Thermometers in Low Magnetic Fields

• Published in: International journal of thermophysics 2010-09, Vol.31 (8-9), p.1622-1632
• Main Authors: Gersak, G, Begus, S
• Format: Article
• Language: English
• Subjects: Classical Mechanics; Condensed Matter Physics; Direct current; Industrial Chemistry/Chemical Engineering; Magnetic fields; Physical Chemistry; Physics; Physics and Astronomy; Plating baths; Platinum; Resistance thermometers; Thermistors; Thermocouples; Thermometers
• ISSN: 0195-928X; 1572-9567
• DOI: 10.1007/s10765-010-0818-5

In this article the effect of low amplitude DC magnetic fields on different types of thermometers is discussed. By means of a precision water-cooled electromagnet, the effect of a magnetic field on platinum resistance thermometers, thermistors, and type T, J, and K thermocouples was investigated, while thermometers were thermally stabilized in thermostatic baths. Four different baths were used for temperatures from 77 K (−196 °C) to 353 K (80 °C): liquid nitrogen bath (nitrogen boiling point at atmospheric pressure), ice-point bath, room-temperature air bath, and hot-water bath. The generated DC magnetic field of high relative precision (2 × 10 −4 at 1 T, 4 × 10 −5 short-term stability) and high relative uniformity (2 × 10 −5 over 1 cm 2 , 10 mm gap) had a magnetic flux density of 1 T in the center of the gap between the magnet pole caps. The results indicate a magnetic effect of up to 100 mK due to a 1 T magnetic field for the types of thermocouples composed of ferromagnetic materials (Fe, Cr, Ni). For platinum resistance thermometers, thermistors, and non-magnetic type T thermocouples, the detected magnetic effect was weaker, i.e., under 10 mK.