1、Designation: E2593 12E2593 17Standard Guide forAccuracy Verification of Industrial Platinum ResistanceThermometers1This standard is issued under the fixed designation E2593; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide describes the techniques and apparatus required for the accuracy verification of industrial platinum res
3、istancethermometers constructed in accordance with Specification E1137/E1137M and the evaluation of calibration uncertainties. Theprocedures described apply over the range of 200C to 650C. -200 C to 650 C.1.2 This guide does not intend to describe procedures necessary for the calibration of platinum
4、 resistance thermometers usedas calibration standards or Standard Platinum Resistance Thermometers. Consequently, calibration of these types of instrumentsis outside the scope of this guide.1.3 Industrial platinum resistance thermometers are available in many styles and configurations. This guide do
5、es not purport todetermine 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 ISO/TAG 4/WG 3 “GuideJCGM 100:2008 “Evaluation of measuremen
6、t dataGuide to the Evaluationexpression of Uncertaintyuncertainty in Measure-ment”measurement” and ANSI/NCSL Z540-2-1997Z540.2-1997 “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.
7、It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized pri
8、nciples on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E344 Terminology Relating to The
9、rmometry and HydrometryE563 Practice for Preparation and Use of an Ice-Point Bath as a Reference TemperatureE644 Test Methods for Testing Industrial Resistance ThermometersE1137/E1137M Specification for Industrial Platinum Resistance ThermometersE1502 Guide for Use of Fixed-Point Cells for Reference
10、 TemperaturesE1750 Guide for Use of Water Triple Point CellsE2623 Practice for Reporting Thermometer CalibrationsE2488 Guide for the Preparation and Evaluation of Liquid Baths Used for Temperature Calibration by Comparison2.2 ANSI Publication:Publications:3ANSI/NCSL Z540-2-1997Z540.2-1997 U.S. Guide
11、 to the Expression of Uncertainty in MeasurementANSI/NCSL Z540.3-2006 Requirements for the Calibrations of Measuring and Test Equipment2.3 Other Publication:4ISO/TAG 4/WG 3JCGM 100:2008 Guide Evaluation of measurement dataGuide to the Evaluationexpression of Uncertain-tyuncertainty in Measurementmea
12、surement1 This guide is under the jurisdiction of ASTM Committee E20 on Temperature Measurement and is the direct responsibility of Subcommittee E20.03 on ResistanceThermometers.Current edition approved Nov. 1, 2012Nov. 1, 2017. Published December 2012November 2017. Originally approved in 2007. Last
13、 previous edition approved in 20112012as D5456E2593 12.11E01. DOI: 10.1520/E2593-12.10.1520/E2593-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Do
14、cument Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.4 JCGM 100:2008, Evaluation of measurement dataGuide to the expression of uncertainty in measurement. Available from the BIPM, Sevr
15、es, France,http:/www.bipm.org/en/publications/guides/gum.html.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all ch
16、anges accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
17、United States13. Terminology3.1 DefinitionsThe definitions given in Terminology E344 shall be considered as applying to the terms used in this guide.3.2 Definitions of Terms Specific to This Standard:3.2.1 annealing, va heat treating process intended to stabilize resistance thermometers prior to cal
18、ibration and use.3.2.2 check standard, na thermometer similar in design to the unit under test, but of superior stability, which is included inthe calibration process for the purpose of quantifying the process variability.3.2.3 coverage factor, nnumerical factor used as a multiplier of the combined
19、standard uncertainty in order to obtain anexpanded uncertainty.3.2.4 dielectric absorption, nan effect in an insulator caused by the polarization of positive and negative charges within theinsulator which manifests itself as an in-phase current when the voltage is removed and the charges recombine.3
20、.2.5 expanded uncertainty, U, nquantity defining an interval about the result of a measurement that may be expected toencompass a large fraction of the distribution of values that could reasonably be attributed to the measurand.3.2.5.1 DiscussionNormally,Typically, U is given at a coverage factor of
21、 2, approximating to a 95 % confidence interval.95.45 % confidence intervalfor a normal distribution.3.2.6 hysteresis, nproperty associated with the resistance of a thermometer whereby the value of resistance at a temperatureis dependantdependent upon previous exposure to different temperatures.3.2.
22、7 normal distribution, na frequency distribution characterized by a bell shaped bell-shaped curve and defined by twoparameters: mean and standard deviation.3.2.8 platinum resistance thermometer (PRT), na resistance thermometer with the resistance element constructed fromplatinum or platinum alloy.3.
23、2.9 rectangular distribution, na frequency distribution characterized by a rectangular shaped rectangular-shaped curve anddefined by two parameters: mean and magnitude (semi-range).3.2.10 standard deviation of the mean, nan estimate of the standard deviation of the sampling distribution of means, ba
24、sedon the data from one or more random samples.3.2.10.1 DiscussionNumerically, it is equal to the standard deviation obtained (s) when divided by the square root of the size of the sample (n).Standard Deviation of the Mean5 s=n(1)3.2.11 standard platinum resistance thermometer (SPRT), na specialized
25、 platinum resistance thermometer constructed in sucha way that it fulfills the requirements of the ITS-90.53.2.12 standard uncertainty, nuncertainty of the result of a measurement expressed as a standard deviation, designated as S.3.2.13 Type A evaluation (of uncertainty), nmethod of evaluation of u
26、ncertainty by the statistical analysis of a series ofobservations.43.2.14 Type B evaluation (of uncertainty), nmethod of evaluation of uncertainty by means other than statistical analysis of aseries of observations.43.2.15 test uncertainty ratio (TUR), nthe ratio of the tolerance of the unit under t
27、est to the expanded calibration uncertainty.3.2.16 uncertainty budget, nan analysis tool used for assembling and combining component uncertainties expected in ameasurement process into an overall expected uncertainty.3.2.17 unit under test (UUT), nthe platinum resistance thermometer to be calibrated
28、.4. Summary of Guide4.1 The UUT is calibrated by determining the electrical resistance of its sensing element at one or more known temperaturescovering the temperature range of interest. The known temperatures may be established by means of fixed-point systems or by5 Mangum, B. W., NIST Technical No
29、te 1265, Guidelines for Realizing the International Temperature Scale of 1990 (ITS-90).E2593 172using a reference thermometer. Either an SPRT or a PRT is recommended for use as the reference thermometer. However, a liquidin glass (LIG) thermometer, thermistor, or thermocouple may be acceptable, depe
30、nding upon the temperature of calibration,required accuracy, or other considerations.4.2 The success of the calibration depends largely upon the ability of the UUT to come to thermal equilibrium with thecalibration temperature of interest (fixed point cell or comparison system) and upon accurate mea
31、surement of the sensing elementresistance at that time. Instructions are included to guide the user in achieving thermal equilibrium and proper resistancemeasurement, including descriptions of apparatus and instrumentation.4.3 Industrial platinum resistance thermometers are available in many styles
32、and configurations. This guide includes limitedinstructions pertaining to the preparation of the UUT into a configuration that facilitates proper calibration.4.4 Proper evaluation of calibration uncertainties is critical for the result of a calibration to be useful. Therefore, a considerableportion
33、of this guide is devoted to uncertainty budgets and the evaluation of uncertainties.5. Significance and Use5.1 This guide is intended to be used for verifying the resistance-temperature relationship of industrial platinum resistancethermometers that are intended to satisfy the requirements of Specif
34、ication E1137/E1137M. It is intended to provide a consistentmethod for calibration and uncertainty evaluation while still allowing the user some flexibility in the choice of apparatus andinstrumentation. It is understood that the limits of uncertainty obtained depend in large part upon the apparatus
35、 and instrumentationused. Therefore, since this guide is not prescriptive in approach, it provides detailed instruction in uncertainty evaluation toaccommodate the variety of apparatus and instrumentation that may be employed.5.2 This guide is intended primarily to satisfy applications requiring com
36、pliance to Specification E1137/E1137M. However, thetechniques described may be appropriate for applications where higher accuracymore accurate calibrations are needed.5.3 Many applications require tolerances to be verified using a minimum test uncertainty ratio (TUR). This standard providesguideline
37、s for evaluating uncertainties used to support TUR calculations.6. Sources of Error6.1 Uncertainties are present in all calibrations. Errors arise when the effects of uncertainties are underestimated or omitted. Thepredominant sources of uncertainty are described in Section 12 and listed in Table 2.
38、7. Apparatus7.1 Resistance Measuring InstrumentsThe choice of a specific instrument to use for measuring the UUT and referencethermometer resistance will depend upon several factors. Some of these factors are ease of use, compatibility with computerizeddata acquisition systems, method of balancing,
39、computation ability, etc. and so forth.All of the instruments listed are commerciallyavailable in high precision designs and are suitable for use. They require periodic linearity checks or periodic calibration. (Referto Appendix X2 for detailed descriptions and schematics.) The accuracyuncertainty o
40、f the resistance measurements directlyimpacts the accuracyuncertainty of the temperature measurement as shown in Eq 2.Accuracyt 5AccuracySensitivity (2)Uncertaintyt 5UncertaintySensitivity (2)where:.Accuracyt = temperature accuracy at temperature (t), C,Accuracy = resistance accuracy at temperature
41、(t), , andSensitivity = sensitivity at temperature (t), C-1Uncertaintyt = equivalent temperature uncertainty at temperature (t), C,Uncertainty = resistance uncertainty at temperature (t), , andSensitivity = sensitivity at temperature (t), C-17.1.1 BridgePrecision bridges with linearity specification
42、s ranging from 10 ppm of range to 0.01 ppm of range and with 612to 912 digit resolution are available. These instruments are available in models using either AC or DC alternating current (AC) ordirect current (DC) excitation. The linearity is typically based upon resistive or inductive dividers and
43、is generally quite stable overtime. Modern bridges are convenient automatic balancing instruments but manual balancing types are also suitable. Theseinstruments typically require external reference resistors and do not perform temperature calculations.7.1.2 Digital Thermometer ReadoutDigital instrum
44、ents designed specifically to measure resistance thermometers areavailable. Modern versions function essentially as automatic potentiometers and reverse the current to eliminate spurious thermalemf. minimize DC offset errors caused by thermal emf and residual voltages inherent to the electronic comp
45、onents and relatedE2593 173circuitry. Precision instruments with linearity specifications ranging from 20 ppm of indication to 1 ppm of indication and with612 to 812 digit resolution are commercially available. Some models have extensive internal computation capability, performingboth temperature an
46、d statistical calculations. Periodic calibration is required.7.1.3 Digital Multimeter (DMM)Digital multimeters are convenient direct indication instruments typically able to indicate inresistance or voltage. Some models have extensive internal computation ability, performing both temperature and sta
47、tisticalcalculations. The use of DC offset compensation is recommended. Caution must be exercised to ensure that the excitation currentis appropriate for the UUT and reference thermometer to avoid excessive self-heating. Periodic calibration is required.7.1.4 Reference ResistorReference resistors ar
48、e specially designed and manufactured to be stable over long periods of time.Typically, they have significant temperature coefficients of resistance and require maintenance in a temperature enclosedtemperature-enclosed air or oil bath. Some have inductive and capacitive characteristics that limit th
49、eir suitability for use withACbridges. Periodic (yearly or semi-yearly) calibration is required. Resistors (AC or DC) are required to match the type ofmeasurement (AC or DC) system in use.7.2 Reference ThermometersThe choice of a specific instrument to use as the reference thermometer will depend upon severalfactors, including the uncertainty desired, temperature range of interest, compatibility with existing instrumentation and apparatus,expertise of staff, cost limitations, etc. and so forth. All of the instruments listed
