ASTM E207 Thermal EMF Test of Single Thermo-element Materials

Scope:

ASTM E207 is a thermal EMF test of single thermo-element materials by comparison with a reference thermo-element of similar EMF-temperature properties. This test applies to new thermocouple materials over the temperature ranges normally associated with thermocouples and their extension wires. This test does not apply to stability testing or inhomogeneity testing.

Test procedure:

The EMF of a thermoelement sample is determined by comparison to a reference thermoelement with similar Seebeck coefficients (Figure 1). The ASTM E207 test is conducted on one or more lengths of specimens connected to a single length of the reference thermoelement at a single point. The joined ends are held at the test temperature, and their opposite ends are held at a constant reference temperature. The EMF of the reference thermoelement relative to Pt-67 at several test temperatures is provided by a reference facility. The EMF of the test thermoelement relative to Pt-67 is determined by algebraically adding the measured EMF to the EMF of the reference thermoelement at each test temperature.

Figure 01: Basic circuit diagram for a thermoelectric EMF test

Test Specimen:

The sample shall represent one continuous spool or coil of thermoelectric material. The sample shall consist of two specimens, one cut from each end of the spool or coil.

Data:

In ASTM E207, the calibrated relative EMF value Exp, for each test temperature Tt, shall be calculated by:

where:

=the EMF of the reference thermoelement (r) that has been calibrated relative to NIST Pt-67,

= the measured EMF for the tested thermoelement relative to the reference thermoelement, when their common junction is at the test temperature, Tt, and their reference junctions are at the ice point.

Conclusion:

ASTM E207 is a thermal EMF test of single thermo-element materials by comparison with a reference thermo-element of similar EMF-temperature properties.