I use DS18B20s to monitor the temperatures in my still. The 85C issue is a real pain because that's right around the temperatures I have to measure. Fortunately my system is pretty much 100% reliable so I never see 85C error readings.
Hot 96% ethanol vapour is pretty aggressive so I came up with a nice little package. I cut some slots and closed the end of a piece of 1/4" refrigeration tube with silver solder. The leads on the chip are soldered to some cable with heatshrink for insulation. The chip goes into the tube with some heatsink compound for thermal conductivity. The cable comes out the end of the tube and is sealed to the tube with some special shrink tubing with gooey resin on the inside. It all works reliably (so far) and seems to be utterly watertight. I also have nice fitting made out of a brass compression fitting. I get a compression union, throw away the compression rings, cut it in half, and drill it out to 1/4". Now the 1/4" tubing goes straight through. Connect it somehow to the housing you want the sensor inside - I silver soldered it to the copper still but you could thread it and use a gasket or whatever. Now I put the compression nut on the sensor tube and follow it with a little O-ring. Put the tube into the fitting and tighten the nut, which squeezes the O-ring making a perfect and reliable seal. It's really an excellent scheme. For less demanding situations (e.g. boiling beer) I have another one that is basically a sensor epoxied into the end of a stainless tube with the end of the package sticking out, otherwise similar to the copper one. It works really well too and would also fit into the compression fitting thing. Copper is not only permitted inside a still but it has a positive chemical function!
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