ASTM E1137-97
(Specification)Standard Specification for Industrial Platinum Resistance Thermometers
Standard Specification for Industrial Platinum Resistance Thermometers
SCOPE
1.1 This specification covers the requirements for metal-sheathed industrial platinum resistance thermometers (PRT's) suitable for direct immersion temperature measurement. It applies to PRT's with an average temperature coefficient of resistance between 0 and 100°C of 0.385%/°C and nominal resistance at 0°C of 100 [omega] or other specified value. This specification covers PRT's suitable for all or part of the temperature range -200 to 650°C. The resistance-temperature relationship and tolerances are specified as well as physical, performance, and testing requirements.
1.2 The values of temperature in this specification are based on the International Temperature Scale of 1990 (ITS-90) .
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
An American National Standard
Designation: E 1137 – 97
Standard Specification for
Industrial Platinum Resistance Thermometers
This standard is issued under the fixed designation E1137; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 Definitions of Terms Specific to This Standard:
3.2.1 cable end closure, n—moisturebarrieratthecableend
1.1 This specification covers the requirements for metal-
of the sheath.
sheathed industrial platinum resistance thermometers (PRT’s)
3.2.2 connecting wires, n—wires that run from the element
suitable for direct immersion temperature measurement. It
through the cable end closure and external to the sheath.
applies to PRT’s with an average temperature coefficient of
3.2.2.1 Discussion—The closure does not necessarily con-
resistance between 0 and 100°C of 0.385%/°C and nominal
stitute a hermetic seal.
resistance at 0°C of 100 V or other specified value. This
3.2.3 excitation, n—electrical current passing through the
specification covers PRT’s suitable for all or part of the
element.
temperature range−200 to 650°C. The resistance-temperature
3.2.4 g-level, n—acceleration of an object relative to the
relationship and tolerances are specified as well as physical,
local acceleration of gravity.
performance, and testing requirements.
3.2.4.1 Discussion—For example, a g-level of 5 is equiva-
1.2 Thevaluesoftemperatureinthisspecificationarebased
lent to an acceleration of approximately 5 39.8 m/s =49.0
on the International Temperature Scale of 1990 (ITS-90).
m/s .
2. Referenced Documents
3.2.5 minimum immersion length, n—depththatathermom-
eter should be immersed, in a uniform temperature environ-
2.1 ASTM Standards:
ment,suchthatfurtherimmersiondoesnotproduceachangein
A269 Specification for Seamless and Welded Austenitic
indicated temperature greater than the specified tolerance.
Stainless Steel Tubing for General Service
3.2.6 PRT design, n—generic term used to differentiate
B 167 Specification for Nickel-Chromium-Iron Alloys
between different PRT construction details, such as element
(UNS N06600, N06601, and N06690) Seamless Pipe and
and connecting wire construction, insulation methods, sealing
Tube
techniques,andmountingmethods(forexample,springloaded
E344 Terminology Relating to Thermometry and Hydrom-
or direct mounting).
etry
3.2.7 self-heating, n—change in temperature of the element
E644 Test Methods for Testing Industrial Resistance Ther-
caused by the heating effect of the excitation.
mometers
3.2.8 sheath, n—cylindrical metal tube with an integral
E1652 Specification for Magnesium Oxide and Aluminum
welded closure at the end in which the element is located.
Oxide Powder and Crushable Insulators Used in the
ManufactureofMetal-SheathedPlatinumResistanceTher-
4. Significance and Use
mometers and Noble Metal Thermocouples
4.1 This specification is written to provide common termi-
3. Terminology
nology, resistance versus temperature characteristics, accuracy
classification, and inspection requirements for a specified
3.1 Definitions—For definitions of terms used in this speci-
configuration of a typical industrial platinum resistance ther-
fication see Terminology E344.
mometer (PRT).
4.2 This specification may be used as part of the documen-
This specification is under the jurisdiction of ASTM Committee E-20 on
tation to support negotiations for the purchase and discussion
Temperature Measurement and is the direct responsibility of Subcommittee E20.03
of such thermometers.
on Resistance Thermometers.
Current edition approved Nov. 10, 1997. Published May 1998. Originally
5. Classification of Tolerances
published as E1137–87. Last previous edition E1137–95.
Preston-Thomas, H., “The International Temperature Scale of 1990 (ITS-90),”
5.1 The PRT shall conform to the resistance-temperature
Metrologia, Vol 27, No. 1, 1990, pp. 3–10. For errata see ibid, Vol 27, No. 2, 1990,
relation (see 9.2.1) within the following tolerances:
p. 107.
Annual Book of ASTM Standards, Vol 01.01. Grade A56[0.13 10.0017|t|]°C (1)
Annual Book of ASTM Standards, Vol 02.04.
Annual Book of ASTM Standards, Vol 14.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
E1137–97
Grade B56[0.25 10.0042|t|]°C (2)
where:
| t | = value of temperature without regard to sign, °C.
5.1.1 The tolerances are given in Table 1 for a PRT with a
nominal resistance of 100 V at 0°C.
6. Ordering Information
6.1 The purchase order documents shall specify the follow-
inginformationtoensurethatthePRTisadequatelydescribed:
6.1.1 The number of this specification,
FIG. 1 Platinum Resistance Thermometer
6.1.2 Sheath diameter and overall length (see Fig. 1),
6.1.3 Sheath material,
6.1.4 Minimum and maximum sensed temperature,
7.1.5 Connecting Wires—Typically, materials of connecting
6.1.5 Maximum temperature at cable end closure,
wiresare:nickelplatedcopper,nickel,platinum,constantan,or
6.1.6 Connection configuration; 2-Wire, 3-Wire, 4-Wire
manganin.Anymaterialusedinjoiningtheconnectingwiresto
(potentiometric), and compensating loop (4-Wire) (see Fig. 2),
the PRT element must withstand the maximum operating
6.1.7 Tolerance, (Grade A, or Grade B), and
temperature of the PRT.
6.1.8 Nominal resistance at 0°C (100 V unless otherwise
8. Other Requirements
specified).
8.1 Pressure—ThePRTshallwithstandanexternalpressure
7. Materials and Manufacture
of 21 MPa (3000 psig) and shall be tested in accordance with
7.1 All materials used shall be in accordance with the
TestMethodsE644pressuretest.ThePRTshallremainwithin
following requirements:
the tolerance specified in 5.1.
7.1.1 Sheath Materials—For temperatures not exceeding
8.2 Vibration:
480°C, austenitic stainless steel tubing, conforming to Speci-
8.2.1 ThePRTshallwithstandvibrationtestingasdescribed
fication A269. For temperatures not exceeding 650°C, high-
in Test Methods E644 using the test in Table 2.
nickel alloy tubing, conforming to Specification B167.
8.2.2 The PRT shall be mounted by installation in the
7.1.2 Sensing Element—Sensing element shall be platinum.
thermowell or by threaded connection to simulate normal
7.1.3 Insulation—The insulating material within the PRT
mounting procedure as limited by Table 2.
shall be compatible with the temperature range−200 to 650°C
8.2.3 The PRT shall be continuously energized with an
or as specified in 6.1.4. Magnesium oxide (MgO) and alumi-
oscilloscope-monitored 1.0-mA dc excitation. There shall be
numoxide(Al O )Powdersandcrushableinsulatorsconform-
no discontinuity of the monitored trace during the test.
2 3
ing to Specification E1652 satisfy this requirement.
8.2.4 After the PRT is tested for vibration the insulation
7.1.4 Cable End Potting Materials—Potting materials shall
resistanceofthePRTshallremainwithinthetoleranceofTable
provide a barrier against water and other liquids and generally
3andtheresistanceat0°Cwithinthetolerancespecifiedin5.1.
prevent the penetration of water vapor. Any potting material
8.3 Mechanical Shock:
used shall be compatible with the ambient temperatures speci-
8.3.1 The PRT shall withstand mechanical shock testing as
fied for the application.
described in Test Methods E644. The half-sine pulse shall
have a peak g-level of 50 and duration of 11 ms.
NOTE 1—Typically, epoxy materials are used for ambient temperatures
8.3.2 The PRT shall be continuously energized with an
lessthan200°Candmoistureimperviousceramicadhesivesareusedover
oscilloscope-monitored 1.0-mA dc excitation. There shall be
200°C, but the cable end potting shall not be limited to these materials if
the end seal meets all other requirements of this specification.
no discontinuity of the monitored trace during the test.
8.3.3 After the PRT is tested for mechanical shock the
A, B insulationresistanceofthePRTshallremainwiththetolerance
TABLE 1 Classification Tolerances
ofTable 3and the resistance at 0°C within the tolerance in5.1.
Temperature, t,
Grade A Grade B
8.4 Thermal:
°C
8.4.1 ThePRTshallbecapableofcontinuousoperationover
°C V °C V
− 200 0.47 0.20 1.1 0.47 the specified temperature range (see 6.1).
− 100 0.30 0.12 0.67 0.27
8.4.2 The cable end closure and external connecting wires
0 0.13 0.05 0.25 0.10
need not withstand the maximum PRT operating temperature.
100 0.30 0.11 0.67 0.25
200 0.47 0.17 1.1 0.40
300 0.64 0.23 1.5 0.53 9. Performance
400 0.81 0.28 1.9 0.66
9.1 Excitation:
500 0.98 0.33 2.4 0.78
600 1.15 0.37 2.8 0.88
9.1.1 The PRT must be constructed such that it is usable in
650 1.24 0.40 3.0 0.94
ac or dc measurement systems. In ac measuring systems,
A
The table represents values for 3-wire and 4-wire PRT’s. Caution must be
reactance effects shall be considered.
exercised with 2-wire PRT’s because of possible errors caused by connecting
9.1.2 ThePRTshallbecapableofoperatingwithcontinuous
wires.
B
Tabulated values are based on elements of 100.0 V (nominal) at 0°C. excitation of 10 mA. However, excitation of 1 mA or less is
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
E1137–97
FIG. 2 Connection Configurations
TABLE 2 Vibration Test Parameters
requirements of Table 3 when tested in accordance with Test
Methods E644. The PRT shall be tested with at least the
NOTE 1— The values in Table 2 apply to a PRT mounted in a
minimum immersion length exposed to the temperature envi-
thermowell with nominal clearance of less than 0.25 mm (0.01 in.) in
diameter. If the PRT is not mounted in a thermowell, the values in Table ronment.
2 apply to a PRT with an unsupported stem length less than 102 mm (4
9.4 Self-Heating—A power of at least 33 mW shall be
in.).
required to produce a self-heating of 1°C when the PRT is
Frequency 5 to 500 Hz
tested in water in accordance with Test Methods E644.
Test Level 1.27-mm (0.05-in.) double amplitude displacement or
9.5 Thermal Response Time—The 63.2% response time
peak g-level of 3, whichever is less
Resonant Dwell Time 30 min for each resonant point
shall not exceed the values in Table 5 when determined in
Cycling Time 3 h per axis less the time spent at resonant dwells at
accordance with Test Methods E644. The step change in
the axis.
temperature shall be from 20 6 5°C air to 77 6 5°C water
Mounting As normally mounted including the mating thermowell,
if applicable.
flowing at 0.9 6 0.09 m/s (3.0 6 0.3 ft/s).
9.6 Thermoelectric Effect—Wire connections between the
PRT sensing element, inner connecting wires, and external
TABLE 3 Insulation Resistance
connecting wires can generate small voltages when these
Applied dc Voltage, Volts dc Minimum Insulation Resistance
connection points are exposed to different temperatures. This
min max °C MV
thermoelectric voltage can add or subtract from the voltage
10 50 25 6 5 100
10 50 300 6 10 10
measuredacrossaPRTandcauseanunknownvariableerrorin
10 50 650 6 15 2
measurement. When tested in accordance with Test Methods
E644, the PRT shall remain within the tolerances specified in
5.1 with an excitation of 1-mA dc, regardless of polarity.
9.7 Stability—When tested in accordance with Test Meth-
recommendedtominimizemeasurementerrorsassociatedwith
odsE644,thePRTshallremainwithinthetolerancesspecified
self-heating (see 9.4).
in 5.1 for a four-week test. During this test, the resistance at
9.2 Resistance versus Temperature Relation:
0°C shall be checked at regular intervals (2 times per week).
9.2.1 Resistance-Temperature Equations—Withinthespeci-
9.8 Minimum Immersion Length—When determined in ac-
fied tolerances (see 5.1), the PRT shall have resistance-
cordance with Test Methods E644, the PRT minimum immer-
temperature characteristics defined as follows:
sion length shall be less than 51 mm (2 in.). The limit of
for the range−200° C# t < 0°C:
uncertainty shall be 0.13°C and 0.25°C for GradeAand Grade
2 3
R 5 R 1 1 At 1 Bt 1 C t 2100!t V (3)
@ ~ #
t o
B PRT’s respectively.
for the range 0 °C# t# 650°C:
10. Dimensions, Mass, and Permissible Variations
R 5 R @1 1 At 1 Bt # V (4)
t o
10.1 A PRT without a process fitting or other means of
where:
attachment is shown in Fig. 1.
t = temperature (ITS-90), °C,
10.2 PRT’s manufactured in accordance with this specifica-
R = resistance at temperature (t),
t
tion shall be able to pass through the straightness ring gage
R = resistance at 0°C,
o
−3 −1
with the gage sizes listed in Table 6.
A = 3.9083 310 °C ,
−7 -2
B = −5.775 310 °C , and
−12 −4
C = −4.183 310 °C .
11. Required Tests
9.2.2 Resistance Table—Resistance values of the PRT ver-
11.1 Qualification Tests—The PRTshall be subjected to the
sus temperature using the equations of 9.2.1 and R of 100 V
o
tests outlined in Table 7 to demonstrate conformance to this
are given in Table 4.
specification. The manufacturer shall perform these tests at
NOTE 2—The resistance versus temperature relationship for a specific least one time to qualify the PRT design. Thereafter, it is
thermometer may be computed from measured resistance of that specific
recommended these tests be used on a periodic basis to verify
thermometer.
process control.
9.2.3 Inverse equations that may be used to compute values 11.1.1 Qualification Test Report—The manufacturer shall
of temperature (°C) as a function of resistance are given in prepare and retain a qualification test report applicable to the
Appendix X1. PRT design that documents the model number, test procedure
9.3 Insulation Resistance—The insulation resistance be- (by reference to Test Methods E644 and this specification),
tween each connecting wire and the sheath shall meet the and the results obtained.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
International (www.astm.org) for the latest information.
E1137–97
A, B
TABLE 4 Resistance versus Temperature
ITS-90° C 0 –1 –2 –3 –4 –5 –6 –7 –8 –9 –10
−200 18.52
−190 22.83 22.40 21.97 21.54 21.11 20.68 20.25 19.82 19.38 18.95 18.52
−180 27.10 26.67 26.24 25.82 25.39 24.97 24.54 24.11 23.68 23.25 22.83
−170 31.34 30.91 30.49 30.07 29.64 29.22 28.80 28.37 27.95 27.52 27.10
−160 35.54 35.12 34.70 34.28 33.86 33.44 33.02 32.60 32.18 31.76 31.34
−150 39.72 39.31 38.89 38.47 38.05 37.64 37.22 36.80 36.38 35.96 35.54
−140 43.88 43.46 43.05 42.63 42.22 41.8
...
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