Standard Guide for Measuring Electromotive Force (EMF) Stability of Base-Metal Thermoelement Materials With Time in Air

Importancia y uso:

5.1 This test is important because the accuracy of a temperature measurement by a thermocouple is directly related to the emf stability of the thermoelements.

5.2 This test is used to verify that the tested thermoelements meet the intended requirements.

5.3 This test is useful in comparing the emf stability of two base metal thermoelements under the same conditions. The test and reference emf may be measured either simultaneously or alternately.

5.4 The relative stabilities of base metal thermoelements determined by this test are valid only under the specified test conditions. Results will be affected by changes in any of the following conditions: (1) temperature profile or gradient along the length of the thermoelements, (2) abundance, velocity and composition of the air surrounding the test pieces, (3) thermoelectric inhomogeneity of the test thermoelements, and (4) stability of the platinum thermoelement.

5.5 The test does not address the determination of base metal thermoelement stabilities over a series of temperature changes.

5.6 The reliability of this test depends on the emf stability of the reference platinum thermoelement. For testing the relative emf stability of base-metal thermoelements, a reference element of platinum that has sufficient thermoelectric stability to determine any significant change in emf of base-metal thermoelements shall be used. To ascertain that the experimental method protects the platinum sufficiently from degradation, the method shall be validated by performing the procedure described in Appendix X1 prior to the actual test.

5.7 The test result does not apply to applications in which the temperature distribution, for a given measuring junction temperature, changes with time.

Subcomité:

E20.11

Referida por:

E0344-23

Volúmen:

14.03

Número ICS:

17.200.20 (Temperature-measuring instruments)