Any NMEA 2000 certified device must go through a stringent certification process before being given the badge of ‘NMEA 2000 certified’, where both hardware and software are tested to check a variety of parameters, from Power through to CAN interfacing. Although the price tag on an uncertified device may look appealing, here are the reasons why you should always use NMEA 2000 certified devices in your boat network.
“The National Marine Electronics Association provides a self-certification tool to aid manufacturers in testing their product(s) during development and prior to final release. The NMEA requires that any device providing a NMEA 2000® interface must pass the self-certification test before that product may claim that it offers NMEA 2000®. This is to ensure that all NMEA 2000® based devices implement the network protocols properly. This testing also ensures that the automatic self-configuring capabilities defined by the NMEA 2000® standard are properly implemented and do not for any reason, cause or generate problems for other equipment on the network. The testing is designed to expose any flaws or weaknesses in the NMEA 2000® protocol implementation and ensure that all devices from all manufacturers behave in a known and predictable manner on the network. This testing does not validate the data or measurements provided by a device, only how it interacts on the network.”
The most important point to highlight is that if the device has NOT been put through the certification tool and signed off by the NMEA, then it cannot be marketed as NMEA 2000 Certified. The number of products that fall into this category seems to have grown dramatically over the last few years, attracting a number of buyers as these products are typically cheaper.
Devices that have not been tested and certified can suffer from interoperability problems with the NMEA 2000 network. These can come in different ways, such as source address conflicts and power issues. As NMEA 2000 is a CAN BUS network, it is essential that all devices communicate with one another correctly to avoid conflicts and data issues.
With non-certified devices on the network, it isn’t just those ones that will suffer, they also affect certified devices as well… For example;
Our NGT-1 NMEA 2000 Gateway is a high-priority device that will claim a low source address on the network. Once the device has performed all of the necessary address and interfacing processes, it will operate as expected as an NMEA 2000 to PC Gateway.
If a device is introduced onto the network that does not follow the address claim procedure and always goes for the highest priority address, it may conflict with the NGT-1. At best this will result in temporary data loss from the NGT-1, however, the more likely outcome is that the other device continues to interfere, resulting in the NGT-1 not operating.
Another common scenario with un-tested and certified devices is the amount of power they pull from the network. All NMEA 2000 certified devices are required to operate on 9-16V, with most being designed with a 12V network supply in mind.
There are certain regulations that an NMEA 2000 must conform to with current pull and how much current it draws from a network. If too much is required by the device then an independent power supply is required. Using devices that aren’t tested for this can result in too much power being drawn from your NMEA 2000 network, causing the devices nearer the extremities of the network to often switch off or be intermittent.
In summary, the user cannot be sure that an uncertified product will behave safely and correctly on an NMEA 2000 network. If you aren’t certain about whether a device is certified, there is a full list of certified devices listed on the NMEA’s website.
