### Abstract

We describe a new noncontacting method for measuring the temperature of electrically conducting objects by sensing the magnetic field noise. When a high‐

*Q*antenna is placed close to a conductive material, e.g., a hot metal plate, the effective noise temperature of the antenna becomes proportional to the temperature of the material. Contrary to the conventional noise thermometer in which a resistor is embedded in the material, the method requires neither galvanic nor thermal contact. If the antenna impedance at different frequencies is known, the temperature of the object can be calculated from the total voltage noise of the antenna. We show, however, that for high‐*Q*antennae the knowledge of the impedance at resonance is adequate to determine the unknown temperature. Consequently, the temperature of moving objects can be measured via synchronous monitoring of the total noise of the antenna and its impedance at resonance. Since only electrically conductive objects create magnetic field noise, the method is immune to nonconductive contamination of the surface.Original language | English |
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Pages (from-to) | 771 - 776 |

Number of pages | 6 |

Journal | Journal of Applied Physics |

Volume | 74 |

Issue number | 2 |

DOIs | |

Publication status | Published - 1993 |

MoE publication type | A1 Journal article-refereed |

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## Cite this

Seppä, H., & Varpula, T. (1993). Inductive noise thermometer: Theoretical aspects.

*Journal of Applied Physics*,*74*(2), 771 - 776. https://doi.org/10.1063/1.354865