cRio ground?

So, today while mapping out the electronics for this years robot, I notice that on the back of the new cRio (4port) is a screw. There wasn’t one on the old cRio (8port). I was wondering is that for grounding the body of the cRio, and if it is for grounding should it be grounded to the frame or to the PDB or if it’s just for mounting?

The cRIO needs to be electrically isolated from the frame. Our old 8-slot had a screw just like it, but you don’t need to use it. Do not connect it to anywhere on the main frame that could conduct electricity through it.

Both Crio types have a chassis that is tied to the negative lead of the battery. Both need to be isolated from the frame to prevent other electrical faults from disturbing the power that keeps the Crio running.

[R38]
All wiring and electrical devices, including all control system components, shall be electrically isolated from the
Robot frame. The Robot frame must not be used to carry electrical current.
The chassis for the cRIO and the supplied KOP camera have grounded enclosures.
Under this rule (and for their protection), it is required that they be electrically isolated
from the Robot frame when installed on the Robot.

Al,

Could you describe how to check that [R38] is being followed?

In a way that even us software guys can understand?

Richard,
Inspectors are trained to look for insulation material around and under the Crio and cameras since these are the two most often used devices with the case tied to power supply. If a team cannot convincingly state that there is insulation or if the inspector sees none, then an inspector should make an ohmmeter/continuity check with the power off. One probe on the frame and the other probe checking to each terminal on the PD. Normal is open or in the meg ohm range. It is possible for there to be electrical leakage but as long as it exceeds 10Kohms there should be no problem.