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Old 25-09-2010, 07:30   #1
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Depth Sounder Damaged if Operated in Air ?

My boat is presently hauled out and the depth sounder has been inadvertently turned on for a few hours. This happened once before about 12 years ago. In that event it displayed distance to the pavement through the air. This time the display is blank so I am concerned that something went poof.

The system is a Simrad IS-11.

The questions are: (1) How to test it before launching again? (2) If it has failed is it likely to be the transducer, or the electronics that would be damaged? If it is the transducer, it should be repaired, or replaced before it is back in the water.

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Old 25-09-2010, 07:42   #2
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I'm surprised the sounder was able to reach the pavement and read anything. To test your sounder now, get a tube of KY jelly or similar (any 'medical' jellied lubricant will do), spread that on the surface of the sounder and then press a large plastic bottle of water onto the surface. Wrap a couple of layers of tinfoil on the bottom surface of the bottle. A square sided bottle will work best, like the bulk bottled water you can get in most supermarkets. That will certain produce an echo is there is any impulse. If there is no echo, then sorting out if it is the transducer or the electronics is beyond my pay grade


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Old 25-09-2010, 08:07   #3
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It should be fine.
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Old 25-09-2010, 08:17   #4
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Generally depth transducers require the medium of water to transmit/receive signal. I too am surprised you got a reading through air.

There is no reason to assume that it will be damaged though whilst operating out of the water. My B & G one never has.

I don't think handheld depth sounders would sell well if they failed whilst operating out of water either.

BTW my HawkEye handheld can look through the hull of the boat (fiberglass or thin aluminum) if you have water or petroleum jelly seal between it & inside of hull.

If in doubt RTFM
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Old 25-09-2010, 09:40   #5
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I have heard of the warning that the transducer can be damaged (by overheating) if operated out of water for a prolonged period. I have never heard it causing damage in practice however.
I think the risk is mainly to higher powered fish finders.
You can test the depth sounder on the hard by placing a large bowl of water on the ground underneath the transducer (note the transducer is still in air). The water provides a flat reflective surface, a lot of power is lost in the air / transducer interface, but often enough remains to get a reading.
The speed in air and water is different so you need to multiply the "depth" by a correction factor.
I installed 2 new depth units on my yacht 18 months ago (one as backup) and gave the bowl of water a try, before launch. It only worked for one unit, but both functioned OK in the water.

Of course a very deep bowl in contact with the transducer would work better to test the unit, but as most instrument have a minimum reading of around 1m it is hard to find a suitable container to hold the water. The beam also spreads out and unless the container was large reflections from the side would cause problems.

I think damage is very unlikely, but try the bowl on the ground trick if it reads correctly you will at least be reassured.
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Old 25-09-2010, 10:13   #6
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You will probably be able to feel a "tick" on its face when running.
I seriously doubt it's been damaged.
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Old 25-09-2010, 11:16   #7
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These units do not put out enough power to worry about damage by heat when out of the water. As for testing, you should be able to hear or feel a 'tick'.
I also get a blank display when either too shallow water or not enough oil between hull and transducer.( I have a through hull)

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