Been using fluke digital therms for many years in trouble shooting chillers and boiler problems. Found out you can buy thermocouple wire in rolls. One wire is magnetic it either goes on - or + cant remember which way but it wont hurt meter if wrong just wont read right. Key is getting correct temp resistant coating and making a well to insert into lead pot. I made well out of 1/4 copper tubing bent over at one end and beat flat with hammer so it wont leak. Works very well last 3 months.