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Magnetically Insensitive Precision Thermometer

IP.com Disclosure Number: IPCOM000050548D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hoechli, UT: AUTHOR [+3]

Abstract

Precise measurements of the temperature below approx. 800K rest on the calibration of temperature-dependent resistences, like Pt or Ge:Li, by means of the international gas thermometer. These secondary standards, distributed by the National Bureau of Standards, are however strongly sensitive to an external magnetic field H, leading to an erroneous reading of several K in a field of 0.3 T.

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Magnetically Insensitive Precision Thermometer

Precise measurements of the temperature below approx. 800K rest on the calibration of temperature-dependent resistences, like Pt or Ge:Li, by means of the international gas thermometer. These secondary standards, distributed by the National Bureau of Standards, are however strongly sensitive to an external magnetic field H, leading to an erroneous reading of several K in a field of 0.3 T.

The vibration frequency of piezoelectric KTa(1-x) Nb(x)0(3) provides a field- independent standard. The main properties of the compound, frequency f independent of H and f = c + erf((T-T )/ delta T(c)), where the error function erf((T-T(c))/delta T(c)) = pi(1/2) integral exp(-t(2))dt and delta T(c)a = 3K, allow a calibration of delta T approx. mk in a region of +/- 10K around T(c). The critical temperature T(c) can be chosen in the range from 10K to 700K by appropriate composition of the compound. Readout is achieved by the ultrasonic resonance method, or, in an improved version, the resonator may be plugged into an oscillator circuit analogous to a digital watch. * J.J. Van de Klink and D. Rytz with Ecole Polytechnique Federale de Lausanne, Switzerland.

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