ASTM E3186-19
(Guide)Standard Guide for Use and Testing of Dry-Block Temperature Calibrators
Standard Guide for Use and Testing of Dry-Block Temperature Calibrators
SIGNIFICANCE AND USE
5.1 This guide applies to temperature sources with controlled temperature solid blocks. They are known under various names such as dry-well calibrators, dry-block calibrators, and temperature block calibrators. They are typically comprised of solid block materials such as metal or ceramic, a temperature-regulating device, a control sensor, and some built-in indicator of temperature in a portable package. Dry-block calibrators are commonly used for calibration of industrial thermometers. These calibrators are commonly used in either two modes: (1) the direct mode in which the calibrator is used as the calibrated reference, or (2) comparison mode in which the calibrator is an isothermal temperature source for comparing thermometers under test to a separate calibrated reference thermometer. The uncertainty of these calibrations is dependent on which of these two modes is used and a variety of thermal properties of the specific dry-block designs.
5.2 A thermally uniform, stable, and accurate temperature zone for calibration may be achieved with given measurement uncertainty. Various thermal properties of dry-block calibrator blocks have been identified that shall be characterized and/or quantified to determine uncertainty of measurements and care taken during the calibration process to optimize results appropriately. Temperature stability has been long recognized as a variable to be characterized. Others include axial temperature uniformity, radial temperature uniformity, stem conduction, block loading, hysteresis, and controller accuracy. External factors that influence results include ambient temperature, drafts, and power fluctuations. Recognizing and testing these properties will greatly improve calibration results.
SCOPE
1.1 The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.3 This guide is intended for use with dry-block temperature calibrators without the use of fluids or thermal contact-enhancing media over a range of -100 °C to 1700 °C.
1.4 In this guide, the essential features of dry-block calibrators used for the purpose of thermometer calibration in either the direct or comparison mode are described. The direct mode is defined as using the dry-block calibrator as a standalone instrument with the control sensor and the calibrator display serving as the reference while the comparison mode uses an external sensor and ancillary measurement system as the reference.
1.5 Measurement practices to optimize the accuracy of a dry-block calibrator to obtain optimum results are proposed in this guide.
1.6 Tests that can be performed to define uncertainty limits and how they may be used in creating uncertainty budgets are proposed in this guide.
1.7 Dry-block calibrator accessories such as built-in reference thermometers, switch testing circuitry, computer communications, or current loops will not be discussed.
1.8 It is advised that liquid-in-glass thermometers not be used in dry-block calibrators, as using liquid-in-glass thermometers with a metal block may cause damage to the readout of the thermometer.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E3186 − 19
Standard Guide for
1
Use and Testing of Dry-Block Temperature Calibrators
This standard is issued under the fixed designation E3186; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 The values stated in SI units are to be regarded as the
Barriers to Trade (TBT) Committee.
standard. No other units of measurement are included in this
standard.
2. Referenced Documents
1.2 This standard does not purport to address all of the
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2.1 ASTM Standards:
safety concerns, if any, associated with its use. It is the
E344 Terminology Relating to Thermometry and Hydrom-
responsibility of the user of this standard to establish appro-
etry
priate safety, health, and environmental practices and deter-
E644 Test Methods for Testing Industrial Resistance Ther-
mine the applicability of regulatory limitations prior to use.
mometers
1.3 This guide is intended for use with dry-block tempera-
ture calibrators without the use of fluids or thermal contact-
2.2 Other Documents:
enhancing media over a range of -100 °C to 1700 °C.
JCGM 100:2008 “Evaluation of Measurement Data – Guide
to the Expression of Uncertainty in Measurement”, BIPM,
1.4 In this guide, the essential features of dry-block calibra-
3
Severes, France, 2008.
tors used for the purpose of thermometer calibration in either
the direct or comparison mode are described. The direct mode
3. Terminology
is defined as using the dry-block calibrator as a standalone
instrument with the control sensor and the calibrator display
3.1 Definitions:
serving as the reference while the comparison mode uses an
3.1.1 The definitions given in Terminology E344 shall be
external sensor and ancillary measurement system as the
considered as applying to the terms used in this guide.
reference.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 axial temperature uniformity, n—temperature differ-
1.5 Measurement practices to optimize the accuracy of a
ences along the immersed length of the thermometer boring
dry-block calibrator to obtain optimum results are proposed in
under test.
this guide.
3.2.1.1 Discussion—Axial temperature uniformity is some-
1.6 Tests that can be performed to define uncertainty limits
times referred to as axial temperature homogeneity.
and how they may be used in creating uncertainty budgets are
3.2.2 block-loading error, n—temperature reading error as a
proposed in this guide.
result of temperature uniformity profile in the block changes
1.7 Dry-block calibrator accessories such as built-in refer-
with the number and size of thermometers in the block.
ence thermometers, switch testing circuitry, computer
3.2.3 boring, n—machined hole in the dry block that can
communications, or current loops will not be discussed.
accommodate various sizes of thermometers and removable
1.8 It is advised that liquid-in-glass thermometers not be
sleeves.
used in dry-block calibrators, as using liquid-in-glass ther-
3.2.3.1 Discussion—These are also referred to as wells.
mometers with a metal block may cause damage to the readout
3.2.4 hysteresis, n—property of a device or instrument
of the thermometer.
whereby it gives different output values in relation to its input
1.9 This international standard was developed in accor-
values depending upon the directional sequence in which the
dance with internationally recognized principles on standard-
thermal input values have been applied.
ization established in the Decision on Principles for the
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This test method is under the jurisdiction of ASTM Committee E20 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Temperature Measurement and is the direct responsibility of Subcommittee E20.07 contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
on Fundamentals in Thermometry. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2019. Published December 2019. DOI: the ASTM website.
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10.1520/E3186-19. Availible for download from http://www.bipm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E3186 − 19
3.2.4.1 Discussion—In practice hysteresis it is typically uncertaintyofthesecalibrationsisdependentonwhic
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