his standard has either been su Contact ASTM Interns Aly Designation: D 648 - 01 ude Standard Test Method for nal (www.astm.org) seed and replaced by a new version or withdrawn, F the latest information Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position’ ‘This stand is ssid der the ed designation D 64%; the number imme following the designation ines the year of vigil adoption on he ese of revision, the year of ast revision, A umber panes iia the yar of st eappova. A ‘spencitepilon ( iadcats an edt chaage sae the last revision or eapeova Ths standard has boon approved for use by ances of he Department of Defense 1. Scope * 1.1 This test method covers the determination of the tem- perature at which an arbitrary deformation occurs when speci ‘mens are subjected to an arbitrary set of testing conditions. 1.2 This test method applies to molded and sheet materials available in thicknesses of 3 mm (J4in.) or greater and which are rigid or semirigid at normal temperature. Nore [Sheet stock less than 3 mm (0.125 in) but more than 1 (0.040 in. in thickness may be tested by use ofa composite sample having 4 minimam thickness of 3 mm. The laminae must be oF uniform stress lstibution. One type of composite specimen has been prepared by cementing the ends of the laminae together and then smoothing the edges With sandpaper. The direction of loading shall be perpendicular to the exigs ofthe individual laminae 1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information, onl 114 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 appro- priate safety and health practices and determine the applica bility of regulatory limitations prior to use. Nort 2—The test method described asa Method B ofthis test method, and test methods Ae and Be of ISO 75-1 and ISO 75.2, 1993, are technically equivalent. 2. Referenced Documents 2.1 ASTM Standards: D618 Practice for Conditioning Plastics for Testing D883 Terminology Relating to Plastics? D 1898 Practice for Sampling of Plastics? D 1999 Guide for Selection of Specimens and Test Param- "Tis test method is under the juriscton of ASTM Commitee D20 on Pastis and isthe diet respensibiiy of Subeommitee D2030 on Thermal Properties (Section 20300), ‘Cent elton approve August 10, 200. Pushed October 201, Orga palishod a= D 648-4 T. Las previous ofton D648 0s, * Annual Book of ASTM Standands, Vol O80 > Discontinue See 1997 Annual Book of ASTM Standards, Vo O81 eters from ISO/IEC Standards? 1D 5947 Test Methods for Physical Dimensions of Solid Plastics Specimens* ELI Specification for ASTM Thermometers’ E77 Test Method for Inspection and Verification of Ther- ‘mometers? E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods? E220 Test Method for Calibration of Thermocouples by Comparison Techniques® E 608 Specification for Metal-Sheathed Base-Metal Ther- ‘mocouples* E 64 Test Methods for Testing Industrial Resistance Ther- mometers* E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method® E879 Specification for Thermistor Sensors for Clinical Laboratory Temperature Measurement* E1137 Specification for Industrial Platinum Resistance ‘Thermometers* 22-180 Standards:? ISO 75-1 Plasties—Determination of Temperature of De- flection Under Load—Part 1: General Test Method ISO 75-2 Plasties—Determination of Temperature of De- flection Under Load—Part 2: Plastics and Ebonite 23. NIST Document:* NBS Special Publication 250-22 3. Terminology 3.1 General—The definitions of plastics used in this test ‘method are in accordance with Terminology D 883 unless otherwise indicated, {noua Sook of ASTM Stondands Vol ORAS. Anau Book of ASTM Sond, Ol 1803, ‘Annual Book of ASTM Standards, ol 1402 ‘valle fom American Naina Sundae Intute, 11 W. 42nd St, 13th * Mang, BW, “Patinum Resistance Themomte Calibration,” NBS Special Publication 250-22, 1987. Avaliable fons National lsat of Sanda and “A Summary of Changes section appears atthe end of this standard, cepyont © ASTM nates, 0 ar Hare he PO Box TO, est Certo, PA 28.209, Unig Sine 1(Gy v 648 4. Summary of Test Method 4.1 A bar of rectangular cross section is tested in the edgewise position as a simple beam with the load applied at its center to give maximum fiber stresses of 0.455 MPa (66 psi) or 1.82 MPa (264 psi) (Note 3). The specimen is immersed under load in a heat-transfer medium provided with a means of raising the temperature at 2 * 0.2°C/min, The temperature of the medium is measured when the test bar has deflected 0.25 mm (0.010 in.). This temperature is recorded as the deflection temperature under flexural load of the test specimen. [Nort 3A round robin has boon conduct that showed that theres no advantage to using higher loads when measuring deflection temperature of present-day plastics with present-day instruments Significance and Use 5.1 This test is particularly suited t0 control and develop- ‘ment work. Data obtained by this test method may not be used. to predict the behavior of plastic materials at elevated tempera- tures except in applications in which the factors of time temperature, method of loading, and fiber stress are similar 10 those specified in this test method. The data are not intended for use in design or predicting endurance at elevated tempera- I 6, Interferences 6.1. The results of the test may depend on the rate of heat transfer between the fluid and the specimen and the thermal conductivity of the fuid, 6.2 The results of this test may depend on the measured ‘width and depth of the specimen and the final deflection at which the deflection temperature is determined, 6.23 The type of mold and the molding process used to produce test specimens affects the results obtained in this test. Molding conditions shall be in accordance with the standard for that material or shall be agreed upon by the cooperating laboratories. 64 Results of testing may be affected by the design of the {est equipment. The test span (either 100 mm or 101.6 mm) will influence the resultant measurement. Instrumentation equipped with metal clips or other types of auxiliary supports designed to maintain specimens perpendicular to the applied load may affect the test results if the pressure is sufficient t0 restrict the downward motion of the specimen at its center. 7. Apparatus 7.1 The apparatus shall be constructed essentially as shown in Fig. 1 and shall consist of the following: Wt | sca fo P| zim = Metal AW1014 + 05 men (40 = 062i) ‘Medod 81000 © 05 man (3937 * 0.00 in) FIG. 1 Apparatus for Deflection Temperature Testfh © 7... Speinen Seppo, etl supports, allowing the load tbe applied ontop o he spoinen vel and miley bummer apport which fal be syuted by adam, Ocined in LE or 1.2 cont ge of he supports and ofthe pices by which aud is apd shal be rounded fo sadn oh = 02 min (118 OAR in) 1 Maino’ A101. = 63 mm (4.0 06 in) TIL2 Method B—1000 = 03 mm 3937 2 0030) Nore 4—A test shouldbe made on each apparatus using atest bar made ‘fa material having a low coefficient of expansion.” The temperature range fo be used should be covered and a eorectin factor determined foe cach temperature, IF this factor is 0.013 mm (0.0005 in.) or greater, it Algebraic sign should be noted and the fator shouldbe applied to each est, by adding it algebraically tothe reading of apparent deflection of the test, specimen, 7.1.2 Immersion Bath—A suitable liquid heatransfer me- dium (Note 5) in which the specimen shall be immersed. It shall be wellstirred during the test and shall be provided with ‘4 means of raising the temperature at a uniform rate of 2 0.2°C/min, This heating rate shall be considered to be met if, cover every S-min interval during the test, the temperature of the bath shall rise 10 + 1°C at each specimen location. Nort 5—A liquid heat-ransfer medium shall be chosen which will not alfet the specimen, Mineral ols considered ste from ignition to 115°C. Silicone cil may be heated to about 260°C for short periods of time. For sill higher temperatures, special heatransfer media. should be used improved performance with longer oil life may be obtained bythe wse of COs or other inert gt to isolate the oil surface from the atmosphere, Nore 6—A circulating ait oven may be used if team be shown that equivalent results are obtained 7.1.3 Deflection Measurement Device, suitable for measur- ing specimen deflection of at least 0.25 mm (0.010 in). It shall bee readable to 0.01 mm (0.0005 in.) or better. The device may be a dial gage or any other indicating or recording device including electric displacement sensing apparatus. 7.1.4 Weights—A set of weights of suitable sizes so that the specimen can be loaded to a fiber stress of 0.455 MPa (66 psi) 2.5 % or 1.82 MPa (264 psi) # 2.5 %. The mass of the rod that applies the testing force shall be determined and included as part of the total load. Ifa dial gage is used, the force exerted, by its spring shall be determined and shall be included as part of the load (Note 8). Calculate the testing force and the mass that must be added to achieve the desired stress as follows: Shi SL o = P9.sn66s (PF) 9.80665, Fe load, N, Toad, kgf, fiber stress in the specimen (0.43 MPa or MPa), width of specimen, mm, = depth of specimen, mm, 1.82 "iva o bors glass have Ben ound stale fr thi purpose 648, L distance between supports, (101.6 mm—Method A, ‘or 100 mm—Method B), see 7.1.1.1 and 7.1.1.2 added mass, kg, force exerted by any spring-loaded component in- volved, N; this isa positive value if the thrust of the spring is towards the test specimen (downwards), or negative value if the thrust ofthe spring is opposing the descent of the rod, or zero if no such component is involved, and ‘mass of the rod that applies the testing force to the specimen, kg, Nore 7—In some designs of this apparatus, the spring force ofthe dial tage is directed upward (opposite the direction of specimen loading), hich reduces the nt foree applied tothe specimen. In oer designs, the spring force of the dial gage acts downward (inthe direction of specimen Toading), which ineteases the net force applies tothe specimen, The mass applied to the loading rod must be adjusted accordingly (increased for ‘upward dal force and dereased for dvinwvard dial force) to compensate Since the force exerted by the spring in certain dial pages varies considerably over the stoke, tis force should be measured in that pat of the stroke that isto be used. Suggested procedures to determine the total Joad required 10 coroet for the force of the dial gage sping ae given in Appendix XI and Appendix X2. Other procedures may be used if equivalent results are obtained. Appendix X3 provides a method of determining the spring force, uniformity of the fore inthe gage's test, ‘measurement range, and whether the gage is contaminated and sticking. 7LLS Temperature Measurement System—Consisting of a thermocouple, thermometer, resistance thermometer, ther- mistor, etc., as the sensor, together with its associated condi tioning and readout instrumentation to cover a suitable range. ‘The thermometer shall be one of the following, or its equiva lent, as prescribed in Specification E 1: Thermometer 1°C or °C, having ranges from -20 to 150°C or -5 to 300°C respectively, whichever temperature range is most suitable ‘Mercury in glass thermometers shall be calibrated for the depth, of immersion in accordance with Test Method E 77. Thermo- couples shall comply with the requirements of Specification E608. Thermocouples shall be calibrated in accordance with Test Method E220. Resistance thermometers shall comply ‘with the requirements of Test Methods E 644 and Specification E1137, Thermistors shall comply with the requirements of Specification E 879 and be calibrated in accordance with NIST Special Publication 250-22. 7.2 Micrometers shall meet the requirements of Test Meth- ods D 5947 and be calibrated in accordance with that test method. 8. Sampling 8.1 Unless otherwise specified, sampling shall be in accor dance with the sampling procedure prescribed in Practice D 1898. Adequate statistical sampling shall be considered an acceptable alternative, 9. Test Specimen 9.1 At least two test spesimens shall be used f0 test each sample at each fiber stress. The specimen shall be 127 mm (5 in) in length, 13 mm (1 in.) in depth by any width from 3 msm (Vein, to 13 mm (4 in), Tolerances on dimensions (for highly reproducible work) should be of the order of 0.13 mm (0.005 in) over the length of the specimen.(Gy v 648 None §—TRe test sults bined on specimens approuching 13 ma in width may be 204° above tone obained from 4 mm or narawe est Specimens because of por Heat wane though the spine. 9.2 The specimens shall have smooth fat surfaces froe from saw cuts, excessive sink marks, or flash 9.3. Molding conditions shall be in accordance with the specification for that material or shall be agreed upon by the cooperating laboratories. Diserepancies in test results due to variations in molding conditions may be minimized by anneal- ing the test specimens before the test. Since different materials require different annealing conditions, annealing, procedures shall be employed only if required by the material standard or if agreed upon by the cooperating laboratories. 10. Preparation of Apparatus 10.1 The apparatus shall be arranged so that the deflection of the specimen at midspan is measured by the deflection ‘measurement device described in 7.1.3. The apparatus may be arranged to shut off the heat automatically and sound an alarm, or record the temperature when the specific deflection has been reached, Sufficient heat transfer liquid shall be used to cover the thermometers to the point specified in their calibration, ot 76 mm (3 in.) in the case of the ASTM thermometers referred. to in 7.15. Nome 91 ie desirable t have @ means to cool the Bath in order to reduce the time reguited o Tower the temperature of the bath after the test has been completed. This may be accomplished by using a cooling coi installed inthe bat, or an extemal heat transfer system that pases the hot oil throug it the rate of temperature ise of the el is adversely affected hy the presence of residual coolant inthe cols the coolant should be Purged prior to starting the next fx. 11, Conditioning 11.1. Conditioning—Condition the test specimens at 23. 2°C (73.4 + 3.6°F) and 50 * 5 % relative humidity for not less than 40 h prior to test in accordance with Procedure A of Practice D618 unless otherwise specified in the material standard or contract between interested parties. In cases of disagreement, the tolerances shall be *1°C (.8°F) and +2.% relative humidity. Nort. [0—Shorter conditioning periods may be sed when iis shown that they do not alec the results ofthis test. Longer conditioning times ray be requted for some materials that continue to change with time 12, Procedure 12.1. Measure the width and depth of each specimen with a suitable micrometer (as described in 7.2) at several points along the span, Average these respective readings to obtain the ‘nominal width and depth value for the specimen. These values are used to determine the amount of applied force necessary 10 produce the specified fiber stress in each specimen (see 7.1.4) 12.2 Position the test specimens edgewise in the apparatus and ensure that they are properly aligned on the supports so that the direction of the testing force is perpendicular to the direction of the molding flow. Ifthe specimen support unit has ‘metal clips or auxiliary supports on it to hold the specimen perpendicular to the load and to prevent the specimen from being displaced by the circulating oil, only one surface of the clip or auxiliary support may touch the specimen at any one time, The presence of any clip or auxiliary support shall not impede the deflection of the specimen or place additional force ‘on the specimen that will result in more load having to be applied to achieve deflection [Nore 11-—Holding ofthe specimens upright on the specimen supports by the use of elips or auxiliary supports that apply pressure to the specimen have been shown to alter the deflection temperature when testing a the 0.65 MPa ses level 12.3 The thermometer bulb or sensitive part of the tempera- ture measuring device shall be positioned as close as possible to the test specimen (within 10 mm) without touching it, The stirring of the liqud-heat transfer medium shall be sufficient to ensure that temperature of the medium is within 1.0°C at any point within 10 mm of the specimen. If tiring is not sufficient {fo meet the 1.0°C requirement, then the temperature measuring, device shall be placed at the same evel as the specimen and within 10 mm of the point at which the specimen is loaded. 124 Ascertain that the temperature of the bath is suitable, ‘The bath temperature shall be at ambient temperature at the start of the test unless previous tests have shown that, for the particular material under test, no error is introduced by starting at a higher temperature, 12.5 Carefully apply the loaded rod to the specimen and lower the assembly into the bath 12.6 Adjust the load so that the desired stress of 0.455 MPa. (66 psi) or 1.82 MPa (264 psi) is obtained. Nore. 12—Verifcaion of the Toad should be made on all new equip: ‘ment, after replacement of dial gages, or following any other change that, ‘could affect the loading. Verifieation ofthe oad should also be performed, Periodically to ensure that the equipment is within calibration (See “Appendix X1, Appendix X2, and Appendix X3). Depending on the type of defection measurement device used, it may be necessary to adjust the device such that it records the deflection in the displacement range of the device where the test is to be made 12.7 Five minutes after applying the load, adjust the def tion measurement device to zero or record its starting position. Heat the liquid heat-ransfer medium at a rate of 2.0 + 0.2°C/min, Nore 13—The S-min waiting period is provided to compensate pat tially forthe erep exhibited by some materials at room temperature when subjected to the specified nominal surface stress. That part of the ereep that occurs in the intial S min is usually a significant faction of that which ‘ocurs inthe frst 30 min, 12.8 Record the temperature of the liquid heat-transfer ‘medium at which the specimen has deflected the specified amount at the specified fiber stress. Nore 14—Continuous reading of the deflsction versus temperature even beyond the standard dellction might be usetu n spect stations. 13. Report 13.1. Report the following information: 13.1.1 Full identification of the material tested, 13.1.2. Method of test specimen preparation, 13.1.3 Conditioning procedure, 13.1.4 Test method, reported as D 648 Method A or D648 Method B, 13.1.5 The width and depth of the specimen, measured to 0.025 mm,(Gy v 648 13.1.6 The standard deflection, the deflection temperature, and the resultant maximum fiber stress for each specimen, 13.1.7 The immersion medium, the temperature at the start of the test, and the actual heating rate, 13.1.8 Average deflection temperature, 13.1.9 Any nontypical characteristics of the specimen noted during the test or after removal from the apparatus, (such as twisting, nonuniform bending, discoloration, swelling), and 13.1.10 ‘Type of apparatus: automated or manual 14, Precision and Bias 14.1. Precision—An interlaboratory test program!" was car- ried out with seven laboratories participating and utilizing both ‘manual and automated instruments. Four polymers were in- cluded in the program, Statistical information is summarized in Table 1. The critical difference limits are the limits beyond which observed differences should be considered suspect. 14.2 In 1995 a second round-robin"! study was conducted. ‘Table 2 is based on this round robin conducted in accordance with Practice E691, involving 3 materials tested by 15 laboratories. For each material, all the samples were prepared at one source, but the individual specimens were prepared at the laboratories that tested them. Each test result was the average of 2 individual determinations. Each laboratory ob- tained 4 test results for each material Nore 1$—Caution: The following explanation for r and R (143- 143.3) are only intended to presenta meaningful way of considering the approximate precision ofthis test method. The data in Table 2 should not bo applied to acceptance or rejection of material, as these data apply only Sunpotng dts are avaible hm ASTM Headquarters, Request RR: D20- "Supporting data are valle frm ASTM Headgurrs. Request RR: D20- a0 ‘TABLE 1 Statistical Information mer —-—-‘arape" — Standard Oforece, ference, Pon "valve ovation Witin_Botweon Poyetnjene, 0455653 —~=C« 60 24 a Povearbonte, 0455 142020 za a8 Matyi metnecyae, 7828 40 sr "82 MPa Poyaulene, 182MPa_ 373828 2a 55: “Al valves a6 given NG, average of ars. Betwoon values of ai, ‘TABLE 2 Precision, Deflection Temperature tris Sreesedin CT ABS, 181 aie is 1a) az) 48 PP natal 045 Pa ae oan Arr ayo 1320 Piles, 0.45 KPa 147246402 6081292 7s, = wahinaborsiony standard deviaton fo te indies mera tained by ooing the wihivlaborsory standard deviation of he test resus from al ofthe partiptng aborts: SSF =F sm (SAV 89 = batmoenboratoras repos, expressed as standard dovaton: S! = 52% where 5; = standard doviaton of aboatory means wirsbortoy eles! nena between wo test resus =2 8 8, reeraboratais cial inal between two fst resus = 28 Sy to materials texted in the round robin and are unlikely to be sgorusly representative ofthe ether los. formulations, cnditons, material. Inbortris. Users ofthis ext metho shoul apply the principles otlined inProte E691 to generate data specif to ther material and aboatry (or between specie laboratories). The principles of 143-1433 would then be vid Tor such dat, 143 Concept of rand R in Table 2—If , and $5 have been calculated from a large enough body of data, and fr test results that were averages from testing two specimens for each test resull then: 143.1 Repeatabii—ris the interval representing the criti cal difference between two test results for the same material, obiained by the same operator using the same equipment on the same day’ in the same laboratory. Two test results shall be judged not equivalent if they differ by more than the r value for the material 14.3.2 Reproducibili—R is the interval representing the critical difference between two test results for the same material, obtained by different operators using different equip- ‘ment in different laboratories, not necessarily on the same day. Two test resulls shall be judged not equivalent if they difer by more than the R value for that material 143.3 Any judgment in accordance with 14.3.1 or 14.3.2 would have an approximate 95 % (0.95) probability of being correc. 14.4 There are no recognized standards by which to esti mate bias of this test method. Nore 16—Based on the round-robin test dat!" a bias may exist between data obiained on test equipment with span between supports of 101.6 mm (4.0 in.) (Method A) and 100 mn (3.937 in.) (Method B), with results being of 1,015 higher for the equipment with a span width between supports of 100 mm, and the value of the diffrence is material dependent (see Table 3). 15. Keywords 15.1 deflection temperature; flexural loads flexure106-8857) Matt nee 101.6-nm.(4.0-n) Span RTT a8 a0 PP natu 45 MPa 852 a3 P filed, 0.45 MPa 166 120 lon 18 Nea 1505) 1508 ANNEX (Mandatory Information) Al. CALIBRATION OF SING! TRAI AL.L Ifthe unit in operation is of the type that has only one temperature probe in the bath, and this probe is monitored 10 record the deflection temperature of the specimen at all the stations in the unit, then the following calibration and checks must be undertaken to ensure comparable results with units that have a temperature probe at each station A1.2 This procedure must be performed annually as a ‘minimum to ensure proper temperature distribution and accu- racy of probe and display. 1.3. Calibration will require the use of temperature meter and probe traceable to NIST, with accuracy and display resolution of 0.1°C or better, a stopwatch, and any tools needed, to open and adjust the unt A13.L Low-temperature calibration of the unit is aecom= plished by placing the NIST traceable probe within 10 mm of specimen height, in the bath at three different points in the bath. The three points will be atthe center and left and right ends of the bath, Start with the station closest to the centralized probe, while the unit is programmed to maintain a constant tempera ture between 20 and 50°C, with all stirers operating. Allow the bath to stabilize for a minimum of 5 min, Read and record the readout of the calibrated probe and the units internal tempera- ture display to the nearest 0.1°C. Make any necessary adjust- ‘ments to the unit's temperature conteoller to bring the bath t0 +0,1°C of the bath set point, allowing a stabilization time of a ‘minimum of 5 min between adjustment(s) and readings. Once the calibrated probe indicates the bath is atthe set point, make adjustments to the centralized probe's display as necessary. 1.3.1.1 Move the NIST traceable probe to the other two points maintaining the probe within 10 mm of specimen height. Read and record the temperatures at these points, after allow= ing the probe to stabilize a minimum of 5 min. ‘A1.3.2 High-temperature calibration will be accomplished by programming the unit to maintain an elevated temperature near, but not exceeding the highest temperature allowed by the heat transfer media, All covers and stations must be in place tnd stirrer motors operating, Place the NIST probe within 10 1mm of specimen height at the station closest o the centralized probe, and allow the bath to stabilize for a minimum of 5 min, Read and record the readout of the calibrated probe and the unit, :D) TEMPERATURE PROBE UNITS internal temperature display to the nearest 0.1°C. Make any necessary adjustments to the unit's temperature controller to bring the bath to £0.1°C of the bath set point, allowing a stabilization time of a minimum of 5 min between adjust- ‘ment(s) and readings. Once the calibrated probe indicates the bath is at the set point make adjustments to the centralized probe's display as necessary. 1.3.2.1 Move the NIST traceable probe to the other two points maintaining the probe within 10 mm of specimen height. Read and record the temperatures at these points, after allow= ing the probe to stabilize a minimum of S min. ‘A1.3.3 Evaluate the data from each of the three points in the bath at both low and high temperature. If any point is greater than -40,5°C from the set point, have the unit serviced ot repaired to correct this error. IP it is nat possible to correct the bath uniformity to less than 0.5°C, then a thermal sensing, device must be placed at each station and used to record the {temperature of the bath atthe time of deflection while running, tests, The unit may be electronically modified or the use of glass thermometers (as outlined in 7.1.5) may be placed at each, station and manually read and recorded at the moment of specimen deflection. A134 If the preceding steps have been taken and suocess- fully completed, cool the bath down to a normal start tempera ture and allow the bath to stabilize, Place the NIST probe at the point in the bath that the preceding gathered data shows the greatest error, Start a test at 120°C. Read and record the temperature of both the unit's display and the readout of the NIST probe. An offset of 10 to 15 s between the two readings is aeceptable as long as this interval is maintained throughout this test. Start the stopwatch when the first temperature is recorded. Read and record the temperature ofthe unit's display and the NIST probe, maintaining any delay interval, if used, every S min for 1 h. AL.3.5 Evaluate the data acquired during the preceding tet. Ensure that the temperature of the bath is rising at the correct rate as outlined in 7.1.2, at both the centralized probe and the other selected test point. If either is outside the limits for the rate of rise, the unit must be serviced and rechecked before further use. If unit fails to pass this calibration test the unit must be serviced or replaced. Placing a temperature sensing,