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NMEA Connectors and Wiring Nomenclature

Posted: Wed Nov 15, 2017 10:20 am
by jimh
In NMEA-2000 network construction there are three variants of cable used and two variants of connectors. The terms can become a bit confusing.

CABLE CONDUCTOR GRADES
Three grades of four-conductor shielded cable are used:

LIGHT CABLE used only with MICRO connectors
Data conductors = 24-AWG
Power conductors = 22-AWG
Capacity = 3-Ampere per backbone segment
Maximum length = 100-meters or 328-feet

MID CABLE used with either MICRO or MINI connectors
Data conductors = 20-AWG
Power conductors = 16-AWG
Capacity = 4 or 8-Ampere per backbone segment depending on connector
Maximum length = 200-meters or 656-feet

HEAVY CABLE used only with MINI connector
Data conductors = 18-AWG
Power conductors = 16-AWG
Capacity = up to 8-Ampere per backbone segment
Maximum length = 200-meters or 656-feet

CONNECTORS
Two grades of five-pole connectors are used:

MICRO or DeviceNET MIcro C connector, which can be used with either LIGHT or MID cable

MINI or DeviceNET Mini C connector, which can be used with either MID or HEAVY cable.

APPLICATION GUIDELINES

For small-boat NMEA-2000 networks, where the total length of the backbone will be much less than 328-feet and the number of connected devices will have a total LEN (load equivalent number) of far less than 60, MICRO connectors with LIGHT cable are universally used. Most devices attached to a NMEA-2000 network will have a LEN of 1 or 2. A small network with a few devices might have a LEN total of less than 10. LIGHT cable and MICRO connectors are clearly adequate for such networks.

For more information, review the slides from a presentation by NMEA on this topic. A PDF document that reproduces the slides from a presentation can be downloaded from

https://www.nmea.org/Assets/2012%20ibex%20full%20%20nmea%20installation.pdf