Smoothed Thermocouple Tables of Extended Significance (°C), Volume 2: Section 2.1 Page: 1
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SMOOTHED THERMOCOUPLE TABLES OF EXTENDED SIGNIFICANCE (C)
R. K. Adams E. G. Davisson
Volume 2
SECTION 2.1 PLATINUM VS PLATINUM-10% RHODIUM THERMOCOUPLES
This section contains tables of emf (in absolute millivolts) vs temperature (in degrees Celsius on the
International Temperature Scale of 1948) for Platinum vs Platinum-10% rhodium thermocouples. The
values in these tables, derived from those given in National Bureau of Standards Circular 561, Table 2, 1
are computed to more significant digits, that is, to the nearest 0.001 lv. The techniques of computation
are described in Vol. 1 of this report.
Figure 1, a plot of the difference in microvolts between the values in the smoothed table and those in
the original table vs temperature, illustrates how the values in the smoothed table compare with those in
the original table.
In Table 1 a smoothed emf value is tabulated in absolute millivolts for every degree Celsius in the
range of the table.
In Table 1A the first two columns contain the same information as given in Table 1. To the right of
these two columns is a difference table of the millivolt values in column 2. The difference table is ex-
pressed in thousandths of microvolts and contains orders 0 through 5. This difference table gives a
convenient tabulation of differences for those engaged in temperature difference work.
Although these tables are expressed to the nearest 0.001 iv, which is roughly equivalent to 0.00010C,
this in no way implies that temperature measurements to this accuracy are possible. The user of these
tables is reminded of the accuracy tolerances on thermocouples published by the American Society for
Testing and Materials 2 and the Instrument Society of America, 3 which state limits of error equivalent to
about 2.80C from 0 to 5400C, 0.5% of reading from 540 to 14800C for "standard" materials, and one-
half these limits for "special" materials. Individual calibration of platinum vs platinum-10% rhodium
thermocouples in the ORNL Standards Laboratory can improve their accuracy to better than 0.50C in the
range of 0 to 11000C, and the reproducibility will be better than 0.250C.
After a thermocouple has been used in the field to measure temperature, the reproducibility of the
characteristic calibration curve for that thermocouple, previously standardized in the ORNL Standards
Laboratory, depends on such factors as the temperatures to which the thermocouple had been exposed, the
length of exposure to elevated or depressed temperatures, and the conditions of exposure.4
1H. Shenker et al., "Reference Tables for Thermocouples," Nat. Bur. Std. (U.S.) Circ. 561, GPO, Washington,
1955.
2"Temperature Electromotive Force (EMF) for Thermocouples, ASTM E 230-63," Am. Soc. Testing Mater.,
ASTM Std. 1964, Pt. 30, pp. 646-704; see Table XIII, p. 700.
3"Thermocouples and Thermocouple Extension Wires - Terminology, Limits of Error, and Wire Sizes," Recom-
mended Practice RP 1.3, Instrument Society of America, Pittsburgh, Pa., 1959.
4"Temperature Electromotive Force (EMF) Tables for Thermocouples, ASTM E 230-63," Am. Soc. Testing
Mater., ASTM Std. 1964, Pt. 30, pp. 646-704; see Note 3 to Table XIII, p. 700.
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Adams, R. K. & Davisson, E. G. Smoothed Thermocouple Tables of Extended Significance (°C), Volume 2: Section 2.1, report, March 1965; Oak Ridge, Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc100366/m1/7/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.