Determination of pressure effect on thermocouple electromotive force using multi-anvil apparatus

ABSTRACT

We developed a method to determine the absolute pressure effect on thermocouple electromotive force (EMF), based on a single wire method using Kawai-type multi-anvil apparatus. In this method, pressure conditions along the wires were evaluated based on in situ X-ray diffraction using synchrotron X-ray radiation. The pressure effect of the Seebeck coefficients of chromel and alumel was determined up to 7 GPa and 600°C by the analyses of single wire EMFs and pressure-temperature profiles along the wires. The temperature correction for the type K thermocouple was calculated to be from 0°C to –3°C in the studied conditions. Since the multi-anvil apparatus is capable of achieving much higher pressure and temperature, the method presented in this study promises to reveal absolute temperature correction for thermocouples over a wide range of pressure and temperature conditions.

KEYWORDS:

• Thermocouple
• multi-anvil apparatus
• chromel–alumel
• electromotive force
• pressure effect

Acknowledgements

We thank S. Kakizawa and T. Arimoto for their helpful support during the in situ X-ray diffraction experiments, and H. Dekura, M. Nishi, T. Ohuchi, and K.N. Matsukage for constructive discussions. We also thank T. Shinmei for his help in the off-line experiments, and T. Irifune for allowing us to conduct this study in his project at SPring-8. The in situ X-ray experiments were performed by using the SPEED-1500 system at BL04B1 in SPring-8 (proposal no. 2015A0075). Constructive comments by an anonymous reviewer are appreciated.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Japan Society for the Promotion of Science (JSPS) under Grant-in-Aid for Scientific Research (B) (15H03749).