1、Designation: D7962 16D7962 17Standard Practice forDetermination of Minimum Immersion Depth andAssessment of Temperature Sensor Measurement Drift1This standard is issued under the fixed designation D7962; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice describes a two procedures for use with temperature measurement device
3、s. Methodology is described fordetermining minimum immersion depth for thermal sensors, in particular RTDs or similar temperature sensors. Included is aprocedure for consistently preparing a reference bath for the purpose of monitoring measurement drift of thermal sensors such asliquid-in-glass or d
4、igital 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 meas
5、urement 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 responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimi
6、tations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Tec
7、hnical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E563 Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature3. Terminology3.1 Definitions:3.1.1 digital contact thermometer (DCT), nan electronic device consisting of a digital display and as
8、sociated temperaturesensing temperature-sensing probe.3.1.1.1 DiscussionThis 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 dig
9、ital output. This digitaloutput goes to a digital display and/or recording device that may be internal or external to the device. These devices are sometimesreferred to as a “digital thermometer”.thermometer.”3.1.1.2 DiscussionPortable electronic thermometers (PET) is an acronym sometimes used to re
10、fer to a subset of the devices covered by this definition.1 This practice is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of SubcommitteeD02.91 on Coordinating Subcommittee on Thermometry.Current edition approved De
11、c. 1, 2016May 1, 2017. Published January 2017May 2017. Originally approved in 2015. Last previous edition approved in 20152016 asD7962 15a.D7962 16. DOI: 10.1520/D7962-16.10.1520/D7962-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at servicea
12、stm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Beca
13、useit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appea
14、rs at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.2 ice-point bath, nphysical system containing ice and water assembled to realize the ice point as a reference temperature,or to establish a constant tem
15、perature near 0 C.3.1.3 minimum immersion depth, ndepth that a thermometer should be immersed, in a uniform temperature environment, suchthat further immersion does not produce a change in indicated temperature greater than the specified tolerance.4. Summary of Practice4.1 This practice describes a
16、procedure for consistently preparing an ice bath that is an intimate mixture of crushed ice or iceparticles and water in a thermally insulating vessel open to the atmosphere.4.1.1 Cautionwhen the ice bath is not made from distilled water, its temperature will differ from the natural fixed-pointtempe
17、rature by a consistent amount, typically less than 0.02 C. If the user needs a more accurate ice point, then they should usePractice 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 icebath.4.2.1 This p
18、rocedure determines minimum immersion depth with a 25 C differential between sensed temperature and ambienttemperature. If the probe is subjected to a greater differential temperature, a larger immersion depth may be required to correctlymeasure the temperature.5. Significance and Use5.1 This practi
19、ce provides a means for the users of ASTM Committee D02 standards to monitor the drift in sensed temperatureof liquid-in-glass thermometer (LiG), and digital contact thermometers (DCT). Digital contact thermometers are sometimesreferred to as portable electronic thermometers (PET) or simply digital
20、thermometers.5.2 This practice is not suitable for determining the accuracy or calibration of a temperature measuring temperature-measuringdevice as the error in the ice bath temperature can be greater than 0.02 C. For greater accuracy, the user should use Practice E563to prepare the ice bath.5.3 Th
21、e ice point is a common practical industrial reference point of thermometry. The ice point is relatively simple to realizeand 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 chang
22、e in measurement responsewith change in temperature. Temperature measuring Temperature-measuring devices should be recalibrated at set intervals. Seedevice supplier for recommendations.5.5 This practice provides a technique to determine minimum immersion depth of the sensing probe of the thermometer
23、 usingan ice bath. The minimum immersion depth determined by this practice may change when the differential temperature differssignificantly from the conditions described. A greater differential will likely increase the minimum immersion depth.6. Reagents and Equipment6.1 WaterGood quality drinking
24、distilled or deionized water from a consistent source.6.2 IceCrushed ice prepared from the water in 6.1.6.3 Insulated containerContaineranAn insulated container large enough to hold the thermometer and provide severalcentimeters of water-ice slush around the measuring portion of the thermometer.7. P
25、rocedureDrift Procedure Drift in Temperature Measurement7.1 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 measurementdrift and note the water source with the measurement. Altering the water source bet
26、ween uses of the practice when monitoring atemperature sensor may result in observing a false drift.7.1.2 Ensure that all equipment is clean and free of any oily residue. Rinse the equipment with the type of water used for theice-point bath medium.media. Use clean, “powder free” powder-free laborato
27、ry gloves to handle the ice and equipment.7.1.3 Prepare ice by using the water from the source determined in 7.1.1. Chill a quantity of the water to near 0 C in a flaskthen shake vigorously to aerate the water before freezing in small cubes or thin sheets.7.1.3.1 Prepare finely divided ice by shavin
28、g or crushing. Shaved ice resembling snow is preferred, but crushed ice is acceptableif the particles are small (approximately 2 mm to 6 mm in diameter) and there is a large distribution in size.7.1.4 Prepare the bath in a clean, thermally insulated vessel, preferably a wide-mouthed Dewar vacuum fla
29、sk fitted with aninsulating closure such as a stopper. The vessel should be large enough that its size does not affect the water-ice equilibriumtemperature and of such diameter and depth that in thermal equilibrium the test objects will not significantly modify thetemperature of the bath over the re
30、gion to which the ice point is to be applied. For usual applications, a diameter of 70 mm anda depth of 300 mm may be adequate.D7962 1727.1.5 Alternately, add shaved ice and chilled water to the vessel, using enough water to saturate the ice but not enough to floatit. As the vessel fills, compress t
31、he ice-water mixture to force out excess water. The objective is to surround each particle of icewith water, filling all voids, but to keep the ice particles as close together as possible. Continue adding ice and water andcompressing until the vessel is filled to the required level. Decant or siphon
32、 off excess water.7.1.6 Cover the ice-point bath, leaving just enough open space to access the thermometer probe and agitate the mix. Allow thebath and vessel to equilibrate for at least 30 min before using.7.2 Determination of Measurement Drift:7.2.1 Form a well in the ice-point bath that has the d
33、iameter and intended immersion depth of the test object.7.2.2 It is preferable to cool the test object to less than 3 C before immersing it in the bath. This reduces the time to reachequilibrium at the ice point. Pre-cooling the sensor helps to preserve the bath at the ice point for a prolonged time
34、 and helps ensurethat the water-ice interface will be in contact with the thermometer because negligible melting will occur to increase the water filmthickness.7.2.3 Insert the test object to the appropriate depth. This could be (1) the scribed immersion line, (2) the depth of the minimumimmersion d
35、epth determined by this practice, or (3) the same depth as it is used. For total immersion liquid-in-glass thermometers,immerse to the 0 C (32 F) mark. For partial immersion liquid-in-glass thermometers, immerse to the immersion line or statedimmersion depth. Keep the sensor portion of the object se
36、veral centimeters above the bottom of the flask to avoid the zone at thebottom where denser melt water tends to accumulate.7.2.4 Cover the top of the vessel around the test object but leave sufficient access to periodically agitate the ice-water slush.7.2.5 Allow the bath and test object to come to
37、thermal equilibrium.7.3 Maintaining the Bath:7.3.1 As ice particles in the bath melt, excess water begins to accumulate. This melt water has a temperature slightly warmerthan 0 C. Since the density of water is at a maximum at 4 C, the slightly warm melt water will collect at the bottom of the bathan
38、d around the test object if its tip is placed near the bottom of the bath. For this reason, surplus water should be removed, as itaccumulates, from the bottom of the bath by decanting or siphoning.The presence of excess water can be detected if water overspilloccurs when the ice is depressed. Add ic
39、e particles, and chilled water, as necessary so that the ice slush column always extendsto at least 30 mm below the lowest point of the test object.7.3.2 In order to sustain the ice point over prolonged periods, the ice-point bath may be immersed in another bath that is keptnear 0 C.7.4 When the det
40、ermination is complete, record the date, sensor identifier, immersion depth, observed temperature, roomtemperature, water source, and any other relevant observations.8. Procedure for Minimum Immersion Depth8.1 Measure the distance from the sensors tip to a reference mark on the sheath or other refer
41、ence point.Mark the sensor at 1 cmintervals starting at the tip until 8 cm is reached, or the upper end of the probe if less than 8 cm.8.2 Using either an ice bath as prepared in 7.1 or a constant temperature bath, slowly insert the test sensor into the bath untilno further insertion causes a signif
42、icant change in observed temperature. The portion inserted may include the mounting flange,threads, etc.sensor to a depth of 1 cm.NOTE 1Environmental conditions will have a greater impact on the minimum immersion depth of “metal sheathed” sensors than is observed for “glasssheathed” sensors.8.3 Wait
43、 until equilibrium is achieved. Ten minutes shouldat least 2 min or until the displays range of oscillations is less thanshown in Table 1be sufficient, but the user will need to determine if more time is required If using an ice bath, add ice and drainexcess water to maintain the ice slush at the im
44、mersion mark.8.4 Record the distance between reference mark on sensor and top of ice slush.temperature and depth of insertion.8.5 Slowly withdraw the sensor from the bath by a small increment.8.6 Repeat 8.3 through 8.6 until a change in temperature is observed.8.5 Subtract final value obtainedIf the
45、 temperature recorded in 8.4 from the reference mark value established inis the same asthe previous observation, 8.1. The resultthen go to 8.7is the minimum distance the sensing probe shall be immersed in order toobtain an accurate temperature measurementTABLE 1 Temperature OscillationDisplay Precis
46、ion, C Oscillation Range, C1 00.1 0.10.01 0.050.001 0.01D7962 1738.6 Lower the sensor 1 cm and repeat steps 8.3 8.5.8.7 The minimum immersion depth is the last recorded observation less 1 cm.8.8 Record the date, temperature sensor ID, minimum immersion depth, ambient temperature, and constant temper
47、ature bathused. If the constant temperature bath was an ice bath, then record the water source.9. Keywords9.1 fixed-point temperature references; ice bath; minimum immersion depth; temperature measurement driftSUMMARY OF CHANGESSubcommittee D02.91 has identified the location of selected changes to t
48、his standard since the last issue(D7962 16) that may impact the use of this standard. (Approved May 1, 2017.)(1) Revised 6.1.(2) Revised Section 8.SUMMARY OF CHANGESSubcommittee D02.91 has identified the location of selected changes to this standard since the last issue(D7962 15a) that may impact th
49、e use of this standard. (Approved Dec. 1, 2016.)(1) Revised 3.1.3 for minimum immersion depth.Subcommittee D02.91 has identified the location of selected changes to this standard since the last issue(D7962 15) that may impact the use of this standard. (Approved Dec. 1, 2015.)(1) Added definition for DCT as 3.1.1.(2) Reworded portions of Section 8.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised tha
