Temperature Measurements Using Small Quantities of Cerium Magnesium Nitrate

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Abstract
A study is made of the requirements of a mutual inductance system suitable for precise temperature measurements using about one gram of cerium magnesium nitrate. The mutual inductance is measured by a commercial version of the electronic bridge originally proposed by Pillinger, Jastram, and Daunt [Rev. Sci. Instr. 29, 159 (1958)]. A discussion of the effects of spurious magnetic materials, of nearby paramagnetic salts, and of the vacuum jacket is given. The linearity and stability of the electronic bridge, as well as the effects of external circuitry, are also discussed. Results are given for the properties of two coil sets with cerium magnesium nitrate thermometers used to test the stability of the bridge and the validity of expressions for mutual inductance obtained in the text. It may be concluded that if solid air can be kept away from the coils, the long term instabilities for a 1‐g thermometer lead to errors of about 0.004°K−1 in 1/T. A comparison between ballistic and 17‐cps bridge measurements down to 0.015°K showed that 1/T* as determined by the two methods was the same with an error of less than 0.1%.