Don't know if this depthfinder is right... Can you help?

[boltonranger]

I have an Interphase DG-1 Digital depthfinder.<br />It has an LCD (numeric only) readout.<br /><br />It has a shallow alarm setting and a deep water setting as well as a fish alarm.<br /><br />The transducer is mounted at the transom all connections good.<br /><br />Here is my question:<br />When my boat is on the trailer and the transducer is about 2 1/2 feet off the ground-- the readout shows 6.1 to 7 feet.<br /><br />- I don't understand if this discrepancy; I assume the readout is supposed to reflect the distance from the transducer to the bottom. <br /><br />Am I correct about how this should function?<br />I have no experience with a unit like this; can you help?<br />-br

 

[b.gagnon]

Re: Don't know if this depthfinder is right... Can you help?

Most transducers won’t read anything out of the water. Does it seem ok when the boat is in the water? Water density can affect the way it reads (salt,fresh) so transducers are calibrated for this reason. Given the fact that the transducers are not designed for use out of water it may just be giving you junk readings..

 

[boltonranger]

Re: Don't know if this depthfinder is right... Can you help?

Thank you bg.<br />I will check it in the water.<br />I was scrolling through the depth finder's menu and then noticed the reading discrepancy when it was on the trailer.<br />I did not know that it would not read (properly) unless in the water.<br />I appreciate the help.<br />-br

 

[Boatist]

Re: Don't know if this depthfinder is right... Can you help?

Boltonranger<br />The reason for the difference is sound travels much faster in water than it air. As I remember it is 3 or 4 times faster in water.<br /><br />If you want your transducer to reflect the actual depth then it would need to be adjusted. Since the transducer is not at the surface of the water. I do not think the digital only units I have seen a<br />had a keel offset adjustment.<br /><br /> http://www.engineeringtoolbox.com/35_82.html