speed/FD, USB CAN Interface Device is powered over the USB bus and there is no need to use an external power source. But the Windows power-saving options can occur to a loss of connection with the device as it needs more power than the USB output of the PC can provide in the power-saving mode. If there is a problem with the PC you can try using a USB hub with an external power supply in order to provide the device with the needed energy.
Another possible source of this issue can be the improper grounding of the DUT (Device Under Test). The ground of the DUT must be the same as the main computer and the measuring device. In case you are testing high voltage supplied DUTs (for example a component from a car that uses 12V), you have to isolate everything from the test system using a UPS and check for safe electrical grounding before starting the test.

When you use third-party devices or DUTs it is recommended to use NI CAN Breakout Box as a connector. It can provide the NI USB-8502 with the needed power and can prevent reverse voltage flow.