Sea Water Temperature -50 C ??!!

peterjaw

peterjaw

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Merry Christmas, captains,

My Simrad NSS EVO 3 shows the Sea Water Temperature is -50 C which is totally impossilbe. I am in Taiwan, a tropical country. My transducer is HDI medium/high Chirp 455/800 w/ Downscan.

https://www.simrad-yachting.com/sim...ack-hdi-skimmer-medhigh-455800-9pin-63f2ca90/

I know it showed correct sea water temperature in the past summer, but now there is something wrong.

Do you think this is just a calibration problem? or a melfunction problem?
 
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Too convenient a number to be calibration I suspect.

Who ever designed it set the calibration to be from minus 50 .... So likely it has no data going in. Could be as simple as a lose wire, or just dead.
 
ShinyShoe said:
Too convenient a number to be calibration I suspect.

Who ever designed it set the calibration to be from minus 50 .... So likely it has no data going in. Could be as simple as a lose wire, or just dead.
Click to expand...

Thank you very much for your "estimation". I will check the connection and see if that will work. (Hope it will work.)
 
peterjaw said:
Merry Christmas, captains,

My Simrad NSS EVO 3 shows the Sea Water Temperature is -50 C which is totally impossilbe. I am in Taiwan, a tropical country. My transducer is HDI medium/high Chirp 455/800 w/ Downscan.

https://www.simrad-yachting.com/sim...ack-hdi-skimmer-medhigh-455800-9pin-63f2ca90/

I know it showed correct sea water temperature in the past summer, but now there is something wrong.

Do you think this is just a calibration problem? or a melfunction problem?
Click to expand...

I don't think it's a calibration problem. It is most likely due to the transducer having an NTC (Negative Thermal Coefficient) Thermister as a sensing device. These loosely have high resistance at low temperatures and low resistance at high temperatures. It is definitely Non-linear, but that will be mapped by the calibration program. If it thinks it's -50C then it is perhaps open circuit somewhere - or a corroded contact perhaps.

Our Webasto heater uses a similar thermister and refused to even start - as it considered the external temperature setting to be -56C. I replaced the thermister in the sensor and convinced the device to run again.
It is just possible that ALL the calibration table data is lost?
Manuals out!
 
pagoda said:
I don't think it's a calibration problem. It is most likely due to the transducer having an NTC (Negative Thermal Coefficient) Thermister as a sensing device. These loosely have high resistance at low temperatures and low resistance at high temperatures. It is definitely Non-linear, but that will be mapped by the calibration program. If it thinks it's -50C then it is perhaps open circuit somewhere - or a corroded contact perhaps.

Our Webasto heater uses a similar thermister and refused to even start - as it considered the external temperature setting to be -56C. I replaced the thermister in the sensor and convinced the device to run again.
It is just possible that ALL the calibration table data is lost?
Manuals out!
Click to expand...
Agree. I don't think it's a calibration issue either.
I checked the connection terminal this afternoon and it is secured. I also checked if any corrosion but found nothing.

I called the dealer already and they will go to marina for some professional checks.
Fortunately, the devices are still in warranty. I will come back to report the result.
 
Hadenough said:
To decide do I, or do I not need a wet suit for a swim. :)
Click to expand...

or in the Med, to decide if I'll dive off the bathing platform, or slowly go down the steps :D
[28C+ vs 25C]

to the OP, can you follow the cable from the sensor to the plotter?
can you check that nothing is pulled/damaged where the cable goes through the hull?
 
if you can find the "pin out" connection details of the 9 pin plug you could check the resistance on a meter. That may give you a clue. Unless its a multiplexed or digital signal of course, but worth trying if you can find the plug details.
 
LittleSister said:
What do people use the sea temp reading (for when it is working correctly)?
Click to expand...
My boat was delivered on August, brand new. Therefore, everything on the boat is still under warranty.

In fact, the number of sea temperature reading does not bother me, but it indicates there is something wrong, maybe the transducer, the
cable, the connecter, the plotter, or any combination of above. I would like to make sure everything is right before the warranty expires.

So now, this is the dealer's job. If they can't fix it, they need to replace with a new set.
 
vas said:
to the OP, can you follow the cable from the sensor to the plotter?
can you check that nothing is pulled/damaged where the cable goes through the hull?
Click to expand...
We checked the cable from transducer all the way up to plotter and found nothing damaged.
The dealer will go to check today and we will see what is the problem in a few days.

Thank you very much for your suggestion.
 
greeny said:
if you can find the "pin out" connection details of the 9 pin plug you could check the resistance on a meter. That may give you a clue. Unless its a multiplexed or digital signal of course, but worth trying if you can find the plug details.
Click to expand...
Thank you very much for your suggestion.

I have called the dealer and will leave this job to them. Since these equipments are still in warranty.
 
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