ASTM E563-2002e1 Standard Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature《作为参考温度的冰点浴的制备和使用的标准规程》.pdf

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1、Designation: E 563 02e1Standard Practice forPreparation and Use of an Ice-Point Bath as a ReferenceTemperature1This standard is issued under the fixed designation E 563; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l

2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEFootnote 1 was editorially corrected in March 2005.1. Scope1.1 This practice covers a method of preparing, maintaining,and u

3、sing a temperature reference bath of a mixture of shavedice and water, saturated with air at a pressure of 101 325 Pa (1atm).1.2 An industrial practice for relating values referenced tothe ice point and to the water triple point on the ITS-90 isincluded.1.3 Methods to promote uniformity of bath temp

4、erature bymechanical stirring or agitation are not described in detail.1.4 Methods of approximating the ice point, as bythermostatically-controlled refrigeration, are not covered bythis practice.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use.

5、 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.2. Referenced Documents2.1 ASTM Standards:2D 1193 Standard Specification for Reagent WaterE 344 Terminology Relating to

6、Thermometry and Hydrom-etryE 1594 Guide for Expression of Temperature3. Terminology3.1 DefinitionsDefinitions given in Terminology E 344,unless otherwise defined herein, apply to terms as used in thispractice.3.2 Temperature relationships given in Guide E 1594, un-less otherwise defined herein, appl

7、y to temperature values asused in this practice.3.3 Definitions of Terms Specific to This Standard:3.3.1 ice-point bath, nphysical system containing ice andwater assembled to realize the ice point as a referencetemperature, or to establish a constant temperature near 0C.4. Summary of Practice4.1 The

8、 ice-point bath described by this practice consists ofan intimate mixture, without voids, of pure shaved ice or iceparticles and distilled air-saturated water in a thermally insu-lating vessel open to the atmosphere.4.2 The ice bath realization of the ice point physicallyapproximates, with small unc

9、ertainty, a natural fixed-pointtemperature.4.2.1 An ice-point bath prepared using distilled-water iceand air-saturated, chilled distilled water, typically has a tem-perature of 0.000 6 0.002C. Consequently, when the bath isused as a fixed-point temperature reference, the bath tempera-ture is assumed

10、 to be 0C, with an uncertainty that depends onthe care with which the bath was established and maintained.4.2.2 The ice-point bath is open to the atmosphere; the effectof barometric pressure on the ice point is 75 nK/Pa (7.6mK/atm). The solubility of air in the water is directly propor-tional to the

11、 atmospheric pressure.4.3 The ice-bath temperature can also be measured with anaccurately calibrated thermometer or compared to a watertriple point cell and the bath temperature is reported as themeasured temperature with an uncertainty that is attributed tothe measurement, not to the ice point.5. S

12、ignificance and Use5.1 This practice is adequate for use with other ASTMstandards that specify the ice point as a reference. It is alsointended to be adequate for most other ice-point referencepurposes.1This practice is under the jurisdiction ofASTM Committee E20 onTemperatureMeasurement and is the

13、direct responsibility of Subcommittee E20.07 on Funda-mentals in Thermometry.Current edition approved October 10, 2002. Published May 2003. Originallyapproved in 1976. Discontinued February 1996 and reinstated in 1997 asE 563 97.2For referenced ASTM standards, visit the ASTM website, www.astm.org, o

14、rcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 The ice point

15、 is a common practical industrial referencepoint of thermometry. The ice point is relatively simple torealize and provides a readily available natural fixed-pointreference temperature.5.3 Use in Resistance Thermometry:5.3.1 The ice point was a defining fixed point on practicaltemperature scales prio

16、r to 1960.5.3.2 The ITS-90 defines W(T90) = R(T90)/R(273.16 K), themeasured resistance ratio of a Standard Platinum ResistanceThermometer (SPRT), in reference to the water triple point, notthe ice point (1).3In many instances, where the water triplepoint is not available, or when the accuracy obtain

17、able with thewater triple point is not required, reference to a properlyestablished and maintained ice-point reference is used. Forindustrial-quality resistance thermometers, the resistance valueis determined for 0C, and an uncertainty is assigned that isappropriate for the quality of the ice-point

18、realization.5.4 Use in Thermoelectric Thermometry:5.4.1 In thermoelectric thermometry, the ice point is ordi-narily used as the reference temperature (2).5.4.2 Adequate thermoelectric reference requires that ther-mocouple junctions be well-coupled thermally to the bath,electrically isolated from eac

19、h other and from the bath, andadequately immersed to avoid perturbing the reference-junction temperatures by radiation and longitudinal conductionof 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 ordi-narily used

20、as the reference temperature (6).5.5.2 The periodic recalibration of a liquid-in-glass ther-mometer at the ice point provides a reliable indication of theeffect of gradual relaxation of residual mechanical strains in theglass that have a significant effect on the volume of the bulb,and provides a me

21、ans for the accurate adjustment of theremainder of the scale (6).6. Hazards6.1 Excess water accumulating in any region, particularlyaround the reference location, can elevate the temperature inthat vicinity above the ice point. Errors, usually somewhat lessthan 4C, can occur from this cause in poorl

22、y maintained bathsand with poorly positioned test objects (3 and 4).6.2 For a stirred bath, the temperature of the bath willdepend on the heat gained by the bath, the amount of water andice, and the vigor of stirring. The uniformity of temperature ofthe bath can be enhanced by slowly stirring or agi

23、tating theslush of ice and water either manually or by a powered stirringmeans so that all of the ice and water in the bath come intointimate contact.6.3 Ice making machines operate below 0C. Therefore,when excessively large ice particles are used to prepare theice-point bath, the initial temperatur

24、e of the bath can briefly beslightly below the ice point.Also, some of the water may freezeand bridge some of the particles. Use of the bath must bedelayed long enough to establish thermal equilibrium, and theparticles shall be sufficiently small so that the bath approachesthe required state of ice

25、and air-saturated water in intimatecontact.6.4 Cleanliness is essential as small amounts of dissolvedsalts, and other contaminants can cause the equilibrium tem-perature to be below that of the ice-point temperature.7. Procedure7.1 In the practical use of the ice-point bath, two objectivesshall be a

26、ccomplished: (1) the bath shall be established andmaintained so that its temperature is a good approximation tothat of the ice point, and (2) the object for which the referencetemperature is to be obtained shall be in thermal equilibriumwith the water-ice equilibrium temperature (water-ice interface

27、temperature).7.2 Establishing the Ice-Point:7.2.1 All equipment that comes in contact with the waterand ice of an ice-point bath shall be clean. Thoroughly rinse theequipment with tap water, then rinse with the type of waterused for the ice-point bath medium. Use clean plastic gloves tohandle the ic

28、e and equipment.7.2.2 Use water of purity equivalent to or purer than type IVreagent water, Specification D 1193, for the ice-point bathmedium. Chill a quantity of the water to near 0C in a flask andshake vigorously to aerate the water. Freeze another portion ofthe water to produce ice for the bath.

29、7.2.3 Prepare finely divided ice by shaving or crushing.Shaved ice resembling snow is preferred, but crushed ice isacceptable if the particles are small (not exceeding 2 to 3 mmdiameter).7.2.4 Prepare the bath in a clean thermally insulated vessel,preferably a wide-mouthed Dewar vacuum flask fitted

30、with aninsulating closure such as a stopper. The vessel should be largeenough that its size does not affect the water-ice equilibriumtemperature and of such diameter and depth that in thermalequilibrium the test objects will not significantly modify thetemperature of the bath over the region to whic

31、h the ice pointis to be applied. For usual applications, a diameter of at least 70mm and a depth of at least 300 mm may be adequate.7.2.5 Alternately add shaved ice and chilled water to thevessel, using enough water to saturate the ice but not enough tofloat it. As the vessel fills, compress the ice

32、-water mixture toforce out excess water. The objective is to surround eachparticle of ice with water, filling all voids, but to keep the iceparticles as close together as possible. Continue adding ice andwater and compressing until the vessel is filled to the requiredlevel. Decant or siphon off exce

33、ss water.7.2.6 Cover the ice-point bath to protect it. Use an opaqueand thermally insulating cover or stopper that is suitable for theapplication.Allow the bath and vessel to equilibrate for at least30 minutes before using.7.3 Using the Ice-Point Bath:7.3.1 Form a well in the ice-point bath that is

34、the diameterof the test object and intended immersion depth of the testobject.7.3.2 Cool the test object to equilibrium in water withtemperature less than 3C before immersing it in the bath. Thisreduces the time to reach equilibrium at the ice point. Coolinghelps to preserve the bath at the ice poin

35、t for prolonged use.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.E56302e12Cooling also helps to ensure that the water-ice interface will bein contact with the thermometer because negligible meltingwill have occurred to increase the water film thickn

36、ess.7.3.3 Insert the test object with the sensor portion of theobject, such as the sensing element of an SPRT, to a depth ofat least ten object diameters below the surface. For thermo-electric thermo-elements of high thermal conductivity, as muchas 200 mm immersion may be necessary. For total immers

37、ionliquid-in-glass thermometers, immerse to the 0 C (32 F)mark. For partial immersion liquid-in-glass thermometers,immerse to the immersion line or stated immersion depth.Keep the sensor portion of the object several centimeters abovethe bottom of the flask to avoid the zone at the bottom wheredense

38、r melt water tends to accumulate.7.3.4 Close the top of the vessel around the test object withan opaque insulating stopper or other thermal barrier to reduceheat transfer through the surface of the bath.NOTE 1When liquid-in-glass thermometers are tested in an ice pointbath, the bath may be left unco

39、vered. The loss of precision between acovered and uncovered bath may be below the resolution of liquid-in-glassthermometers. The user must test for this condition.7.3.5 Allow the bath and test object to come to thermalequilibrium.7.4 Maintaining the Bath:7.4.1 As ice particles in the bath melt, exce

40、ss water beginsto accumulate. This melt water has a temperature slightlywarmer than 0C. Since the density of water has its maximumat 4C, the slightly warm melt water will collect at the bottomof the bath and, hence, around the test object. Under theseconditions, the bath will no longer be at 0C and

41、cannot serveas an ice-point bath. For this reason surplus water should beremoved, as it accumulates, from the bottom of the bath bydecanting or siphoning. The presence of excess water can bedetected if water overspill occurs when the ice is depressed.Add ice particles, and chilled water, as necessar

42、y so that the iceslush column always extends to at least 30 mm below thelowest point of the test object.7.4.2 In order to sustain the ice point over prolongedperiods, the ice-point bath may be immersed in another baththat is kept near 0C.8. Precision and Bias8.1 If a succession of ice-point baths is

43、 prepared by follow-ing all of the procedures described in this practice, routinedetermination of the temperature of each of the baths with astable, well-calibrated standard platinum resistance thermom-eter will yield values of temperature that vary over a range ofabout 4 mK with a sample standard d

44、eviation of about 1 mK(5).8.2 The variability represents the reproducibility of the icepoint under the conditions of this practice, and the standarddeviation may be interpreted as a measure of the imprecision ofrealizing an ice point.8.3 The mean of values determined under the conditions of8.1 will

45、be biased from 0C by an amount negligible comparedto the variability (5).8.4 An ice-point bath prepared by rigorous application ofthis practice may be assigned a temperature of 0C with anexpanded total uncertainty (k = 2) of about 2 mK (5).8.5 Sources of Error and Uncertainty:8.5.1 The temperature o

46、f a poorly made or poorly main-tained ice-point bath can differ from 0C by as much as severalkelvins. Impurities in the water usually lower the temperature.Excessive water in the bath can cause an increase in tempera-ture as denser warm water settles to the bottom. Large chunksof very cold ice added

47、 to a bath can produce local temperaturedepression.8.5.2 Type IV grade of reagent water prepared with differentapparatus can produce ice-point baths with slightly differenttemperatures that are detectable with very precise thermom-etry. Temperature differences of 0.4 mK have been observed inice-poin

48、t baths made from water purified in different stills (5).8.5.3 The temperature of an ice-point bath made withtypical potable city tap water may be low by 10 to 20 mK (3,5).8.5.4 The temperature of the ice-point bath is slightlydependent on pressure. The temperature is lowered by about6.3 K for each

49、centimeter of depth below the liquid surfacedue to hydrostatic pressure. There is a corresponding effect forchanges in atmospheric pressure. In most cases, pressureeffects can be ignored (4).8.5.5 In an ice-point bath, the actual temperature of a pointin an immersed test object that conducts heat into the bathdepends on time, position in the bath, and the amount of heatconducted into the bath. A water-ice interface in the bath actsas a heat sink.As ice melts, the interface moves away from thetest object, and a temperature difference, which can be as muchas seve