scholarly journals Platinum resistance thermometer calibration on the international practical temperature scale of 1968. [-182. 962 to +630. 74/sup 0/C; PRT68 code]

1977 ◽  
Author(s):  
S.R. Drake
1972 ◽  
Vol 94 (2) ◽  
pp. 381-386 ◽  
Author(s):  
R. P. Benedict ◽  
R. J. Russo

The International Practical Temperature Scale has been redefined recently. It follows that the interpolating equations relating platinum resistance to temperature must be reevaluated for all platinum resistance thermometers which are used as standards for calibration work. After a brief review of the former calibration procedure, the new temperature scale is discussed as it affects resistance thermometry in the temperature range from 0 C to 630.74 C. An example based on new experimental data is given to illustrate the method of determining thermometer constants for the new scale, and to indicate the magnitude of the changes required.


1960 ◽  
Vol 38 (8) ◽  
pp. 1027-1047 ◽  
Author(s):  
R. J. Berry

The reproducibility of the normal boiling point of sulphur, a fixed calibration point on the International Temperature Scale, has been investigated using a closed manometer-boiler system. Measurements embracing several sources of sulphur and a number of changes in the operating conditions have shown that the sulphur point can be reproduced with a standard deviation of about 0.001 °C with our apparatus.Tests were made on eight samples of sulphur from three different sources in an attempt to resolve the uncertainty in the time the sulphur takes to reach temperature equilibrium after it has been brought to the boiling point. The results indicate that pure sulphur will reach equilibrium almost immediately but that an impurity content of as little as 0.01% can delay equilibrium up to 10 days. The temperature–time dependence can be ascribed to the effect of impurities on the time required for allotropic equilibrium to be attained. This hypothesis is discussed in detail and it is shown that it gives a consistent interpretation of the results presented here and those of previous investigations. The merits of replacing the sulphur point with the freezing point of zinc on the International Temperature Scale are also examined.The long-term stability of the coefficients of a Meyers platinum resistance thermometer is determined and a method of improving this stability for prolonged use at high temperatures is outlined.


In a paper entitled “ The Practical Measurement of Temperature/’ read before the Royal Society in 1886, Professor Callendar drew attention to the method of measuring temperature based on the determination of the electrical resistance of a platinum wire. He showed that the method was capable of a very general application, and that the platinum resistance thermometer was an instrument giving consistent and accurate results over a very wide temperature range. Callendar pointed out that if R 0 denote the resistance of the spiral of a particular platinum thermometer at 0°, and R 1 its resistance at 100, we may establish for the particular wire a temperature scale, which we may call the scale of platinum temperatures,such that if R be the resistance at any temperature T° on the air-scale, this temperature on the platinum scale will be R-R 0 /R 1 -R 0 X 100°. For this quantity, Callendar employs the symbol pt , its value depending on the sample of platinum chosen.


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