ASTM E2309-05
(Practice)Standard Practices for Verification of Displacement Measuring Systems and Devices Used in Material Testing Machines
Standard Practices for Verification of Displacement Measuring Systems and Devices Used in Material Testing Machines
SIGNIFICANCE AND USE
Testing machines that apply and measure displacement are used in many industries. They may be used in research laboratories to determine material properties, and in production lines to qualify products for shipment. The displacement measuring devices integral to the testing machines may be used for measurement of crosshead or actuator displacement over a defined range of operation. The accuracy of the displacement value shall be traceable to the National Institute of Standards and Technology (NIST) or another recognized National Laboratory. Practices E 2309 provides a procedure to verify these machines and systems, in order that the measured displacement values may be traceable. A key element to having traceability is that the devices used in the verification produce known displacement characteristics, and have been calibrated in accordance with adequate calibration standards.
SCOPE
1.1 These practices cover procedures and requirements for the calibration and verification of displacement measuring systems by means of standard calibration devices for static and quasi-static testing machines. This practice is not intended to be complete purchase specifications for testing machines or displacement measuring systems. Displacement measuring systems are not intended to be used for the determination of strain. See Practice E 83.
1.2 These procedures apply to the verification of the displacement measuring systems associated with the testing machine, such as a scale, dial, marked or unmarked recorder chart, digital display, etc. In all cases the buyer/owner/user must designate the displacement-measuring system(s) to be verified.
1.3 Since conversion factors are not required in this practice, either SI units, or inch units, can be used as the standard.
1.4 Displacement values indicated on displays/printouts of testing machine data systems-be they instantaneous, delayed, stored, or retransmitted-which are within the Classification criteria listed in , comply with Practices E 2309.
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.
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Designation: E2309 – 05
Standard Practices for
Verification of Displacement Measuring Systems and
Devices Used in Material Testing Machines
This standard is issued under the fixed designation E2309; 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 3.1.1 accuracy, n—degree of conformity of a measure to a
standard.
1.1 These practices cover procedures and requirements for
3.1.2 error, n—the amount of deviation from a standard.
the calibration and verification of displacement measuring
3.1.2.1 Discussion—The word “error” shall be used with
systemsbymeansofstandardcalibrationdevicesforstaticand
numericalvalues,forexample,“Atadisplacementof+1.00in.,
quasi-static testing machines. This practice is not intended to
the error of the displacement measuring system was +0.001
be complete purchase specifications for testing machines or
in.”
displacement measuring systems. Displacement measuring
3.1.3 tolerance, n—theallowabledeviationfromastandard.
systems are not intended to be used for the determination of
3.2 Definitions of Terms Specific to This Standard:
strain. See Practice E83.
3.2.1 calibration, n—in the case of displacement measuring
1.2 These procedures apply to the verification of the dis-
systems used with testing machines, the process of comparing
placement measuring systems associated with the testing
thedisplacementindicationofthemachineorsystemundertest
machine, such as a scale, dial, marked or unmarked recorder
to that of a standard, making adjustments as needed to meet
chart, digital display, etc. In all cases the buyer/owner/user
error requirements.
must designate the displacement-measuring system(s) to be
3.2.2 capacity range, n—inthecaseoftestingmachines,the
verified.
range of displacement for which it is designed. Some testing
1.3 Since conversion factors are not required in this prac-
machines have more than one capacity range, that is, multiple
tice, either SI units, or inch units, can be used as the standard.
ranges.
1.4 Displacement values indicated on displays/printouts of
3.2.3 correction, n—in the case of a testing machine, the
testing machine data systems—be they instantaneous, delayed,
difference obtained by subtracting the measured displacement
stored, or retransmitted—which are within the Classification
from the correct value of the applied displacement.
criteria listed in Table 1, comply with Practices E2309.
3.2.4 displacement, n—a movement or measurement of
1.5 This standard does not purport to address all of the
length expressed in terms of millimeters, inches, etc.
safety concerns, if any, associated with its use. It is the
3.2.5 displacement measuring system, n—a device or set of
responsibility of the user of this standard to establish appro-
devicescomprisedofadisplacementtransducerandassociated
priate safety and health practices and determine the applica-
instrumentation.
bility of regulatory limitations prior to use.
3.2.6 lower limit of verification range, n—the lowest value
2. Referenced Documents
ofdisplacementatwhichadisplacementmeasuringsystemcan
be verified.
2.1 ASTM Standards:
3.2.7 percent error, n—in the case of a displacement mea-
E83 Practice for Verification and Classification of Exten-
suring system, the ratio, expressed as a percent, of the error to
someter Systems
the correct value of the applied displacement.
3. Terminology
3.2.7.1 Discussion—The measured displacement, as mea-
sured by the testing machine, and the applied displacement, as
3.1 Definitions:
computed from the readings of the verification device, shall be
recorded at each verification displacement data point. The
These practices are under the jurisdiction of ASTM Committee E28 on
error,andthepercenterror,shallbecalculatedfromthisdataas
Mechanical Testing and is the direct responsibility of Subcommittee E28.01 on
follows:
Calibration of Mechanical Testing Machines and Apparatus.
Current edition approved Feb. 1, 2005. Published February 2005. DOI: 10.1520/
Error 5 A 2 B
E2309-05.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
PercentError 5 A 2 B!/B 3100
@~ #
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2309 – 05
TABLE 1 Classification of Displacement Measuring Systems
Resolution not to Exceed the Greater of: Error not to Exceed the Greater of:
Classification
Relative Error
Fixed Error, mm (in.) % of Reading Fixed Error, mm (in.)
(% of Displacement)
Class A 0.013 (0.0005) 60.25 60.025 (0.001) 60.5
Class B 0.038 (0.0015) 60.5 60.075 (0.003) 61.0
Class C 0.064 (0.0025) 61.0 60.125 (0.005) 62.0
Class D 0.13 (0.005) 61.5 60.25 (0.010) 63.0
paring the displacement indication of the machine or system
where:
under test to that of a standard and reporting results, without
A = displacement measured by the machine being verified,
making adjustments.
mm (in.), and
B = correct value of the applied displacement, mm (in.), as 3.2.16 verification displacement, n—a displacement with
traceability derived from national standards of length with a
determined by the calibration device.
specific uncertainty of measurement, which can be applied to
3.2.8 reference standard, n—a standard used to measure
displacement measuring systems.
displacement applied by the testing machine and measured by
3.2.17 verified range of displacement, n—in the case of
the displacement measuring system to be verified.
testing machines, the range of measured displacement for
3.2.9 resolution of the displacement indicator, n—smallest
which the testing machine gives results within the permissible
changeofdisplacementthatcanbeestimatedorascertainedon
variations specified.
thedisplacementmeasuringapparatusofthetestingmachineor
system, at any applied displacement.Appendix X1 describes a
4. Significance and Use
method for determining resolution.
3.2.10 resolution of analog type displacement indicators 4.1 Testing machines that apply and measure displacement
are used in many industries. They may be used in research
(scales, dials, recorders, etc.), n—theresolutionisthesmallest
change in displacement indicated by a displacement of a laboratoriestodeterminematerialproperties,andinproduction
lines to qualify products for shipment. The displacement
pointer,orpenline.Theresolutioniscalculatedbymultiplying
the displacement corresponding to one graduation by the ratio measuringdevicesintegraltothetestingmachinesmaybeused
of the width of the pointer or pen line to the center to center for measurement of crosshead or actuator displacement over a
distance between two adjacent graduation marks. defined range of operation. The accuracy of the displacement
value shall be traceable to the National Institute of Standards
3.2.11 resolution of digital type displacement indicators
and Technology (NIST) or another recognized National Labo-
(numeric, displays, printouts, etc.), n—the resolution is the
ratory. Practices E2309 provides a procedure to verify these
smallest change in displacement that can be displayed on the
machinesandsystems,inorderthatthemeasureddisplacement
displacement indicator, at any applied displacement.Appendix
values may be traceable. A key element to having traceability
X1 describes a method for determining resolution.
is that the devices used in the verification produce known
3.2.11.1 Discussion—If the displacement indication, for
displacement characteristics, and have been calibrated in ac-
either type of displacement indicator, fluctuates by more than
cordance with adequate calibration standards.
twice the resolution, as described in 3.2.9 or 3.2.10, the
resolution, expressed as displacement, shall be equal to one-
5. Calibration Devices
half the range of the fluctuation.
3.2.12 relative repeatability, n—the closeness of the agree-
5.1 Reference standards used for calibration and or verifi-
ment between the results of successive measurements from the cationofdisplacementmeasuringsystemsshallhaveestimated
same applied displacement, carried out under the same condi- measurement uncertainties. The reported uncertainty of refer-
tionsofmeasurement.Itisexpressedaspercentageofthemean ence standards must be equal to or less than ⁄3 the allowable
indicated output for the same applied displacement on two errorforthemeasuringsystemClassificationasshowninTable
successive calibrations for the given displacement. 1. The estimated measurement uncertainty of the reference
standard should have a confidence level of 95% (k = 2).
3.2.13 relative reversibility, n—the difference between the
mean measured displacement obtained for a given applied
6. System Verification
displacement applied in an increasing mode and the mean
indicated displacement obtained for the same given displace-
6.1 Displacement measuring systems shall be verified as a
ment applied in a decreasing mode.
system with the displacement sensing and measuring devices
3.2.14 testing machine, n—a mechanical device for apply-
(see 1.2 and 1.4) in place and operating as in actual use.
ing force and displacement to a specimen.
6.2 System verification is invalid if the displacement sens-
3.2.14.1 Discussion—The instrumentation may be either an ing devices are removed and checked independently of the
electrical or a mechanical device, that is, a scale or pointer
testing machine.
system.
6.3 A Practices E2309 verification consists of at least two
3.2.15 verification, n—in the case of displacement measur- verificationrunsofdisplacementcontainedinthedisplacement
ing systems used with testing machines, the process of com- range(s) selected. See 8.1 and 8.2.
E2309 – 05
6.3.1 If the initial verification run produces values within displacement value is reached prior to completing all displace-
the Practices E2309 requirements of Section 15, the data may ment application ratios. Report all displacement values and
be used “as found” for run one of the two required for the new their percent errors.
verification report.
NOTE 1—Example: If full scale is 200 mm and the minimal resolution
6.3.2 If the initial verification run produces any values
is 0.025 mm, the minimum verified displacement would be 5 mm (0.025
which are outside of the Practices E2309 requirements, the “as 3 200). Two decades of 20 and 200 mm could be selected to cover the
displacement application range. Suitable verification test displacement
found” data may be reported and may be used in accordance
values would then be approximately 5, 10, 15, 20, 50, 100, 150, 200 mm.
with applicable quality control programs.
The largest reported error of the two sets of the test runs is the maximum
6.3.3 Calibration adjustments may be made to improve the
error for the displacement range.
accuracy of the system. They shall be followed by the two
required verification runs, and issuance of a new verification
9. Preliminary Procedure
report.
9.1 Alignment:
9.1.1 When fixturing the calibration device, it is important
7. Application of Displacement
to minimize any misalignment. Significant errors can be
inducedduetomisalignment.Gaugeblocksorasquaremaybe
7.1 In the verification of the displacement measuring sys-
used to ensure that the calibration device operates parallel to
tem, approach the displacement test value by applying the test
the actuator in hydraulic testing machines or perpendicular to
displacement from a lower value of displacement. To reduce
the crosshead in electro-mechanical testing machines.
theerrorindisplacementmeasurementduetointernalbacklash
9.2 Temperature Considerations:
of the testing machine, associated fixtures and or apparatus,
9.2.1 Where the displacement measuring systems are elec-
make sure to approach the starting zero position of the testing
trical,connectthedisplacementtransducer,indicator,interface,
machine from a point less than zero and in the direction for
etc. using the appropriate cabling used in the actual machine
which the resultant verification data will be acquired. This
setup.Turnonpowerandallowthecomponentstowarmupfor
procedure shall be followed when acquiring descending veri-
a period of time recommended by the manufacturer. In the
fication data as well. When acquiring descending verification
absence of any recommendations, allow at least 15 min for the
data apply a displacement greater than the starting point and
components to be energized.
adjust the testing machine to re-establish a starting zero
9.2.2 Position a temperature measuring device in close
position in the direction for which verification data is to be
proximity to the machine being verified. Allow the displace-
acquired.
mentmeasuringdeviceandallrelevantpartsoftheverification
7.2 Displacement measuring systems that are used to ac-
equipment to reach thermal stability.
quire test data in both ascending and descending directions,
9.2.3 Include any bias due to temperature effects in the
shall be verified in both directions.
expandeduncertaintystatementassociatedwiththeverification
displacement values if required.
8. Selection of Verification Displacement Values
8.1 For any displacement range, verify the displacement
10. Procedure
measuring system by applying at least five test displacement
10.1 General:
values, at least two times, with the difference between any two
10.1.1 After completing the preliminary procedure given in
successive displacement value applications being no larger
Section 9 and before commencing with the verification proce-
than one-third the difference between the selected maximum
dure, adjust the testing machine to the maximum verification
and minimum test displacement values. Applied displacement
displacement to ensure that the maximum displacement can be
values on the second run are to be approximately the same as
achieved, and the machine has adequate space for the calibra-
those on the first run. Report all values.
tion device.
8.2 The low limit of displacement measurement must be
NOTE 2—Care should be given to the way a testing machine is used in
equal to or greater than:
determining the appropriate procedure for verifying a given machine. If a
400 times the resolution for Class A
testing machine used to measure both positive and negative displacement
200 times the resolution for Class B
values during normal testing, the system must be verified through zero,
100 times the resolution for Class C
67 times the resolution for Class D and both positive and negative verification values must be obtained.
10.1
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