1、Designation: D6027/D6027M 15Standard Practice forCalibrating Linear Displacement Transducers forGeotechnical Purposes1This standard is issued under the fixed designation D6027/D6027M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision,
2、 the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice outlines the procedure for calibratingdisplacement transducers and their readout systems f
3、or geo-technical purposes. It covers any transducer used to measuredisplacement, which gives an electrical output that is linearlyproportional to displacement. This includes linear variabledisplacement transducers (LVDTs), linear displacement trans-ducers (LDTs) and linear strain transducers (LSTs).
4、1.2 This calibration procedure is used to determine therelationship between output of the transducer and its readoutsystem and change in length. This relationship is used toconvert readings from the transducer readout system intoengineering units.1.3 This calibration procedure also is used to determ
5、ine theaccuracy of the transducer and its readout system over therange of its use to compare with the manufacturers specifica-tions for the instrument and the suitability of the instrument fora specific application.1.4 The values stated in either SI units or inch-pound unitsgiven in brackets are to
6、be regarded separately as the standard.The values stated in each system may not be exact equivalents;therefore, each system shall be used independently of the other.Combination values from the two systems may results innon-conformance with standard.1.5 All observed and calculated values shall confor
7、m to theguidelines for significant digits and rounding established inPractice D6026 unless superseded by this standard.1.5.1 The procedures used to specify how data are collected,recorded or calculated in this standard are regarded as theindustry standard. In addition they are representative of thes
8、ignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider-ation for the users objectives; it is common practice toincrease or reduce significant digits of reported data to beco
9、mmensurate with these consideration. It is beyond the scopeof this standard to consider significant digits used in analyticalmethods for engineering design.1.6 This practice offers a set of instructions for performingone or more specific operations. This standard cannot replaceeducation or experienc
10、e and should be used in conjunction withprofessional judgment. Not all aspects of this practice may beapplicable in all circumstances. This ASTM standard is notintended to represent or replace the standard of care by whichthe adequacy of a given professional service must be judged,nor should this do
11、cument be applied without consideration ofa projects many unique aspects. The word “standard” in thetitle of this document means only that the document has beenapproved through the ASTM consensus process.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with
12、 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD3740 Pr
13、actice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 DefinitionsDefinitions of terms used in this practiceare in accordance with
14、Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibrated range, ndistance for which the transduceris calibrated.1This practice is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.95 on InformationRetrieval a
15、nd Data Automation.Current edition approved July 1, 2015. Published July 2015. Originally approvedin 1996. Last previous edition approved in 2004 as D602796(2004), which waswithdrawn February 2013 and reinstated in July 2015. DOI: 10.1520/D6027_D6027M-15.2For referenced ASTM standards, visit the AST
16、M website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Ha
17、rbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2 core, ncentral rod that moves in and out of thetransducer body.3.2.3 displacement transducer, nan electrical transducerwhich converts linear displacement to electrical output.3.2.4 null position, nthe core position within
18、 the sensorbody at which the transducer voltage output is zero (sometransducers may not have a null position).3.2.5 power supply, na voltage source with output equal tothat required by the sensor.3.2.6 readout system, nelectronic equipment that acceptsoutput from the signal conditioner for the trans
19、ducer andprovides a visual display or digital record of the transduceroutput.3.2.7 signal conditioner, nelectronic equipment thatmakes the output of the transducer compatible with the readoutsystem. The signal conditioner may also filter the transduceroutput to remove noise.3.2.8 total linear range
20、(TLR), ntotal distance that thecore may move from the position of maximum voltage outputto the position of minimum voltage output with a linearrelationship between displacement and voltage.3.2.9 traceability certificate, na certificate of inspectioncertifying that the transducer meets indicated spec
21、ifications forits particular grade or model and whose accuracy is traceable tothe National Institute of Standards and Technology or toanother international standard.4. Summary of Practice4.1 Adisplacement transducer is mounted in such manner topermit it to be subjected to a precise, known displaceme
22、nt.4.2 Displacement is applied in steps over the full range ofthe transducer and readings taken from the readout device.4.3 The slope of the best-fit straight line relating sensorreadout data to displacement is determined by linear regres-sion.4.4 The percent error of the transducer readout system i
23、scalculated and compared with the requirements for the specificuse of the sensor.5. Significance and Use5.1 The displacement transducer plays an important role ingeotechnical applications to measure change in dimensions ofspecimens.5.2 The displacement transducer must be calibrated for usein the lab
24、oratory to ensure reliable conversions of the sensorselectrical output to engineering units.5.3 The displacement transducer should be calibrated beforeinitial use, at least annually thereafter, after any change in theelectronic configuration that employs the sensor, after anysignificant change in te
25、st conditions using the transducer thatdiffer from conditions during the last calibration, and after anyphysical action on the transducer that might affect its response.5.4 Displacement transducer generally has a working rangewithin which voltage output is linearly proportional to dis-placement of t
26、he transducer. This procedure is applicable to thelinear range of the transducer. Recommended practice is to usethe displacement transducer only within its linear workingrange.6. Apparatus6.1 Linear Displacement Transducer, to be calibrated.6.2 Power Supply with Output, equal to that required by the
27、sensor.NOTE 1Some LVDTs use ac voltage while others use dc. The LVDTsand displacement transducer may be damaged if connected to the incorrectpower supply.6.3 Signal Conditioning, Readout Equipment, and RelatedCables and Fittings.6.4 Test Method APrecision Gauge Block Calibration:6.4.1 Precision Gaug
28、e Blocks, a set of precision referenceblocks traceable to the National Institute for Standards andTechnology or other recognized standard agency. A gaugeblock set should contain sizes necessary to perform satisfacto-rily the calibration procedures as outlined in Section 9 over thetotal linear range
29、of the transducer.6.4.2 Comparator Stand, consisting of a base of warp-freestability and ground to a guaranteed flatness, a support column,and an adjustable arm onto which the sensor mounting blockcan be securely attached. Alternatively, mount the sensor in theconfiguration it will be used in such a
30、 way that gauge blockscan be inserted to displace the core for calibration purposes.6.4.3 Sensor Mounting Block, a device used to attach thesensor to the comparator stand. Alternatively, mount the sensorto the test equipment in which the transducer is to be used. Themounting holder shall be antiferr
31、omagnetic.6.5 Test Method BMicrometer Fixture Calibration:6.5.1 Micrometer Fixture, a precision instrument for linearmeasurement capable of obtaining readings over the total linearrange of the displacement transducer. The spindle must benonrotating. The micrometer fixture is to be calibrated annuall
32、yby the manufacturer or other qualified personnel.7. Hazards7.1 Safety Hazards:7.1.1 This practice involves electrical equipment. Verifythat all electrical wiring is connected properly and that thepower supply and signal conditioner are grounded properly toprevent electrical shock to the operator. T
33、ake necessary pre-cautions to avoid exposure to power signals.7.2 Safety Precautions:7.2.1 Examine the sensor body for burrs or sharp edges, orboth. Remove any protrusions that might cause harm.7.2.2 The transducer can be permanently damaged if incor-rectly connected to the power supply or if connec
34、ted to a powersupply with the wrong excitation level.7.2.3 Follow the manufacturers recommendations with re-gard to safety.7.3 Technical Precautions:7.3.1 The core and body of the displacement transducer area matched set. For best performance, do not interchange coreswith other displacement transduc
35、er bodies.D6027/D6027M 1527.3.2 Replace the core and body if either shows any signs ofdents, bending, or other defects that may affect performance ofthe device.7.3.3 Store the body and core in a protective case when notin use.7.3.4 Do not exceed the allowable input voltage of thesensor as specified
36、by the manufacturer.7.3.5 Do not connect a voltage source to the output leads ofthe sensor.7.3.6 Do not over tighten the sensor within the mountingblock.7.3.7 The behavior of some transducers may be affected bymetallic holders. If possible, the working holder should be usedduring calibration.8. Cali
37、bration and Standardization8.1 If using Test Method A, verify that the gauge blocks areof sufficient precision and bias and in a clean, unscratchedcondition.8.2 If using Test Method B, verify that the micrometerfixture is in good working order and of sufficient precision andbias.9. Procedure9.1 Perf
38、orm this calibration in an environment as close tothat in which the sensor will be used as possible. Thedisplacement transducer, calibration gauge blocks, micrometerfixture, and comparator stand should be in the environment inwhich they are to be calibrated for at least 1 h prior tocalibration to st
39、abilize temperature effects.9.2 Verify that the power supply is adjusted to supply therecommended voltage to the sensor.9.3 With equipment turned off, connect all power supply,signal conditioning, and recording equipment exactly as it willbe used in service. Allow all electronics to warm up for at l
40、east30 min before beginning any readings.9.4 Record type and serial number of the sensor to becalibrated. If it has no serial number, record the model numberand other identifying markings.9.5 Record the maximum allowable input voltage specifiedby the manufacturer and the input voltage used for thisc
41、alibration.9.6 Record the total linear range of the sensor and the rangeover which the transducer will be calibrated.9.7 Record the type and serial number of the referencestandard used.9.8 Test Method APrecision Gauge Block Calibration:9.8.1 Attach the sensor mounting block to the adjustablearm of t
42、he comparator stand or mount into test equipment as itwill be used in service.9.8.2 Slide the displacement transducer core and core ex-tension rod assembly into the displacement transducer body.NOTE 2Some displacement transducers require the core to be in placebefore powering the displacement transd
43、ucer.NOTE 3Displacement transducer should be checked use for freedomof movement particularly if the core rod and body of the transducer aremanufactured as a single unit with a spring loaded core as part of thecalibration procedure.9.8.3 Place the sensor body into the sensor mounting blockand tighten
44、 the appropriate screw on the mounting block. Donot over tighten the screw on the mounting block. This candamage the sensor body.9.8.4 Place a gauge block (or series of blocks) that has aheight equal to the total linear range of the sensor under thecore.9.8.5 Adjust the sensor body up or down on the
45、 comparatorstand support column as necessary to obtain a reading on thereadout equipment that is approximately equal to the readingfor the transducer with the core pushed into the transducerbody to the end of the linear operating range as indicated by themanufacturers calibration data.9.8.6 Secure t
46、he adjustable arm on the support column ofthe comparator stand in this position by tightening the screw ofthe adjustable arm.9.8.7 Remove the gauge block (or series of blocks) frombeneath the core rod and allow the core rod to rest on thecomparator base. Note the transducer reading with the corenow
47、extended from the transducer body. It should equalapproximately the voltage reading for the transducer with thecore pulled from the transducer body to the end of the linearoperating range as indicated by the manufacturers calibrationdata.9.8.8 Record the value of sensor output as sensor reading forz
48、ero displacement.9.8.9 Select appropriate gauge blocks to displace the corethrough its total linear range in steps. It is recommended that aminimum of five readings equally spaced throughout the sensortotal linear range be used.9.8.10 Raise the core rod and place the appropriate gaugeblock(s) on the
49、 comparator stand base beneath the core rod ina manner to raise incrementally the core step-by-step into thetransducer body.9.8.11 Record the gauge block height in Column 1 and thecorresponding output of the sensor readout equipment inColumn 2 as shown in Table 1.9.8.12 Continue to add gauge blocks at the selected dis-placement increments and record readings in Table 1 until thecore has been displaced through its total linear range.9.8.13 Remove the gauge blocks in reverse order and recordreadings in Table 1 until the core again rests on the comparatorbase.9.8.
