Dodgy depth gauge

G

Gerry

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Devon
www.gerryantics.blogspot.com
Our B&G (depth transducer401-00-012)depth gauge seems to have developed a life of its own, whilst most of the time it works just fine sending lovely reassuring messages of the amount of water under our keel it has started to suddenly stop working at the most crucial of moments! This has the effect of raising stress levels to an unacceptable high as it usually fails as we are negotiating tricky reef passages or muddy river inlets.
We have taken the whole thing apart, tested every connection etc over the last few days as we sat in the murky waters of the Rio Dulce. Just when we decided there was no hope and were headed back up river it leaps in to action again.
Now I know that bottom conditions can have a big effect on the efficiency of these things but it seems to be reacting in a very random fashion.
What I am interested to know is whether more modern units, ours is about 15 years old, are more efficient at sounding in less than ideal conditions. If they are which brand do you recommend?
 
Has this just started when you have changed sailing areas? I sail in the Bristol channel and my Autohelm log/sounder goes to zero depth when waiting outside the Cardiff barrage locks. These are large (drop can be 10m plus) locks that dump water into a small silty outer harbour. I'm sure it is the silt suspended in the water that makes it go to zero. Could this be the same with yours?
Allan
 
I get something a bit similar on occasion with mine (a 2 yr old transducer) - it continues to read - but just gives say 10.8 m - when I know I'm in about 3 !

I've traced this I think down to the oil bath that it sist in in that very minor adjustments of the transducer position can make the problem worse - or almost non existent - juts not quite worked out how to fix it permanenly in a "no problem" position

So certainly check your fitting and oil bath (assuming its not actually through a hole in your hull)
 
I have had quite a few problems on the East coast of the UK with our sounder in shallow silty water. Often it will lock up and give an unreliable measurement signal. This usually happens when only in 1.5-2.5m of water. I haven't found a way around the problem, but luckily we have a lift keeler!

K
 
Fitting the transducer in an oil bath....... for what it's worth I buried my transducer in a plastic box (actually one that contained 50 or 100 business cards) in silicon, then silconed the box to the hull. Occassionally when it gets v. hot there are whiffs but in a 24 footer that doesn't matter , we never sleep on board. Just a thought; no liquids, etc.
 
i don't think the new ones are any different for most models
i fitted a target 2 into the boat,thought i'd try the old transducer from the seafarer as it was in place etc,worked a treat,so on that basis i'd guess they have not altered alot,not sure tho if they lose there effectivness over time,i would assume being electronic that they either work or don't
 
I had this problem on a previous boat. I found that the lead was by a coax cable and that this had become defective as it left the top lead from the actual transducer. I had to cut the coax, cut the plastic hard lead on the top of the transducer back a bit and then resolder the centre wire of the coax. Remaking the wire mesh shield part of the coax did tease me awhile, but I used small strands of wire to make a new mesh and spot soldered that together and it did work [after a fashion!]
 
Had exactly the same problem when we acquired our current boat, which was then 10 years old. The Depth reading was easily 'upset', either at lower depths (< 3 metres) or in disturbed or silty water (just when you need it most!!!).

Checked all connections etc, all OK.

So I replaced the transducer. Cured!

Aparently Airmar make many of the transducers, as OEM suppliers to many of the marine instrument manufacturers, and have a cross-reference on their website.
 
Thank you so much for the ideas, we will set to and give them a try. This is exactly the sort of stuff we were looking for. Not a mention of depth gauges in The Electronics Bible or any of the other hefty tomes that we are carting around the world with us!
 
I'm not clear if your depth sounder stops working altogether or starts to give erratic readings. A simple possibility for the latter - do the problems correspond to your turning on anything else? Fluorescent light strips for example can interfere with depth sounders.
 
It goes to ----. usually nothing has changed as we are in the cockpit navigating in to a tricky anchorage! We use paper charts so no computer interference and nothing different is turned on!
 
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