E20.07 - Fundamentals in Thermometry

SIGNIFICANCE AND USE
4.1 This guide describes a procedure for placing a water triple-point cell in service and for using it as a reference temperature in thermometer calibration.  
4.2 The reference temperature attained is that of a fundamental state of pure water, the equilibrium between coexisting solid, liquid, and vapor phases.  
4.3 The cell is subject to qualification but not to calibration. The cell may be qualified as capable of representing the fundamental state (see 4.2) by comparison with a bank of similar qualified cells of known history, and it may be so qualified and the qualification documented by its manufacturer.  
4.4 The temperature to be attributed to a qualified water triple-point cell is exactly 273.16 K on the ITS-90, unless corrected for isotopic composition (refer to Appendix X3).  
4.5 Continued accuracy of a qualified cell depends upon sustained physical integrity. This may be verified by techniques described in Section 6.  
4.6 The commercially available triple point of water cells described in this standard are capable of achieving an expanded uncertainty (k=2) of between ±0.1 mK and ±0.05 mK, depending upon the method of preparation. Specified measurement procedures shall be followed to achieve these levels of uncertainty.  
4.7 Commercially-available triple point of water cells of unknown isotopic composition should be capable of achieving an expanded uncertainty (k=2) of no greater than 0.25 mK, depending upon the actual isotopic composition (3). These types of cells are acceptable for use at this larger value of uncertainty.
SCOPE
1.1 This guide covers the nature of two commercial water triple-point cells (types A and B, see Fig. 1) and provides a method for preparing the cell to realize the water triple-point and calibrate thermometers. The qualifications concerning preparation and the types of glass used for a cell are discussed. Tests for assuring the integrity of a qualified cell and of cells yet to be qualified are given. Precautions for handling the cell to avoid breakage are also described.  
FIG. 1 Configurations of two commonly used triple point of water cells, Type A and Type B, with ice mantle prepared for measurement at the ice/water equilibrium temperature. The cells are used immersed in an ice bath or water bath controlled close to 0.01 °C (see 5.5)  
1.2 The effect of hydrostatic pressure on the temperature of a water triple-point cell is discussed.  
1.3 Procedures for adjusting the observed SPRT resistance readings for the effects of self-heating and hydrostatic pressure are described in Appendix X1 and Appendix X2.  
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 The design of a controlled temperature bath will determine what thermometers can be calibrated and to what extent an isothermal condition is achieved. The lack of thermal stability and uniformity of the bath are sources of error that contribute to the overall calibration uncertainty.  
5.2 This guide describes a procedure for determining the effective working space for a controlled temperature fluid bath.  
5.3 This guide describes a procedure for determining the thermal stability within a controlled temperature fluid bath. Overall thermal stability is composed of the bath performance as specified by the manufacturer of the bath equipment and as a component of calibration uncertainty.  
5.4 This guide describes a procedure for determining the temperature uniformity of the working space of the controlled temperature fluid bath.
SCOPE
1.1 This guide is intended for use with controlled temperature comparison baths that contain test fluids and operate within the temperature range of –100 °C to 550 °C.  
1.2 This guide describes the essential features of controlled temperature fluid baths used for the purpose of thermometer calibration by the comparison method.  
1.3 This guide does not address the details on the design and construction of controlled-temperature fluid baths.  
1.4 This guide describes a method to define the working space of a bath and evaluate the temperature variations within this space. Ideally, the working space will be as close as possible to isothermal.  
1.5 This guide does not address fixed point baths, ice point baths, or vapor baths.  
1.6 This guide does not address fluidized powder baths.  
1.7 This guide does not address baths that are programmed to change temperature.  
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.9 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.  
1.10 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 A pure material has a well defined phase transition behavior, and the phase transition plateau, a characteristic of the material, can serve as a reproducible reference temperature for the calibration of thermometers. The melting or freezing points of some highly purified metals have been designated as defining fixed points on ITS-90. The fixed points of other materials have been determined carefully enough that they can serve as secondary reference points (see Tables 1 and 2). This guide presents information on the phase transition process as it relates to establishing a reference temperature. (A) Defining fixed point for ITS-90.(B) Realized as melting point.(C) Based on recommendation of International Bureau of Weights and Measures (BIPM) Working Group 2 of the Comité Consultatif de Thermométrie (CCT-WG2); published as: Bedford, R. E., Bonnier, G., Maas, H., and Pavese, F., "Recommended Values of Temperature on the International Temperature Scale of 1990 for a Selected Set of Secondary Reference Points", Metrologia, Vol 33, 1996, pp. 133. DOI: 10.1088/0026-1394/33/2/3.  (A) Values for cells of good design, construction, and material purity used with careful technique. Cells of lesser quality may not approach these values.(B) Realized as melting point.  
5.2 Fixed-point cells provide users with a means of realizing melting and freezing points. If the cells are appropriately designed and constructed, if they contain material of adequate purity, and if they are properly used, they can establish reference temperatures with uncertainties of a few millikelvins or less. This guide describes some of the design and use considerations.  
5.3 Fixed-point cells can be constructed and operated less stringently than required for millikelvin uncertainty, yet still provide reliable, durable, easy-to-use fixed points for a variety of industrial calibration and heat treatment purposes. For example, any freezing-point cell can be operated, often advantageously, as a melting-po...
SCOPE
1.1 This guide describes the essential features of fixed-point cells and auxiliary apparatus, and the techniques required to realize fixed points in the temperature range from 29 °C to 1085 °C.3  
1.2 Design and construction requirements of fixed-point cells are not addressed in this guide. Typical examples are given in Figs. 1 and 2.
FIG. 1 Examples of Fixed-Point Cells  
FIG. 2 Example of Fixed-Point Furnace  
Note 1: This example shows an insulated furnace body and two alternative types of furnace cores. The core on the left is a three-zone shielded type. The core on the right employs a heat pipe to reduce temperature gradients.  
1.3 This guide is intended to describe good practice and establish uniform procedures for the realization of fixed points.  
1.4 This guide emphasizes principles. The emphasis on principles is intended to aid the user in evaluating cells, in improving technique for using cells, and in establishing procedures for specific applications.  
1.5 For the purposes of this guide, the use of fixed-point cells for the accurate calibration of thermometers is restricted to immersion-type thermometers that, when inserted into the reentrant well of the cell, (1) indicate the temperature only of the isothermal region of the well, and (2) do not significantly alter the temperature of the isothermal region of the well by heat transfer.  
1.6 This guide does not address all of the details of thermometer calibration.  
1.7 This guide is intended to complement special operating instructions supplied by manufacturers of fixed-point apparatus.  
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.9 The following hazard caveat pertains only to the test method portion, Section 7, of this guide. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of th...

SIGNIFICANCE AND USE
5.1 This practice is adequate for use with other ASTM standards that specify the ice point as a reference. It is also intended to be adequate for most other ice-point reference purposes.  
5.2 The ice point is a common practical industrial reference point of thermometry. The ice point is relatively simple to realize and provides a readily available natural fixed-point reference temperature.  
5.3 Use in Resistance Thermometry:  
5.3.1 The ice point was a defining fixed point on practical temperature scales prior to 1960.  
5.3.2 The ITS-90 defines W(T90) = R(T90)/R(273.16 K), the measured resistance ratio of a Standard Platinum Resistance Thermometer (SPRT), in reference to the water triple point, not the ice point (1).3 In many instances, where the water triple point is not available, or when the accuracy obtainable with the water triple point is not required, reference to a properly established and maintained ice-point reference is used. For industrial-quality resistance thermometers, the resistance value is determined for 0 °C, and an uncertainty that is appropriate for the quality of the ice-point realization is assigned.  
5.4 Use in Thermoelectric Thermometry:  
5.4.1 In thermoelectric thermometry, the ice point is ordinarily used as the reference temperature (2).  
5.4.2 Adequate thermoelectric reference requires that thermocouple junctions be well-coupled thermally to the bath, electrically isolated from each other and from the bath, and adequately immersed to avoid perturbing the reference-junction temperatures by radiation and longitudinal conduction of heat along the thermoelements (3 and 4).  
5.5 Use in Liquid-in-Glass Thermometry:  
5.5.1 In liquid-in-glass thermometry, the ice point is ordinarily used as the reference temperature (5).  
5.5.2 The periodic recalibration of a liquid-in-glass thermometer at the ice point provides a reliable indication of the effect of gradual relaxation of residual mechanical strains in the glass that have a...
SCOPE
1.1 This practice covers a method of preparing, maintaining, and using a temperature reference bath of a mixture of shaved ice and water, saturated with air at a pressure of 101 325 Pa (1 atm).  
1.2 An industrial practice for relating values referenced to the ice point and to the water triple point on the ITS-90 is included.  
1.3 Methods to promote uniformity of bath temperature by mechanical stirring or agitation are not described in detail.  
1.4 Methods of approximating the ice point, as by thermostatically-controlled refrigeration, are not covered by this practice.  
1.5 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.  
1.6 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 This practice is adequate for use with all ASTM Test Methods which require the reporting of temperature measurements.  
5.2 The Report of Calibration, however named, is the physical output of the calibration laboratory. It shall be prepared so that both the results of the measurement(s) and the non-technical information necessary to support those results are conveyed in a manner that ensures accurate communication and justification of the results.  
5.3 This practice is not meant to supersede requirements of other standards practice such as ISO/IEC 17025 or ANSI/NCSL Z540.3.
SCOPE
1.1 This practice contains reporting requirements for thermometer calibrations included in ASTM Committee E20 Test Methods.  
1.2 This practice covers reports of calibration for radiation thermometers, liquid-in-glass thermometers, resistance thermometers, digital thermometers, and new thermocouples.
Note 1: This practice does not apply to used thermocouples.  
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 This guide applies to temperature sources with controlled temperature solid blocks. They are known under various names such as dry-well calibrators, dry-block calibrators, and temperature block calibrators. They are typically comprised of solid block materials such as metal or ceramic, a temperature-regulating device, a control sensor, and some built-in indicator of temperature in a portable package. Dry-block calibrators are commonly used for calibration of industrial thermometers. These calibrators are commonly used in either two modes: (1) the direct mode in which the calibrator is used as the calibrated reference, or (2) comparison mode in which the calibrator is an isothermal temperature source for comparing thermometers under test to a separate calibrated reference thermometer. The uncertainty of these calibrations is dependent on which of these two modes is used and a variety of thermal properties of the specific dry-block designs.  
5.2 A thermally uniform, stable, and accurate temperature zone for calibration may be achieved with given measurement uncertainty. Various thermal properties of dry-block calibrator blocks have been identified that shall be characterized and/or quantified to determine uncertainty of measurements and care taken during the calibration process to optimize results appropriately. Temperature stability has been long recognized as a variable to be characterized. Others include axial temperature uniformity, radial temperature uniformity, stem conduction, block loading, hysteresis, and controller accuracy. External factors that influence results include ambient temperature, drafts, and power fluctuations. Recognizing and testing these properties will greatly improve calibration results.
SCOPE
1.1 The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.  
1.2 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.  
1.3 This guide is intended for use with dry-block temperature calibrators without the use of fluids or thermal contact-enhancing media over a range of -100 °C to 1700 °C.  
1.4 In this guide, the essential features of dry-block calibrators used for the purpose of thermometer calibration in either the direct or comparison mode are described. The direct mode is defined as using the dry-block calibrator as a standalone instrument with the control sensor and the calibrator display serving as the reference while the comparison mode uses an external sensor and ancillary measurement system as the reference.  
1.5 Measurement practices to optimize the accuracy of a dry-block calibrator to obtain optimum results are proposed in this guide.  
1.6 Tests that can be performed to define uncertainty limits and how they may be used in creating uncertainty budgets are proposed in this guide.  
1.7 Dry-block calibrator accessories such as built-in reference thermometers, switch testing circuitry, computer communications, or current loops will not be discussed.  
1.8 It is advised that liquid-in-glass thermometers not be used in dry-block calibrators, as using liquid-in-glass thermometers with a metal block may cause damage to the readout of the thermometer.  
1.9 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 A pure material has a well defined phase transition behavior, and the phase transition plateau, a characteristic of the material, can serve as a reproducible reference temperature for the calibration of thermometers. The melting or freezing points of some highly purified metals have been designated as defining fixed points on ITS-90. The fixed points of other materials have been determined carefully enough that they can serve as secondary reference points (see Tables 1 and 2). This guide presents information on the phase transition process as it relates to establishing a reference temperature. (A) Defining fixed point for ITS-90.(B) Realized as melting point.  (A) Values for cells of good design, construction, and material purity used with careful technique. Cells of lesser quality may not approach these values.(B) Realized as melting point.  
5.2 Fixed-point cells provide users with a means of realizing melting and freezing points. If the cells are appropriately designed and constructed, if they contain material of adequate purity, and if they are properly used, they can establish reference temperatures with uncertainties of a few millikelvins or less. This guide describes some of the design and use considerations.  
5.3 Fixed-point cells can be constructed and operated less stringently than required for millikelvin uncertainty, yet still provide reliable, durable, easy-to-use fixed points for a variety of industrial calibration and heat treatment purposes. For example, any freezing-point cell can be operated, often advantageously, as a melting-point cell. Such use may result in reduced accuracy, but under special conditions, the accuracy may be commensurate with that of freezing points (see 6.3.10).  
5.4 The test procedure described in this guide produces qualification test data as an essential part of the procedure. These data furnish the basis for quality control of the fixed-point procedure. They provide for evaluation of results, assure continuing rel...
SCOPE
1.1 This guide describes the essential features of fixed-point cells and auxiliary apparatus, and the techniques required to realize fixed points in the temperature range from 29 to 1085°C.3  
1.2 Design and construction requirements of fixed-point cells are not addressed in this guide. Typical examples are given in Figs. 1 and 2.  
Note 1: This example shows an insulated furnace body and two alternative types of furnace cores. The core on the left is a three-zone shielded type. The core on the right employs a heat pipe to reduce temperature gradients.  
1.3 This guide is intended to describe good practice and establish uniform procedures for the realization of fixed points.  
1.4 This guide emphasizes principles. The emphasis on principles is intended to aid the user in evaluating cells, in improving technique for using cells, and in establishing procedures for specific applications.  
1.5 For the purposes of this guide, the use of fixed-point cells for the accurate calibration of thermometers is restricted to immersion-type thermometers that, when inserted into the reentrant well of the cell, (1) indicate the temperature only of the isothermal region of the well, and (2) do not significantly alter the temperature of the isothermal region of the well by heat transfer.  
1.6 This guide does not address all of the details of thermometer calibration.  
1.7 This guide is intended to complement special operating instructions supplied by manufacturers of fixed-point apparatus.  
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.9 The following hazard caveat pertains only to the test method portion, Section 7, of this guide. 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 det...

SIGNIFICANCE AND USE
5.1 This practice is adequate for use with other ASTM standards that specify the ice point as a reference. It is also intended to be adequate for most other ice-point reference purposes.  
5.2 The ice point is a common practical industrial reference point of thermometry. The ice point is relatively simple to realize and provides a readily available natural fixed-point reference temperature.  
5.3 Use in Resistance Thermometry:  
5.3.1 The ice point was a defining fixed point on practical temperature scales prior to 1960.  
5.3.2 The ITS-90 defines W(T90) = R(T90)/R(273.16 K), the measured resistance ratio of a Standard Platinum Resistance Thermometer (SPRT), in reference to the water triple point, not the ice point (1).3 In many instances, where the water triple point is not available, or when the accuracy obtainable with the water triple point is not required, reference to a properly established and maintained ice-point reference is used. For industrial-quality resistance thermometers, the resistance value is determined for 0 °C, and an uncertainty that is appropriate for the quality of the ice-point realization is assigned.  
5.4 Use in Thermoelectric Thermometry:  
5.4.1 In thermoelectric thermometry, the ice point is ordinarily used as the reference temperature (2).  
5.4.2 Adequate thermoelectric reference requires that thermocouple junctions be well-coupled thermally to the bath, electrically isolated from each other and from the bath, and adequately immersed to avoid perturbing the reference-junction temperatures by radiation and longitudinal conduction of heat along the thermoelements (3 and 4).  
5.5 Use in Liquid-in-Glass Thermometry:  
5.5.1 In liquid-in-glass thermometry, the ice point is ordinarily used as the reference temperature (5).  
5.5.2 The periodic recalibration of a liquid-in-glass thermometer at the ice point provides a reliable indication of the effect of gradual relaxation of residual mechanical strains in the glass that have a...
SCOPE
1.1 This practice covers a method of preparing, maintaining, and using a temperature reference bath of a mixture of shaved ice and water, saturated with air at a pressure of 101 325 Pa (1 atm).  
1.2 An industrial practice for relating values referenced to the ice point and to the water triple point on the ITS-90 is included.  
1.3 Methods to promote uniformity of bath temperature by mechanical stirring or agitation are not described in detail.  
1.4 Methods of approximating the ice point, as by thermostatically-controlled refrigeration, are not covered by this practice.  
1.5 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
4.1 This guide describes a procedure for placing a water triple-point cell in service and for using it as a reference temperature in thermometer calibration.  
4.2 The reference temperature attained is that of a fundamental state of pure water, the equilibrium between coexisting solid, liquid, and vapor phases.  
4.3 The cell is subject to qualification but not to calibration. The cell may be qualified as capable of representing the fundamental state (see 4.2) by comparison with a bank of similar qualified cells of known history, and it may be so qualified and the qualification documented by its manufacturer.  
4.4 The temperature to be attributed to a qualified water triple-point cell is exactly 273.16 K on the ITS-90, unless corrected for isotopic composition (refer to Appendix X3).  
4.5 Continued accuracy of a qualified cell depends upon sustained physical integrity. This may be verified by techniques described in Section 6.  
4.6 The commercially available triple point of water cells described in this standard are capable of achieving an expanded uncertainty (k=2) of between ±0.1 mK and ±0.05 mK, depending upon the method of preparation. Specified measurement procedures shall be followed to achieve these levels of uncertainty.  
4.7 Commercially-available triple point of water cells of unknown isotopic composition should be capable of achieving an expanded uncertainty (k=2) of no greater than 0.25 mK, depending upon the actual isotopic composition (3). These types of cells are acceptable for use at this larger value of uncertainty.
SCOPE
1.1 This guide covers the nature of two commercial water triple-point cells (types A and B, see Fig. 1) and provides a method for preparing the cell to realize the water triple-point and calibrate thermometers. Tests for assuring the integrity of a qualified cell and of cells yet to be qualified are given. Precautions for handling the cell to avoid breakage are also described.  
1.2 The effect of hydrostatic pressure on the temperature of a water triple-point cell is discussed.  
1.3 Procedures for adjusting the observed SPRT resistance readings for the effects of self-heating and hydrostatic pressure are described in Appendix X1 and Appendix X2.  
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 practice is adequate for use with all ASTM Test Methods which require the reporting of temperature measurements.  
5.2 The Report of Calibration, however named, is the physical output of the calibration laboratory. It shall be prepared so that both the results of the measurement(s) and the non-technical information necessary to support those results are conveyed in a manner that ensures accurate communication and justification of the results.  
5.3 This practice is not meant to supersede requirements of other standards practice such as ISO/IEC 17025 or ANSI/NCSL Z540.3.
SCOPE
1.1 This practice contains reporting requirements for thermometer calibrations included in ASTM Committee E20 Test Methods.  
1.2 This practice covers reports of calibration for radiation thermometers, liquid-in-glass thermometers, resistance thermometers, digital thermometers, and new thermocouples.
Note 1: This practice does not apply to used thermocouples.  
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 The design of a controlled temperature bath will determine what thermometers can be calibrated and to what extent an isothermal condition is achieved. The lack of thermal stability and uniformity of the bath are sources of error that contribute to the overall calibration uncertainty.  
5.2 This guide describes a procedure for determining the effective working space for a controlled temperature fluid bath.  
5.3 This guide describes a procedure for determining the thermal stability within a controlled temperature fluid bath. Overall thermal stability is composed of the bath performance as specified by the manufacturer of the bath equipment and as a component of calibration uncertainty.  
5.4 This guide describes a procedure for determining the temperature uniformity of the working space of the controlled temperature fluid bath.
SCOPE
1.1 This guide is intended for use with controlled temperature comparison baths that contain test fluids and operate within the temperature range of –100°C to 550°C.  
1.2 This guide describes the essential features of controlled temperature fluid baths used for the purpose of thermometer calibration by the comparison method.  
1.3 This guide does not address the details on the design and construction of controlled-temperature fluid baths.  
1.4 This guide describes a method to define the working space of a bath and evaluate the temperature variations within this space. Ideally, the working space will be as close as possible to isothermal.  
1.5 This guide does not address fixed point baths, ice point baths or vapor baths.  
1.6 This guide does not address fluidized powder baths.  
1.7 This guide does not address baths that are programmed to change temperature.  
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.9 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
This practice is adequate for use with other ASTM standards that specify the ice point as a reference. It is also intended to be adequate for most other ice-point reference purposes.
The ice point is a common practical industrial reference point of thermometry. The ice point is relatively simple to realize and provides a readily available natural fixed-point reference temperature.
Use in Resistance Thermometry:  
The ice point was a defining fixed point on practical temperature scales prior to 1960.
The ITS-90 defines W(T90) = R(T90)/R(273.16 K), the measured resistance ratio of a Standard Platinum Resistance Thermometer (SPRT), in reference to the water triple point, not the ice point (1). In many instances, where the water triple point is not available, or when the accuracy obtainable with the water triple point is not required, reference to a properly established and maintained ice-point reference is used. For industrial-quality resistance thermometers, the resistance value is determined for 0 °C, and an uncertainty that is appropriate for the quality of the ice-point realization is assigned.
Use in Thermoelectric Thermometry:  
In thermoelectric thermometry, the ice point is ordinarily used as the reference temperature (2).
Adequate thermoelectric reference requires that thermocouple junctions be well-coupled thermally to the bath, electrically isolated from each other and from the bath, and adequately immersed to avoid perturbing the reference-junction temperatures by radiation and longitudinal conduction of heat along the thermoelements (3 and 4).
Use in Liquid-in-Glass Thermometry:  
In liquid-in-glass thermometry, the ice point is ordinarily used as the reference temperature (6).
The periodic recalibration of a liquid-in-glass thermometer at the ice point provides a reliable indication of the effect of gradual relaxation of residual mechanical strains in the glass that have a significant effect on the volume of the bulb (6).
SCOPE
1.1 This practice covers a method of preparing, maintaining, and using a temperature reference bath of a mixture of shaved ice and water, saturated with air at a pressure of 101 325 Pa (1 atm).
1.2 An industrial practice for relating values referenced to the ice point and to the water triple point on the ITS-90 is included.
1.3 Methods to promote uniformity of bath temperature by mechanical stirring or agitation are not described in detail.
1.4 Methods of approximating the ice point, as by thermostatically-controlled refrigeration, are not covered by this practice.
1.5 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
A pure material has a well-defined phase transition behavior, and the phase transition plateau, a characteristic of the material, can serve as a reproducible reference temperature for the calibration of thermometers. The melting or freezing points of some highly purified metals have been designated as defining fixed points on ITS-90. The fixed points of other materials have been determined carefully enough that they can serve as secondary reference points (see Table 1 and Table 2). This guide presents information on the phase transition process as it relates to establishing a reference temperature.
Fixed-point cells provide users with a means of realizing melting and freezing points. If the cells are appropriately designed and constructed, if they contain material of adequate purity, and if they are properly used, they can establish reference temperatures with uncertainties of a few millikelvins or less. This guide describes some of the design and use considerations.
Fixed-point cells can be constructed and operated less stringently than required for millikelvin uncertainty, yet still provide reliable, durable, easy-to-use fixed points for a variety of industrial calibration and heat treatment purposes. For example, any freezing-point cell can be operated, often advantageously, as a melting-point cell. Such use may result in reduced accuracy, but under special conditions, the accuracy may be commensurate with that of freezing points (see 6.3.10).  
The test procedure described in this guide produces qualification test data as an essential part of the procedure. These data furnish the basis for quality control of the fixed-point procedure. They provide for evaluation of results, assure continuing reliability of the method, and yield insight into the cause of test result discrepancies. The test procedure is applicable to the most demanding uses of fixed-point cells for precise thermometer calibration; it may not be appropriate or cost-effective for all applicatio...
SCOPE
1.1 This guide describes the essential features of fixed-point cells and auxiliary apparatus, and the techniques required to realize fixed points in the temperature range from 29 to 1085°C.  
1.2 Design and construction requirements of fixed-point cells are not addressed in this guide. Typical examples are given in Fig. 1 and Fig. 2.
1.3 This guide is intended to describe good practice and establish uniform procedures for the realization of fixed points.
1.4 This guide emphasizes principles. The emphasis on principles is intended to aid the user in evaluating cells, in improving technique for using cells, and in establishing procedures for specific applications.
1.5 For the purposes of this guide, the use of fixed-point cells for the accurate calibration of thermometers is restricted to immersion-type thermometers that, when inserted into the reentrant well of the cell, (1) indicate the temperature only of the isothermal region of the well, and (2) do not significantly alter the temperature of the isothermal region of the well by heat transfer.
1.6 This guide does not address all of the details of thermometer calibration.
1.7 This guide is intended to complement special operating instructions supplied by manufacturers of fixed-point apparatus.
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.9 The following hazard caveat pertains only to the test method portion, Section 7, of this guide. 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
This guide describes a procedure for placing a water triple-point cell in service and for using it as a reference temperature in thermometer calibration.
The reference temperature attained is that of a fundamental state of pure water, the equilibrium between coexisting solid, liquid, and vapor phases.
The cell is subject to qualification but not to calibration. The cell may be qualified as capable of representing the fundamental state (see 4.2) by comparison with a bank of similar qualified cells of known history, and it may be so qualified and the qualification documented by its manufacturer.
The temperature to be attributed to a qualified water triple-point cell is exactly 273.16 K on the ITS-90, unless corrected for isotopic composition (refer to Appendix X3).
Continued accuracy of a qualified cell depends upon sustained physical integrity. This may be verified by techniques described in Section 6.
The commercially available triple point of water cells described in this standard are capable of achieving an expanded uncertainty (k=2) of between ±0.1 mK and ±0.05 mK, depending upon the method of preparation. Specified measurement procedures shall be followed to achieve these levels of uncertainty.
Commercially-available triple point of water cells of unknown isotopic composition should be capable of achieving an expanded uncertainty (k=2) of no greater than 0.25 mK, depending upon the actual isotopic composition (3). These types of cells are acceptable for use at this larger value of uncertainty.
SCOPE
1.1 This guide covers the nature of two commercial water triple-point cells (types A and B, see Fig. 1) and provides a method for preparing the cell to realize the water triple-point and calibrate thermometers. Tests for assuring the integrity of a qualified cell and of cells yet to be qualified are given. Precautions for handling the cell to avoid breakage are also described.
1.2 The effect of hydrostatic pressure on the temperature of a water triple-point cell is discussed.
1.3 Procedures for adjusting the observed SPRT resistance readings for the effects of self-heating and hydrostatic pressure are described in Appendix X1 and Appendix X2.
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
The design of a controlled temperature bath will determine what thermometers can be calibrated and to what extent an isothermal condition is achieved. The lack of thermal stability and uniformity of the bath are sources of error that contribute to the overall calibration uncertainty.  
This guide describes a procedure for determining the effective working space for a controlled temperature fluid bath.  
This guide describes a procedure for determining the thermal stability within a controlled temperature fluid bath. Overall thermal stability is composed of the bath performance as specified by the manufacturer of the bath equipment and as a component of calibration uncertainty.
This guide describes a procedure for determining the temperature uniformity of the working space of the controlled temperature fluid bath.
SCOPE
1.1 This guide is intended for use with controlled temperature comparison baths that contain test fluids and operate within the temperature range of -100 °C to 550 °C.
1.2 This guide describes the essential features of controlled temperature fluid baths used for the purpose of thermometer calibration by the comparison method.
1.3 This guide does not address the details on the design and construction of controlled-temperature fluid baths.
1.4 This guide describes a method to define the working space of a bath and evaluate the temperature variations within this space. Ideally, the working space will be as close as possible to isothermal.
1.5 This guide does not address fixed point baths, ice point baths or vapor baths.
1.6 This guide does not address fluidized powder baths.
1.7 This guide does not address baths that are programmed to change temperature.
1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.9 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
This guide describes a procedure for placing a water triple-point cell in service and for using it as a reference temperature in thermometer calibration.
The reference temperature attained is that of a fundamental state of pure water, the equilibrium between coexisting solid, liquid, and vapor phases.
The cell is subject to qualification but not to calibration. The cell may be qualified as capable of representing the fundamental state (see 4.2) by comparison with a bank of similar qualified cells of known history, and it may be so qualified and the qualification documented by its manufacturer.
The temperature to be attributed to a qualified water triple-point cell is exactly 273.16 K on the ITS-90, unless corrected for isotopic composition (refer to Appendix X3).
Continued accuracy of a qualified cell depends upon sustained physical integrity. This may be verified by techniques described in Section 6.
The commercially available triple point of water cells described in this standard are capable of achieving an expanded uncertainty (k=2) of between ±0.1 mK and ±0.05 mK, depending upon the method of preparation. Specified measurement procedures shall be followed to achieve these levels of uncertainty.
SCOPE
1.1 This guide covers the nature of two commercial water triple-point cells (types A and B, see Fig. 1) and provides a method for preparing the cell to realize the water triple-point and calibrate thermometers. Tests for assuring the integrity of a qualified cell and of cells yet to be qualified are given. Precautions for handling the cell to avoid breakage are also described.
1.2 The effect of hydrostatic pressure on the temperature of a water triple-point cell is discussed.
1.3 Procedures for adjusting the observed SPRT resistance readings for the effects of self-heating and hydrostatic pressure are described in Appendix X1 and Appendix X2.
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.
FIG. 1 Configurations of two commonly used triple point of water cells, Type A and Type B, with ice mantle prepared for measurement at the ice/water equilibrium temperature. The cells are used immersed in an ice bath or water bath controlled close to 0.01°C (see 5.4)

SIGNIFICANCE AND USE
This practice is adequate for use with all ASTM Test Methods which require the reporting of temperature measurements.
The Report of Calibration, however named, is the physical output of the calibration laboratory. It shall be prepared so that both the results of the measurement(s) and the non-technical information necessary to support those results are conveyed in a manner that ensures accurate communication and justification of the results to the benefit of all concerned.
This practice is not meant to supersede requirements of other standards practice such as ISO/IEC 17025 or ANSI/NCSL Z540-1.
SCOPE
1.1 This practice contains reporting requirements for thermometer calibrations included in ASTM Committee E20 Test Methods.
1.2 This practice covers reports of calibration for radiation thermometers, liquid-in-glass thermometers, resistance thermometers, and new thermocouples.
Note 1—This practice does not apply to used thermocouples.
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
This practice is adequate for use with other ASTM standards that specify the ice point as a reference. It is also intended to be adequate for most other ice-point reference purposes.
The ice point is a common practical industrial reference point of thermometry. The ice point is relatively simple to realize and provides a readily available natural fixed-point reference temperature.
Use in Resistance Thermometry:  
The ice point was a defining fixed point on practical temperature scales prior to 1960.
The ITS-90 defines W(T90) = R(T90)/R(273.16 K), the measured resistance ratio of a Standard Platinum Resistance Thermometer (SPRT), in reference to the water triple point, not the ice point (1). In many instances, where the water triple point is not available, or when the accuracy obtainable with the water triple point is not required, reference to a properly established and maintained ice-point reference is used. For industrial-quality resistance thermometers, the resistance value is determined for 0 °C, and an uncertainty that is appropriate for the quality of the ice-point realization is assigned.
Use in Thermoelectric Thermometry:  
In thermoelectric thermometry, the ice point is ordinarily used as the reference temperature (2).
Adequate thermoelectric reference requires that thermocouple junctions be well-coupled thermally to the bath, electrically isolated from each other and from the bath, and adequately immersed to avoid perturbing the reference-junction temperatures by radiation and longitudinal conduction of heat along the thermoelements (3 and 4).
Use in Liquid-in-Glass Thermometry:  
In liquid-in-glass thermometry, the ice point is ordinarily used as the reference temperature (6).
The periodic recalibration of a liquid-in-glass thermometer at the ice point provides a reliable indication of the effect of gradual relaxation of residual mechanical strains in the glass that have a significant effect on the volume of the bulb (6).
SCOPE
1.1 This practice covers a method of preparing, maintaining, and using a temperature reference bath of a mixture of shaved ice and water, saturated with air at a pressure of 101 325 Pa (1 atm).
1.2 An industrial practice for relating values referenced to the ice point and to the water triple point on the ITS-90 is included.
1.3 Methods to promote uniformity of bath temperature by mechanical stirring or agitation are not described in detail.
1.4 Methods of approximating the ice point, as by thermostatically-controlled refrigeration, are not covered by this practice.
1.5 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
This practice is adequate for use with all ASTM Test Methods which require the reporting of temperature measurements.
The Report of Calibration, however named, is the physical output of the calibration laboratory. It shall be prepared so that both the results of the measurement(s) and the non-technical information necessary to support those results are conveyed in a manner that ensures accurate communication and justification of the results to the benefit of all concerned.
This practice is not meant to supersede requirements of other standards practice such as ISO/IEC 17025 or ANSI/NCSL Z540-1.
SCOPE
1.1 This practice contains reporting requirements for temperature calibrations included in ASTM Test Methods.
1.2 This practice includes radiation thermometers, liquid-in-glass thermometers, resistance thermometers, and new thermocouples. The appendices include sample reports compliant with this practice.
Note 1—This practice does not apply to used thermocouples.
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.

SCOPE
1.1 This guide describes the essential features of freezing-point cells and auxiliary apparatus, and the techniques required to realize freezing points in the temperature range from 29 to 1085 °C.
1.2 Detailed design and construction are not addressed in this guide.
1.3 This guide is intended to describe good practice and establish uniform procedures for the realization of freezing points.
1.4 This guide emphasizes principles. The emphasis on principles is intended to aid the user in evaluating cells, in improving technique for using cells, and in establishing procedures for specific applications.
1.5 For the purposes of this guide, the use of freezing-point cells for the accurate calibration of thermometers is restricted to immersion-type thermometers that, when inserted into the reentrant well of the cell, (1) indicate the temperature only of the isothermal region of the well, and (2) do not significantly alter the temperature of the isothermal region of the well by heat transfer.

SCOPE
1.1 This practice covers a method of preparing, maintaining, and using a temperature reference bath of a mixture of shaved ice and water, saturated with air at a pressure of 101 325 Pa (1 atm).
1.2 An industrial practice for relating values referenced to the ice point and to the water triple point on the ITS-90 is included.
1.3 Methods to promote uniformity of bath temperature by mechanical stirring or agitation are not described in detail.
1.4 Methods of approximating the ice point, as by thermostatically-controlled refrigeration, are not covered by this practice.
1.5 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.

SCOPE
1.1 This practice covers a method of preparing, maintaining, and using a temperature reference bath of a mixture of shaved ice and water, saturated with air at a pressure of 101 325 Pa (1 atm).
1.2 An industrial practice for relating values referenced to the ice point and to the water triple point on the ITS-90 is included.
1.3 Methods to promote uniformity of bath temperature by mechanical stirring or agitation are not described in detail.
1.4 Methods of approximating the ice point, as by thermostatically-controlled refrigeration, are not covered by this practice.
1.5 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
This guide describes a procedure for placing a water triple-point cell in service and for using it as a reference temperature in thermometer calibration.
The reference temperature attained is that of a fundamental state of pure water, the equilibrium between coexisting solid, liquid, and vapor phases.
The cell is subject to qualification but not to calibration. The cell may be qualified as capable of representing the fundamental state (see 4.2) by comparison with a bank of similar qualified cells of known history, and it may be so qualified and the qualification documented by its manufacturer.
The temperature to be attributed to a qualified water triple-point cell is exactly 273.16 K on the ITS-90.
Continued accuracy of a qualified cell depends upon sustained physical integrity. This may be verified by techniques described in Section 6.
The commercially available triple point of water cells described in this standard are capable of achieving an expanded uncertainty (k=2) of between ±0.1 mK and ±0.05 mK, depending upon the method of preparation. Specified measurement procedures shall be followed to achieve these levels of uncertainty.
SCOPE
1.1 This guide covers the nature of two commercial water triple-point cells (types A and B, see Fig. 1) and provides a method for preparing the cell to realize the water triple-point and calibrate thermometers. Tests for assuring the integrity of a qualified cell and of cells yet to be qualified are given. Precautions for handling the cell to avoid breakage are also described.
1.2 The effect of hydrostatic pressure on the temperature of a water triple-point cell is discussed.
1.3 Procedures for adjusting the observed SPRT resistance readings for the effects of self-heating and hydrostatic pressure are described in Appendix X1 and Appendix X2.
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.

SCOPE
1.1 This guide describes the essential features of freezing-point cells and auxiliary apparatus, and the techniques required to realize freezing points in the temperature range from 29 to 1085°C.  
1.2 Detailed design and construction are not addressed in this guide.
1.3 This guide is intended to describe good practice and establish uniform procedures for the realization of freezing points.
1.4 This guide emphasizes principles. The emphasis on principles is intended to aid the user in evaluating cells, in improving technique for using cells, and in establishing procedures for specific applications.
1.5 For the purposes of this guide, the use of freezing-point cells for the accurate calibration of thermometers is restricted to immersion-type thermometers that, when inserted into the reentrant well of the cell, (1) indicate the temperature only of the isothermal region of the well, and (2) do not significantly alter the temperature of the isothermal region of the well by heat transfer.
1.6 This guide does not address all of the details of thermometer calibration.
1.7 This guide is intended to complement special operating instructions supplied by manufacturers of freezing-point apparatus.
1.8 The following hazard caveat pertains only to the test method portion, Section 7, of this guide. This standard does not purport to address all of the safety problems, 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.

SCOPE
1.1 This practice covers a method of preparing, maintaining, and using a temperature reference bath of a mixture of shaved ice and water, saturated with air at a pressure of 101 325 Pa (1 atm).
1.2 An industrial practice for relating values referenced to the ice point and to the water triple point on the ITS-90 is included.
1.3 Methods to promote uniformity of bath temperature by mechanical stirring or agitation are not described in detail.
1.4 Methods of approximating the ice point, as by thermostatically-controlled refrigeration, are not covered by this practice.
1.5 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.

SCOPE
1.1 This guide covers the nature of two commercial water triple-point cells (types A and B, see Fig. 1) and provides a method for preparing the cell to realize the water triple-point and calibrate thermometers. Tests for assuring the integrity of a qualified cell and of cells yet to be qualified are given. Precautions for handling the cell to avoid breakage are also described.  
1.2 The effect of hydrostatic pressure on the temperature of a water triple-point cell is discussed.  
1.3 Procedures for adjusting the observed SPRT resistance readings for the effects of self-heating and hydrostatic pressure are described in Appendixes X1 and X2.  
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.