raymarine depth randomly switches to fathoms rather than metres

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homer

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Has anyone else come across this weird fault? Every so often, the depth display switches units from metres to fathoms. Turning the system off and on again does not sort it. Going into settings mode and looking at the units set shows it is still set at metres and if the settings are then saved (but without actually changing anything) the display reverts to metres. Any advice gratefully received.
 
It's just a feature of old Seatalk systems. Mine occasionally changes the distance units to statute miles and the maximum boat speed to 655.55 knots (a value that is meaningful to geeks). The message packets in Seatalk have no checksum or any error detection at all. A bit of interference on the line - and junk is what you get. The transient values that are transmitted frequently would only show as an error briefly before the next correct value came along, but the network data that is in some way stored shows up, i.e. units and maximum values.
 
AngusMcDoon said:
The message packets in Seatalk have no checksum or any error detection at all. A bit of interference on the line - and junk is what you get.
Click to expand...

So if the OP wants to try to fix it, I guess he should be checking that all the Seatalk connections are well made (including any random splices that might be buried deep in the bowels of the boat and unknown about), that the cables are separated from sources of interference like transmitting aerial feeds or engine cables, and possibly consider some shielding in problematic areas.

Pete
 
Thanks for the input. I can appreciate that there may be some noise on the network but it seems odd to me that it always results in this particular fault and no other. Also, whereabouts does the system store the selected units? If it is in the multiview itself, how come that going into setting mode still shows it as metres, not fathoms? And how come that saving that existing setting (without changing it) sorts it out?
 
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