When you have finished properly mounting the Single-Board RIO controller in the metal enclosure, you need to consider all the connections you can make to and from the ports on the product.
Connect the power input, as specified in the user manual, to a power supply that provides an adequate level of power line filtering. Power ports may require you to place a ferrite bead (Fair-Rite Type 43 or 44 materials or equivalent) around the power cable close to the chassis to control emissions that could be radiated from an unshielded power cable.
Protective Earth Port and Ground Lug
You do not need to connect the protective earth port or ground lug on the Single-Board RIO controllers for proper operation. However, depending on the application, you may need to connect the protective earth port to the protective earth grounding system of the facility in which you install the product to enhance EMC performance. In addition, connecting this lug to earth ground usually results in less noise on the analog input measurements.
Many Single-Board RIO controllers allow you to add C Series modules to the system. You should connect these ports only to C Series modules. When integrating these modules into the overall system, you should follow the same installation recommendations discussed above for the chassis.
Analog and Digital I/O Headers
You should connect header I/O ports, such as the digital or analog I/O connectors, only to other PCBs within the same enclosure because no EMI protection or filtering is included on these ports. The enclosure can help prevent any undesired emissions from leaving or entering the system through these ports. If, however, you need to connect one or more of these connectors outside the enclosure, be careful to connect these ports first to a connector that supports an overall shield and that is mounted on the enclosure. Then use a shielded cable from the enclosure connector to the outside connection.
With all remaining connectors that must be wired outside the enclosure such as the Ethernet or RS232 connectors, you need to use high-quality, shielded cables to minimize any undesirable interference.
Any custom I/O you add externally to the Single-Board RIO controller should incorporate connectors that include termination for an integral cable shield (for example, coaxial, twinaxial, D-SUB, Ethernet, USB, IEEE 1394, and so on).