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UNITED STATES DEPARTMENT OF THE INTERIORBUREAU OF RECLAMATIONPROCEDURE FORCALIBRATING FORCE TRANSDUCERSUSBR 1045-89(LOAD CELLS)INTRODUCTIONThis procedure is under the jurisdiction of the Geotechnical Services Branch, code D-3760, Research and Laboratory ServicesDivision, Denver Office, Denver, Colorado. The procedure is issued under the fixed designation USBR 1045. The number immediatelyfollowing the designation indicates the year of acceptance or the year of last revision.1.5.2 This calibration procedure is to be performed uponreceipt of the force transducer and annually thereafter.Scope1.1 This designation outlines the procedure forcalibrating force transducers (load cells) for laboratory use.Two calibration methods are described. Method A outlinesa calibration procedure using a platform scale load frameand a set of calibration masses for applying compressiveforces or banging a set of calibration masses to apply tensileforces. Method B describes a calibration procedure usinga universal testing machine. Force transducers (load cells)can be calibrated in tension or compression using eithermethod.2.Auxiliary6.6.1TestsApplicable Documents3.1USBR Procedure:USBR 1012 Calibrating Balances or Scales3.2 ASTM Standard:E 4 Load Verification of Testing Machines4.Summary of Method4.1 A force transducer (load cell) is loaded in eithertension or compression using either a platform scale loadframe and mass standards (method A, compression) andhanging standard masses (method A, tension), or auniversal testing machine (method B). Forces are appliedto the force transducer in increments over its rated capacity.The electrical output of the force transducer is comparedto the known force applied at each force increment; andthe linearity, hysteresis, repeatability, and creep of the forcetransducer are determined.5.Definitions are in accordance with USBR 3900.6.2 Terms not included in USBR 3900 specific to thisdesignation are:6.2.1 Creep.-Time-dependentstrain or deformation;for example, continuing strain with sustained stress (ASTMdefinition).6.2.2 Hermedcalljsealed-Sealedand guaranteed tobe airtight.6.2.3 UniversaL-Inthe text of this procedure, theterm universal implies that the device can apply eithercompression or tension loads.6.2.4 Linearicy.-Thevariation of force transduceroutput values from a straight line. The measurements areobtained using a series of standard loads applied over thetotal rated capacity of the force transducer.6.2.5 Repeacabilicy.-Themaximum differencebetween force transducer output readings for repeatedloadings under identical loading and environmentalconditions.6.2.6 Hysceresis.-Themaximum difference betweenforce transducer output for the same applied load; onereading obtained by increasing the load from zero to theforce transducer rated capacity, and the other by decreasingthe load from the force transducer rated capacity to zero.6.2.7 Raced Capacity(maximum capacity).-Themaximum axial load the force transducer is designed tomeasure within its specifications.2.1 The universal testing machine used in thisprocedure must be calibratedin accordance with ASTME 4. The platform scale load frame used in this proceduremust be calibrated in accordance with USBR I012 priorto performing this calibration procedure.3.Terminology7.Apparatus7.1 Force Transducer (load cell).-A transducer (fig. 1)which converts changes in force into an electrical output.7.1.1 Components of the force transducer shouldpossess the following characteristics:7.1.1.1 The force transducer should be hermetically sealed to prevent damage to the internal electricalcomponents in the event of exposure to moisture.Significance and Use5.1 A calibrated force transducer (load cell) must beused in the laboratory to ensure reliable test results.74
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USBR 10457-23s8 (8-86),Bureau of ReclamationMANUFACTURERFORCE TRANSDUCERT1 Designation USBR(LOAD CELL) CALIBRATION2001176ExampleMODEL NO.SERIAL NO.CALIBRATION METHOD: E] A - PLATFORM SCALE[] S - UNIVERSAL MACHINERC (RATED CAPACITY) (a)200IbfN FORCETRANSDUCERFAC' OR(c) (@)/(b) 20,000VOLTAGE OUTPUT*l 0.000(b)1045-89- llbf/V[--]N/VV"CALIBRATION PERFORMED BYiDATECALIBRATION CHECKED BYDATECALIBRATION MASS REQUIREMENTSMASS REQUIREDFORCE INCREMENTS.2x (RC} .4 x {RC) Ibm"40.0N4'0.080.0.80.0-6x (RC) 120.0120.0.8x (RC) 160.0160.01.0x (RC) 200.0200.0"IMPLIES Ibm IbfACTUAL MASS USEDIbm"120.0160.0200.0FORCE TRANSDUCER CALIBRATION: [] COMPRESSIONINCREASING FORCE INCREMENTSFORCE INCREMENT[]Ibm"(1)[] NN40.080.0[] TENSIONDECREASING FORCE INCREMENTSFORCE TRANSDUCER FORCE TRANSDUCERVOLTAGE OUTPUTOUTPUT (2)x(c) ] IbfON(V)(2)(3)FORCE INCREMENT[] Ibm"(4)FORCE TRANSDUCER FORCETRANSDUCERVOLTAGE OUTPUT(V)(5)(6)OUTPUT%:,[][] NT/'ial No. I0.00180.0Jt o4(3.0O. 021.98639.723.9786.00(20.0050. 102. 00040.0079.563. 994120.005 9947.987159.7
Method B describes a calibration procedure using auniversal testing machine. Force transducers (loadcells) can be calibrated in tension or compression using either method. 2. Auxiliary Tests 2.1 The universal testing machine used in this procedure must be calibrated in accordance with ASTM E4. Theplatform scaleload frame used in this procedure must be calibrated in accordance with USBR I012 .
