Dallas One Wire Thermistor

[EricV]

I'm puttering with my Arduino and going to start attaching sensors. I want to make a dip tube from copper (for the tank) with the thermistor inside it. My question is can I submerge the thermistor in thermal paste or will that kill the thermistor?

Thanks

 

[jebatty]

Dallas 1-wire sensors are typically mounted in epoxy sealed stainless steel capsules. I don't see any problem with using a thermal paste so long as you are not insulating the probe from the heated surface or interrupting the electrical/digital connections. Any insulation likely will result in either inaccurate readings or a delay in getting accurate readings while the heat travels to and from the insulation. Might not be important depending on what you want to do.

 

[Medman]

Also, a copper dip tube may allow heat to travel along its surface, giving you inaccurate readings. I used PVC instead to avoid this. You can do some experimenting to see if there is a temperature offset from being inside the PVC and adjust for the offset in software.

 

[in hot water]

The thermal paste is important if the thermistor is not a tight fit in the well. It can make a bit if difference in the readings. Most thermo wells include a small tube of paste with them.

I cut open a thermistor to see what makes them tick. They tell be it is the 1/4" at the tip that does the sensing.

Looks like the same thermal paste is used inside the thermistor also.

hr

 

[henfruit]

Fill the well with oil.

 

[kabbott]

Are you using ds1820 in the to-92 (i think) plastic case? I epoxied them in a 1/4 inch copper tube which worked fine until a lightening
strike killed the whole lot of them.

I now have a cpvc dip tube in my tank with tee's at each sensor level and a cpvc to fpt adapter and the sensor epoxied in a brass mpt plug.

I also found 1-wire sensors are not reliable at all above 170-180 or so when using parasitic power... must use data, ground, AND 5 volts.
Some sensors do not have the 5 volt lead connected internally even though they have 3 leads, can't remember the number... may be ds1822.

 

[EricV]

Great info.

I was thinking of the pvc with a copper fitting with the sensor in thermal paste.

I'll check out the 5v lead.

Thanks

 

[jebatty]

I provide 5v on all of my DS18B20 1-wire temperature sensors. About 195F is the highest temp they see in my system, although as high as about 210F would be possible in an overheat situation.