1、Designation: F377 03 (Reapproved 2009)Standard Practice forCalibration of Braking/Tractive Measuring Devices forTesting Tires1This standard is issued under the fixed designation F377; the number immediately following the designation indicates the year of originaladoption or, in the case of revision,
2、 the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice gives procedures for the calibration of:reference load cellscalibration platform systems by
3、 using a reference load cellstatic calibration of braking/tractive force on locked wheelsof tire test trailers, instrumented vehicles, and laboratory tiretesting machines by using the calibration platform system as acalibration fixture.1.2 The values stated in SI units are to be regarded asstandard.
4、 The values in parentheses are for information only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of
5、 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E74 Practice of Calibration of Force-Measuring Instru-ments for Verifying the Force Indication of Testing Ma-chinesF538 Terminology Relating to the Characteristics and Per-formance of Tires3. Terminology3.1 Definitions:3
6、.2 bias, nthe difference between the average measuredtest result and the accepted reference value; it measures in aninverse manner the accuracy of a test.3.3 longitudinal force, F, of a tire, nthe component ofthe tire force vector in the X direction.3.4 vertical load, nthe normal reaction of the tir
7、e on theroad which is equal to the negative of normal force.4. Summary of Practice4.1 Reference-load cells shall be calibrated using proce-dures and equipment traceable to the National Institute ofStandards and Technology (NIST), or appropriate nationalstandards organization.NOTE 1Practice E74 may b
8、e used as an alternative method forload-cell calibration.4.2 The calibrated reference-load cell is used to calibrate thecalibration-platform systems or used as the longitudinal forcesensor. The tire test trailer, instrumented vehicle, or laboratorytire testing machine is calibrated with the platform
9、.5. Significance and Use5.1 Calibration is essential in the use of various test plat-forms and devices to insure that the test results generated bythese test devices are accurate, repeatable and meaningful. Thisstandard gives the necessary instructions for the calibration ofall of the test devices c
10、ited in the Scope.6. Apparatus6.1 The calibration system consists of the following basiccomponents:6.1.1 PlatformThe platform on which the test wheel isplaced shall have a flat high friction top surface. The platformshall be of sufficient dimensions to support the entire tirecontact patch throughout
11、 the calibration process. A low frictionbearing (an air bearing is recommended) permitting freehorizontal motion and capable of sustaining a vertical loadequal to the largest anticipated wheel load shall support theplatform. The longitudinal movement shall be sufficient toobtain the necessary requir
12、ed force levels. The platform mayalso be instrumented with integrated transducers (Force Sen-sors) to measure vertical and longitudinal forces.6.1.2 Force Generation ApparatusA system, capable ofdeveloping a longitudinal force sufficient for the calibration ofthe operating range of the device, shall
13、 be used. The force shallbe applied along the longitudinal centerline of the platform.1This practice is under the jurisdiction of ASTM Committee F09 on Tires and isthe direct responsibility of Subcommittee F09.10 on Equipment, Facilities andCalibration.Current edition approved Nov. 1, 2009. Publishe
14、d March 2010. Originallyapproved in 1974. Last previous edition approved in 2003 as F377 03. DOI:10.1520/F0377-03R09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to
15、 the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.1.3 Force SensorsSensors to measure applied forces inthe vertical and longitudinal directions that shall be used tocalibrate br
16、aking/tractive measuring devices. These sensorscan be integrated force transducers located in the platform,scales or tension load cells. Sensors shall have sufficientmeasurement range to cover the maximum anticipated testwheel forces. Sensors shall be mounted in a manner such thatcross-axis forces w
17、ill not adversely affect the accuracy. Theforce sensor instrumentation shall have the capability to allowfor the recording of data, such as a chart recorder, data logger,or visual output that allows for manual logging of data.6.1.4 Reference Load CellThe force standard that pro-vides direct traceabi
18、lity to NIST or appropriate national stan-dards organization that shall be used to certify other forcesensors or weights used within this standard. If integratedplatform transducers are not used, the reference load cell maybe used as the longitudinal force sensor during calibration ofthe braking/tra
19、ctive measuring device. The reference load cellshall have sufficient measurement range to cover the maximumanticipated forces.7. Calibration of the Reference Load Cell and ForceSensors7.1 Three procedures are covered: (1) calibration of thereference-load cell, (2) calibration of the longitudinal for
20、cesensor, and (3) calibration of the vertical load sensor. Repeatthe appropriate calibrations when any relevant component ischanged or altered (see ASTM Manual 7). Repeat the calibra-tions annually unless the changes between the most recentcalibration equation values and those from the previous cali
21、-bration do not exceed 0.1%. Calibration intervals may belengthened to a maximum of 2 years provided that thesechanges do not exceed 0.1% of the value. Record the ambienttemperature during load cell calibrations. Force sensor gainvalues (or their equivalent) shall be consistent throughoutsections 7.
22、3 and 7.4.7.2 Reference Load Calibration:7.2.1 Set up the reference load cell, indicator and requiredequipment to perform the calibration. List all equipment used,including signal conditioning and output devices. Recordequipment identification and calibration dates.7.2.2 Set the bridge-excitation vo
23、ltage and gain, or itsequivalent, in accordance with the instructions on the unitbeing used.7.2.3 Adjust the 9bridge zero,9 or its equivalent, to 9zero.9Be certain that the reference load cell is not being stressed.7.2.4 Using force measuring instruments or weights knownto 0.01% or better of applied
24、 force, perform a calibration on thereference load cell. Class F weights of 8.9N (2 lb) or greaterhave a tolerance of 0.01%. Apply the calibration forces in atleast 8 appropriately spaced increments to a maximum of notless than the anticipated maximum force seen in use. Allow allforce indicators to
25、come to rest at each increment and recordthe force readings.7.2.5 Determine bias values at each applied force.7.2.6 The biases of the reference-load cell and indicatorsystem shall be 0.25% or less of the known applied force(minimum of 62.2N(60.5lbf).7.3 Calibration of Longitudinal Force Sensor Fig.
26、1:Section 7.3 does not apply when the reference load cell isused as the longitudinal force sensor during calibration of thebraking/tractive measuring device.7.3.1 Mount the reference-load cell such that its longitudi-nal axis is parallel to the direction of motion of the platformwithin 62 and in lin
27、e with the applied force. If necessary,place a tension spring in the longitudinal force applicationsystem to allow for longitudinal motion.7.3.2 Apply sufficient force to both channels of the systemthrough the full range of expected calibration forces to exerciseto platform. Release all forces.7.3.3
28、 Set the bridge-excitation voltage and gain, or itsequivalent, for all instrumentation in accordance with theinstructions on the unit being used.7.3.4 Adjust the “bridge zeros,” or its equivalent, to “zero”on all instrumentation. Be certain that the reference load celland platform are not being stre
29、ssed.7.3.5 Using weights known to 0.1% of applied load orbetter, apply a test load, representative of a load which will beencountered on the braking/tractive test device to be calibrated,to the top of the platform near the geometric center of the top.The platform must be maintained level within 60.2
30、5 duringcalibration. Record all force readings.NOTE 2The platform may be sensitive to the support structure usedduring calibration. Therefore during calibration, the platform shall besupported in a manner similar to that which will subsequently be usedduring the calibration of the braking/tractive m
31、easuring device.7.3.6 Apply the longitudinal calibration force in at least 6approximately equally spaced increments to a maximum of notless than the anticipated maximum longitudinal wheel forceseen in use. Allow all force indicators to come to rest at eachincrement and record the force readings.FIG.
32、 1 Force Calibration of a Platform Force TransducerF377 03 (2009)27.3.7 Repeat 7.3.3 and 7.3.6 as necessary to collect at least12 calibration points.7.3.8 Determine longitudinal force bias values at eachapplied force.7.3.9 The biases of the longitudinal force sensor and indi-cator system shall be 1.
33、0 % or less of the applied force and 0.5% or less than the maximum applied force (minimum of 0.1%of anticipated maximum braking/tractive measuring device testforce or 4.4 N (1lbf) whichever is greater).7.3.10 Determine cross talk of longitudinal force, read aspart of the vertical load at each applie
34、d longitudinal force. Thebias of the vertical load sensor and indicator system at eachapplied longitudinal force shall be 61.0 % or less (minimum of64.4N(61lbf) of the applied vertical load.7.4 Calibration of Vertical Load Sensor:7.4.1 Level the vertical load sensor (platform with integraltransducer
35、s or appropriate scale) within 60.25.7.4.2 Set the bridge-excitation voltage and gain, or itsequivalent, for all instrumentation in accordance with theinstructions on the unit being used. Use gain values (or theirequivalent) from 7.3.3 if a two-axis platform with integraltransducers is utilized.7.4.
36、3 Adjust the “bridge zeros,” or its equivalent, to “zero”on all instrumentation. Be certain that the platform or scale isnot being stressed.7.4.4 Using force measuring instruments or weights knownto 0.1 % of applied load or better, apply the vertical calibrationforce to the top of the platform/scale
37、 near the geometric centerof the top in at least six approximately equally spacedincrements. The platform/scale shall be maintained levelwithin 60.25 during calibration. Begin at a load less than theminimum test load of the braking/tractive measuring deviceand continue to a load greater than or equa
38、l to the anticipatedmaximum wheel load. Allow all force indicators to come torest at each increment and record all force readings.NOTE 3The platform may be sensitive to the support structure usedduring calibration. Therefore during calibration, the platform shall besupported in a manner similar to t
39、hat which will subsequently be usedduring the calibration of the braking/tractive measuring device.7.4.5 Repeat 7.4.1 through 7.4.4 as necessary to collect atleast 12 calibration points.7.4.6 Determine vertical load bias values at each appliedforce.7.4.7 The biases of the vertical sensor and indicat
40、or systemshall be 1.0 % or less of the applied force and 0.5 % or less thanthe maximum applied force (minimum of 0.1% of anticipatedmaximum braking/tractive measuring device test force or 4.4 N(1lbf) whichever is greater).7.4.8 Determine cross talk of vertical load, read as part ofthe longitudinal f
41、orce at each applied vertical load. The bias ofthe longitudinal force sensor and indicator system at eachapplied vertical load shall be 61.0 % or less (minimum of64.4N(61lbf) of the applied longitudinal force.8. Calibration of Braking/Tractive Force on a LockedWheel (Fig. 2, Fig. 3,orFig. 4)8.1 Thre
42、e procedures are covered: (1) for vertical calibra-tion of the test wheel load cell, (2) for longitudinal drivingtractive force calibration of the test wheel load cell, and (3) aprocedure identical to (2) above except for direction of theapplied force, ie. for the longitudinal braking force calibrat
43、ionof the test wheel load cell. Repeat the appropriate calibrationswhen any relevant component is changed or altered (seeASTMManual 7). At a minimum, repeat the calibrations annually.Record the ambient temperature during load cell calibrations.Force sensor gain values (or their equivalent) must be c
44、onsis-tent throughout sections 8.3 and 8.4.8.2 Equipment Preparation:8.2.1 Prior to starting calibration verify all reference equip-ment is in calibration in accordance with Section 6. List allequipment used, both test vehicle and reference force measure-ment, signal conditioning and output devices.
45、 Record equip-ment identification and calibration dates.8.2.2 Turn on the test vehicle system instrumentation andcalibration system instrumentation suitably in advance to allowwarm-up before attempting calibration.FIG. 2 Force Calibration of a Locked WheelF377 03 (2009)38.2.3 If necessary, clean the
46、 low friction bearing or airbearing plate surface to allow for free movement of theplatform.8.2.4 Position the test wheel over the platform such that thetest wheel is located as near as possible to the geometric centerof the platform throughout each calibration procedure. Ifnecessary, to maintain no
47、rmal vehicle orientation and toprevent movement, place blocks with a high friction surfaceunder the other vehicle wheels so that the test wheel mountingface is perpendicular to level within 1. In the case of a trailer,the hitch point should be externally secured by a fixture or bythe tow vehicle. If
48、 the tow vehicle is used, engage the brakesand block the wheels to prevent slippage.8.2.5 Level the platform to within 0.25 and align it laterallywithin 3 of the trailer or vehicle longitudinal axis along thecenterline of the test wheel. Maintain platform level throughoutall calibration procedures.8
49、.3 Vertical Calibration Procedure:8.3.1 Ensure the system force sensors are not stressed bylifting the test wheel from the calibration platform. Verify thatthe test wheel is locked/unlocked from rotation as appropriateto the test device. The suspension may be further unloaded bytapping the test wheel with a mallet. Adjust the zeros/gains ofall systems.8.3.2 Start the data-logging device and lower the test wheelonto the platform. Increase the load in no less than fourincrements until the full weight (not less than the anticipatedmaximum test load) has been pl
