ASTM E 230/E230M : 2023

1.1This specification contains reference tables (Tables 8 to 25) that give temperature-electromotive force (emf) relationships for Types B, C, E, J, K, N, R, S, and T thermocouples.2 These are the thermocouple types most commonly used in industry. The tables contain all of the temperature-emf data currently available for the thermocouple types covered by this standard and may include data outside of the recommended upper temperature limit of an included thermocouple type.

1.2In addition, the specification includes standard and special tolerances on initial values of emf versus temperature for thermocouples (Table 1), thermocouple extension wires (Table 2), and compensating extension wires for thermocouples (Table 3). Users should note that the stated tolerances apply only to the temperature ranges specified for the thermocouple types as given in Tables 1, 2, and 3, and do not apply to the temperature ranges covered in Tables 8 to 25.

1.3Tables 4 and 5 provide insulation color coding for thermocouple and thermocouple extension wires as customarily used in the United States.

1.4Recommendations regarding upper temperature limits for the thermocouple types referred to in 1.1 are provided in Table 6.

1.5Tables 26 to 45 give temperature-emf data for single-leg thermoelements referenced to platinum (NIST Pt-67). The tables include values for Types BP, BN, JP, JN, KP (same as EP), KN, NP, NN, TP, and TN (same as EN).

1.6Tables for Types RP, RN, SP, and SN thermoelements are not included since, nominally, Tables 18 to 21 represent the thermoelectric properties of Type RP and SP thermoelements referenced to pure platinum. Tables for the individual thermoelements of Type C are not included because materials for Type C thermocouples are normally supplied as matched pairs only.

1.7Polynomial coefficients which may be used for computation of thermocouple emf as a function of temperature are given in Table 7. Coefficients for the emf of each thermocouple pair as well as for the emf of most individual thermoelements versus platinum are included. Coefficients for type RP and SP thermoelements are not included since they are nominally the same as for types R and S thermocouples, and coefficients for type RN or SN relative to the nominally similar Pt-67 would be insignificant. Coefficients for the individual thermoelements of Type C thermocouples have not been established.

1.8Coefficients for sets of inverse polynomials are given in Table 46. These may be used for computing a close approximation of temperature (°C) as a function of thermocouple emf. Inverse functions are provided only for thermocouple pairs and are valid only over the emf ranges specified.

1.9This specification is intended to define the thermoelectric properties of materials that conform to the relationships presented in the tables of this standard and bear the letter designations contained herein. Topics such as ordering information, physical and mechanical properties, workmanship, testing, and marking are not addressed in this specification. The user is referred to specific standards such as Specifications E235, E574, E585/E585M, E608/E608M, E1159, or E2181/E2181M for guidance in these areas.

1.10The temperature-emf data in this specification are intended for industrial and laboratory use.

1.11Thermocouple color codes per IEC 584–3 are given in Appendix X1.

1.12The values stated in either SI units or inch-pound units are to be regarded separately as standard.

1.13This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.14This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.