HIGH-PRECISION INDIUM RESISTANCE THERMOMETERS J . F. Kos, i\4. DROLET, A N D J. L. G. LAMARCHE

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Department of Physics, University of Ottawa, Ottawa, Canada Received May 15, 1967 An account is given of the design, construction, calibration, and reproducibility of two types of indium thermometers. The type B thermometer was found to be reprod~~cible t o better than 0.01 "I< between 4.2 "K and room temperature. However, thermometers employing indi~unfroin the same spool and constructed in the same way d o not show the s a m e Z function; consequently each thermometer must be calibrated over the range in which it is t o be used. INTRODUCTION

The merits of employing an indium element in a resistance thermometer designed for use between 4.2 "E( and room temperature have been discussed by several authors. White and Woods (1957)pointed out the advantages of indium over other possible materials. The results of their ~neasurementson several samples indicated that the reproducibility was affected by strains introduced in the indium filaments by the formers on whicli they were wound. In a follo\ving paper, Wliite et al. (1958)reported that a filament wound on a mica cross and having a nominal room-temperature resistance of four ohms proved to be reproducible "to about A0.01 OK a t most temperatures". The effects of cycling on the ice-point resistance were found to be small, corresponding to changes of less than A 3 m deg. Their values were tabulated in the form Z = (R - 1