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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: http://j109.org/forum/download/file.php?id=44

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.

Questions:
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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