* Achieved by optimizing thermal treatment of platinum wires and sensor structure
* Contributes to the improvement of temperature measurement and control at high temperatures, such as in materials manufacturing processes
Platinum resistance thermometers equipped with platinum wire in their sensors are used when precise temperature measurement is necessary, such as in semiconductor manufacturing. However, at high temperatures near 1000 °C, the resistance value of the platinum wire becomes unstable, and thermal strain occurs in the platinum wire due to high temperature, causing it to become even more unstable, and making precise measurement of high temperatures difficult.
By heat-cycling tests employing the AIST national standard (temperature standard), the platinum wire of the sensor was examined in detail to find optimum conditions for stabilizing the resistance value. As a result, it was found that when an appropriate thermal treatment is applied to the platinum wire, the resistance value is stable even at high temperatures around 1000 °C. Furthermore, a new sensor structure was devised, which reduces thermal strain that occurs in the platinum wire at high temperatures. From these findings, a new platinum resistance thermometer capable of temperature measurement at the 0.001 °C level of precision even at high temperature was developed. This thermometer has a bright prospect of highly precise temperature measurement and temperature control at high temperature, such as in materials processing.
The stability of the newly developed platinum resistance thermometer against heat cycle tests is of the world’s top level. In the future, it can contribute to the realization of high-precision temperature measurement and temperature control at high temperatures, such as in materials processes. Mutual comparisons of temperature standard near 1000 °C are carried out among various national metrology institutes, each of which maintains the temperature national standard of its own country. The newly developed thermometer can also play a very important role in such a world top-level comparison.
In the future, Chino Corporation will continue evaluating the long-term stability of the newly developed platinum resistance thermometer, while also working towards its commercialization. Additionally, AIST plans to advance research and development of highly precise thermometers at temperatures exceeding 1000° C, based on this thermometer.