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Significance and Use
5.1 Many electronic instruments that are designed to be used with thermocouples use some method of reference junction compensation. In many industrial applications it may be impractical to use a physical ice bath as a temperature reference in a thermocouple circuit. The instrument must therefore be able to measure the temperature at the point of electrical connection of the thermocouple and either add or subtract voltage to give a corrected equivalent of what that thermocouple would indicate had there physically been 0 °C reference junctions present in the circuit. There are two types of instruments that generally apply these techniques: electronic thermometer readouts that use a thermocouple as the sensor, and calibrators designed to calibrate these digital thermometer readouts. Additionally, the probe and circuit described in this guide can be used with a voltmeter to emulate a thermometer or a voltage source to calibrate temperature-indicating instrumentation. In all cases the probe must be calibrated if traceability or an uncertainty analysis, or both, is required.
1.1 This guide covers methods of calibration and use of thermocouple reference junction probes (cold junction compensation probes) in the evaluation of electronic reference junction compensation circuits. Their use with instruments that measure only voltage is also covered.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This 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.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
Other ReferencesBIPM JCGM 100:2008 Evaluation of Measurement DataGuide to the Expression of Uncertainty in Measurement Available from Pavillon de Breteuil, F-92312 Svres Cedex, FRANCE, https://www.bipm.org/. NIST Monograph 175 Temperature-Electromotive Force Reference Functions and Tables for the Letter-Designated Thermocouple Types Based on the ITS-90 Available from National Institute of Standards and Technology (NIST), 100 Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, USA, http://www.nist.gov.
E220 Test Method for Calibration of Thermocouples By Comparison Techniques
E230/E230M Specification for 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
E1129/E1129M Specification for Thermocouple Connectors
E1684/E1684M Specification for Miniature Thermocouple Connectors
E1750 Guide for Use of Water Triple Point Cells
E2623 Practice for Reporting Thermometer Calibrations
ICS Number Code 17.200.20 (Temperature-measuring instruments)
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ASTM E2730-21, Standard Guide for Calibration and Use of Thermocouple Reference Junction Probes in Evaluation of Electronic Reference Junction Compensation Circuits, ASTM International, West Conshohocken, PA, 2021, www.astm.orgBack to Top