Ensuring that a Garmin® Marine Chartplotter is Outputting NMEA 0183 Data

There are two ways to see if a Garmin chartplotter is outputting the NMEA 0183 (National Marine Electronics Association) sentences. Before performing either of these steps, ensure that the device's communication port that is being tested is set to NMEA In / NMEA Out and that all sentences required are turned on. Review the Owner's Manual of the device to find out how to change this setting.

The first way to test the NMEA 0183 output uses a multimeter to test for DC voltage coming out of the NMEA out wires. Follow these steps to test the device:

1. Power the device on

2. Connect the Red lead (positive) of the multimeter to the NMEA Out + wire from the chartplotter

3. Connect the Black lead (negative) of the multimeter to the NMEA Out - wire from the chartplotter

   • Note:  If the chartplotter being used only has one NMEA Out wire, use that wire as the NMEA Out + and connect it to the Red lead (positive). Since there is not an NMEA Out - wire, connect the Black lead (negative) of the multimeter to the common ground of the boat

4. Once connected, the multimeter should show a rhythmic voltage jump from 0-5 volts DC approximately every 1-2 seconds

If the multimeter shows the jumping voltage, that is an indication that the device is outputting the NMEA 0183 data properly. If the multimeter shows a steady voltage, or no voltage at all, there is no data being sent through the NMEA wires. In this case, check to make sure the device is set to output NMEA data, and that the wires are connected to the multimeter properly.

The NMEA 0183 output can also be tested by connecting the chartplotter to a DB-9 serial port connection. For instructions on this connection, review Related Content below.