The shield / drain wire is connected to the NMEA 2000 network common reference ground at only one power supply location.

• A. True
• B. False
• C. Not specified
• D. Always connected to ground at every device

Answer: (A)

Shielding a NMEA 2000 CAN network is most effective when the shield is tied to the network's reference ground at a single point. The shield and its drain wire provide a controlled path for EMI to escape, but if you connect the shield to ground at many locations, you can create ground loops that pick up and inject noise into the CAN signals. Since all devices on an NMEA 2000 network share one common reference ground, bonding the shield to that ground at only one power-supply location keeps the ground potential consistent across the whole network and minimizes unwanted currents through the shield. In practice, the drain wire grounds the shield to the network ground at that single point, typically at the power supply or a designated ground point, ensuring effective shielding without introducing ground-loop noise.