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S1G Fluxgate Compass Alignment Drifts - Use External Compass?
11-20-16, 05:44 PM
Post: #1
S1G Fluxgate Compass Alignment Drifts - Use External Compass?
Problem: When engaging S1G Autopilot there is sometimes a course jump a few degrees.

Diagnosis: The S1G course computer is connected to a Type 1 drive, a Raymarine fluxgate compass and rudder sensor. It is also interfaced via a Seatalk to Seatalk NG converter to a Nexus multi-axis compass used for my instruments (Nexus & B&G) and Raymarine e97 & e125 multifunction displays. The MFDs are set to use the Nexus multi-axis compass which has a 10 Hz update rate. Per the manual, the S1G defaults to the Fluxgate compass over the heading received via Seatalk since the Fluxgate compass is connected. Interconnections diagrams are at this link:

The Nexus compass is very accurate and responsive. The Raymarine compass appears to drift a few degrees over time (weeks). When the Raymarine and Nexus Compass read the same value, there is no course jump when the Autopilot is engaged. If there is a difference between the two compass readings, there is a course jump when engaging the Autopilot. I can adjust the Raymarine fluxgate compass so it tracks the Nexus compass every few weeks, but this is inconvenient.

I notice in the S1G manual that the course computer will accept a NMEA or Seatalk compass and if it is used, the fluxgate compass should be disconnected.

1. Will the S1G perform as well using an external Seatalk connected compass (actually Nexus HPC multi-axis compass over NMEA 2000 -> Setalk NG -> Seatalk)?

2. Can the Raymarine Fluxgate compass be disabled by removing only a single lead (e.g. power or ground), or does it require that all leads (power ground and coils) be disconnected from the course computer?

Bill Kneller
Vento Solare, J/109 #266
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11-21-16, 11:14 AM
Post: #2
RE: S1G Fluxgate Compass Alignment Drifts - Use External Compass?
Welcome to the Raymarine Forum Bill,

The data rate for heading on the SeaTalk, not to be confused with SeaTalkng, bus is 1Hz. Accordingly, a SeaTalk source of heading data would be too slow for the S1G. In this case, it would be recommended that
- the fluxgate compass be disconnected (all leads) from the S1G
- the 4800 BAUD NMEA 0183 10Hz output (heading-only) of the third party heading source be interfaced to the S1G's NMEA 0183 input port 1.
- should drift continue to be observed, then the S1G's gyro should be unplugged from the S1G's circuit board.
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