The completed copper vessel temperature probe
The temperature probes I have used in the brewery are made using Maxim one wire DS18B20 Programmable Resolution 1-Wire Digital Thermometers.
I originally intended on using K type thermocouples, But after purchasing several types I found it hard to make them waterproof and interface them into the overall system. I realise I could have purchased more expensive versions of these and probably wouldn’t have any problems but I have more knowledge of how the Dallas one wire thermometers work anyway.
The outside of the temperature probe ready for the actual thermometer to be inserted
I constructed the actual temperature probes by first off all cutting the required length of 8mm copper pipe and soldering an end stop onto this pipe. After this I cut approximately a 2 inch piece of 15mm copper pipe and straightened it out so I could drill a 8mm hole in the middle of this piece. Then I threaded the 8mm probe through this flat piece and soldered them together.
DS18b20 temperature thermometer with cable and JB weld epoxy around it
Then I wired up a DS18b20 thermometer and sealed this with some JB weld to try and stop any condensation problems when the thermometer is placed into the pipe.
Level probe with heat sink compound ready to be inserted into copper pipe
I then put a little bit of heat sink compound on the end of the thermometer and pushed it all the way down into the copper pipe to form the whole temperature probe assembly. I then wrapped a little tap around the top to stop the thermometer from ever falling out of the copper pipe assembly.
The Pokeys57e module I am using to interface with all the items I use already has all the communications built in to talk to one wire temperature thermometers, So all I had to do was configure it within the Pokeys57e software and the temperature values were available for use.