Sea temp

[All U Get]

Hi Maine Sail,
I have an older Autohelm ST-50 Multi-function display that includes sea temperature. Since the boat is in Maine, I'm a bit skeptical that it's 80 degrees. I've checked the manual and calibration mode without finding how to change the temperature. Can this be done or is the sensor toast?
All U Get

 

[Bob S]

Don't know but was wondering what is the usefulness of knowing? I usually hold my breath and jump in

 

[Gudenuph]

Colder water has a smoothing effect on warmer air particularly so in light winds.
FWIW, Geohan

 

[Bill Roosa]

Check all the connections. the thermistor (temp sensor) is just a resistor that changes its resistance with temperature. Now if your connections are corroded that counts as part of the total resistance the control head sees and tries to interpolate as a temperature.

 

[bria46]

why don't you drop an old mercury type thermometer over the side and check the reading. then compare it to your digital unit

 

[Rich Stidger]

I checked my copy of the user manual and there is no calibration for temperature. If your unit says it is 80 F then I would jump in and go for a swim. But I would have some warm towels close at hand in case your swim turns out to be cold and short.

Perhaps you could toss your wife in first and see if she turns blue"?

 

[All U Get]

I checked my copy of the user manual and there is no calibration for temperature. If your unit says it is 80 F then I would jump in and go for a swim. But I would have some warm towels close at hand in case your swim turns out to be cold and short.

Perhaps you could toss your wife in first and see if she turns blue"?

Uh Rich,
There's only so much room in my doghouse, can't throw her in. I'll be checking the connections. Since Maine Sails post on packing glands being twenty degrees above ambient seawater while running, I thought "Here's something that could be useful".
This is my year to figure out how my multi-function displays should work. I'm working on chartplotter, auto-pilot, and binnacle compass all reading the same direction within two degrees.
All U Get

 

[jdhohmann]

I checked my copy of the user manual and there is no calibration for temperature. If your unit says it is 80 F then I would jump in and go for a swim. But I would have some warm towels close at hand in case your swim turns out to be cold and short.

Perhaps you could toss your wife in first and see if she turns blue"?

It will be short indeed!!!!:dance::dance:

 

[Mick143]

I have a ST-50, and its telling me Narragansett Bay is 34 degrees. I also had the ST-50 Depth sounder. Replaced with the ST-40 used the same transducer and it is so far working.

 

[All U Get]

Hi Mick,
My depth is right on so it's just the temp that's a little wacko.
All U Get

 

[Joe2954]

ST-60 cal instructions for Sea Temp attached - part of User Cal. Might work for ST-50.

Mine has been reading about 50F too high for several years - tried all connections but no luck. I think temp reading is a high failure item for Raymarine if you check the web.

I happen to have a handheld depthsounder with temp so I'll hang it over the side if I'm interested enough - especially if I'm going to get wet.

 

[Steve Dion]

from Raymarine.....

My instrument is not reporting the correct speed or temperature


Testing the Speed Sensor:

• Verify that the transducer’s paddle wheel is free of marine growth and rotates freely on its shaft
• Power down the instrument
• Disconnect the GREEN and SHIELD transducer leads from the instrument display or instrument pod.
• Connect a multimeter to the GREEN and SHIELD transducer leads and configure the multimeter to measure continuity or resistance.

• Slowly rotate the transducer paddle wheel by hand. Note that as the paddlewheel is rotated, the multimeter should alternate between an open circuit and a closed circuit with each quarter turn. As such one complete revolution of the paddle wheel should open and close the circuit four times.

Should the multimeter respond as indicated above, then the speed sensor element of the transducer would be deemed functional. If not, then the transducer has failed and should be replaced.

Testing the Temperature Sensor:

The temperature sensor employs a thermistor as its sensing element. The impedance through a thermistor will change as the thermister temperature changes. Increases in temperature will cause a decrease in impedance through the thermister. Correspondingly, decreases in temperature will cause an increase in impedance through the thermister.

Example: If the thermister is immersed in water is 77 degrees F, the multimeter will report an impedance of approximately 10,000 Ohms. If the thermister is immersed in water is 68 degrees F, the multimeter will report an impedance of approximately 12,495 Ohms.

Other examples:

81 degrees F = 9,164 Ohms
77 degrees F = 10,000 Ohms
68 degrees F = 12,495 Ohms
61 degrees F = 15,004 Ohms
57 degrees F = 16,470 Ohms
54 degrees F = 18,098 Ohms
50 degrees F = 19,911 Ohms

It is not possible to directly test the thermistor. Testing is performed indirectly by applying a known resistance to the BROWN and WHITE terminals of the instrument display or instrument pod and noting the temperature reported by the instrument display.

Testing is performed as follows:

• Power down the instrument

• Disconnect the BROWN and WHITE transducer leads from the instrument display or pod.
• Install a 10,000 Ohm resistor across the BROWN and WHITE terminals of the instrument display or instrument pod
• Power on the instrument
• The display should report a temperature of approximately 77 degrees F.

Should the display respond as indicated above, then the thermistor has failed and should be replaced. If not, then the instrument display or instrument pod has failed and should be serviced by Raymarine's Factory Repair Center.

 

[RonRelyea]

Water temperature

I've read that water temp changes noticeably when you enter/leave the Gulf Stream ... might be useful knowing when you enter and exit that current ... (for those considering a trip to the Bahamas maybe?)

 

[All U Get]

Re: Water temperature

Thanks Steve,
If cleaning the connections doesn't help, I'll follow your post.
Good point Ron, that would be good to know.
All U Get

 

[Stu Jackson]

Uh Rich,
...working on chartplotter, auto-pilot, and binnacle compass all reading the same direction within two degrees.
All U Get

Might not be worth the effort. The compass has its own deviation and will "swing" differently than any digital compass reading. I went through this exercise 12 years ago.

 

[All U Get]

Hi Stu,
I was told somewhere onboard there's an electronic compass for the chartplotter. Between the stereo and Barnacle Buster there are over a dozen magnets on board. I've been removing those BB's in the bilges as I find them since they don't work, but having the auto-pilot and chartplotter read near the same direction would reduce the error factor. We usually make a course from the paper charts and then compare to the electronic devices. Just for peace of mind I'd like to see everything match.
All U Get

 

[Stu Jackson]

Those two are a good choice. I was only commenting on the "normal" binnacle compass. Good luck, you should be able to do what you plan.

Thing to remember is the headings on the two. The fluxgate should give you boat heading, but the GPS will give you course made good.