[TG] ST70 and DST800 speed calibration issue

[Tom - Raymarine - Moderator]

Hello Azura,

I'm sorry to say that there's no way to test an NMEA2000 transducer: they're sealed and potted and no diagnostics on the analogue signals can be done. I can rule out some things though: it's definitely not either the network or the display. NMEA2000/SeatalkNG, in common with all modern networks, has extensive and effective error-checking that means that corrupted data will automatically be rejected at the hardware level by the CAN transceiver chip. If you have a network problem the result you will get will be missing or intermittent data rather than wrong data. Similarly, the display shows only what it receives over NMEA2000, it does no modifications or corrections to that speed data. It does calculate True wind from Apparent+STW, or True heading from magnetic+variation, but can't read (for example) 7 knots STW and display 5. The only way to do that would be a re-write of the software.

If there's a fault - and I have to say that your large temperature error makes it sound like there could well be - then it's inside the transducer, you can be sure of that. I'd guess that it's got water inside, I'm sorry to say.

Regards,
Tom