ASTM E77-1998(2003) Standard Test Method for Inspection and Verification of Thermometers《温度计检验和验证的标准试验方法》.pdf

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1、Designation: E 77 98 (Reapproved 2003)Standard Test Method forInspection and Verification of Thermometers1This standard is issued under the fixed designation E 77; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last re

2、vision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method covers visual and dimensio

3、nal inspec-tion, test for permanency of pigment, test for bulb stability, andtest for scale accuracy to be used in the verification ofliquid-in-glass thermometers as specified in Specification E 1.However, these procedures may be applied to other liquid-in-glass thermometers.2NOTE 1The use of NIST S

4、P250-232is recommended.1.2 This standard does not purport to address all of thesafety problems, if 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

5、 to use.2. Referenced Documents2.1 ASTM Standards:3E 1 Specification for ASTM ThermometersE 344 Terminology Relating to Thermometry and Hydrom-etry3. Terminology3.1 Definitions:3.1.1 The definitions given in Terminology E 344 apply.Some that are considered essential to this standard are givenbelow.3

6、.1.2 complete-immersion thermometer, na liquid-in-glass thermometer, not specified in ASTM documents, de-signed to indicate temperature correctly when the entirethermometer is exposed to the temperature being measured.3.1.3 partial-immersion thermometer, na liquid-in-glassthermometer designed to ind

7、icate temperature correctly whenthe bulb and a specified part of the stem are exposed to thetemperature being measured.3.1.4 total-immersion thermometer, na liquid-in-glassthermometer designed to indicate temperature correctly whenjust that portion of the thermometer containing the liquid isexposed

8、to the temperature being measured.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration, nthe determination of the indications ofa thermometer with respect to temperatures established by astandard resulting in scale corrections to be applied whenmaximum accuracy is required.3.2.2 refe

9、rence point, na temperature at which a ther-mometer is checked for changes in the bulb volume.3.2.3 verification, nthe process of testing a thermometerfor compliance with specifications.3.2.4 verification temperatures, nthe specified tempera-tures at which thermometers are tested for compliance with

10、scale error limits.3.2.5 Other descriptions of terms relating to thermometersare included in Sections 3 and 17 of Specification E 1.4. Significance and Use4.1 The test method described in this standard will ensurethat the thermometers listed in Specification E 1 will indicatetemperatures within the

11、maximum scale errors listed, becompatible with the apparatus, and serve the purpose for whichthey were designed.Fig. 14.2 Thermometers that do not pass the visual and dimen-sional inspection tests may give erroneously high or lowtemperature readings, or may not fit into existing equipmentused in AST

12、M methods. If the pigment in the scale etchingswashes out or fades, the thermometer will be difficult to read.Improper annealing of the bulb, as determined by the bulbstability test, will result in thermometer readings rapidlychanging with time and use. For accurate temperature mea-surements the sca

13、le readings of the thermometer should beverified as described in this test method.1This test method is under the jurisdiction of ASTM Committee E20 onTemperature Measurement and is the direct responsibility of Subcommittee E20.05on Liquid-in-Glass Thermometers and Hydrometers.Current edition approve

14、d Nov. 1, 2003. Published November 2003. Originallyapproved in 1949. Last previous edition approved in 1998 as E 77 98.2“Liquid-in-Glass Thermometer Calibration Service,” NIST Special Publication250-23, 1988, Superintendent of Documents, U.S. Government Printing Office,Washington, DC 20402-9325.3For

15、 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 Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700

16、, West Conshohocken, PA 19428-2959, United States.5. Apparatus5.1 Graduated Metal Scales or TemplatesMaximum andminimum specified linear dimensions are measured withgraduated metal sales and templates on which lines are ruled atsuitable distances from reference points corresponding to themaximum and

17、 minimum values of the several specified dimen-sions.5.2 Micrometers and Ring GagesSpecified diameters ofASTM thermometers are checked using micrometers, or moreconveniently with ring gages consisting of metal plates inwhich holes have been formed corresponding to the maximumand minimum values of th

18、e several specified dimensions. Thethickness of such gages should approximate the diameters ofthe holes to minimize errors resulting from the axis of thethermometer stem being other than normal to the plane of thegage. When specified, diameters may also be checked withconventional snap gages having

19、plane parallel working faces.5.3 ComparatorsComparators are required for verifica-tion of scale accuracy of liquid-in-glass thermometers. Suitabletypes are described in Appendix X1.5.4 OvenThe test for permanency of pigment may beconducted with any suitable oven, such as the type shown inFig. 1.5.5

20、Metal Block BathsThe bulb stability test may beconducted with a variety of devices. Metal block baths and thesalt and tin comparator baths, described in Appendix X1, areexamples of the type of equipment that has been found to besuitable for this purpose.5.6 Primary Standard ThermometerThe primary st

21、andardthermometer in the range from 183 to 630 C (297 to 1166F) is the platinum-resistance thermometer. Temperatures arenot measured directly with this instrument. Its electricalresistance is determined by comparison with a standard resis-tor, using a potentiometer, a Kelvin-type double bridge, or a

22、Wheatstone bridge, (preferably of the Mueller type) or an ACresistance bridge. Temperatures may then be calculated usingsuitable resistance-temperature equations. In order that it shallbe satisfactory for such use, the thermometer should meet therequirement that the ratio of resistances at the steam

23、 and icepoints shall be greater than 1.3925. More complete informationon the construction and use of primary standard thermometersmay be obtained from NIST SP250-22.44“Platinum Resistance Thermometer Calibrations,” NIST Special Publication250-22, Superintendent of Documents, U.S. Government Printing

24、 Office, Washing-ton, DC 20402-9325.FIG. 1 Oven for Permanency of Pigment TestE 77 98 (2003)25.7 Secondary Standard ThermometersSecondary stan-dard thermometers are more suitable for routine work, and maybe of various types as described below. They are simpler to usethan a primary standard thermomet

25、er with its accessory equip-ment, the latter being capable of an order of precision andaccuracy far in excess of that attainable with liquid-in-glassthermometers. The choice of a secondary standard will begoverned by various factors. The following criteria should, inso far as possible, be satisfied:

26、 The standard should be acalibrated thermometer of equal or preferably higher sensitivitythan the thermometer to be verified, and it should be capable ofgiving results of an equal or preferably higher order ofaccuracy and also of an equal or preferably higher order ofreproducibility or precision. Sc

27、ale corrections should alwaysbe applied in the use of these standards. Secondary standardsmay be of the following types.5.7.1 Direct-Reading Resistance ThermometersDirect-reading resistance thermometers are available commercially,are very convenient to use, and have the advantage over theprimary typ

28、e that temperature indications are given directly inthe instrument reading. They should be completely recalibratedevery 6 to 12 months, depending upon the temperatures ofusage. Ice points should be taken every 3 months.5.7.2 Liquid-in-Glass ThermometersLiquid-in-glass ther-mometers, when used as sec

29、ondary standards, may be classi-fied into two groups, those intended for testing general purposetotal or partial-immersion thermometers, and those for testingspecial use partial-immersion thermometers.5.7.2.1 Total-Immersion ThermometersIn the case of gen-eral purpose total-immersion thermometers, t

30、he sensitivity ofthe thermometers to be tested will govern the choice ofstandard. For thermometers graduated in 1, 2, or 5 divisions,a set of well-made thermometers will be adequate whencalibrated and used with applicable corrections. For fraction-ally graduated thermometers a calibrated set of the

31、followingthermometers is recommended. Specifications for these ASTMPrecision Thermometers appear in Specification E 1.ASTMTher-mometerNumber RangeCelsiusDivisionsLength,mm62C 38 to +2C 0.1C 38063C 8 to +32C 0.1C 38064C 25 to 55C 0.1C 38065C 50 to 80C 0.1C 38066C 75 to 105C 0.1C 38067C 95 to 155C 0.2

32、C 38068C 145 to 205C 0.2C 38069C 195 to 305C 0.5C 38070C 295 to 405C 0.5C 380ASTMTher-mometerNumber RangeFahrenheitDivisionsLength,mm62F 36 to +35F 0.2F 38063F 18 to 89F 0.2F 38064F 77 to 131F 0.2F 38065F 122 to 176F 0.2F 38066F 167 to 221F 0.2F 38067F 203 to 311F 0.5F 38068F 293 to 401F 0.5F 38069F

33、 383 to 581F 1.0F 38070F 563 to 761F 1.0F 380The foregoing set is calibrated for total immersion. With theexception of the first two, each thermometer is provided withan auxiliary scale including 0 C (32 F), thus providing meansfor checking at a fixed point, which should be done each timethe thermom

34、eter is used. The change in ice-point readingshould then be applied to all readings. It is only necessary tohave a liquid-in-glass thermometer completely calibrated onetime. Recalibration is performed as described in 6.5.8.5.7.2.2 Partial-Immersion ThermometersGeneral purposepartial-immersion thermo

35、meters, as commonly listed in manu-facturers catalogs according to their own specifications, arenormally bought and sold without specification of the tempera-tures of the emergent column for the various temperatureindications of the thermometers. In such cases, verification isusually carried out for

36、 the emergent column temperaturesprevailing with the verification equipment being employed.5.7.2.3 Special Use Partial-Immersion ThermometersSpecial use partial-immersion thermometers, such as thosecovered in Specification E 1, have specified emergent mercurycolumns or stem temperatures. These therm

37、ometers can beused as standards to calibrate other thermometers similar in alldetails of construction above the immersion point, but maydiffer below the immersion point to the extent of including anauxiliary ice point scale.5.8 Engraving Date on ASTM ThermometersIf a ther-mometers specification was

38、changed, the year that it waschanged is engraved on the back of the thermometer after theASTM designation. For example, “12C-98.”6. Procedure6.1 Visual Inspection:6.1.1 Gas Bubbles and SeparationsGas bubbles arereadily detected and are more likely to occur in shipment thanduring service. No method h

39、as been discovered that willentirely prevent such displacement of the gas. If bubbles areobserved in the bulb, they can generally be removed by coolingthe bulb with dry ice or other convenient coolant until all theliquid is drawn into the bulb. Gentle tapping of the thermom-eter while held upright w

40、ill cause the bubbles to rise to thesurface. It is very important that, if the bulb is cooled in thisprocess below the freezing point of the liquid, care should beexercised to warm the stem sufficiently during the meltingprocess so that no solidification occurs in the stem; otherwisethe bulb may bur

41、st or the capillary may split internally becauseof the expansion forces generated in the bulb.6.1.1.1 If a mercury separation is observed in the stem,several different ways are suggested for joining the columns,depending on the construction of the thermometer and the typeof separation. If a small po

42、rtion of the liquid has separated atthe top of the column and the thermometer is provided with anexpansion chamber, the liquid usually can be joined bycarefully and slowly heating the bulb until the separatedportion is driven into the expansion chamber. Never heat thebulb in an open flame. When the

43、column itself follows into thechamber, the separated portion usually will join onto the maincolumn. A slight tapping of the thermometer against the palmof the hand will facilitate this joining. This method should notbe employed for high-temperature thermometers (above 260C or 500 F), because the hea

44、ting of the bulb, which isE 77 98 (2003)3necessary to drive the liquid into the expansion chamber, mayoverheat the glass and either break the bulb, because of thepressure of the gas, or destroy the accuracy of the thermometerby expanding the bulb. Thermometers that have a contractionchamber below th

45、e lowest graduation are likely to developseparations either in the chamber or above it. It is frequentlypossible to join such separations by cooling the thermometer sothat the separated portion as well as the main column bothstand in the chamber. Tapping the tube against the hand or thebulb on a sof

46、t spongy material, such as a rubber stopper,usually will bring the liquid together. For more stubbornseparations it may be necessary to cool the bulb in dry ice to apoint low enough to bring all of the liquid into the bulb itself.By softly tapping on a soft spongy material or against the handit usua

47、lly is possible to bring the liquid together in the bulb.The bulb should be allowed to warm up slowly. The liquidshould emerge into the bore with no separation.6.1.1.2 In organic-liquid-filled thermometers distillationmay occur, with subsequent condensation of the colorlessparent liquid in the upper

48、 part of the thermometer. Suchthermometers should always be inspected for these separations,which can be repaired by the procedures described above. Ifthe thermometer has an expansion chamber that is observed tobe filled with liquid, the column can be reunited by very carefulheating of the chamber t

49、o drive the liquid into the bore whereit can be rejoined to the main body as described above.6.1.1.3 Organic liquids as used in thermometers, in contrastto mercury, wet the glass. Sufficient time should always beallowed for drainage to occur, particularly when using orverifying such thermometers below 0 C (32 F). It is fre-quently a good practice to immerse only the bulb of thethermometer. This keeps the viscosity of the liquid in thecapillary low and aids in hastening drainage.6.1.2 Globules of LiquidGlobul