1、Designation: E644 11Standard Test Methods forTesting Industrial Resistance Thermometers1This standard is issued under the fixed designation E644; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number i
2、n parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 te
3、st 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 test m
4、ethods 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 of
5、 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 any
6、, 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 5, 6, 8, 16, and 17.2. Referenced Documents2.
7、1 ASTM Standards:2E1 Specification for ASTM Liquid-in-Glass ThermometersE77 Test Method for Inspection and Verification of Ther-mometersE230 Specification and Temperature-Electromotive Force(EMF) Tables for Standardized ThermocouplesE344 Terminology Relating to Thermometry and Hydrom-etryE563 Practi
8、ce for Preparation and Use of an Ice-Point Bathas a Reference TemperatureE1137/E1137M Specification for Industrial Platinum Resis-tance ThermometersE1502 Guide for Use of Fixed-Point Cells for ReferenceTemperaturesE1750 Guide for Use of Water Triple Point CellsE1751 Guide for Temperature Electromoti
9、ve Force (EMF)Tables for Non-Letter Designated Thermocouple Combi-nations3E2251 Specification for Liquid-in-Glass ASTM Thermom-eters with Low-Hazard Precision Liquids2.2 Military Standard:4MIL-STD-202 Test Methods for Electronic and ElectricalComponent Parts3. Terminology3.1 Definitions of Terms Spe
10、cific to This Standard:3.1.1 The definitions given in Terminology E344 shall applyto these test methods.3.1.2 bath gradient error, 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 i
11、n which the temperature gradients are insig-nificant.)3.1.3 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 not at thetemperature that is being determined. Thermometers are avail-abl
12、e in two-, three-, and four-wire configurations. There is no1These test methods are under the jurisdiction of ASTM Committee E20 onTemperature Measurement and are the direct responsibility of Subcommittee E20.03on Resistance Thermometers.Current edition approved May 1, 2011. Published June 2011. Ori
13、ginallyapproved in 1978. Last previous edition approved in 2008 as E644 09. DOI:10.1520/E0644-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Docum
14、ent Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.4Available from Superintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20234.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
15、 Conshohocken, PA 19428-2959, United States.satisfactory way to compensate for the wire resistance in themeasurement with a two-wire thermometer although the wireresistance can be compensated for in three and four-wirethermometers.)3.1.4 immersion error, nan error caused by the heatconduction or rad
16、iation, or both, between the resistance 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.3.1.5 interchangeability, nthe extent to which the ther-mometer matche
17、s a resistance-temperature relationship. (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.)3.1.6 self-heating, nthe increase in
18、the temperature of thethermometer element caused by the electric power dissipated inthe element, the magnitude depending upon the thermometercurrent and heat conduction from the thermometer element tothe surrounding medium.3.1.7 self-heating error, nthe error caused by variationsfrom the calibration
19、 conditions in the self-heating of thethermometer element at a given current, arising from thevariations in the heat conduction from the thermometer to thesurrounding medium.3.1.8 thermoelectric effect error, nthe error caused by athermal emf in the measurement circuit as a result of dissimilarmetal
20、s and temperature gradients in the circuit.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
21、 thelimits of repeatability given in Appendix 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 appli
22、cations to meet a particu-lar specification such as Specification E1137/E1137M,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 reproduc
23、ibility of se-lected test methods are 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 m
24、ayproduce.PROCEDURES5. Insulation Resistance 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 c
25、ircuit, or any circuit failure if the 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 mechanicalbreakdo
26、wn due to physical damage to the device. 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 shouldt
27、herefore approximate the most severe conditions 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 methodscusto
28、marily applied with the test article at 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
29、 thelead wires and case, does not represent 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 resi
30、stance is to be measured inconjunction 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.(Warnin
31、gSome instruments designed for insulation 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 measurem
32、ents on a reference resistor of10 gigohms (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 wit
33、h a specified 100 megohm(108V) minimum 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 co
34、nditions of any concurrenttest (calibration, 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.E644 1125.3.3 Apply the spe
35、cified measuring voltage between thejoined connecting 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 lowerreading. Take the reading within 10 s of voltage application.Since only minimum value
36、s of insulation resistance are ofconcern, 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 resistanc
37、e.5.4 The repeatability of the measurements 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 wa
38、ys ofcalibrating industrial resistance 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,r
39、ate of flow of the medium, etc. These and 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 m
40、aybe used to assess interchangeability, 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 envi
41、ron-ment, or when withdrawing it from a 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
42、 maychange its calibration at lower temperatures. 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
43、 method consists of mea-suring the resistance 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
44、of sufficient accuracythat has been calibrated 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 fixed
45、point provides a calibration of the test 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
46、 be repeated to60.1 mC or better.6.3 Apparatus 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 certainc
47、onditions exist. Users of this test method are referred toPractice E563 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 po
48、ints. The metal freezing point materials identified inGuide E1502 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
49、 cell is used. This cell must be prepared andhandled in a specific manner. The user is directed to GuideE1750 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
