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Old 16-08-2008, 21:39   #1
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How to test if a tranducer works

it's a long story but I had to cut out my transducer which was unfortunately located behind the little keel.
I patched up the hole with fibreglass and on layer of 1/8th marine grade plywood.

My first idea was to take the transducer inside the hull in a well over the patch. However I'm not sure how to test if this works while still hauled out.

My second idea is to put a new through hull before the keel and place the transducer there.

My big worry is - is this transducer still working at all - and is there a way to test this whilst still out of the water.

Simply would hate to drill a hole in my boat just to find out that the transcuder is not working any more.

Any comment's on my different ideas and my worry are highly welcome.


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Old 17-08-2008, 01:12   #2
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You could just try switching it on. I had a trailer boat once where if you switched the fishfinder on when the boat was on the trailer, it still gave an indication of the ground below. The transducer would probably need to be fairly close to the ground though, within 1/2 a metre, but it might work.

A reading would possibly prove that it does work, but no reading probably wouldn't conclusively prove it doesnt.

You could take your complete sonar, and a battery, to a swimming pool.

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Old 17-08-2008, 03:41   #3
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I agree with cruisingcat. Sound travels at around 4 times the speed in water compared to air, but air has a much higher sonic impedance, and transducers for water use a different design between the piezo crystal and the plastic housing for impedance adjustment.

Safest is to try it in water, a length of PVC pipe filled with water is fine, the largest diameter (within reason) will give you the most accurate reading. 2" -3" about 4-6 feet long is ideal.

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Old 17-08-2008, 08:41   #4
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Thru-hull (needs a hole in the hull) transducers are as cheap as $100. Are you trying to salvage an out of production intrument? I have heard that Airmar, who builds almost all the transducers sold today can help you replace an older one they built.
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Old 17-08-2008, 08:50   #5
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A 5 gallon bucket filled with water, and a 8 inch piece of iron pipe laying on the bottom of it, should definitely give you a reading....
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Old 17-08-2008, 09:06   #6
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Don't know if 5 gallons will work or not but we have used 35 gallon trash cans filled with water to check transducers in the yard.
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Old 17-08-2008, 13:00   #7
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Try and get at least a couple of feet, preferably more between the transducer and the bottom of whatever it is you use. The reason for this is that some older tranducers have more "ringing". They work by having a high frequency AC current across a piezo crystal. When the AC (send mode) is switched off, some transducers need a few milliseconds to stop "ringing" before they can "hear" anything, so these units have a bit of a "dead zone" close to the transducer. All sensors have this, it just varies a bit.

Hope this helps


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