ASTM D8278-20

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Designation: D8278 − 19 D8278 − 20
Standard Specification for
Digital Contact Thermometers for Test Methods Measuring
Flow Properties of Fuels and Lubricants
This standard is issued under the fixed designation D8278; 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 Scope*
1.1 This specification establishes criteria for digital contact thermometers (DCT) for use in test methods that measure flow
properties of materials within the scope of Committee D02. The DCT criteria are based on the design and sensing characteristics
of the liquid-in-glass thermometers that are used successfully in Committee D02 test methods.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
D97 Test Method for Pour Point of Petroleum Products
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D2162 Practice for Basic Calibration of Master Viscometers and Viscosity Oil Standards
D2500 Test Method for Cloud Point of Petroleum Products and Liquid Fuels
D2983 Test Method for Low-Temperature Viscosity of Automatic Transmission Fluids, Hydraulic Fluids, and Lubricants using
a Rotational Viscometer
D3829 Test Method for Predicting the Borderline Pumping Temperature of Engine Oil
D4539 Test Method for Filterability of Diesel Fuels by Low-Temperature Flow Test (LTFT)
D4684 Test Method for Determination of Yield Stress and Apparent Viscosity of Engine Oils at Low Temperature
D5481 Test Method for Measuring Apparent Viscosity at High-Temperature and High-Shear Rate by Multicell Capillary
Viscometer
D5853 Test Method for Pour Point of Crude Oils
D6371 Test Method for Cold Filter Plugging Point of Diesel and Heating Fuels
D6821 Test Method for Low Temperature Viscosity of Drive Line Lubricants in a Constant Shear Stress Viscometer
D6896 Test Method for Determination of Yield Stress and Apparent Viscosity of Used Engine Oils at Low Temperature
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.07 on Flow Properties.
Current edition approved July 1, 2019Sept. 1, 2020. Published July 2019October 2020. Originally approved in 2019. Last previous edition approved in 2019 as D8278 – 19.
DOI: 10.1520/D8278-19.10.1520/D8278-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 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.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8278 − 20
D7279 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids by Automated Houillon Viscometer
D7962 Practice for Determination of Minimum Immersion Depth and Assessment of Temperature Sensor Measurement Drift
D8210 Test Method for Automatic Determination of Low-Temperature Viscosity of Automatic Transmission Fluids, Hydraulic
Fluids, and Lubricants Using a Rotational Viscometer
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E563 Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
E644 Test Methods for Testing Industrial Resistance Thermometers
E1750 Guide for Use of Water Triple Point Cells
E2877 Guide for Digital Contact Thermometers
2.2 ISO Standard:
ISO 17025 General requirements for the competence of testing and calibration laboratories
3. Terminology
3.1 Definitions:
3.1.1 accuracy, n—the closeness of agreement between a test result and an accepted reference value. E177
3.1.2 digital contact thermometer (DCT), n—an electronic device consisting of a digital display and associated temperature
sensing probe.
3.1.2.1 Discussion—
This device consists of a temperature sensor connected to a measuring instrument; this instrument measures the temperature-
dependent quantity of the sensor, computes the temperature from the measured quantity, and provides a digital output. This digital
output goes to a digital display and/or recording device that may be internal or external to the device.
3.1.2.2 Discussion—
The devices are often referred to as a “digital thermometers,” however the term includes devices that sense temperature by means
other than being in physical contact with the media.
3.1.2.3 Discussion—
PET is an acronym for portable electronic thermometers, a subset of digital contact thermometers (DCT).
3.1.3 DCT immersion depth, n—depth that a DCT sensor should be is immersed in a uniform temperature environment, such that
further immersion does not produce a change in indicated temperature greater than the specified tolerance.
3.1.3.1 Discussion—
This is a DCT probe characteristic and establishes a baseline immersion for the probe. This is separate and distinct from how the
probe is located in a test method. The use and positioning of a DCT probe in a test method is to be described in the test method.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 range-of-use, n—a subset of the nominal DCT temperature range.
3.2.1.1 Discussion—
This is the temperature range over which a particular DCT is to be used. For example, if a DCT is to be used for viscosity
measurements as 40 °C and 100 °C, then its “range-of-use” is 60 °C.
4. Summary
4.1 This specification sets the criteria for digital contact thermometers (DCT) used in measuring flow properties of fuels and
lubricants. The DCT criteria were selected so that DCT temperature measurements would be essentially the same as those
measured using a liquid-in-glass (LiG) thermometer. For some of the noted test methods, the temperature of a small static sample
volume is measured, thus, the difference in thermal conductivity between the different types of devices will have an impact on
measurement equivalence.
4.2 The DCT temperature sensing elements noted in this specification are platinum resistance temperature (PRT) detectors or
thermistors whose sheath or enclosure is in direct contact with the substance being measured and are referred to as a digital contact
thermometers. Both PRTs and thermistors are members of a group referred to as resistance temperature detectors (RTD) as their
resistance is a function of temperature.
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D8278 − 20
5. Significance and Use
5.1 The DCTs meeting the indicated requirements have been found to be suitable for replacing the liquid-in-glass thermometers
in the noted test methods. The criteria are based on key elements of liquid-in-glass (LiG) thermometers, such as bulb length,
immersion depth, measurement precision, and thermometer positioning. The prescribed dimensions for sensor length, immersion
depth, and sheath diameter are critical variables when measuring the temperature of small static samples due to differences in
temperature probe thermal conductivity. Therefore, a DCT that is suitable for use in a stirred constant temperature bath will likely
result in temperature measurement errors when used to measure the temperature of small static sample volumes.
6. DCT Criteria
6.1 The DCT requirements shown in Table 1 are for various temperature measurement applications used in Subcommittee D02.07
test methods.methods and reference in the test method. The DCT response time requirements are shown in Table 2 with the
procedure for determining a probe’s response time in 6.4.
NOTE 1—DCT with a PRT element that is a suspended wire, such as those used in a SPRT, are extremely sensitive to mechanical shock which usually
will alter its calibration. Other PRT sensing element designs such as thin film and mandrel wrapped wire can be sensitive to vibrations which alter their
calibration or result in failure.
6.1.1 When considering the use of a DCT criteria in Table 1 for test methods other than those noted, careful consideration must
be given to the DCT probe’s placement in the new application versus its placement in the media, bath, or sample of the noted
method. The metal construction of DCT probes can have a significant impact on measured value when compared to a
liquid-in-glass thermometer in a similar environment due to its greater thermal conductivity. Each of the DCT criteria in the table
were developed for the indicated method’s unique test environment. Other factors can impact the ability of a DCT to mimic the
temperature measurement of a LiG thermometer. When a DCT probe is immersed in the sample, its immersion depth and ratio of
probe volume to sample volume will have an impact on the measured value. Thus the smaller the probe diameter the smaller the
impact on sample temperature.
NOTE 2—The DCT’s electronics are typically limited to an environment of 0 °C to 35 °C. A DCT’s temperature limits can be found in its manual or in
the manufacturer’s specifications.
6.2 DCT Probe Immersion Depth—This criteria quantifies the length of the DCT probe above the tip that needs to be covered by
the material being measured in order to obtain an accurate temperature measurement. Immersing the probe in a material by less
than its minimum immersion depth can result in temperature measurements that significantly differ from actual temperature. The
error is dependent on the temperature difference between the material being measured and surrounding (ambient) temperature. A
test method will set the immersion requirements for the DCT probe.
6.3 Measurement Drift—The drift in calibration should be checked periodically and at least yearly. This can be accomplished using
Practice D7962, Practice E563, Test Methods E644, or similar procedure. When the DCT calibration drift just exceeds the noted
limit for calibration drift, then it is to be rechecked within a short period of time but no longer than month. If the subsequent
measurement of DCT calibration drift exceeds the specified limit, it is to be fully recalibrated consistent with its range-of-use. If
the DCT calibration drift significantly exceeds the noted limit, then it must be recalibrated consistent with its range-of-use. See
Practice E563, Test Methods E644, or Guide E1750 for more information regarding checking calibrations.
NOTE 3—For reference temperatures, additional information on preparing and using an ice bath can be found in Practice E563. Guide E1750 provides
guidance for preparing and using a water triple point cell.
6.4 Response Time—Applies to a digital contact thermom
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