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

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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.    ",
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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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