ASTM E601 - 07a(2013)

    Standard Test Method for Measuring Electromotive Force (emf) Stability of Base-Metal Thermoelement Materials with Time in Air

    Active Standard ASTM E601 | Developed by Subcommittee: E20.04

    Book of Standards Volume: 14.03

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    Significance and Use

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

    5.3 This test method 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 method are valid only under the specified test conditions. Results would be affected by changes in 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; (4) stability of the platinum thermoelement.

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

    5.6 The reliability of this test method 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.

    1. Scope

    1.1 This test method measures emf stability of base-metal thermoelement materials in air referenced to platinum at specified constant elevated temperatures using dual, simultaneous, emf indicators, or using a single emf indicator, with the test and reference emf measured alternately. This test is conducted over a period of weeks.

    1.2 A calibrated platinum-rhodium/platinum thermocouple is used as a reference standard to establish the test temperature.

    1.3 The useful life of a thermocouple depends on the stability of the emf generated at given temperatures for a required time interval. This method provides a quantitative measure of the stability of individual thermoelements. By combining the results of the positive (P) and negative (N) thermoelements, the stability of a thermocouple comprised of both P and N thermoelements may be obtained. The emf of an individual thermoelement is measured against platinum, which may be the platinum leg of the platinum-rhodium/platinum reference thermocouple, or an additional platinum reference.

    Note 1Some thermoelements may show insignificant emf drift while undergoing relatively rapid oxidation. In these cases, failure of the thermoelement may be indicated only by a large rise in the electrical resistance between joined thermoelements, as measured at the reference junctions.
    Note 2See ASTM MNL 12 for recommended upper temperature limits in air.2
    Note 3This test method is only applicable for initially new thermoelements. Base-metal thermoelements exposed to temperatures above 200 °C become thermoelectrically inhomogeneous, and stability testing of inhomogeneous thermoelements will give ambiguous results.

    1.4 This 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 and health practices and determine the applicability of regulatory limitations prior to use.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    E220 Test Method for Calibration of Thermocouples By Comparison Techniques

    E230 Specification and Temperature-Electromotive Force (EMF) Tables for Standardized Thermocouples

    E344 Terminology Relating to Thermometry and Hydrometry

    E563 Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature

    E1159 Specification for Thermocouple Materials, Platinum-Rhodium Alloys, and Platinum

    ICS Code

    ICS Number Code 17.200.20 (Temperature-measuring instruments)

    UNSPSC Code

    UNSPSC Code

    Referencing This Standard

    DOI: 10.1520/E0601

    ASTM International is a member of CrossRef.

    Citation Format

    ASTM E601-07a(2013), Standard Test Method for Measuring Electromotive Force (emf) Stability of Base-Metal Thermoelement Materials with Time in Air, ASTM International, West Conshohocken, PA, 2013,

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