ASTM D6027-96(2004)
(Test Method)Standard Test Method for Calibrating Linear Displacement Transducers for Geotechnical Purposes (Withdrawn 2013)
Standard Test Method for Calibrating Linear Displacement Transducers for Geotechnical Purposes (Withdrawn 2013)
SIGNIFICANCE AND USE
The LDTs play an important role in geotechnical applications to measure change in dimensions of specimens.
The LDTs must be calibrated for use in the laboratory to ensure reliable conversions of the sensor’electrical output to engineering units.
The LDTs should be calibrated before initial use, at least annually thereafter, after any change in the electronic configuration that employs the sensor, after any significant change in test conditions using the transducer that differ from conditions during the last calibration, and after any physical action on the transducer that might affect its response.
LDTs generally have a working range within which voltage output is linearly proportional to displacement of the transducer. This procedure is applicable to the linear range of the transducer. Recommended practice is to use the LDT only within its linear working range.
SCOPE
1.1 This test method outlines the procedure for calibrating linear displacement transducers (LDTs) and their readout systems for geotechnical purposes. It covers any transducer used to measure displacement which gives an electrical output that is linearly proportional to displacement. This includes linear variable displacement transducers (LVDT's), linear displacement transducers (LDTs) and linear strain transducers (LST's).
1.2 This calibration procedure is used to determine the relationship between output of the transducer and its readout system and change in length. This relationship is used to convert readings from the transducer readout system into engineering units.
1.3 This calibration procedure also is used to determine the accuracy of the transducer and its readout system over the range of its use to compare with the manufacturer's specifications for the instrument and the suitability of the instrument for a specific application.
1.4 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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
WITHDRAWN RATIONALE
This practice outlines the procedure for calibrating linear displacement transducers (LDTs) and their readout systems for geotechnical purposes.
Formerly under the jurisdiction of Committee D18 on Soil and Rock, this practice was withdrawn in February 2013 in accordance with section 10.5.3.1 of the Regulations Governing ASTM Technical Committees, which requires that standards shall be updated by the end of the eighth year since the last approval date.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6027 − 96(Reapproved 2004)
Standard Practice for
Calibrating Linear Displacement Transducers for
Geotechnical Purposes
This standard is issued under the fixed designation D6027; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 Definitions of Terms Specific to This Standard:
3.2.1 calibrated range, n—distanceforwhichthetransducer
1.1 This practice outlines the procedure for calibrating
is calibrated.
linear displacement transducers (LDTs) and their readout
systems for geotechnical purposes. It covers any transducer 3.2.2 core, n—central rod that moves in and out of the
transducer body.
used to measure displacement which gives an electrical output
that is linearly proportional to displacement. This includes
3.2.3 linear displacement transducer (LDT) or linear vari-
linear variable displacement transducers (LVDTs), linear dis-
able displacement transducer (LVDT), n—an electrical trans-
placement transducers (LDTs) and linear strain transducers
ducer which converts linear displacement to electrical output.
(LSTs).
ALVDTconsistsofaLVDTbodyandaLVDTcorewhichcan
be removed. A LDT holds the core within the sensor body.
1.2 This calibration procedure is used to determine the
relationship between output of the transducer and its readout
3.2.4 null position, n—the core position within the sensor
system and change in length. This relationship is used to
body at which the transducer voltage output is zero (some
convert readings from the transducer readout system into
transducers may not have a null position).
engineering units.
3.2.5 percent error, n—the difference between a measure-
1.3 This calibration procedure also is used to determine the
ment of a reference standard and the actual length of the
accuracy of the transducer and its readout system over the
reference standard divided by the reference standard and the
range of its use to compare with the manufacturer’s specifica-
result converted to percent.
tionsfortheinstrumentandthesuitabilityoftheinstrumentfor
3.2.6 power supply, n—avoltagesourcewithoutputequalto
a specific application.
that required by the sensor.
1.4 This standard does not purport to address all of the
3.2.6.1 Discussion—Some LVDTs use ac voltage while
safety concerns, if any, associated with its use. It is the
others use dc. The LVDTs and LDTs may be damaged if
responsibility of the user of this standard to establish appro-
connected to the incorrect power supply.
priate safety and health practices and determine the applica-
3.2.7 readout system, n—electronic equipment that accepts
bility of regulatory limitations prior to use.
output from the signal conditioner for the transducer and
2. Referenced Documents
provides a visual display or digital record of the transducer
output.
2.1 ASTM Standards:
D653Terminology Relating to Soil, Rock, and Contained 3.2.8 repeatability voltage error, n—the difference in volt-
Fluids age output for successive measurements of the same reference
standard.
3. Terminology
3.2.9 signal conditioner, n—electronic equipment that
3.1 Definitions—Definitions of terms used in this practice
makestheoutputofthetransducercompatiblewiththereadout
are in accordance with Terminology D653.
system. The signal conditioner may also filter the transducer
output to remove noise.
This practice is under the jurisdiction of ASTM Committee D18 on Soil and
Rock and is the direct responsibility of Subcommittee D18.95 on Information 3.2.10 total linear range (TLR), n—total distance that the
Retrieval and Data Automation.
core may move from the position of maximum voltage output
Current edition approved Nov. 1, 2004. Published December 2004. Originally
through the null position to the position of minimum voltage
e1
approved in 1996. Last previous edition approved in 1996 as D6027–96 . DOI:
output with a linear relationship between displacement and
10.1520/D6027-96R04.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
voltage.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3.2.11 traceability certificate, n—a certificate of inspection
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. certifying that the transducer meets indicated specifications for
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6027 − 96 (2004)
itsparticulargradeormodelandwhoseaccuracyistraceableto 6.4.3 Sensor Mounting Block, a device used to attach the
the National Institute of Standards and Technology or to sensortothecomparatorstand.Alternatively,mountthesensor
another international standard. to the test equipment in which the transducer is to be used.
6.5 Test Method B—Micrometer Fixture Calibration:
4. Summary of Practice
6.5.1 Micrometer Fixture, a precision instrument for linear
4.1 A displacement transducer is mounted in a manner to measurementcapableofobtainingreadingsoverthetotallinear
range of the LDT. The spindle must be nonrotating and spring
permit it to be subjected to a precise, known displacement.
loaded. The micrometer fixture is to be calibrated annually by
4.2 Displacement is applied in steps over the full range of
the manufacturer or other qualified personnel.
the transducer and readings taken from the readout device.
4.3 The slope of the best-fit straight line relating sensor
7. Hazards
readout data to displacement is determined by linear regres-
7.1 Safety Hazards:
sion.
7.1.1 This practice involves electrical equipment. Verify
4.4 The percent error of the transducer readout system is
that all electrical wiring is connected properly and that the
calculated and compared with the requirements for the specific
power supply and signal conditioner are grounded properly to
use of the sensor.
prevent electrical shock to the operator. Take necessary pre-
cautions to avoid exposure to power signals.
5. Significance and Use
7.2 Safety Precautions:
5.1 The LDTs play an important role in geotechnical appli-
7.2.1 Examine the sensor body for burrs or sharp edges, or
cations to measure change in dimensions of specimens.
both. Remove any protrusions that might cause harm.
7.2.2 The transducer can be permanently damaged if incor-
5.2 TheLDTsmustbecalibratedforuseinthelaboratoryto
rectlyconnectedtothepowersupplyorifconnectedtoapower
ensure reliable conversions of the sensor’s electrical output to
supply with the wrong excitation level.
engineering units.
7.2.3 Follow the manufacturer’s recommendations with re-
5.3 TheLDTsshouldbecalibratedbeforeinitialuse,atleast
gard to safety.
annually thereafter, after any change in the electronic configu-
7.3 Technical Precautions:
ration that employs the sensor, after any significant change in
7.3.1 The core and body of the LDT are a matched set. For
test conditions using the transducer that differ from conditions
best performance, do not interchange cores with other LDT
during the last calibration, and after any physical action on the
bodies.
transducer that might affect its response.
7.3.2 Replacethecoreandbodyifeithershowsanysignsof
5.4 LDTs generally have a working range within which
dents, bending, or other defects that may affect performance of
voltage output is linearly proportional to displacement of the
the device.
transducer. This procedure is applicable to the linear range of
7.3.3 Store the body and core in a protective case when not
the transducer. Recommended practice is to use the LDT only
in use.
within its linear working range.
7.3.4 Do not exceed the allowable input voltage of the
sensor as specified by the manufacturer.
6. Apparatus
7.3.5 Do not connect a voltage source to the output leads of
6.1 Linear Displacement Transducer, to be calibrated.
the sensor.
7.3.6 Do not over tighten the sensor within the mounting
6.2 Power Supply with Output, equal to that required by the
block.
sensor.
7.3.7 The behavior of some transducers may be affected by
NOTE 1—Some LVDTs use ac voltage while others use dc. The LVDTs
metallicholders.Ifpossible,theworkingholdershouldbeused
and LDTs may be damaged if connected to the incorrect power supply.
during calibration.
6.3 Signal Conditioning, Readout Equipment, and Related
Cables and Fittings.
8. Calibration and Standardization
6.4 Test Method A—Precision Gage Block Calibration:
8.1 If using Test Method A, verify that the gage blocks are
6.4.1 Precision Gage Blocks, a set of precision reference
of sufficient precision and bias and in a clean, unscratched
blocks traceable to the National Institute for Standards and
condition.
Technology.Agageblocksetshouldcontainsizesnecessaryto
8.2 If using Test Method B, verify that the micrometer
perform satisfactorily the calibration procedures as outlined in
fixture is in good working order and of sufficient precision and
Section 9 over the total linear range of the transducer.
bias.
6.4.2 Comparator Stand, consisting of a base of warp-free
stabilityandgroundtoaguaranteedflatness,asupportcolumn,
9. Procedure
and an adjustable arm onto which the sensor mounting block
canbesecurelyattached.Alternatively,mountthesensorinthe 9.1 Perform this calibration in an environment as close to
configurationitwillbeusedinsuchawaythatgageblockscan that in which the sensor will be used as possible. The LDT,
be inserted to displace the core for calibration purposes. calibration gage blocks, micrometer fixture, and comparator
D6027 − 96 (2004)
stand should be in the environment in which they are to be minimumoffivereadingsequallyspacedthroughoutthesensor
calibrated for at least 1 h prior to calibration to stabilize total linear range be used.
temperature effects.
9.8.10 Raise the core rod and place the appropriate gage
block(s) on the comparator stand base beneath the core rod in
9.2 Verify that the power supply is adjusted to supply the
a manner to raise incrementally the core step-by-step into the
recommended voltage to the sensor.
transducer body.
9.3 With equipment turned off, connect all power supply,
9.8.11 Record the gage block height in Column 1 and the
signal conditioning, and recordin
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