What do thermocouple tolerance Class 1 and Class 2 mean ?
Per JIS C1602-1995 These tolerance classes follow: * Class 1 more than -40℃、max 375℃：±1.5℃ more than 375℃、max 1000℃：±0.004・|t|（±0.4% of measuring temperature) * Class 2: more than -40℃, max +333℃： ±2.5℃ more than 333℃、max 1200℃ : ±0.0075 |t| (±0.75% of measuring temperature) A thermocouple measures temperature by generating an electromotive force that is based on the difference between the temperature being measured and a reference temperature at the other end of the thermocouple. The tolerance is the maximum deviation from the actual temperature being measured by the thermocouple. There is a Class 3 with a large tolerance then Class 2.
