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Old 03-07-2013, 17:14   #1
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Dumb Question

Ok, I think I need to replace my depth sounder. Will it work on the hard stand or does the transducer need to be in the water?
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Old 03-07-2013, 18:00   #2
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Re: Dumb Question

my belief is that it won't work on the hard....needs water as a medium to transfer pulse!
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Old 03-07-2013, 18:03   #3
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Re: Dumb Question

It would only work if the boat park/hard stand area were severely flooded.
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Old 03-07-2013, 18:17   #4
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Re: Dumb Question

I've done it on the hard. You get a reading but its not great since air is a much poorer transmitter of sound than water. Plus, you get to hear the "click" of the transducer.
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Old 03-07-2013, 18:30   #5
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Re: Dumb Question

You *might* get a reading, and if you do the indicated depth will be way off. This is because sound (sonar) travels through air much more slowly than through water.
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Old 03-07-2013, 19:29   #6
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Re: Dumb Question

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Originally Posted by MollyJo View Post
Ok, I think I need to replace my depth sounder. Will it work on the hard stand or does the transducer need to be in the water?
Water.
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Old 03-07-2013, 19:36   #7
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Re: Dumb Question

Replace it while on the hard, test it when in the water.

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Old 03-07-2013, 19:48   #8
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Re: Dumb Question

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Originally Posted by MollyJo View Post
Ok, I think I need to replace my depth sounder. Will it work on the hard stand or does the transducer need to be in the water?

Make a depth line, position your boat on the water where it's not drifting. Use the depth line to set your depth finder.
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Old 04-07-2013, 07:39   #9
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Re: Dumb Question

Depth is measured by determining the propagation time of a sound wave as it bounces off the bottom and back.

The nominal speed of sound is approximately:
1500 m/s (4917 feet/sec) in water
343.2 m/s (1,126 ft/s) in air
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Old 05-07-2013, 06:33   #10
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Re: Dumb Question

And I believe that a transducer can be damaged if run too long out of water. I think they can overheat.
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Old 05-07-2013, 06:50   #11
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Re: Dumb Question

So, GordMay... Can you divide the "air" reading by 4.37 (1500/343) to approximate what the "water" reading should be (since it takes 4.37 times longer for the signal to reach land in air than it does in water)?

(As an old accountant, I just can't help looking for a "numbers" answer.)
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Old 05-07-2013, 08:17   #12
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Re: Dumb Question

You may, or may not be able to get a reading from the transducer on the hard. I have done it a few times when replacing depth units (to check they are working). The success rate is about 50/50 so the test is only useful to show it does work, you should not draw the conclusion its not working from a negative result.

You need a good reflective surface on the ground and the best seem a big bowl of water. The displayed depth needs adjusting for the speed of sound in air as opposed to water, as has been said.

I did have concerns about overheating the transducer and asked a question on the forum, but the consensus was that unless it was a high powered fish finder there was no risk.

The simpler test is just to check its clicking, if it is it is probably working.
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Old 06-07-2013, 01:55   #13
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Thanks for your thoughts on this. If the transducer is not clicking, could the issue be just at the transducer rather than the display end?
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Old 06-07-2013, 02:07   #14
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Re: Dumb Question

Quote:
Originally Posted by MollyJo View Post
Thanks for your thoughts on this. If the transducer is not clicking, could the issue be just at the transducer rather than the display end?
Yes it can be the transducer, display, or connections.
Its worth both listening and feeling for the clicking (more inside the boat) some people have difficulty hearing it.

Some units adjust the power to the transducer. I have a fish finder (as a backup to my primary depth) that gets so loud at 200m (600feet) that it can be heard thought most of the interior of the boat when offshore sailing. In shallow water it can only be heard lifting the floorboards.
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Old 06-07-2013, 04:30   #15
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Re: Dumb Question

I successfully mounted my transducer on the hard, instead of using water I used glycerine and it worked perfectly as a medium for transferring the pulse.
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