Inductive noise thermometer: Theoretical aspects

Heikki Seppä, Timo Varpula

    Research output: Contribution to journalArticleScientificpeer-review

    5 Citations (Scopus)

    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 languageEnglish
    Pages (from-to)771 - 776
    Number of pages6
    JournalJournal of Applied Physics
    Volume74
    Issue number2
    DOIs
    Publication statusPublished - 1993
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    thermometers
    antennas
    impedance
    temperature
    metal plates
    noise temperature
    magnetic fields
    resistors
    electric contacts
    contamination
    conduction
    electric potential

    Cite this

    Seppä, Heikki ; Varpula, Timo. / Inductive noise thermometer : Theoretical aspects. In: Journal of Applied Physics. 1993 ; Vol. 74, No. 2. pp. 771 - 776.
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    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.    ",
    author = "Heikki Sepp{\"a} and Timo Varpula",
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    Inductive noise thermometer : Theoretical aspects. / Seppä, Heikki; Varpula, Timo.

    In: Journal of Applied Physics, Vol. 74, No. 2, 1993, p. 771 - 776.

    Research output: Contribution to journalArticleScientificpeer-review

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    T1 - Inductive noise thermometer

    T2 - Theoretical aspects

    AU - Seppä, Heikki

    AU - Varpula, Timo

    N1 - Project code: SÄH 1204

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    AB - 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.    

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