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Autohelm ST50 speed instrument

Posted: Fri 31 May 13, 8:56
by Mika Harju
After winter storage my speed log does not work anymore. Power is on and timer etc. are working but the speed shows zero.
I have checked the impeller is rotating and also disconnected and connected again all connectors.
I could not find a proper connection diagrams from net. Here is the manual, but it does not help at all.
http://www.raymarine.com/view/?id=1964& ... 3&col=3458

Any tips? Is there some electronics inside the tranducer? Is the output a pulse train or analog voltage/current? 0-10V, 0-20mA or 4-20mA?

I know this is an ancient system, but I do not want to upgrade all instruments at this point.

Posted: Fri 07 Jun 13, 8:52
by Paul
My speed log died also, I now just use SOG from the gps on my plotter. My A50 Raymarine plotter acts as a log.

Posted: Fri 07 Jun 13, 16:04
by Double Horizon
The reason you will want to repair it (and not just use the GPS SOG) is because it integrates with the wind transducer to give true wind readings.

You can buy these on eBay, from Raymarine, or from Raymarine resellers. They are made by Airmar. I believe the ST50 uses the same transducer as the ST60, but they make a 4-vane and a 6-vane version. I'm not sure whether it matters because the rotational speed should not change with the number of vanes, but you should try to get the same type just in case.

Also, I have spliced the wire to this type of transducer without any issues.