3 common mistakes when installing NMEA devices

Installing new and exciting equipment on A ship should be a stress-free and easy process, but it doesn't always go according to plan. We know that there will always be challenges, changes in scenario and requests, or sometimes things simply won't work as they were intended. Unfortunately, some of the problems we see are due to poor practice and installation and much of this can be avoided.

This article focuses on; Some of the simple mistakes we've seen, the easy to avoid problems and how to make sure everything works as it should. The following points will be covered:

• NMEA 2000 Termination
• NMEA 2000 Network Design and Installation
• NMEA 0183 Cabling

NMEA 2000 Termination

NMEA 2000 is a CAN (Controller Area Network) system, designed to be plug and play with simple and easy way to expand and manipulate the network layout to suit any installation requirements. Although this is done successfully most of the time, there are still some issues that can potentially cause problems.

The most common mistake we see is terminator usage, which whether it is only one present, or having more than two; present. There should only be 2 NMEA 2000 terminators per a network, a placed på either end of the trunk (in line terminators are an exception to this). The terminators act as a resistive load to properly terminate the network and help reduce signal reflections.

Minimum NMEA 2000 Network

A properly terminated network will have a resistance of 60 Ohms on the mains, which can easily be tested with a multimeter. A quick indication of the that something is wrong if the resistance is 120 or 40 ohms. 120 means there is only 1 terminator present and 40 means there are 3. This problem occurs very often when using devices that have internal terminators. These terminators work exactly på the same way as your regular external, and should be treated as such.

NMEA 2000 Network Design and Installation

Considering ; how flexible CAN is by nature, it is quite possible that a NMEA 2000 network can be installed incorrectly, for example with the wrong topology, and it will still work correctly under current conditions the rhåland. However, this is not good practice and can lead to problems over time, especially if the network drops out.

Some methods such as daisy-chaining devices or running a 4- the drop off of a 4-way drop is not ideal for Something like this, but chances are that if the network is not excessively busy, all devices will appear to be working and transferring data as they should. However, these can create "bus network" style, rather the typical bus network found in NMEA 2000 installations.

When the number of devices in nä network, you may experience things like data loss and corrupt data, along with devices starting to disappear from the network.

There are also; the other problem caused by having a "wrong" network topology, which is the problems it can cause an installer. If there is a problem with the network that needs a certified technician support, they must be able to easily first; your network and perform diagnostic tests on the. With a poor installation choice with the wrong layout, the technician is already fighting an uphill battle before they have really started.

To avoid this, always make sure to follow the BUS line The network method, where each device is connected individually to the main network via a drop cable or 4-way drop cable. This makes the network easier to trace and complies with all NMEA 2000 standards, plus it makes it easier to document the network with diagrams etc...

NMEA 0183 Wiring

NMEA 0183 wiring poses some problems and a degree of confusion, especially among those who are inexperienced of installations and standards. There are 2 "main versions" of NMEA 0183;

NMEA 0183 V1.5 and RS-232, which use single ended speaker/listener connections.

NMEA 0183 V2. 0+ is RS-422, which uses differential speaker/listener connections.

In principle, it is easy to connect RS-232 to RS-232 and likewise; for RS-422. The errors usually occur when trying to connect a combination of the two. There is a fundamental flaw with the way RS-422 and RS-232 work when connecting together, where connecting a V2.0+ Differential Talker to a V1.5 Single Ended Listener can cause; drastic consequences if not done safely and correctly. It is possible to damage or completely overload the differential unit.

The reasoning behind this is that the older single ended units use ground as the return, but differential units actually fluctuate through to run 0v-5v through the '-/B' connection. If they were connected together, the speaker would draw too much current as it tries to output to ground, causing overheating and component failure, along with damage to the the device.

Fortunately, Actisense has a solution that makes this risky connection completely safe and among other things We know that there will always be challenges, changes in scenario and changes requests, or sometimes things just won't work as intended. Unfortunately, some of the problems we see are due to poor practice and installation and much of this can be avoided.

Unlike NMEA 2000 which had a wiring standard from the beginning that makes wiring much easier, NMEA 0183 not the same levelå of continuity. For the most accurate method, always refer to the user manuals for the products you are connecting, and don't just use a color-matching method for cabling. In NMEA 0183, a company can Rx – be red, and in another company it is their Tx + color code. Although this would not damage the units, it can still be confusing, especially when trying to diagnose a fault.

Become a NMEA expert, learn how Best practices and NMEA tips by downloading our free guides to NMEA 2000 and NMEA 0183 networks.