The primary difference between Type J and Type K thermocouples is the measuring range, and the sensitivity. Type K is the most common general purpose thermocouple with a sensitivity of approximately 41 µV/°C.
A wide variety of probes are available in its −50°C to +900°C / -58°F to +1652°F range. Type K wire color standard is yellow (+) and red (-). Type J has a more restricted range of −50 to +400°C, but higher sensitivity of about 50 µV/°C. Type J wire color standard is white (+) and red (-).
