ASTM D7962-21

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Designation: D7962 − 17 D7962 − 21
Standard Practice for
Determination of Minimum Immersion Depth and
Assessment of Temperature Sensor Measurement Drift
This standard is issued under the fixed designation D7962; 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*
1.1 This practice describes two procedures for use with temperature measurement devices. Methodology is described for
determining minimum immersion depth for thermal sensors, in particular RTDs or similar temperature sensors. Included is a
procedure for consistently preparing a reference bath for the purpose of monitoring measurement drift of thermal sensors such as
liquid-in-glass or digital contact thermometers.
1.2 This practice focuses on temperature measurement drift in a laboratory. If the user requires greater measurement accuracy, then
they should follow the instructions in Practice E563.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 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:
E563 Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
3. Terminology
3.1 Definitions:
3.1.1 digital contact thermometer (DCT), n—an electronic device consisting of a digital display and associated temperature-
sensing probe.
3.1.1.1 Discussion—
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.91 on Coordinating Subcommittee on Thermometry.
Current edition approved May 1, 2017May 1, 2021. Published May 2017May 2021. Originally approved in 2015. Last previous edition approved in 20162017 as
D7962 – 16.D7962 – 17. DOI: 10.1520/D7962-17.10.1520/D7962-21.
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
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D7962 − 21
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. These devices are sometimes
referred to as a “digital thermometer.”
3.1.1.2 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.
3.1.1.3 Discussion—
Portable electronic thermometers (PET) is an acronym sometimes used to refer to a subset of the devices covered by this definition.
3.1.2 ice-point bath, n—physical system containing ice and water assembled to realize the ice point as a reference temperature,
or to establish a constant temperature near 0 °C.
3.1.3 minimum immersion depth, n—depth that a thermometer should be immersed, in a uniform temperature environment, such
that further immersion does not produce a change in indicated temperature greater than the specified tolerance.
4. Summary of Practice
4.1 This practice provides a procedure for determining measurement drift of a temperature sensor and a procedure for determining
the minimum immersion depth of temperature sensor using an ice bath.
4.2 This practice describes a procedure for consistently preparing an ice bath that is an intimate mixture of crushed ice or ice
particles and water in a thermally insulating vessel open to the atmosphere.
4.2.1 Caution—when the ice bath is notCaution—the ice and water used to prepare an ice bath should be made from distilled
water, its temperature will differ from the natural fixed-point temperature by a consistent amount, typically less than 0.02 °C. or
deionized water. A bath so prepared can provide a temperature uncertainty of about 60.005 °C. If the user needs a more accurate
ice point, then they should use Practice E563 to prepare the ice bath.
4.2 This practice includes a procedure for determining the minimum immersion depth of the temperature sensor using an ice bath.
4.2.1 This procedure determines minimum immersion depth with a 25 °C differential between sensed temperature and ambient
temperature. If the probe is subjected to a greater differential temperature, a larger immersion depth may be required to correctly
measure the temperature.
5. Significance and Use
5.1 This practice provides a means for the users of ASTM Committee D02 standards to monitor the drift in sensed temperature
of liquid-in-glass thermometer (LiG), and digital contact thermometers (DCT). Digital contact thermometers are sometimes
referred to as portable electronic thermometers (PET) or simply digital thermometers.
5.2 This practice is not suitable for determining the accuracy or calibration of a temperature-measuring device as the error in the
ice bath temperature can be greater than 0.02 °C. For greater accuracy, the user should use Practice E563 to prepare the ice bath.
5.3 The ice point is a common practical industrial reference point of thermometry. The ice point is relatively simple to realize and
provides a readily available natural fixed-point reference temperature.
5.4 This practice only checks the measurement drift at a single temperature. It will not detect a change in measurement response
with change in temperature. Temperature-measuring devices should be recalibrated at set intervals. See device supplier for
recommendations.
5.5 This practice provides a technique to determine minimum immersion depth of the sensing probe of the thermometer using an
ice bath. The minimum immersion depth determined by this practice may change when the differential temperature differs
significantly from the conditions described. A greater differential will likely increase the minimum immersion depth.
D7962 − 21
6. Reagents and Equipment
6.1 Water—Good distilled or deionized water from a consistent source.
6.2 Ice—Crushed ice prepared from the water in 6.1.
6.3 Insulated Container—An insulated container large enough to hold the thermometer and provide several centimeters of
water-ice slush around the measuring portion of the thermometer.
7. Procedure – Drift in Temperature Measurement
7.1 Preparation of the Ice-Point Bath:
7.1.1 Determine the water source to be used each time this practice is followed in your laboratory to determine measurement drift
an
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