ASTM E77-98(2003)
(Test Method)Standard Test Method for Inspection and Verification of Thermometers
Standard Test Method for Inspection and Verification of Thermometers
SIGNIFICANCE AND USE
The test method described in this standard will ensure that the thermometers listed in Specification E 1 will indicate temperatures within the maximum scale errors listed, be compatible with the apparatus, and serve the purpose for which they were designed.Fig. 1
Thermometers that do not pass the visual and dimensional inspection tests may give erroneously high or low temperature readings, or may not fit into existing equipment used in ASTM methods. If the pigment in the scale etchings washes out or fades, the thermometer will be difficult to read. Improper annealing of the bulb, as determined by the bulb stability test, will result in thermometer readings rapidly changing with time and use. For accurate temperature measurements the scale readings of the thermometer should be verified as described in this test method.
FIG. 1 Oven for Permanency of Pigment Test
SCOPE
1.1 This test method covers visual and dimensional inspection, test for permanency of pigment, test for bulb stability, and test for scale accuracy to be used in the verification of liquid-in-glass thermometers as specified in Specification E 1. However, these procedures may be applied to other liquid-in-glass thermometers.
Note 1—The use of NIST SP250-23 is recommended.
1.2 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E 77 – 98 (Reapproved 2003)
Standard Test Method for
Inspection and Verification of Thermometers
ThisstandardisissuedunderthefixeddesignationE77;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (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. Scope 3.1.3 partial-immersion thermometer, n—a liquid-in-glass
thermometer designed to indicate temperature correctly when
1.1 This test method covers visual and dimensional inspec-
the bulb and a specified part of the stem are exposed to the
tion,testforpermanencyofpigment,testforbulbstability,and
temperature being measured.
test for scale accuracy to be used in the verification of
3.1.4 total-immersion thermometer, n—a liquid-in-glass
liquid-in-glass thermometers as specified in Specification E1.
thermometer designed to indicate temperature correctly when
However, these procedures may be applied to other liquid-in-
just that portion of the thermometer containing the liquid is
glass thermometers.
exposed to the temperature being measured.
NOTE 1—The use of NIST SP250-23 is recommended.
3.2 Definitions of Terms Specific to This Standard:
1.2 This standard does not purport to address all of the 3.2.1 calibration, n—thedeterminationoftheindicationsof
safety problems, if any, associated with its use. It is the a thermometer with respect to temperatures established by a
responsibility of the user of this standard to establish appro- standard resulting in scale corrections to be applied when
priate safety and health practices and determine the applica- maximum accuracy is required.
bility of regulatory limitations prior to use. 3.2.2 reference point, n—a temperature at which a ther-
mometer is checked for changes in the bulb volume.
2. Referenced Documents
3.2.3 verification, n—the process of testing a thermometer
2.1 ASTM Standards:
for compliance with specifications.
E1 Specification for ASTM Thermometers 3.2.4 verification temperatures, n—the specified tempera-
E344 Terminology Relating to Thermometry and Hydrom-
tures at which thermometers are tested for compliance with
etry scale error limits.
3.2.5 Other descriptions of terms relating to thermometers
3. Terminology
are included in Sections 3 and 17 of Specification E1.
3.1 Definitions:
4. Significance and Use
3.1.1 The definitions given in Terminology E344 apply.
Some that are considered essential to this standard are given
4.1 The test method described in this standard will ensure
below. that the thermometers listed in Specification E1 will indicate
3.1.2 complete-immersion thermometer, n—a liquid-in-
temperatures within the maximum scale errors listed, be
glass thermometer, not specified in ASTM documents, de- compatiblewiththeapparatus,andservethepurposeforwhich
signed to indicate temperature correctly when the entire
they were designed.Fig. 1
thermometer is exposed to the temperature being measured. 4.2 Thermometers that do not pass the visual and dimen-
sional inspection tests may give erroneously high or low
temperature readings, or may not fit into existing equipment
This test method is under the jurisdiction of ASTM Committee E20 on
used in ASTM methods. If the pigment in the scale etchings
Temperature Measurement and is the direct responsibility of Subcommittee E20.05
on Liquid-in-Glass Thermometers and Hydrometers. washes out or fades, the thermometer will be difficult to read.
Current edition approved Nov. 1, 2003. Published November 2003. Originally
Improper annealing of the bulb, as determined by the bulb
approved in 1949. Last previous edition approved in 1998 as E 77–98.
stability test, will result in thermometer readings rapidly
“Liquid-in-GlassThermometer Calibration Service,” NISTSpecial Publication
changing with time and use. For accurate temperature mea-
250-23, 1988, Superintendent of Documents, U.S. Government Printing Office,
Washington, DC 20402-9325.
surements the scale readings of the thermometer should be
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
verified as described in this test method.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 77 – 98 (2003)
FIG. 1 Oven for Permanency of Pigment Test
5. Apparatus 5.5 Metal Block Baths—The bulb stability test may be
conducted with a variety of devices. Metal block baths and the
5.1 Graduated Metal Scales or Templates—Maximum and
salt and tin comparator baths, described in Appendix X1, are
minimum specified linear dimensions are measured with
examples of the type of equipment that has been found to be
graduatedmetalsalesandtemplatesonwhichlinesareruledat
suitable for this purpose.
suitable distances from reference points corresponding to the
5.6 Primary Standard Thermometer—Theprimarystandard
maximumandminimumvaluesoftheseveralspecifieddimen-
thermometer in the range from−183 to 630 °C (−297 to 1166
sions.
°F) is the platinum-resistance thermometer. Temperatures are
5.2 Micrometers and Ring Gages—Specified diameters of
not measured directly with this instrument. Its electrical
ASTM thermometers are checked using micrometers, or more
resistance is determined by comparison with a standard resis-
conveniently with ring gages consisting of metal plates in
tor, using a potentiometer, a Kelvin-type double bridge, or a
which holes have been formed corresponding to the maximum
Wheatstone bridge, (preferably of the Mueller type) or an AC
and minimum values of the several specified dimensions. The
resistance bridge. Temperatures may then be calculated using
thickness of such gages should approximate the diameters of
suitable resistance-temperature equations. In order that it shall
the holes to minimize errors resulting from the axis of the
be satisfactory for such use, the thermometer should meet the
thermometer stem being other than normal to the plane of the
requirement that the ratio of resistances at the steam and ice
gage. When specified, diameters may also be checked with
pointsshallbegreaterthan1.3925.Morecompleteinformation
conventional snap gages having plane parallel working faces.
on the construction and use of primary standard thermometers
5.3 Comparators—Comparators are required for verifica-
may be obtained from NIST SP250-22.
tionofscaleaccuracyofliquid-in-glassthermometers.Suitable
types are described in Appendix X1.
5.4 Oven—The test for permanency of pigment may be
“Platinum Resistance Thermometer Calibrations,” NIST Special Publication
conducted with any suitable oven, such as the type shown in
250-22, Superintendent of Documents, U.S. Government Printing Office, Washing-
Fig. 1. ton, DC 20402-9325.
E 77 – 98 (2003)
5.7 Secondary Standard Thermometers—Secondary stan- The foregoing set is calibrated for total immersion.With the
dardthermometersaremoresuitableforroutinework,andmay exception of the first two, each thermometer is provided with
beofvarioustypesasdescribedbelow.Theyaresimplertouse anauxiliaryscaleincluding0°C(32°F),thusprovidingmeans
than a primary standard thermometer with its accessory equip- for checking at a fixed point, which should be done each time
ment, the latter being capable of an order of precision and the thermometer is used. The change in ice-point reading
accuracy far in excess of that attainable with liquid-in-glass should then be applied to all readings. It is only necessary to
thermometers. The choice of a secondary standard will be have a liquid-in-glass thermometer completely calibrated one
governed by various factors. The following criteria should, in time. Recalibration is performed as described in 6.5.8.
so far as possible, be satisfied: The standard should be a 5.7.2.2 Partial-Immersion Thermometers—Generalpurpose
calibratedthermometerofequalorpreferablyhighersensitivity partial-immersion thermometers, as commonly listed in manu-
thanthethermometertobeverified,anditshouldbecapableof facturers’ catalogs according to their own specifications, are
giving results of an equal or preferably higher order of normallyboughtandsoldwithoutspecificationofthetempera-
accuracy and also of an equal or preferably higher order of tures of the emergent column for the various temperature
reproducibility or precision. Scale corrections should always indications of the thermometers. In such cases, verification is
be applied in the use of these standards. Secondary standards usually carried out for the emergent column temperatures
may be of the following types. prevailing with the verification equipment being employed.
5.7.2.3 Special Use Partial-Immersion Thermometers—
5.7.1 Direct-Reading Resistance Thermometers—Direct-
Special use partial-immersion thermometers, such as those
reading resistance thermometers are available commercially,
covered in Specification E1, have specified emergent mercury
are very convenient to use, and have the advantage over the
columns or stem temperatures. These thermometers can be
primary type that temperature indications are given directly in
used as standards to calibrate other thermometers similar in all
theinstrumentreading.Theyshouldbecompletelyrecalibrated
details of construction above the immersion point, but may
every 6 to 12 months, depending upon the temperatures of
differ below the immersion point to the extent of including an
usage. Ice points should be taken every 3 months.
auxiliary ice point scale.
5.7.2 Liquid-in-Glass Thermometers—Liquid-in-glass ther-
5.8 Engraving Date on ASTM Thermometers—If a ther-
mometers, when used as secondary standards, may be classi-
mometer’s specification was changed, the year that it was
fiedintotwogroups,thoseintendedfortestinggeneralpurpose
changed is engraved on the back of the thermometer after the
total or partial-immersion thermometers, and those for testing
ASTM designation. For example, “12C-98.”
special use partial-immersion thermometers.
5.7.2.1 Total-Immersion Thermometers—Inthecaseofgen-
6. Procedure
eral purpose total-immersion thermometers, the sensitivity of
6.1 Visual Inspection:
the thermometers to be tested will govern the choice of
6.1.1 Gas Bubbles and Separations—Gas bubbles are
standard. For thermometers graduated in 1, 2, or 5° divisions,
readily detected and are more likely to occur in shipment than
a set of well-made thermometers will be adequate when
during service. No method has been discovered that will
calibrated and used with applicable corrections. For fraction-
entirely prevent such displacement of the gas. If bubbles are
ally graduated thermometers a calibrated set of the following
observedinthebulb,theycangenerallyberemovedbycooling
thermometers is recommended. Specifications for theseASTM
the bulb with dry ice or other convenient coolant until all the
Precision Thermometers appear in Specification E1.
liquid is drawn into the bulb. Gentle tapping of the thermom-
ASTM
eter while held upright will cause the bubbles to rise to the
Ther-
mometer Length,
surface. It is very important that, if the bulb is cooled in this
Celsius
Number Range Divisions mm
process below the freezing point of the liquid, care should be
exercised to warm the stem sufficiently during the melting
62C −38 to +2°C 0.1°C 380
63C −8 to +32°C 0.1°C 380
process so that no solidification occurs in the stem; otherwise
64C 25 to 55°C 0.1°C 380
thebulbmayburstorthecapillarymaysplitinternallybecause
65C 50 to 80°C 0.1°C 380
of the expansion forces generated in the bulb.
66C 75 to 105°C 0.1°C 380
67C 95 to 155°C 0.2°C 380
6.1.1.1 If a mercury separation is observed in the stem,
68C 145 to 205°C 0.2°C 380
several different ways are suggested for joining the columns,
69C 195 to 305°C 0.5°C 380
dependingontheconstructionofthethermometerandthetype
70C 295 to 405°C 0.5°C 380
of separation. If a small portion of the liquid has separated at
ASTM
Ther-
the top of the column and the thermometer is provided with an
mometer Length,
Fahrenheit
expansion chamber, the liquid usually can be joined by
Number Range Divisions mm
carefully and slowly heating the bulb until the separated
62F −36 to +35°F 0.2°F 380
portion is driven into the expansion chamber. Never heat the
63F 18 to 89°F 0.2°F 380
bulb in an open flame.When the column itself follows into the
64F 77 to 131°F 0.2°F 380
65F 122 to 176°F 0.2°F 380 chamber, the separated portion usually will join onto the main
66F 167 to 221°F 0.2°F 380
column. A slight tapping of the thermometer against the palm
67F 203 to 311°F 0.5°F 380
of the hand will facilitate this joining. This method should not
68F 293 to 401°F 0.5°F 380
69F 383 to 581°F 1.0°F 380 be employed for high-temperature thermometers (above 260
70F 563 to 761°F 1.0°F 380
°C or 500 °F), because the heating of the bulb, which is
E 77 – 98 (2003)
necessary to drive the liquid into the expansion chamber, may Undertheseconditionsoxidationofthemercurywilloccurand
overheat the glass and either break the bulb, because of the willnormallybeevidencedbytheproductionofcrystalsofred
pressureofthegas,ordestroytheaccuracyofthethermometer oxide of mercury after 10 to 12 h of exposure.
by expanding the bulb. Thermometers that have a contraction
6.1.4 Glass Faults—Glass faults may be of various types.
chamber below the lowest graduation are likely to develop
Any stones or striae that distort the bore or its appearance
separations either in the chamber or above it. It is frequently
should be cause for rejection. Strains in the glass as observed
possibletojoinsuchseparationsbycoolingthethermometerso
withapolarizedlightstraingagenearenlargementsinthestem
that the separated portion as well as the main column both
orbore,oratthetopofthethermometer,aredetrimental.Ifso,
stand in the chamber. Tapping the tube against the hand or the
severe fire cracks may later occur. Strains near the bulb are
bulb on a soft spongy material, such as a rubber stopper,
indicativeofincompleteglassstabilizationandareparticularly
usually will bring the liquid together. For more stubborn
objectionable in thermometers for use above 150 °C (302 °F).
separations it may be necessary to cool the bulb in dry ice to a The test for bulb stability will normally serve to reject high
point low enough to bring all of the liquid into the bulb itself.
range thermometers in which this defect is most significant.
Bysoftlytappingonasoftspongymaterialoragainstthehand
6.2 Dimensional Inspection
...
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