Airmar speed log - testing/question

[seajayare]

I have an Airmar speed/temp sensor feeding a raymarine ST60 speed/depth display and it has packed in.

I don't know why but I do like having speed through the water as well as SOG so I have been trying to fix. I found the Airmar test instructions but the sensor doesn't seem to read like it should. The test says that every 90deg the volts on the sensing line should go from 0V to 12V and on mine it is every 180deg. So it looks like it is half working but that doesn't seem likely cos I reckon electronic stuff works or doesn't.

The little magnets on the paddle wheel seem to be in pairs with two north pole magnets opposite each other and the other two south pole magnets, does this sound right? I can't see why the polarity of the magnets should change but maybe the detectors only "see" one magnet pole.

And the temp reading is mad too but I don't know if that ever worked

Any one got any clues? New impeller or new transducer or something else?

thanks for any help

 

[pvb]

Why do you say the sensor has packed in? If it's giving a reading when rotated (even though not exactly as Airmar suggest), might it not be a fault in the display or wiring?

 

[Pye_End]

Raymarine do a service pack for the log transducer, which includes an impeller.

 

[seajayare]

The speed display shows a reading when you spin the impeller but you have to spin the impeller very fast to get even a couple of knots to show. When actually sailing you need to have a serious speed to get anything above zero knots, the sort of speed where it would before have been showing 4+. I initially put this down to some fouling on the hull but mow I am wondering if it isn't the actual transducer. The refurb kit looks to be about a third of the price of the whole transducer so I didn't fancy doing a refurb just to discover the whole thing needs replacing

cheers for the help

 

[pvb]

The speed display shows a reading when you spin the impeller but you have to spin the impeller very fast to get even a couple of knots to show. When actually sailing you need to have a serious speed to get anything above zero knots, the sort of speed where it would before have been showing 4+. I initially put this down to some fouling on the hull but mow I am wondering if it isn't the actual transducer.

If Airmar say you should get a pulse every 90 degrees, but you're getting a pulse every 180 degrees, the display should show half the true speed through the water, shouldn't it?

 

[seajayare]

If Airmar say you should get a pulse every 90 degrees, but you're getting a pulse every 180 degrees, the display should show half the true speed through the water, shouldn't it?

I would have thought so. in which case i could probably calibrate differently. It doesn't seem to be reading half speed though it seems even lower/slower. Is it just pulse counting?

 

[seajayare]

just re-read the test procedure and it sounds like the thing should be qtr turn 12V and quarter turn 0V so looks like sensor is working after all (must learn to read more carefully).

so looks like the bad news of the display itself or the wiring between the two.

thanks for the help

 

[rogerthebodger]

I have simrad instruments and my airmar traducer was not giving a reading. I found the transducer worked OK but the temperature was faulty which caused no reading. I replaced the temperature senser with a fixed resistor of the correct value at all worked OK.

 

[Highndry]

Are you sure that the pin that the paddle wheel sits on isn't bent? That was the issue on my trailer sailer. I think the previous owner had nudged it either on drying or on the trailer. I changed the paddle wheel/ metal pin and all was ok.

 

[seajayare]

I have simrad instruments and my airmar traducer was not giving a reading. I found the transducer worked OK but the temperature was faulty which caused no reading. I replaced the temperature senser with a fixed resistor of the correct value at all worked OK.

I will give this a go. There is stuff about 10k resistors in the test method so i will give one of them a go and see what happens

 

[seajayare]

Are you sure that the pin that the paddle wheel sits on isn't bent? That was the issue on my trailer sailer. I think the previous owner had nudged it either on drying or on the trailer. I changed the paddle wheel/ metal pin and all was ok.

pretty certain the shaft is ok. The wheel spins freely and square. thanks for the suggestion