Looking in the manual on page 40, this should be a self-resetting fuse. Are you measuring on the pins of the 6602 or are you going through a breakout? Make sure you reference the 5V signal to DGND.
Additional information on the fuse, found here.
If that's not the case I would recommend calling NI and talking to them about a repair on the board. If you would rather replace it yourself you will have to ask for the PN for the fuse, as it doesn't seem to be listed online. If you do opt to send a damaged board (if it is damaged) to NI the instructions are here.
Aaron W.
National Instruments
CLA, CTA and CPI