On Wed, 14 Aug 2002, Claudio Martin wrote:

>Liquid is wine stored in tanks and the range of temp. is from 10 to 30
>degrees. Regarding the response time isn't that important, because it's a
>huge mass of liquid. I have to check the temperature at a point located at
>the center of the mass of liquid. This point is about 3 meter from the top
>cover of the tank. I guess one stainless steel tube could be a good
>solution, but one point to work out is how to keep the sensor in contact
>with the end of the tube, is there any kind of glue with a good thermal
>conductive coeficient?.

Use heat conductive paste and ram the sensor down the tube. The tube will
conduct enough heat that there will be no difference with or without paste
at 3m of immersed tube imho.

You could just use a LM35 in each tube, attach terminals using individual
heatshrink and that's it. I think 8mm i.d. tube will be fine. This kind of
sheath is made for thermocouple gauges I think, for the food industry. I
do not know about 3m long though. Make sure the tube is strong or it will
bend as the immersed part tries to float. Maybe put a s.s. weight at the
end. I would put a preamp at the top of the tube and send 4-20mA or other
such signal to further processing.

I think that such modules exist (thermometer in s.s. sheath with 4-20mA
output). I have never used one. The ones I saw were at most 1 meter long.

Peter

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu