Is it possible to use an S-type thermocouple at temperatures over 1300 degrees for a long period of time?

The temperature range of S-type thermocouples (platinum-rhodium 10%–platinum) is approximately from 0°C to 1600°C, with the maximum operating temperature under standard conditions usually being 1300°C. Although it can theoretically withstand higher temperatures, long-term use at temperatures above 1300°C will affect the lifespan of the thermocouple as well as the accuracy of the measurements. Using S-type thermocouples at temperatures above 1300 degrees for an extended period of time (that is, above their recommended operating temperature) can lead to accelerated aging of the thermocouples and increased calibration errors. Type B thermocouples (platinum-rhodium 30%–platinum-rhodium 6%) have a wider range of applications; their measurement range is approximately from 600°C to 1700°C, with a maximum of up to 1800°C. Indeed, B-type thermocouples perform worse than S-type thermocouples at low temperatures (below 400°C), especially in terms of the stability and accuracy of temperature readings. Given that your application temperature is around 1370°C, which exceeds the recommended long-term operating temperature for S-type thermocouples but is below the optimal performance range of B-type thermocouples, this is indeed a challenging situation. If long-term measurements within this temperature range are required, an R-type thermocouple (platinum-rhodium 13%–platinum) can be considered; its operating temperature range is similar to that of the S-type, but it may offer better stability and a longer lifespan. Furthermore, for high-temperature measurements, non-contact temperature measurement methods can also be considered, such as infrared thermography or spectral radiometric thermometers; they are usually more stable and accurate for measuring high temperatures compared to contact thermocouples. In practical applications, selecting the appropriate thermocouple requires balancing factors such as cost, accuracy, service life, and environment. In such cases, it may be necessary to consult professional suppliers or experts in temperature measurement equipment to select the thermocouple type that is most suitable for your application. At the same time, to ensure measurement stability and extend the service life of thermocouples, appropriate protective measures and regular calibration are also very important. .

Theoretically, it’s fine to use S pairs at 1300°C, but generally S pairs are used below 1200°C. For 1300 and above, it is still recommended to use B even, though B is costly.