ASTM E644-2006 Standard Test Methods for Testing Industrial Resistance Thermometers《测试工业电阻温度计的标准试验方法》.pdf

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1、Designation: E 644 06Standard Test Methods forTesting Industrial Resistance Thermometers1This standard is issued under the fixed designation E 644; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number

2、 in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the principles, apparatus, andprocedures for calibration and testing of industrial resistancethermometers.1.2 These

3、 test methods cover the tests for insulation resis-tance, calibration, immersion error, pressure effects, thermalresponse time, vibration effect, mechanical shock, self-heatingeffect, stability, thermoelectric effect, humidity, thermal hys-teresis, thermal shock, and end seal integrity.1.3 These tes

4、t methods are not necessarily intended for,recommended to be performed on, or appropriate for everytype of thermometer. The expected repeatability and reproduc-ibility of the results are tabulated in Appendix X4.1.4 These test methods, when specified in a procurementdocument, shall govern the method

5、 of testing the resistancethermometer.1.5 Thermometer performance specifications, acceptancelimits, and sampling methods are not covered in these testmethods; they should be specified separately in the procure-ment document.1.6 This standard does not purport to address all of thesafety concerns, if

6、any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in 6.3.2, 6.3.5, and 8.1.2. Referenced Docume

7、nts2.1 ASTM Standards:2E77 Test Method for Inspection and Verification of Ther-mometersE 230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized ThermocouplesE 344 Terminology Relating to Thermometry and Hydrom-etryE 563 Practice for Preparation and Use of an Ice-Point Bat

8、has a Reference TemperatureE 1137/E 1137M Specification for Industrial Platinum Re-sistance ThermometersE 1502 Guide for Use of Freezing-Point Cells for ReferenceTemperaturesE 1750 Guide for Use of Water Triple Point CellsE 1751 Guide for Temperature Electromotive Force (EMF)Tables for Non-Letter De

9、signated Thermocouple Combi-nations2.2 Military Standard:3MIL-STD-202 Test Methods for Electronic and ElectricalComponent Parts3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 The definitions given in Terminology E 344 shallapply to these test methods.3.1.2 bath gradient error,

10、 nthe error caused by tempera-ture differences in the working space of the bath. (The bath ortemperature equalizing blocks should be explored to determinethe work areas in which the temperature gradients are insig-nificant.)3.1.3 calibration, nthe determination of the indications ofa thermometer wit

11、h respect to temperatures established by astandard resulting in scale corrections to be applied whenmaximum accuracy is required.3.1.4 connecting wire error, nthe error caused by uncom-pensated connecting wire resistance. (Although the connectingwire is part of the measurement circuit, most of it is

12、 not at thetemperature that is being determined. Thermometers are avail-able in two-, three-, and four-wire configurations. There is nosatisfactory way to compensate for the wire resistance in the1These test methods are under the jurisdiction of ASTM Committee E20 onTemperature Measurement and are t

13、he direct responsibility of Subcommittee E20.03on Resistance Thermometers.Current edition approved June 1, 2006. Published July 2006. Originally approvedin 1978. Last previous edition approved in 2004 as E 644 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cu

14、stomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Superintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20234.1Copyright ASTM International, 100 Barr Harbor Dri

15、ve, PO Box C700, West Conshohocken, PA 19428-2959, United States.measurement with a two-wire thermometer although the wireresistance can be compensated for in three and four-wirethermometers.)3.1.5 immersion error, nan error caused by the heatconduction or radiation, or both, between the resistance

16、ther-mometer element and the environment external to the measure-ment system, because of insufficient immersion length andthermal contact of the thermometer with the medium undermeasurement.3.1.6 interchangeability, nthe extent to which the ther-mometer matches a resistance-temperature relationship.

17、 (Theverification of interchangeability can be accomplished only bycalibration. The deviations at the temperature limits and themaximum deviation from the established resistance-temperature relationship shall be specified.)3.1.7 self-heating, nthe increase in the temperature of thethermometer elemen

18、t caused by the electric power dissipated inthe element, the magnitude depending upon the thermometercurrent and heat conduction from the thermometer element tothe surrounding medium.3.1.8 self-heating error, nthe error caused by variationsfrom the calibration conditions in the self-heating of theth

19、ermometer element at a given current, arising from thevariations in the heat conduction from the thermometer to thesurrounding medium.3.1.9 thermoelectric effect error, nthe error caused by athermal emf in the measurement circuit as a result of dissimilarmetals and temperature gradients in the circu

20、it.4. Significance and Use4.1 These test methods provide uniform methods for testingindustrial resistance thermometers so that a given tester mayexpect to obtain the same value of a test result from makingsuccessive measurements on the same test article within thelimits of repeatability given in App

21、endix X4. Independenttesters may also expect to obtain the same result from thetesting of the same article within the limits of reproducibilitygiven in Appendix X4.4.2 These tests may be used to qualify platinum resistancethermometers for use in specific applications to meet a particu-lar specificat

22、ion such as Specification E 1137/E 1137M,ortoevaluate relative merits of equivalent test articles supplied byone or more manufacturers, or to determine the limits of theapplication of a particular design of thermometer.4.3 The expected repeatability and reproducibility of se-lected test methods are

23、included in Appendix X4.4.4 Some non-destructive tests described in these test meth-ods may be applied to thermometers that can be subsequentlysold or used; other destructive tests may preclude the sale oruse of the test article because of damage that the test mayproduce.PROCEDURES5. Insulation Resi

24、stance Test5.1 ScopeThe insulation resistance between the thermom-eter element with its connecting wires and its external shield,case or means for mounting, should be sufficient to preventsignificant electrical shunting or ground loop current in themeasurement circuit, or any circuit failure if the

25、excitationsource is grounded. This test assumes that the thermometer hasa metallic or other electrically conductive sheath or housing.The most probable factors that contribute to insulation failureare contamination, typically from moisture, and mechanicalbreakdown due to physical damage to the devic

26、e. Most ceramicoxide insulation absorbs moisture. This moisture is expected tomigrate inside the thermometer, depending upon the tempera-ture condition of use, and to cause variations in the insulationresistance. Test conditions for insulation resistance shouldtherefore approximate the most severe c

27、onditions of probableuse and shall be specified as a minimum at a specifictemperature, humidity, pressure and test voltage. It is recom-mended that insulation resistance be measured using forwardand reversed polarity on applied dc voltages. The test methodscustomarily applied with the test article a

28、t room temperaturemay also be employed to determine the insulation resistance attemperatures up to the rated application temperature for theresistance thermometer. This is intended to be a non-destructive test.5.1.1 The insulation resistance, as measured between thelead wires and case, does not repr

29、esent the shunt resistance inparallel with the sensing element. Therefore, this test shouldnot be used to estimate temperature measurement errors causedby inadequate insulation resistance across the sensing element.5.2 Apparatus:5.2.1 Because the insulation resistance is to be measured inconjunction

30、 with other tests, the thermometer shall be mountedas required for these tests.5.2.2 Any equipment made for the purpose of insulationresistance testing shall be capable of measuring a resistance ofat least 10 gigohms (1010V) at the specified test voltage.(WarningSome instruments designed for insulat

31、ion resis-tance testing are capable of producing lethal voltages (100 V orgreater) at their measuring terminals. Such instruments shouldhave warning labels and used only by supervised and welltrained personnel.)5.3 Measurement Procedure:5.3.1 Make check measurements on a reference resistor of10 gigo

32、hms (1010V). Check the measurement instrument to65 % at the required minimum insulation resistance using acertified reference resistor. These results should accompany thetest report on the platinum resistance thermometer (PRT). Forexample: When testing a PRT with a specified 100 megohm(108V) minimum

33、 insulation resistance, the meter should betested with a resistor that has a certified resistance of 100megohms 65%.5.3.2 Make insulation resistance measurements between theconnecting wires and the shield or case, (1) before thethermometer is subjected to the conditions of any concurrenttest (calibr

34、ation, pressure, vibration), (2) during the test, and(3) immediately after the thermometer has returned to ambientconditions. All measured values of insulation resistance foreach test condition shall exceed the minimum specified value.5.3.3 Apply the specified measuring voltage between thejoined con

35、necting wires and the thermometer sheath or be-tween circuits that are intended to be isolated. Take measure-ments with normal and reversed polarity and record the lowerE644062reading. Take the reading within 10 s of voltage application.Since only minimum values of insulation resistance are ofconcer

36、n, measurement accuracy need only be sufficient toensure that the minimum requirement is met. Insulation resis-tance measurements made during vibration require a highspeed indicating device, such as an oscilloscope, to detect rapidtransient changes in resistance.5.4 The repeatability of the measurem

37、ents value is ex-pected to be 65 % and the reproducibility 610 %. SeeAppendix X4 for the results of round robin testing used todetermine the repeatability and reproducibility of this test.6. Thermometer Calibration6.1 ScopeThis test method covers recommended ways ofcalibrating industrial resistance

38、thermometers. Methods com-mon to most calibrations will be described, but the testmethods presented do not usually test the thermometer underthe actual conditions of use. The heat transfer conditions canvary widely, depending upon the medium, immersion length,rate of flow of the medium, etc. These a

39、nd other conditionsshould be carefully evaluated before installing a thermometerfor calibration or for temperature measurement. A resistancethermometer can be calibrated by using the comparison methodor the fixed-point method, or both. The calibration results maybe used to assess interchangeability,

40、 to establish a uniqueresistance-temperature relationship for the thermometer undertest, or to verify conformance to a standard. In calibration tests,care should be taken to minimize thermal shock to thethermometer when inserting it into a heated or cooled environ-ment, or when withdrawing it from a

41、 furnace or heated bath.Transitions should be made slowly, preheating or pre-coolingthe thermometer when possible. This test is intended to be anon-destructive test. However, calibration of a thermometer toa higher temperature than it has previously experienced maychange its calibration at lower tem

42、peratures. Resistances takenat ascending temperatures should be compared with thosetaken at descending temperatures to detect any change in thethermometers characteristics (see Section 16, Thermal Hys-teresis).6.2 Calibration Methods:6.2.1 Comparison MethodThis method consists of mea-suring the resi

43、stance of the test thermometer in an isothermalmedium, the temperature of which is determined by a cali-brated reference thermometer. The reference thermometer maybe a thermocouple, a liquid-in-glass thermometer, a resistancethermometer, or another thermometer of sufficient accuracythat has been cal

44、ibrated by an approved method.6.2.2 Fixed-Point MethodThis method consists of mea-suring the resistance of the thermometer at the temperaturedefined by the equilibrium state between different phases of apure substance or a mixture of pure substances. Each fixedpoint provides a calibration of the tes

45、t thermometer at only onetemperature defined by suitable equilibrium phases. The tem-perature is an intrinsic property of a properly specified equi-librium state of a substance, such as the freezing point at 1 atm.The temperature of some fixed-point devices can be repeated to60.1 mC or better.6.3 Ap

46、paratus and Procedure:6.3.1 Ice-Point Bath The most widely used and simplestfixed point is the ice-point. The ice point (0 C) may berealized with an error of less than 0.01 C if properly preparedand used. Significantly greater errors may be realized if certainconditions exist. Users of this test met

47、hod are referred toPractice E 563 which contains a more detailed discussion as tothe proper preparation and use of ice point baths.6.3.2 Freezing Points In addition to the ice-point bath, thefreezing-point temperature of various substances can be usedas fixed points. The metal freezing point materia

48、ls identified inGuide E 1502 are those most commonly employed.6.3.3 Triple Point of WaterThe triple point of water is acommonly used thermometric fixed point used for calibratingthermometers. To accurately realize the triple point of water, atriple point of water cell is used. This cell must be prep

49、ared andhandled in a specific manner. The user is directed to GuideE 1750 for the preparation and use of water triple point cells.6.3.4 Fluid Baths Control the temperature of fluid bathsby adjusting the amount of heating or cooling while agitatingthe bath fluid. Determine the amount of heating or cooling bythe indication of a sensitive thermometer in the bath. Table 1lists some of the common bath media and their useful ranges ofoperating temperatures. The bath medium must be chemicallystable at the operating temperatures and be inert to the bathcontainer and the