E20.14 - Thermocouples - Testing

SIGNIFICANCE AND USE
5.1 This standard provides a description of test methods used in other ASTM specifications to establish certain acceptable methods for characterizing thermocouple assemblies and thermocouple cable. These test methods define how those characteristics shall be determined.  
5.2 The usefulness and purpose of the included tests are given for the category of tests.  
5.3 Warning—Users should be aware that certain characteristics of thermocouples might change with time and use. If a thermocouple’s designed shipping, storage, installation, or operating temperature has been exceeded, that thermocouple’s moisture seal may have been compromised and may no longer adequately prevent the deleterious intrusion of water vapor. Consequently, the thermocouple’s condition established by test at the time of manufacture may not apply later. In addition, inhomogeneities can develop in thermoelements because of exposure to higher temperatures, even in cases where maximum exposure temperatures have been lower than the suggested upper use temperature limits specified in Table 1 of Specification E608/E608M. For this reason, calibration of thermocouples destined for delivery to a customer is not recommended. Because the emf indication of any thermocouple depends upon the condition of the thermoelements along their entire length, as well as the temperature profile pattern in the region of any inhomogeneity, the emf output of a used thermocouple will be unique to its installation. Because temperature profiles in calibration equipment are unlikely to duplicate those of the installation, removal of a used thermocouple to a separate apparatus for calibration is not recommended. Instead, in situ calibration by comparison to a similar thermocouple known to be good is often recommended.
SCOPE
1.1 This document lists methods for testing Mineral-Insulated, Metal-Sheathed (MIMS) thermocouple assemblies and thermocouple cable, but does not require that any of these tests be performed nor does it state criteria for acceptance. The acceptance criteria are given in other ASTM standard specifications that impose this testing for those thermocouples and cable. Examples from ASTM thermocouple specifications for acceptance criteria are given for many of the tests. These tabulated values are not necessarily those that would be required to meet these tests, but are included as examples only.  
1.2 These tests are intended to support quality control and to evaluate the suitability of sheathed thermocouple cable or assemblies for specific applications. Some alternative test methods to obtain the same information are given, since in a given situation, an alternative test method may be more practical. Service conditions are widely variable, so it is unlikely that all the tests described will be appropriate for a given thermocouple application. A brief statement is made following each test description to indicate when it might be used.  
1.3 The tests described herein include test methods to measure the following properties of sheathed thermocouple material and assemblies.  
1.3.1 Insulation Properties:  
1.3.1.1 Compaction—direct method, absorption method, and tension method.
1.3.1.2 Thickness.
1.3.1.3 Resistance—at room temperature and at elevated temperature.  
1.3.2 Sheath Properties:  
1.3.2.1 Integrity—two water test methods and mass spectrometer.
1.3.2.2 Dimensions—length, diameter, and roundness.
1.3.2.3 Wall thickness.
1.3.2.4 Surface—gross visual, finish, defect detection by dye penetrant, and cold-lap detection by tension test.
1.3.2.5 Metallurgical structure.
1.3.2.6 Ductility—bend test and tension test.  
1.3.3 Thermoelement Properties:  
1.3.3.1 Calibration.
1.3.3.2 Homogeneity.
1.3.3.3 Drift.
1.3.3.4 Thermoelement diameter, roundness, and surface appearance.
1.3.3.5 Thermoelement spacing.
1.3.3.6 Thermoelement ductility.
1.3.3.7 Metallurgical structure.  
1.3.4 Thermocouple Assembly Properti...

SIGNIFICANCE AND USE
5.1 These test procedures confirm and document that the thermocouple assembly was not damaged prior to or during the installation process and that the extension wires are properly connected.  
5.2 The test procedures should be used when thermocouple assemblies are first installed in their working environment.  
5.3 In the event of subsequent thermocouple failure, these procedures will provide benchmark data to verify failure and may help to identify the cause of failure.  
5.4 The usefulness and purpose of the applicable tests will be found within each category.  
5.5 These tests are not meant to ensure that the thermocouple assembly will measure temperatures accurately. Such assurance is derived from proper thermocouple and instrumentation selection and proper placement in the location at which the temperature is to be measured. For further information, the reader is directed to MNL 12, Manual on the Use of the Thermocouples in Temperature Measurement2 which is an excellent reference document on metal sheathed thermocouple uses.
SCOPE
1.1 This guide covers methods for users to test metal sheathed thermocouple assemblies, including the extension wires just prior to and after installation or some period of service.  
1.2 The tests are intended to ensure that the thermocouple assemblies have not been damaged during storage or installation, to ensure that the extension wires have been attached to connectors and terminals with the correct polarity, and to provide benchmark data for later reference when testing to assess possible damage of the thermocouple assembly after operation. Some of these tests may not be appropriate for thermocouples that have been exposed to temperatures higher than the recommended limits for the particular type.  
1.3 The tests described herein include methods to measure the following characteristics of installed sheathed thermocouple assemblies and to provide benchmark data for determining if the thermocouple assembly has been subsequently damaged in operation:  
1.3.1 Loop Resistance:  
1.3.1.1 Thermoelements,
1.3.1.2 Combined extension wires and thermoelements.  
1.3.2 Insulation Resistance:  
1.3.2.1 Insulation, thermocouple assembly,
1.3.2.2 Insulation, thermocouple assembly and extension wires.  
1.3.3 Seebeck Voltage:  
1.3.3.1 Thermoelements,
1.3.3.2 Combined extension wires and thermocouple assembly.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 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.

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.
SCOPE
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.

SIGNIFICANCE AND USE
5.1 Thermocouples fabricated from thermocouple cable that has been contaminated by moisture or by other impurities may undergo large changes in thermoelectric properties or may fail catastrophically when exposed to high temperatures. Since such contamination usually lowers the electrical resistance between the thermoelements and the sheath substantially, measurement of the insulation resistance can provide a valuable check of insulation quality and cleanliness, and can serve as a basis for rejection of unsuitable material and unreliable components. For manufacturers in particular, low electrical insulation resistance can also be indicative of displaced thermoelements or conductors or defects in the metal sheath which will require further investigation, but all users should be aware of these potential defects when faced with an unacceptable insulation resistance measurement.  
5.2 This test method is primarily intended for use by manufacturers and users of mineral-insulated, metal-sheathed (MIMS) thermocouples or MIMS cables to verify that measured values of insulation resistance exceed specified minimum values, such as those listed in Specifications E235, E585/E585M, E608/E608M, E2181/E2181M, and E2821. Manufacturers and users should be aware, however, that when the insulation resistance is greater than 1 × 108 Ω, disagreement by an order of magnitude in the results obtained with this test method is not unusual. In addition, users of this test method should appreciate that the room temperature insulation resistance of both MIMS cables and of finished thermocouples will change during shipment, storage, and use if the end seals are damaged or defective. Consequently, values of insulation resistance determined by this test method may not necessarily be repeatable.
SCOPE
1.1 This test method provides the procedures for measuring the room temperature electrical insulation resistance between the thermoelements and between the thermoelements and the sheath, of a mineral-insulated, metal-sheathed (MIMS) thermocouple or mineral-insulated, metal-sheathed (MIMS) thermocouple cable or between the conductors and between the conductors and the sheath, of mineral-insulated, metal-sheathed (MIMS) cable used for industrial resistance thermometers. It may be used to measure the insulation resistance of bulk lengths of mineral-insulated, metal-sheathed MIMS cable previously sealed against moisture intrusion or to test a thermocouple having an ungrounded measuring junction. This method cannot be used to test a thermocouple having a grounded measuring junction unless the measuring junction is removed prior to testing, after which the thermocouple may be dealt with in the same manner as a mineral-insulated, metal-sheathed (MIMS) cable.  
1.2 This test method applies primarily to thermocouple cables and cable used for industrial resistance thermometers conforming to Specifications E585/E585M, E2181/E2181M, and E2821 and to thermocouples conforming to Specifications E608/E608M and E2181/E2181M, but may also be applied to thermocouples or MIMS cables that are suitable for use in air, whose sheath or thermoelements or conductors are comprised of refractory metals, that are tested in a dry and chemically inert environment, and that may employ compacted ceramic insulating materials other than magnesia (MgO) or alumina (Al2O3). Users of this test method should note that specifications dealing with compacted ceramic insulating materials other than magnesia or alumina, which are described in Specification E1652, are not currently available. As a result, acceptance criteria must be agreed upon between the customer and supplier at the time of purchase, or alternatively, judgment and experience must be applied in establishing test voltage levels and acceptable insulation resistance values for these types of thermocouples and MIMS cables.  
1.3 This test method may be used for thermocouples or MIMS cables having an outside...

SIGNIFICANCE AND USE
5.1 These verification tests may be performed by users or calibrators of thermocouples. The methods are useful for both new and used thermocouples. They provide a means to assess the accuracy with which a thermocouple is capable of measuring temperature.  
5.2 Results from these tests may be used to determine whether to use or discard a thermocouple. If the thermocouple is subsequently used, the test results may be included in the measurement uncertainty budget. In many circumstances, the results of in-situ verifications may be used to recalibrate a used thermocouple. Laboratory measurements, on the other hand, may be used only to verify the original thermocouple calibration or to determine the uncertainty of temperature measurements with the tested thermocouple. Laboratory measurements generally do not suffice to determine the emf-versus-temperature response of a thermocouple found to be inhomogeneous.
SCOPE
1.1 This guide describes tests that may be applied to new or previously used thermocouples for the purpose of verification. Some of the tests perform a suitable verification by themselves, but many tests merely alert the user to serious problems if the thermocouple fails the test. Some of the tests examine inhomogeneity and others detect wire or measuring-junction breakage. For Style U mineral-insulated metal-sheathed (MIMS) thermocouples with ungrounded measuring junctions, this guide includes tests that examine the electrical isolation of the sheath as well as sheath deterioration.  
1.2 The first set of tests involves measurement verifications designed to be performed while the thermocouple is in its usage environment. The second set is composed of electrical tests and visual inspections designed to evaluate the functionality of the thermocouple; these tests may be performed either in house or in a calibration laboratory. The third set is made up of homogeneity tests designed to be performed in a calibration laboratory. Some of the tests provide simple methods to identify some, but not all, defective thermocouples, and alone do not suffice to verify a used thermocouple. They may need to be complemented by other tests for a complete verification.  
1.3 The reader of this guide should decide which of the described tests need to be performed. This decision is dependent on whether the reader uses thermocouples for temperature measurement or performs thermocouple calibrations in a laboratory. For users of thermocouples, it is recommended that appropriate tests from the first and second sets be performed initially, as they provide immediate on-site verification of the thermocouples. The appropriateness of a test is dependent upon the user’s temperature measurement uncertainty requirements. Some tests may have lower uncertainties in their verification measurements than others. If these tests do not clearly determine the suitability of the thermocouples, they should be sent to a calibration laboratory for performing appropriate tests from the third set, which give the most complete information on the thermocouple homogeneity. For those who perform thermocouple calibrations in a laboratory, it is recommended that appropriate tests from the second and third sets be performed prior to calibration. The appropriateness of a test is dependent on the calibration laboratory’s capability and convenience for performing the test, as well as the characteristics of the unit under test (UUT).  
1.4 This guide may be used for base metal and noble metal thermocouples. Some of the methods covered may apply to refractory metal thermocouples but caution is advised as suitable reference devices at high temperatures may not be readily available.  
1.5 This guide may involve hazardous materials, operations and equipment. 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 ...

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.
SCOPE
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.

SIGNIFICANCE AND USE
5.1 These test procedures confirm and document that the thermocouple assembly was not damaged prior to or during the installation process and that the extension wires are properly connected.  
5.2 The test procedures should be used when thermocouple assemblies are first installed in their working environment.  
5.3 In the event of subsequent thermocouple failure, these procedures will provide benchmark data to verify failure and may help to identify the cause of failure.  
5.4 The usefulness and purpose of the applicable tests will be found within each category.  
5.5 These tests are not meant to ensure that the thermocouple assembly will measure temperatures accurately. Such assurance is derived from proper thermocouple and instrumentation selection and proper placement in the location at which the temperature is to be measured. For further information, the reader is directed to MNL 12, Manual on the Use of the Thermocouples in Temperature Measurement2 which is an excellent reference document on metal sheathed thermocouple uses.
SCOPE
1.1 This guide covers methods for users to test metal sheathed thermocouple assemblies, including the extension wires just prior to and after installation or some period of service.  
1.2 The tests are intended to ensure that the thermocouple assemblies have not been damaged during storage or installation, to ensure that the extension wires have been attached to connectors and terminals with the correct polarity, and to provide benchmark data for later reference when testing to assess possible damage of the thermocouple assembly after operation. Some of these tests may not be appropriate for thermocouples that have been exposed to temperatures higher than the recommended limits for the particular type.  
1.3 The tests described herein include methods to measure the following characteristics of installed sheathed thermocouple assemblies and to provide benchmark data for determining if the thermocouple assembly has been subsequently damaged in operation:  
1.3.1 Loop Resistance:  
1.3.1.1 Thermoelements,
1.3.1.2 Combined extension wires and thermoelements.  
1.3.2 Insulation Resistance:  
1.3.2.1 Insulation, thermocouple assembly,
1.3.2.2 Insulation, thermocouple assembly and extension wires.  
1.3.3 Seebeck Voltage:  
1.3.3.1 Thermoelements,
1.3.3.2 Combined extension wires and thermocouple assembly.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 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.

SIGNIFICANCE AND USE
5.1 Thermocouples fabricated from thermocouple cable that has been contaminated by moisture or by other impurities may undergo large changes in thermoelectric properties or may fail catastrophically when exposed to high temperatures. Since such contamination usually lowers the electrical resistance between the thermoelements and the sheath substantially, measurement of the insulation resistance can provide a valuable check of insulation quality and cleanliness, and can serve as a basis for rejection of unsuitable material and unreliable components. For manufacturers in particular, low electrical insulation resistance can also be indicative of displaced thermoelements or conductors or defects in the metal sheath which will require further investigation, but all users should be aware of these potential defects when faced with an unacceptable insulation resistance measurement.  
5.2 This test method is primarily intended for use by manufacturers and users of mineral-insulated, metal-sheathed (MIMS) thermocouples or MIMS cables to verify that measured values of insulation resistance exceed specified minimum values, such as those listed in Specifications E235, E585/E585M, E608/E608M, E2181/E2181M, and E2821. Manufacturers and users should be aware, however, that when the insulation resistance is greater than 1 × 108 Ω, disagreement by an order of magnitude in the results obtained with this test method is not unusual. In addition, users of this test method should appreciate that the room temperature insulation resistance of both MIMS cables and of finished thermocouples will change during shipment, storage, and use if the end seals are damaged or defective. Consequently, values of insulation resistance determined by this test method may not necessarily be repeatable.
SCOPE
1.1 This test method provides the procedures for measuring the room temperature electrical insulation resistance between the thermoelements and between the thermoelements and the sheath, of a mineral-insulated, metal-sheathed (MIMS) thermocouple or mineral-insulated, metal-sheathed (MIMS) thermocouple cable or between the conductors and between the conductors and the sheath, of mineral-insulated, metal-sheathed (MIMS) cable used for industrial resistance thermometers. It may be used to measure the insulation resistance of bulk lengths of mineral-insulated, metal-sheathed MIMS cable previously sealed against moisture intrusion or to test a thermocouple having an ungrounded measuring junction. This method cannot be used to test a thermocouple having a grounded measuring junction unless the measuring junction is removed prior to testing, after which the thermocouple may be dealt with in the same manner as a mineral-insulated, metal-sheathed (MIMS) cable.  
1.2 This test method applies primarily to thermocouple cables and cable used for industrial resistance thermometers conforming to Specifications E585/E585M, E2181/E2181M, and E2821 and to thermocouples conforming to Specifications E608/E608M and E2181/E2181M, but may also be applied to thermocouples or MIMS cables that are suitable for use in air, whose sheath or thermoelements or conductors are comprised of refractory metals, that are tested in a dry and chemically inert environment, and that may employ compacted ceramic insulating materials other than magnesia (MgO) or alumina (Al2O3). Users of this test method should note that specifications dealing with compacted ceramic insulating materials other than magnesia or alumina, which are described in Specification E1652, are not currently available. As a result, acceptance criteria must be agreed upon between the customer and supplier at the time of purchase, or alternatively, judgment and experience must be applied in establishing test voltage levels and acceptable insulation resistance values for these types of thermocouples and MIMS cables.  
1.3 This test method may be used for thermocouples or MIMS cables having an outside...

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.
SCOPE
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 the standard. The values given in parentheses are for information only.  
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 and health practices and determine the applicability of regulatory limitations prior to use.

SIGNIFICANCE AND USE
5.1 These verification tests may be performed by users or calibrators of thermocouples. The methods are useful for both new and used thermocouples. They provide a means to assess the accuracy with which a thermocouple is capable of measuring temperature.  
5.2 Results from these tests may be used to determine whether to use or discard a thermocouple. If the thermocouple is subsequently used, the test results may be included in the measurement uncertainty budget. In many circumstances, the results of in situ verifications may be used to recalibrate a used thermocouple. Laboratory measurements, on the other hand, may be used only to verify the original thermocouple calibration or to determine the uncertainty of temperature measurements with the tested thermocouple. Laboratory measurements generally do not suffice to determine the emf-versus-temperature response of a thermocouple found to be inhomogeneous.
SCOPE
1.1 This guide describes tests that may be applied to new or previously used thermocouples for the purpose of verification. Some of the tests perform a suitable verification by themselves, but many tests merely alert the user to serious problems if the thermocouple fails the test. Some of the tests examine inhomogeneity and others detect wire or measuring-junction breakage. For Style U mineral-insulated metal-sheathed (MIMS) thermocouples with ungrounded measuring junctions, this guide includes tests that examine the electrical isolation of the sheath as well as sheath deterioration.  
1.2 The first set of tests involves measurement verifications designed to be performed while the thermocouple is in its usage environment. The second set is composed of electrical tests and visual inspections designed to evaluate the functionality of the thermocouple; these tests may be performed either in house or in a calibration laboratory. The third set is made up of homogeneity tests designed to be performed in a calibration laboratory. Some of the tests provide simple methods to identify some, but not all, defective thermocouples, and alone do not suffice to verify a used thermocouple. They may need to be complemented by other tests for a complete verification.  
1.3 The reader of this guide should decide which of the described tests need to be performed. This decision is dependent on whether the reader uses thermocouples for temperature measurement or performs thermocouple calibrations in a laboratory. For users of thermocouples, it is recommended that appropriate tests from the first and second sets be performed initially, as they provide immediate on-site verification of the thermocouples. The appropriateness of a test is dependent upon the user’s temperature measurement uncertainty requirements. Some tests may have lower uncertainties in their verification measurements than others. If these tests do not clearly determine the suitability of the thermocouples, they should be sent to a calibration laboratory for performing appropriate tests from the third set, which give the most complete information on the thermocouple homogeneity. For those who perform thermocouple calibrations in a laboratory, it is recommended that appropriate tests from the second and third sets be performed prior to calibration. The appropriateness of a test is dependent on the calibration laboratory’s capability and convenience for performing the test, as well as the characteristics of the unit under test (UUT).  
1.4 This guide may be used for base metal and noble metal thermocouples. Some of the methods covered may apply to refractory metal thermocouples but caution is advised as suitable reference devices at high temperatures may not be readily available.  
1.5 This guide may involve hazardous materials, operations and equipment. 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 ...

SIGNIFICANCE AND USE
5.1 These test procedures confirm and document that the thermocouple assembly was not damaged prior to or during the installation process and that the extension wires are properly connected.  
5.2 The test procedures should be used when thermocouple assemblies are first installed in their working environment.  
5.3 In the event of subsequent thermocouple failure, these procedures will provide benchmark data to verify failure and may help to identify the cause of failure.  
5.4 The usefulness and purpose of the applicable tests will be found within each category.  
5.5 These tests are not meant to ensure that the thermocouple assembly will measure temperatures accurately. Such assurance is derived from proper thermocouple and instrumentation selection and proper placement in the location at which the temperature is to be measured. For further information, the reader is directed to MNL 12, Manual on the Use of the Thermocouples in Temperature Measurement2 which is an excellent reference document on metal sheathed thermocouple uses.
SCOPE
1.1 This guide covers methods for users to test metal sheathed thermocouple assemblies, including the extension wires just prior to and after installation or some period of service.  
1.2 The tests are intended to ensure that the thermocouple assemblies have not been damaged during storage or installation, to ensure that the extension wires have been attached to connectors and terminals with the correct polarity, and to provide benchmark data for later reference when testing to assess possible damage of the thermocouple assembly after operation. Some of these tests may not be appropriate for thermocouples that have been exposed to temperatures higher than the recommended limits for the particular type.  
1.3 The tests described herein include methods to measure the following characteristics of installed sheathed thermocouple assemblies and to provide benchmark data for determining if the thermocouple assembly has been subsequently damaged in operation:  
1.3.1 Loop Resistance:
1.3.1.1 Thermoelements,
1.3.1.2 Combined extension wires and thermoelements.  
1.3.2 Insulation Resistance:
1.3.2.1 Insulation, thermocouple assembly,
1.3.2.2 Insulation, thermocouple assembly and extension wires.  
1.3.3 Seebeck Voltage:
1.3.3.1 Thermoelements,
1.3.3.2 Combined extension wires and thermocouple assembly.  
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.

SIGNIFICANCE AND USE
5.1 This standard provides a description of test methods used in other ASTM specifications to establish certain acceptable limits for characteristics of thermocouple assemblies and thermocouple cable. These test methods define how those characteristics shall be determined.  
5.2 The usefulness and purpose of the included tests are given for the category of tests.  
5.3 Warning—Users should be aware that certain characteristics of thermocouples might change with time and use. If a thermocouple’s designed shipping, storage, installation, or operating temperature has been exceeded, that thermocouple’s moisture seal may have been compromised and may no longer adequately prevent the deleterious intrusion of water vapor. Consequently, the thermocouple’s condition established by test at the time of manufacture may not apply later. In addition, inhomogeneities can develop in thermoelements because of exposure to higher temperatures, even in cases where maximum exposure temperatures have been lower than the suggested upper use temperature limits specified in Table 1 of Specification E608/E608M. For this reason, calibration of thermocouples destined for delivery to a customer is not recommended. Because the EMF indication of any thermocouple depends upon the condition of the thermoelements along their entire length, as well as the temperature profile pattern in the region of any inhomogeneity, the EMF output of a used thermocouple will be unique to its installation. Because temperature profiles in calibration equipment are unlikely to duplicate those of the installation, removal of a used thermocouple to a separate apparatus for calibration is not recommended. Instead, in situ calibration by comparison to a similar thermocouple known to be good is often recommended.
SCOPE
1.1 This document lists methods for testing Mineral-Insulated, Metal-Sheathed (MIMS) thermocouple assemblies and thermocouple cable, but does not require that any of these tests be performed nor does it state criteria for acceptance. The acceptance criteria are given in other ASTM standard specifications that impose this testing for those thermocouples and cable. Examples from ASTM thermocouple specifications for acceptance criteria are given for many of the tests. These tabulated values are not necessarily those that would be required to meet these tests, but are included as examples only.  
1.2 These tests are intended to support quality control and to evaluate the suitability of sheathed thermocouple cable or assemblies for specific applications. Some alternative test methods to obtain the same information are given, since in a given situation, an alternative test method may be more practical. Service conditions are widely variable, so it is unlikely that all the tests described will be appropriate for a given thermocouple application. A brief statement is made following each test description to indicate when it might be used.  
1.3 The tests described herein include test methods to measure the following properties of sheathed thermocouple material and assemblies.  
1.3.1 Insulation Properties:  
1.3.1.1 Compaction—direct method, absorption method, and tension method.
1.3.1.2 Thickness.
1.3.1.3 Resistance—at room temperature and at elevated temperature.  
1.3.2 Sheath Properties:  
1.3.2.1 Integrity—two water test methods and mass spectrometer.
1.3.2.2 Dimensions—length, diameter, and roundness.
1.3.2.3 Wall thickness.
1.3.2.4 Surface—gross visual, finish, defect detection by dye penetrant, and cold-lap detection by tension test.
1.3.2.5 Metallurgical structure.
1.3.2.6 Ductility—bend test and tension test.  
1.3.3 Thermoelement Properties:  
1.3.3.1 Calibration.
1.3.3.2 Homogeneity.
1.3.3.3 Drift.
1.3.3.4 Thermoelement diameter, roundness, and surface appearance.
1.3.3.5 Thermoelement spacing.
1.3.3.6 Thermoelement ductility.
1.3.3.7 Metallurgical structure.  
1.3.4 Thermocouple Assembly Prop...