Tables and Reference Functions and tables are given for the eight letter-designated thermocouple types: noble-metal types B, R, and S; and base-metal types E, J, K, N, and T. The reference functions and tables for types B, E, J, K, and T are mathematical conversions of those given in NBS Monograph 125 [1]. The reference function for type N is a conversion of functions given in NBS Monograph 161.[2] The conversions were based on the published differences between the temperatures on the ITS-90 and those on the IPTS-68.[3,4,5] The reference functions given for types R and S thermocouples are taken directly from recently published research [6,7,8], and they were used to compute the reference tables presented for those two types.

The temperature ranges of the letter-designated thermocouple types, nominal compositions, and representative trade names are given in menu items “Thermocouple Types Definition” and “Letter designations, compositions, and trade names.” The temperature ranges given in “Thermocouple Types Definition” are those of the reference functions.

The letter designations used in this database follow the recommendations of the Instrumentation, Systems, and Automation Society (ISA) and the American Society for Testing and Materials (ASTM). The practice of identifying each of the commonly used thermocouple types with a letter was originated by the ISA and adopted in 1964 as an American National Standard (C96.1)[9]. As noted in the present ASTM American National Standard [10], the letter designations identifying the reference tables may be applied to any thermocouple that has a temperature-voltage relationship agreeing within the tolerances specified in the standards with the values given by the table, regardless of the composition of the thermocouple. Substantial variations in composition for a given letter type do occur, particularly for types J, K, and E.

Tables and Reference Functions are given in this database for the various letter-designated thermoelements versus platinum, Pt-67, which is the designation for the platinum thermoelectric reference standard that is maintained by the NIST Standard Reference Materials Program. It replaces the former standard, Pt-27, which was used from 1922 until January 1973. The high-purity platinum standard reference material, designated SRM 680, that was issued in 1967 by the NBS Office of Standard Reference Materials[11] provides the basis for Pt-67. More specifically, Pt-67 is a selected, highly homogeneous portion of SRM 680 that was set aside to serve as the thermoelectric reference standard. This portion of SRM 680 was recertified in 1977 as SRM 1967. The historical development of Pt-67, its characterization and properties are described in NBS Special Publication 260-56.[19] The preparation and characterization of Pt-67 is described in detail in Monograph 175.

NIST Reference functions and Tables of thermocouple electromotive force (emf) versus temperature have been adopted as standards by the American Society for Testing and Materials (ASTM) [13] and the International Electrotechnical Commission (IEC) [14]. All letter-designated thermocouple types are manufactured to match these standards to within specified tolerances. Furthermore, calibrations of individual thermocouples are often expressed in terms of the deviation in emf of the test thermocouple from the emf value given by the reference function.

The thermocouple part of this database reproduces a subset of the Tables and Reference Functions of NIST Monograph 175.[1] All temperatures used by this database are given on the International Temperature Scale of 1990 (ITS-90)[4], and all emf values are given in units of the 1990 SI volt.[5]

A discussion of each thermocouple type is included in Monograph 175.[1] For each thermocouple type, Monograph 175 gives a summary of the history of development, special precautions on usage, recommended temperature ranges of use, initial calibration tolerances, and nominal chemical compositions.

References

1. Powell, R. L.; Hall, W. J.; Hyink, C. H., Jr.; Sparks, L. L.; Burns, G. W.; Scroger, M. G.; Plumb, H. H., “Thermocouple reference tables based on the IPTS-68,” Natl. Bur. Stand. (U.S.) Monograph 125, 1974. 410 p. DOI:https://doi.org//10.6028/NBS.MONO.125
2. Burley, N. A.; Powell, R. L.; Burns, G. W.; Scroger, M. G., “The nicrosil versus nisil thermocouple: properties and thermoelectric reference data, ” Natl. Bur. Stand. (U.S.) Monograph 161, 1978. 167 p. DOI:https://doi.org//10.6028/NBS.MONO.161
3. Preston-Thomas, H., “The International Temperature Scale of 1990 (ITS90). Metrologia 27, 3-10 (1990). DOI:https://doi.org//10.1088/0026-1394/27/1/002
4. Preston-Thomas, H., "The International Practical Temperature Scale of 1968. Amended Edition of 1975," Metrologia 12, 7-17 (1976). DOI:https://doi.org//10.1088/0026-1394/12/1/003
5. Rusby, R. L.; Hudson, R. P.; Durieux, M., “Revised Values for (t90 - t68) from 630 °C to 1064 °C.” Metrologia 31, 149-153 (1994). DOI:https://doi.org//10.1088/0026-1394/31/2/009
6. Burns, G. W.; Strouse, G. F.; Mangum, B. W.; Croarkin, M. C.; Guthrie, W. F.; Marcarino, P.; Battuello, M.; Lee, H. K.; Kim, J. C.; Gam, K. S.; Rhee, C.; Chattle, M.; Arai, M.; Sakurai, H.; Pokhodun, A. I.; Moiseeva, N. P.; Perevalova, S. A.; de Groot, M. J.; Zhang, J.; Fan, K.; Wu, S., “New reference function for platinum-10% rhodium versus platinum (type S) thermocouples based on the ITS-90, Part I and Part II,” in Temperature: Its Measurement and Control in Science and Industry, Vol. 6, Schooley, J. F., ed., New York: American Institute of Physics, 1992. pp. 537-546.
7. Burns, G. W.; Strouse, G. F.; Mangum, B. W.; Croarkin, M. C.; Guthrie, W. F.; Chattle, M., “New reference functions for platinum-13% rhodium versus platinum (type R) and platinum-30% rhodium versus platinum-6% rhodium (type B) thermocouples based on the ITS-90,” in Temperature: Its Measurement and Control in Science and Industry, Vol. 6, Schooley, J. F., ed., New York: American Institute of Physics, 1992. pp. 559-564.
8. Guthrie, W. F.; Croarkin, M. C.; Burns, G. W.; Strouse, G. F.; Marcarino, P.; Battuello, M.; Lee, H. K.; Kim, J. C.; Gam, K. S.; Rhee, C.; Chattle, M.; Arai, M.; Sakurai, H.; Pokhodun, A. I.; Moiseeva, N. P.; Perevalova, S. A.; de Groot, M. J.; Zhang, J.; Fan, K.; Wu, S., “Statistical analysis of type S thermocouple measurements on the International Temperature Scale of 1990,” in Temperature: Its Measurement and Control in Science and Industry, Vol. 6, Schooley, J. F., ed., New York: American Institute of Physics, 1992. pp. 547-552.
9. Anon., “American National Standard: Temperature measurement thermocouples, C96.1,” Pittsburgh, Pennsylvania: Instrument Society of America, 1964.
10. Anon., “Standard E230-98”, 1999 Annual Book of ASTM Standards Vol. 14.03, Philadelphia: American Society for Testing and Materials (ASTM), 1994. pp. 109-284.
11. Anon., “New platinum standards,” Natl. Bur. Stand. (U.S.) Tech. News Bull. 52, 62 (1968).
12. L. L. Sparks and R. L. Powell, “Standard Reference Materials: Standard thermocouple material, Pt-67,” NBS Special Publication (SP) 260-56, National Institute of Standards and Technology, Gaithersburg, MD, 1978. DOI:https://doi.org//10.6028/NBS.SP.260-56
13. Anon., “American Society for Testing and Materials, Standard E230-98,” 1999 Annual Book of ASTM Standards Vol. 14.03, Philadelphia: ASTM; 1994. pp. 109-284.
14. Anon., “Revision of IEC 60 584-1: Thermocouples - Part 1: Reference tables,” Geneva: International Electrotechnical Commission (IEC), 1995. 155 p.