temp diff between graphs

[teamlund]

temp diff on graph...

Hey guys this weekend on the wolf river I noticed about a 5 degree diff in temp from the X67 on my bow to the 917HB on my helm... The HB said 38 while the bow said 33... It could have been vise vesa but you get the idea... Is something broke or how can I be getting a diff like this?

[680 AMERICAN DREAM]

It could be that your bow transducer is on your trolling motor. Which is deeper in the water that your HB ducer. Just a thought.....

[Jason Halfen]

Originally Posted by teamlund

temp diff on graph...

Hey guys this weekend on the wolf river I noticed about a 5 degree diff in temp from the X67 on my bow to the 917HB on my helm... The HB said 38 while the bow said 33... It could have been vise vesa but you get the idea... Is something broke or how can I be getting a diff like this?

The thermocouples in the two transducers obviously have different calibrations.

I don't know how the X67 works, but on your Humminbird 917, you can use the Temp. Offset function found under the Setup menu tab to adjust the displayed temperature. That way, at least your two temperatures would match. Check your manual for more details....page 106. Lose your manual? Download one for free from the Humminbird website (under legacy products > 900 series > 917 > support).

In an ideal world, you would immerse each transducer in a bath of water of known temperature, and then adjust your two displayed temps to match the known temp of the water.

Thermocouples huh? What do they do?

[West Newton River Rat]

Thermalcouples are what read the temp and send the temp signal to the controller. However I agree with 680 and think one temp sensor is lower in the water than the other. That is more likely than needing to adjust someting.

[REW]

Take a pan , bucket or barallel of water and take a theromemeter that can read room temperature very accurately.

Put each transducer in the water at a time and also insert the thermometer into the water.

Let the teperature stablize and check to see if either is right and if not, by how much.

Then you need to decide to either exchange the transducer and or head unit - depending on the problem or live with it.

If you get a reading of temperature that is in the range of what you normally fish, you can just put a temperature correction difference on the unit, or units that are off.

Take care
REW

[REW]

I checked the user manual for each of your units.
The lowrance unit does not appear to have a temperature calibration menu.

But the HP unit does have an offset adjustment for temperature:

http://store.humminbird.com/media/do...7c-957cMan.pdf

So, at a given temperature, you can use the offset button on the Hp to make both temperatures agree.

Take care
REW

[teamlund]

thanks for the info guys... I will run some exparimnets this weekend and see how it goes...

Who would think getting a correct water temp with a $1000 unit would be so difficult or getting a correct reading at all.... These units can link up with satillites in space and give me a read out of location, speed, ect, ect, ect, ect but it cant give me a correct water temp

[3M TA3]

Originally Posted by teamlund

thanks for the info guys... I will run some exparimnets this weekend and see how it goes...

Who would think getting a correct water temp with a $1000 unit would be so difficult or getting a correct reading at all.... These units can link up with satillites in space and give me a read out of location, speed, ect, ect, ect, ect but it cant give me a correct water temp

I agree about the cost and ability to provide correct data however I am a bit curious as to what use that information is since it only reads the temp of the water that the transducer is sitting in. 12 to 18 inches below the surface. Should I be paying more attention to the temp of the water at that depth??? Thanks

[teamlund]

Originally Posted by 3M TA3

I agree about the cost and ability to provide correct data however I am a bit curious as to what use that information is since it only reads the temp of the water that the transducer is sitting in. 12 to 18 inches below the surface. Should I be paying more attention to the temp of the water at that depth??? Thanks

Many times on the lake I will "chase" warm water... Sometimes driving everywhere, into bays, onto flats, points, wind blown shorelines jsut looking for the warmest water on the entire lake....Generally if the water is warmer on top it will also be warmer below but the diff will not be as great as the surface temp.....Also, many times I am in 4 fow or less with a dark bottom so I think I am getting a pretty good idea of temp in that shallow of water...