Hello,
The user manual for the cDAQ-9185/9189 Chassis says on page 10 that "the C terminal is not connected to chassis ground," referring to the power supply connector for the chassis. This same sentence is included in other documents for the chassis as well. We did a resistance measurement on the C pin and we found that this sentence is incorrect; the C pin is shorted to the chassis ground screw (at 0.2 ohms). We did this measurement on multiple chassis of both the 9185 and 9184 varieties. We even removed the PCB from one of the chassis and the C pin was still shorted to chassis ground. Whether intentional or not, it seems like this connection is present, making the user manual and other documentation incorrect. We did base our design on the fact that the C terminal is isolated from the chassis ground, and now we'll need to do some redesign. Just want to point this out to others to prevent inadvertent grounding in future designs.
Can NI confirm that the C pin is connected to Chassis Ground and can NI update the documentation?
Thanks,
Gabe