Thermal noise thermometer

Japanese: 熱雑音温度計 - ねつざつおんおんどけい（英語表記）thermal noise thermometer

When exposed to heat, free electrons in a resistor move irregularly, generating an irregular voltage (known as thermal noise) across the resistor, but the magnitude of the thermal noise varies depending on the temperature of the resistor. A thermometer that makes use of this phenomenon is called a thermal noise thermometer. The principle was clarified in 1928, but it was not until 1949 that an actual thermometer was made. In this thermometer, the resistor acts as a temperature-sensing element, but the characteristics of the thermometer do not change in principle even if the material of the resistor or the pressure applied to the resistor changes. Therefore, in addition to being used academically for thermodynamic temperature measurement, it has also been tried out for practical temperature measurement under high pressure and inside atomic reactors, and in recent years, coupled with improvements in electronic technology, it has gradually become more widely used under several new forms.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

抵抗体の中の自由電子は，熱の作用を受けて不規則に運動し，抵抗体の両端に不規則な電圧(いわゆる熱雑音)を生じさせるが，熱雑音の大きさは，抵抗体の温度によって変わる。このことを利用する温度計を熱雑音温度計という。原理は1928年に明らかにされたが，実際に温度計がつくられたのは49年であった。この温度計では，抵抗体が感温素子の働きをするが，抵抗体の材質が変わっても，また抵抗体にかかる圧力が変わっても，温度計の特性は原理的には変わらないので，学術上で熱力学的な温度測定に応用されるほか，高圧下とか原子炉内などでの実用的な温度測定にも試用され，とくに近年では電子技術的な改良とあいまって，いくつかの新形式のもとにしだいに広く使われるようになってきた。

出典　株式会社平凡社世界大百科事典第２版について　情報

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