Thermocouple Specification Criteria
The best thermocouple for him was a bare wire. Measuring Junction . Copper. Constantan. -200°C to 0°C. ±1°C. -. Blue. Blue+. (Non-Magnetic). (Non-magnetic) or ±.1.5% . A larger gage size will extend the life of the iron wire. T- Copper .
http://www.smartsensors.com/spectherm.pdf