PID controller. Thermocouples

[gle3105]

In experimenting I attached the K- type 800c rated thermocouple to the bottom of the pot on the valve.
My reasoning was to keep the thermocouple clean of lead / dross and sense temperature right at the source to the mold.
Plus no extra clutter on top of the pot.
I accomplished this by removing the crimped end of the thermocouple exposing the end sensor. PICS
The valve on the LEE 4-20 ( wrote in earlier post I had a 10lb , my error) is 3/8” and threaded with a nut on the bottom of the melting pot.
Insert the thermocouple into an “enlarged” 3/8” ring crimp. PIC ( shown is a sample with insulation sleeve still on. Remove before installing.)
Adjust the sensor so upon tightening the valve nut on the crimp ring it’s not crushed.
Removed the valve nut and installed the ring crimp with the thermocouple sensor facing the bottom of the pot.
Drilled a hole in bottom aluminum enclosure to pass the cable through.
Worked like a charm for me.

 

[gle3105]

I tried the top thermocouple. IMO it gets in the way especially if using a ladle. ( well at least the way I do it. LOL)
My preference is the bottom connection. Calibrate the Thermocouple /PID deviation using a known thermometer in the mix. I had to add about 15 degrees to the thermocouple output.
Picture show a current input PV temp reading of 78.0 and a SV Set Value of 83,8 .
The red light is "ON" indicating output.
I turn the Lee pot stat to MAX , plug it into the back of the controller.
Then I try to do everything IdahoLewis says.