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STANDARD ITS-90 THERMOCOUPLE TABLES

The Instrument Society of America (ISA) has assigned standard letter designations to a number of thermocouple types having specified emf-temperature relations. These designations and the approximate metal compositions which meet the required relations, as well as the useful temperature ranges, are given below:

Type B(Pt + 30% Rh) vs. (Pt + 6% Rh) 0 to 1820°C

Type E(Ni + 10% Cr) vs. (Cu + 43% Ni)-270 to 1000°C Type J Fe vs. (Cu + 43% Ni)-210 to 1200°C Type K (Ni + 10% Cr) vs. (Ni + 2% Al + 2% Mn + 1% Si)-270 to 1372°C Type N (Ni + 14% Cr + 1.5% Si) vs. (Ni + 4.5% Si + 0. 1% Mg) -270 to 1300°C Type R(Pt + 13% Rh) vs. Pt-50 to 1768°C Type S (Pt + 10% Rh) vs. Pt -50 to 1768°C

Type T Cu vs. (Cu + 43% Ni)-270 to 400°C

The compositions are given in weight percent, and the positive leg is listed first. It should be emphasized that the standard letter designations do not imply a precise composition but rather that the specified emf-temperature relation is satisfied.

The first set of tables below lists, for each thermocouple type, the emf as a function of temperature on the International Temperature Scale of 1990 (ITS-90). The coefficients in the equation used to generate the table are also given. The second set of tables gives the inverse relationships, i.e., the coefficients in the polynomial equation which expresses the temperature as a function of thermocouple emf. The accuracy of these equations is also stated.

Further details and tables at closer intervals may be found in Reference 1.

REFERENCES

1. Burns, G. W., Seroger, M. G., Strouse, G. F., Croarkin, M. C., and Guthrie, W.F.,

Temperature-Electromotive Force Reference Functions and Tables for the

Letter-Designated Thermocouple Types Based on the ITS-90, Nat. Inst. Stand. Tech.

(U.S.) Monogr. 175, 1993.

2. Schooley, J. F., Thermometry, CRC Press, Boca Raton, FL, 1986.

Type B thermocouples: emf-temperature (°C) reference table and equations

Thermocouple emf in Millivolts as a Function of Temperature in Degrees Celsius (ITS-90)

Reference Junctions at 0°C

t/°C0102030405060708090100

0 0.000 -0.002 -0.003 -0.002 -0.000 0.002 0.006 0.011 0.017 0.025 0.033 100 0.033 0.043 0.053 0.065 0.078 0.092 0.107 0.123 0.141 0.159 0.178 200 0.178 0.199 0.220 0.243 0.267 0.291 0.317 0.344 0.372 0.401 0.431 300 0.431 0.462 0.494 0.527 0.561 0.596 0.632 0.669 0.707 0.746 0.787 400 0.787 0.828 0.870 0.913 0.957 1.002 1.048 1.095 1.143 1.192 1.242

500 1.242 1.293 1.344 1.397 1.451 1.505 1.561 1.617 1.675 1.733 1.792 600 1.792 1.852 1.913 1.975 2.037 2.101 2.165 2.230 2.296 2.363 2.431 700 2.431 2.499 2.569 2.639 2.710 2.782 2.854 2.928 3.002 3.078 3.154 800 3.154 3.230 3.308 3.386 3.466 3.546 3.626 3.708 3.790 3.873 3.957 900 3.957 4.041 4.127 4.213 4.299 4.387 4.475 4.564 4.653 4.743 4.834 1000 4.834 4.926 5.018 5.111 5.205 5.299 5.394 5.489 5.585 5.682 5.780 1100 5.780 5.878 5.976 6.075 6.175 6.276 6.377 6.478 6.580 6.683 6.786 1200 6.786 6.890 6.995 7.100 7.205 7.311 7.417 7.524 7.632 7.740 7.848 1300 7.848 7.957 8.066 8.176 8.286 8.397 8.508 8.620 8.731 8.844 8.956 1400 8.956 9.069 9.182 9.296 9.410 9.524 9.639 9.753 9.868 9.984 10.099

1500 10.099 10.215 10.331 10.447 10.563 10.679 10.796 10.913 11.029 11.146 11.263 1600 11.263 11.380 11.497 11.614 11.731 11.848 11.965 12.082 12.199 12.316 12.433 1700 12.433 12.549 12.666 12.782 12.898 13.014 13.130 13.246 13.361 13.476 13.591 1800 13.591 13.706 13.820

Temperature Ranges and Coefficients of Equations Used to Compute the Above Table

The equations are of the form: E= c0 + c1t + c2t2 + c3t3 + ... c n t n, where E is the emf in millivolts, t is the temperature in degrees Celsius (ITS-90), and c0, c1, c2, c3, etc. are the coefficients. These coefficients are extracted from NIST Monograph 175.

0°C630.615°C

to to

630.615°C1820°C

c0= 0.000 000 000 0-3.893 816 862 1

c1=-2.465 081 834 6 × 10-4 2.857 174 747 0 × 10-2

c2= 5.904 042 117 1 × 10-6-8.488 510 478 5 × 10-5

c3=-1.325 793 163 6 × 10-9 1.578 528 016 4 × 10-7

c4= 1.566 829 190 1 × 10-12-1.683 534 486 4 × 10-10

c5=-1.694 452 924 0 × 10-15 1.110 979 401 3 × 10-13

c6= 6.299 034 709 4 × 10-19-4.451 543 103 3 × 10-17

c7= . . . . . . . . . . . . 9.897 564 082 1 × 10-21

c8= . . . . . . . . . . . .-9.379 133 028 9 × 10-25