NMEA2000 digital network explained simply...
NMEA 2000 is a communications standard that allows certified devices to talk to each other using a single multi-directional, multi-lane cable.
Each onboard device can communicate with up to 50 other devices.
All devices are connected into a backbone cable with various connectors such as T-connectors and drop cables. This is not only very simple to install but also eliminates long cable runs and bundles of wires.
To add a new device you simply connect it to the backbone and it will start communicating with the other NMEA 2000 devices.
Existing sensors can be added to the NMEA 2000 network using an analogue to digital convertor.
The products that meet the NMEA 2000 standard are connected via drop cables to one central cable, known as a backbone cable. The backbone powers each instrument and relays data among all of the instruments on the network. This allows one display unit to show many different types of information. It also allows the instruments to work together, since they share data.
On the backbone cable, one or more power cables supplying the NMEA-2000 devices are connected. Where the power cable is installed depends on the number of devices to be powered and where these are located in the network. To connect a NMEA 2000 device, a drop cable is connected from the device to a T-connector attached to the backbone cable. In order for the network to function properly, there must be a terminator at each end of the backbone cable.
Wema are using micro cables and connector which allows a maximum of 100 meters backbone cable and a total maximum of 72 meters drop cables. Each drop cable can be up to 6 meters long. In a NMEA2000 network there can be up to 50 devices connected.
Communication runs at 250 kilobits-per-second and allows any sensor to talk to any display unit or other device compatible with NMEA 2000 protocols.
Electrically, NMEA 2000 is compatible with the Controller Area Network (CAN Bus) used on road vehicles and fuel engines.
The higher-level protocol format is based on SAE J1939, with specific messages for the marine environment.
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