Different temperature readings from two transducers

I have a new xnt 9 20 t on the transom and a new xtm 9 wide di 20 t on the troller. I am finding the troller mounted transducer to consistently be anywhere from 2-4 degrees warmer. I have set them at the same water depth and no change. Any ideas? Is it the heat generated off the troller itself?

Thanks.

I have 2 on the transom (1 Bird, 1 Garmin) and 1 Bird on the bow mount. They all read different, but within 4-5 degrees. It’s just the nature of the beast, I think.

I cant help you out with the why problem. Other than you are not alone I have the same thing going on. Only mine are almost always 6 degrees different… …rrr

Cheap thermocouples. Not much you can do. It sure would be nice if you could calibrate them on the fly. That would pretty much solve the problem.

tpmorgz wrote:

I have a new xnt 9 20 t on the transom and a new xtm 9 wide di 20 t on the troller. I am finding the troller mounted transducer to consistently be anywhere from 2-4 degrees warmer. I have set them at the same water depth and no change. Any ideas? Is it the heat generated off the troller itself?

Thanks.

If the difference stays with one always reading 2 – 4 degrees higher than the other, then your issue is relativity minor. You could submerge a regular thermometer to see which is the more accurate.

Sounds like this is not an isolated problem to my units. You would think for the cost of these units there would be better quality control. Thanks for the replies.

This winter I noticed I had a difference in water temp between the two units in my boat. In the past they were always close. It was corrosion on the plug on one of my graphs. Cleaned it up and back to reading within 1° of each other.

Is anyone with major temp variation using extension cables?

I believe that thermocouples depend on using the same length cable that it was calibrated with.

i get 3 different readings right now on 3 different new units, covering a 4-degree spread. however, this is in my garage and i noticed the coolest one is the external closest to the floor, middle is about a foot higher on the SI ducer, and the warmest is on the trolling motor ~5′ high.

once i get on the water to control for the influence of the cold garage floor a bit better, i’ll just adjust them to the average.

“If the difference stays with one always reading 2 – 4 degrees higher than the other, then your issue is relativity minor. You could submerge a regular thermometer to see which is the more accurate.”

Funny, I was just having this conversation with my 86 year old dad this weekend. He said in the old days they would just tie a thermometer to their line and submerge. I kind of laughed, sounds too simple in this technological day in age…but then I thought – yeah that’s a great way to do it. I usually have about a 2 degree temp diff between my two units, but you could drop the thermometer in and see which one is most accurate and go from there. Simple solution…