ASTM E2593-17(2023)
(Guide)Standard Guide for Accuracy Verification of Industrial Platinum Resistance Thermometers
Standard Guide for Accuracy Verification of Industrial Platinum Resistance Thermometers
SIGNIFICANCE AND USE
5.1 This guide is intended to be used for verifying the resistance-temperature relationship of industrial platinum resistance thermometers that are intended to satisfy the requirements of Specification E1137/E1137M. It is intended to provide a consistent method for calibration and uncertainty evaluation while still allowing the user some flexibility in the choice of apparatus and instrumentation. It is understood that the limits of uncertainty obtained depend in large part upon the apparatus and instrumentation used. Therefore, since this guide is not prescriptive in approach, it provides detailed instruction in uncertainty evaluation to accommodate the variety of apparatus and instrumentation that may be employed.
5.2 This guide is intended primarily to satisfy applications requiring compliance to Specification E1137/E1137M. However, the techniques described may be appropriate for applications where more accurate calibrations are needed.
5.3 Many applications require tolerances to be verified using a minimum test uncertainty ratio (TUR). This standard provides guidelines for evaluating uncertainties used to support TUR calculations.
SCOPE
1.1 This guide describes the techniques and apparatus required for the accuracy verification of industrial platinum resistance thermometers constructed in accordance with Specification E1137/E1137M and the evaluation of calibration uncertainties. The procedures described apply over the range of -200 °C to 650 °C.
1.2 This guide does not intend to describe procedures necessary for the calibration of platinum resistance thermometers used as calibration standards or Standard Platinum Resistance Thermometers. Consequently, calibration of these types of instruments is outside the scope of this guide.
1.3 Industrial platinum resistance thermometers are available in many styles and configurations. This guide does not purport to determine the suitability of any particular design, style, or configuration for calibration over a desired temperature range.
1.4 The evaluation of uncertainties is based upon current international practices as described in JCGM 100:2008 “Evaluation of measurement data—Guide to the expression of uncertainty in measurement” and ANSI/NCSL Z540.2-1997 “U.S. Guide to the Expression of Uncertainty in Measurement.”
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.
General Information
Relations
Standards Content (Sample)
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.
Designation: E2593 − 17 (Reapproved 2023)
Standard Guide for
Accuracy Verification of Industrial Platinum Resistance
Thermometers
This standard is issued under the fixed designation E2593; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This guide describes the techniques and apparatus re- 2.1 ASTM Standards:
quired for the accuracy verification of industrial platinum E344 Terminology Relating to Thermometry and Hydrom-
resistance thermometers constructed in accordance with Speci- etry
fication E1137/E1137M and the evaluation of calibration E563 Practice for Preparation and Use of an Ice-Point Bath
uncertainties. The procedures described apply over the range of as a Reference Temperature
-200 °C to 650 °C. E644 Test Methods for Testing Industrial Resistance Ther-
mometers
1.2 This guide does not intend to describe procedures
E1137/E1137M Specification for Industrial Platinum Resis-
necessary for the calibration of platinum resistance thermom-
tance Thermometers
eters used as calibration standards or Standard Platinum
E1502 Guide for Use of Fixed-Point Cells for Reference
Resistance Thermometers. Consequently, calibration of these
Temperatures
types of instruments is outside the scope of this guide.
E1750 Guide for Use of Water Triple Point Cells
1.3 Industrial platinum resistance thermometers are avail- E2623 Practice for Reporting Thermometer Calibrations
able in many styles and configurations. This guide does not E2488 Guide for the Preparation and Evaluation of Liquid
purport to determine the suitability of any particular design, Baths Used for Temperature Calibration by Comparison
style, or configuration for calibration over a desired tempera-
2.2 ANSI Publications:
ture range.
ANSI/NCSL Z540.2-1997 U.S. Guide to the Expression of
Uncertainty in Measurement
1.4 The evaluation of uncertainties is based upon current
ANSI/NCSL Z540.3-2006 Requirements for the Calibra-
international practices as described in JCGM 100:2008 “Evalu-
tions of Measuring and Test Equipment
ation of measurement data—Guide to the expression of uncer-
tainty in measurement” and ANSI/NCSL Z540.2-1997 “U.S.
2.3 Other Publication:
Guide to the Expression of Uncertainty in Measurement.”
JCGM 100:2008 Evaluation of measurement data—Guide to
the expression of uncertainty in measurement
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.1 Definitions—The definitions given in Terminology E344
mine the applicability of regulatory limitations prior to use.
shall be considered as applying to the terms used in this guide.
1.6 This international standard was developed in accor-
3.2 Definitions of Terms Specific to This Standard:
dance with internationally recognized principles on standard-
3.2.1 annealing, v—a heat treating process intended to
ization established in the Decision on Principles for the
stabilize resistance thermometers prior to calibration and use.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This guide is under the jurisdiction of ASTM Committee E20 on Temperature the ASTM website.
Measurement and is the direct responsibility of Subcommittee E20.03 on Resistance Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
Thermometers. 4th Floor, New York, NY 10036, http://www.ansi.org.
Current edition approved July 1, 2023. Published July 2023. Originally approved JCGM 100:2008, Evaluation of measurement data—Guide to the expression of
in 2007. Last previous edition approved in 2017 as E2593 – 17. DOI: 10.1520/ uncertainty in measurement. Available from the BIPM, Sevres, France, http://
E2593-17R23. www.bipm.org/en/publications/guides/gum.html.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2593 − 17 (2023)
3.2.2 check standard, n—a thermometer similar in design to 3.2.15 test uncertainty ratio (TUR), n—the ratio of the
the unit under test, but of superior stability, which is included tolerance of the unit under test to the expanded calibration
in the calibration process for the purpose of quantifying the
uncertainty.
process variability.
3.2.16 uncertainty budget, n—an analysis tool used for
3.2.3 coverage factor, n—numerical factor used as a multi-
assembling and combining component uncertainties expected
plier of the combined standard uncertainty in order to obtain an
in a measurement process into an overall expected uncertainty.
expanded uncertainty.
3.2.17 unit under test (UUT), n—the platinum resistance
3.2.4 dielectric absorption, n—an effect in an insulator
thermometer to be calibrated.
caused by the polarization of positive and negative charges
within the insulator which manifests itself as an in-phase
4. Summary of Guide
current when the voltage is removed and the charges recom-
bine. 4.1 The UUT is calibrated by determining the electrical
resistance of its sensing element at one or more known
3.2.5 expanded uncertainty, U, n—quantity defining an
temperatures covering the temperature range of interest. The
interval about the result of a measurement that may be
known temperatures may be established by means of fixed-
expected to encompass a large fraction of the distribution of
point systems or by using a reference thermometer. Either an
values that could reasonably be attributed to the measurand.
SPRT or a PRT is recommended for use as the reference
3.2.5.1 Discussion—Typically, U is given at a coverage
thermometer. However, a liquid in glass (LIG) thermometer,
factor of 2, approximating to a 95.45 % confidence interval for
thermistor, or thermocouple may be acceptable, depending
a normal distribution.
upon the temperature of calibration, required accuracy, or other
3.2.6 hysteresis, n—property associated with the resistance
considerations.
of a thermometer whereby the value of resistance at a tempera-
ture is dependent upon previous exposure to different tempera-
4.2 The success of the calibration depends largely upon the
tures.
ability of the UUT to come to thermal equilibrium with the
3.2.7 normal distribution, n—a frequency distribution char- calibration temperature of interest (fixed point cell or compari-
acterized by a bell-shaped curve and defined by two param- son system) and upon accurate measurement of the sensing
eters: mean and standard deviation.
element resistance at that time. Instructions are included to
guide the user in achieving thermal equilibrium and proper
3.2.8 platinum resistance thermometer (PRT), n—a resis-
resistance measurement, including descriptions of apparatus
tance thermometer with the resistance element constructed
and instrumentation.
from platinum or platinum alloy.
3.2.9 rectangular distribution, n—a frequency distribution
4.3 Industrial platinum resistance thermometers are avail-
characterized by a rectangular-shaped curve and defined by
able in many styles and configurations. This guide includes
two parameters: mean and magnitude (semi-range).
limited instructions pertaining to the preparation of the UUT
into a configuration that facilitates proper calibration.
3.2.10 standard deviation of the mean, n—an estimate of the
standard deviation of the sampling distribution of means, based
4.4 Proper evaluation of calibration uncertainties is critical
on the data from one or more random samples.
for the result of a calibration to be useful. Therefore, a
3.2.10.1 Discussion—Numerically, it is equal to the stan-
considerable portion of this guide is devoted to uncertainty
dard deviation obtained (s) when divided by the square root of
budgets and the evaluation of uncertainties.
the size of the sample (n).
s
5. Significance and Use
Standard Deviation of the Mean 5 (1)
=n
5.1 This guide is intended to be used for verifying the
3.2.11 standard platinum resistance thermometer (SPRT),
resistance-temperature relationship of industrial platinum re-
n—a specialized platinum resistance thermometer constructed
sistance thermometers that are intended to satisfy the require-
in such a way that it fulfills the requirements of the ITS-90.
ments of Specification E1137/E1137M. It is intended to pro-
3.2.12 standard uncertainty, n—uncertainty of the result of
vide a consistent method for calibration and uncertainty
a measurement expressed as a standard deviation, designated evaluation while still allowing the user some flexibility in the
as S.
choice of apparatus and instrumentation. It is understood that
the limits of uncertainty obtained depend in large part upon the
3.2.13 Type A evaluation (of uncertainty), n—method of
apparatus and instrumentation used. Therefore, since this guide
evaluation of uncertainty by the statistical analysis of a series
is not prescriptive in approach, it provides detailed instruction
of observations.
in uncertainty evaluation to accommodate the variety of
3.2.14 Type B evaluation (of uncertainty), n—method of
apparatus and instrumentation that may be employed.
evaluation of uncertainty by means other than statistical
analysis of a series of observations.
5.2 This guide is intended primarily to satisfy applications
requiring compliance to Specification E1137/E1137M.
However, the techniques described may be appropriate for
Mangum, B. W., NIST Technical Note 1265, Guidelines for Realizing the
International Temperature Scale of 1990 (ITS-90). applications where more accurate calibrations are needed.
E2593 − 17 (2023)
5.3 Many applications require tolerances to be verified internal computation ability, performing both temperature and
using a minimum test uncertainty ratio (TUR). This standard statistical calculations. The use of DC offset compensation is
provides guidelines for evaluating uncertainties used to support
recommended. Caution must be exercised to ensure that the
TUR calculations.
excitation current is appropriate for the UUT and reference
thermometer to avoid excessive self-heating. Periodic calibra-
6. Sources of Error
tion is required.
6.1 Uncertainties are present in all calibrations. Errors arise 7.1.4 Reference Resistor—Reference resistors are specially
when the effects of uncertainties are underestimated or omitted.
designed and manufactured to be stable over long periods of
The predominant sources of uncertainty are described in
time. Typically, they have significant temperature coefficients
Section 12 and listed in Table 2.
of resistance and require maintenance in a temperature-
enclosed air or oil bath. Some have inductive and capacitive
7. Apparatus
characteristics that limit their suitability for use with AC
bridges. Periodic (yearly or semi-yearly) calibration is re-
7.1 Resistance Measuring Instruments—The choice of a
quired. Resistors (AC or DC) are required to match the type of
specific instrument to use for measuring the UUT and reference
measurement (AC or DC) system in use.
thermometer resistance will depend upon several factors. Some
of these factors are ease of use, compatibility with computer-
7.2 Reference Thermometers—The choice of a specific in-
ized data acquisition systems, method of balancing, computa-
strument to use as the reference thermometer will depend upon
tion ability, and so forth. All of the instruments listed are
several factors, including the uncertainty desired, temperature
commercially available in high precision designs and are
range of interest, compatibility with existing instrumentation
suitable for use. They require periodic linearity checks or
and apparatus, expertise of staff, cost limitations, and so forth.
periodic calibration. (Refer to Appendix X2 for detailed
All of the instruments listed are commercially available in
descriptions and schematics.) The uncertainty of the resistance
various levels of precision and stability and may be suitable for
measurements directly impacts the uncertainty of the tempera-
use. They all require calibration. The frequency of calibration
ture measurement as shown in Eq 2.
depends a great deal upon the manner in which they are used
Uncertainty
Ω
and the uncertainty required in use.
Uncertainty 5 (2)
t
Sensitivity
7.2.1 SPRT—SPRTs are the most accurate reference ther-
where:.
mometers available and are used in defining the ITS-90 from
approximately -260 °C to 962 °C. The SPRT sensing element
Uncertainty = equivalent temperature uncertainty at tem-
t
is made from nominally pure platinum and is supported
perature (t), °C,
Uncertainty = resistance uncertainty at temperature (t), Ω, essentially strain-free. These instruments are extremely deli-
Ω
and cate and are easily damaged by mechanical shock. They are
-1
Sensitivity = sensitivity at temperature (t), Ω °C
available sheathed in glass or metal and in long-stem and
capsule configurations. The design and materials of construc-
7.1.1 Bridge—Precision bridges with linearity specifications
tion limit the temperature range of a specific instrument type.
ranging from 10 ppm of range to 0.01 ppm of range and with
1 1 Some sheath materials can be damaged by use at high
6 ⁄2 to 9 ⁄2 digit resolution are available. These instruments are
temperatures in metal blocks or molten salt baths. Calibration
available in models using either alternating current (AC) or
on the ITS-90 is required.
direct current (DC) excitation. The linearity is typically based
upon resistive or inductive dividers and is generally quite 7.2.2 Secondary Reference PRT—Secondary Reference
stable over time. Modern bridges are convenient automatic PRTs are specially manufactured PRTs designed to be suitable
balancing instruments but manual balancing types are also calibration standards. These instruments are typically less
suitable. These instruments typically require external reference
delicate than SPRTs but have higher measurement uncertainties
resistors and do not perform temperature calculations.
and narrower usage ranges. They are typically sheathed in
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.