Ray Marine Bidata

[PangurBan]

I had a Raymarine combined speed log and depth sounder fitted about 18 months ago. The depth sounder works fine. I calibrate it regularly with a lead line. But the speed log seems to be a random number generator. It does not retain the calibration factors (SOG from GPS) that I plug into it. Nor does it agree with careful runs I have made and measured with a Walker taffrail log. The instruction manual, quite frankly, is as difficult to follow as a text by Wittgenstein. The guy who fitted is is as vague as a Zen master. Anyone got any ideas?


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[Ex-Calif]

The best way to calibrate is a two way timed run over a fixed period. I found two fixed lights here about 1nk apart and timed a two way run.

I have the ST40. I am not sure how you are doing it but I put it in cal mode, click the button passing the mark and click the button passing the second mark. The cal procedure is set up to stay in cal mode for a two way run.

The speed log is notorious for fouling on my boat. I need to clean it weekly.

(edit - sorry - just read the manual for your unit and it does not have the timed run option - weird)

Just to check - when displaying SOG - it is not internally generated. It is receiving that from seatalk/gps input. When in Speed mode it is reading from the log and applying cal factor.

Cal factor simply appears to be a known speed adjusted up or down - hence the requirement to measure SOG from an external source with zero current. There could be a non-linearity error in the electronics or due to speed log installation/fouling.

When fouled my speed log error gets bigger especially at lower speeds.

[PangurBan]

Thanks for that,ExCalif. I have the ST40 Bidata. It is not connected to the GPS plotter with SeaTalk. The manual describes a procedure for calibration much as you describe. After calibrated it, I get readings of speed, distance run and what is supposed to be a cumulative record of distance which are believable and agree with the GPS and a mechanical log. But when it is switched off it does not retain the calibration or, any of the distance records. Next day the whole damn procedure has to be repeated. It has occurred to me that these things might have a small internal battery that needs replacing.


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[Ex-Calif]

Not sure that the display has any internal battery but there is this caution in the manual about low ship battery.

"The equipment is supplied from a different battery from that used for

engine start. Voltage drops below 10 V in the power supply to our

products, and starter motor transients, can cause the equipment to

reset. This will not damage the equipment, but may cause the loss of

some information and may change the operating mode."

[Jentine]

There is an 800 number in your manual for Raymarine. CALL THEM! I have found them to be quite helpful in the past. In one case, when the instrument was not working properly and was properly wired they had me switch two correctly installed wires and the problem was solved, never to return.