ASTM E1856-97(2002)
(Guide)Standard Guide for Evaluating Computerized Data Acquisition Systems Used to Acquire Data from Universal Testing Machines
Standard Guide for Evaluating Computerized Data Acquisition Systems Used to Acquire Data from Universal Testing Machines
SIGNIFICANCE AND USE
This guide is recommended to be used by anyone acquiring data from a universal testing machine using a computerized data acquisition system.
SCOPE
1.1 This guide is intended to assist the user in the evaluation and documentation of computerized data acquisition systems used to acquire data from quasi-static tests, performed on universal testing machines. The report produced will aid in the correct use and calibration of the computerized universal testing machine.
1.2 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:E1856–97 (Reapproved 2002)
Standard Guide for
Evaluating Computerized Data Acquisition Systems Used to
Acquire Data from Universal Testing Machines
This standard is issued under the fixed designation E 1856; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This guide is intended to assist the user in the evaluation
and documentation of computerized data acquisition systems
used to acquire data from quasi-static tests, performed on
universal testing machines. The report produced will aid in the
correct use and calibration of the computerized universal
testing machine.
1.2 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 appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
E 4 Practices for Force Verification of Testing Machines
E 8 Test Methods forTensionTesting of Metallic Materials
FIG. 1 Basic Data and Derived Data
E 74 Practice for Calibration of Force Measuring Instru-
ments for Verifying the Force Indication of Testing Ma-
chines
3.1.3 data acquisition rate—data acquisition rate is defined
E 83 Practice for Verification and Classification of Exten-
as the rate at which digital samples of each wave-form (that is,
someters Systems
force, strain, displacement, and so forth) are acquired, ex-
E 691 Practice for Conducting an Interlaboratory Study to
pressed in samples/second.
Determine the Precision of a Test Method
3.1.4 resolution—the resolution is the smallest change in
E 1012 Practice for Verification of Specimen Alignment
force, strain, or displacement, or both, that can be displayed or
Under Tensile Loading
obtained, or both, from the computerized testing system at any
applied force, strain, or position, or both (for force resolution
3. Terminology
see Practice E 4).
3.1 Definitions:
3.1.5 transducer-channel bandwidth—the bandwidth of a
3.1.1 basic data—basic data are the digital equivalents of
transducer-measurement channel which is measuring a force,
analog counterparts, such as force and displacement measure-
strain, or displacement in a testing machine is the frequency at
ments, which under static conditions are traceable to national
which the amplitude response of the measurement system has
standards (see Fig. 1).
fallen by 3 dB, that is, the measured signal is in error by about
3.1.2 derived data—derived data are additional numbers
30 % and the phase shift has become 45° or greater. The
derived from the basic data through computation using soft-
precise amplitude and phase responses vary with the electrical
ware algorithms, such as a peak force or a modulus value.
design of the system, but the 3 dB bandwidth (expressed in
Hertz) is a simple single measure of responsiveness (see Fig.
2).
3.1.6 computerized data acquisition system—for the pur-
This guide is under the jurisdiction of ASTM Committee E28 on Mechanical
Testing and is the direct responsibility of Subcommittee E28.15 on Automated
pose of this guide, a computerized data acquisition system is a
Testing.
device which collects basic data from a universal testing
Current edition approved Jan. 10, 1997. Published March 1997.
machine during a test and calculates and presents derived data
Annual Book of ASTM Standards, Vol 03.01.
Annual Book of ASTM Standards, Vol 14.02. based on the basic data collected.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1856–97 (2002)
6.2.1.5 Obtain the results from the computer system or
graphic records of the tests from each machine, or both.
6.2.1.6 From the graphic records obtained, manually calcu-
late the same test results obtained by the computer system.
6.2.1.7 Calculate the average and standard deviation of both
the manually calculated results and the results obtained by the
computer system(s) (derived data) within each group of five or
more specimens.
6.2.1.8 Investigate, identify, and correct, if necessary, the
cause of any average results obtained by the computer which
differ from the manually obtained average results, or the
FIG. 2 Bandwidth
average results obtained by other testing machines, by more
than 2.0 % of the average or more than one standard deviation,
whichever is greater.
4. Summary of Guide
NOTE 5—In all cases, use the smallest non-zero standard deviation for
4.1 Comparative tests are performed to determine if the
evaluations.
derived data acquired with a computerized universal testing
6.2.1.9 Investigate, identify, and correct, if necessary, the
machine agree with results acquired on the same machine from
cause of any standard deviations of the results obtained by the
graphical records or with results acquired on other testing
computerwhicharemorethantwotimesthestandarddeviation
machines to ensure that the materials being tested are correctly
obtained manually or by the other machines.
characterized.
NOTE 6—Differences in averages and standard deviations of these
5. Significance and Use magnitudes are quite often due to variations in the material being tested,
and a complete statistical evaluation of the data using methods such as
5.1 This guide is recommended to be used by anyone
Practice E 691 may be necessary.
acquiring data from a universal testing machine using a
computerized data acquisition system. 6.2.2 Single Machine Procedure:
6.2.2.1 This procedure may be used for testing machines
6. Procedure with the capability of producing graphic records from which
test results (derived data) can be manually calculated.
6.1 Choose at least five different test specimen types which
6.2.2.2 Configure the testing machine in such a way as to be
are representative of the specimens commonly tested on the
able to obtain a graphic record of the tests. The graphic record
testing machine.
may be generated by analog signal sources, the computer
NOTE 1—If the testing machine is used to test less than five different
system, or may be generated manually from digital data
specimen types, choose all those tested.
recorded by the data system.
NOTE 2—Specimen types can be differentiated by material (strength
6.2.2.3 Ascertainthatallreadoutandrecordingdevicesused
level), size, shape, or test performed, or both.
(analog or digital, or both) have been calibrated in accordance
6.2 Use one of the following procedures to evaluate and
with Practices E 4, E 83, or other applicable standards.
document the conformity of the computerized test results.
6.2.2.4 Ascertain that all transducers with their readout or
6.2.1 Round Robin Procedure:
recording devices, or both, including the devices producing the
6.2.1.1 Perform a round robin involving at least two other
graphic record, have the required bandwidth for the tests
testing machines. The other testing machines need not neces-
performed with the machine (see Appendix X2).
sarily be computerized.
6.2.2.5 Test at least five specimens of each specimen type in
NOTE 3—It is preferable to use testing machines of varying types so conformance with the applicable test methods or established
that systemic problems are not masked.
procedures, obtaining both a graphic record and results from
the computer system at the same time.
6.2.1.2 If possible, configure the testing machines in such a
6.2.2.6 From the graphic record, determine the same test
way as to be able to obtain a graphic record of the tests. The
results as are calculated by the computer system.
graphic record may be generated by analog signal sources, the
6.2.2.7 Calculate the average and standard deviation of both
computer system, or may be generated manually from digital
the manually calculated results and the results obtained by the
data recorded by the data system.
computer system (derived data) within each group of five
6.2.1.3 Ascertain that all readout and recording devices
specimens.
have been calibrated in accordance with Practices E 4, E 83, or
6.2.2.8 Investigate, identify, and correct, if necessary, the
other applicable standards.
cause of any average results obtained by the computer which
6.2.1.4 Test at least five specimens of each specimen type
differ from the manually obtained average results by more than
on each machine in conformance with the applicable test
2.0 % of the average or more than one standard deviation,
methods or established procedures.
whichever is greater.
NOTE 4—It may be desirable to test many more specimens after an
initial screening, particularly if high standard deviations are observed on NOTE 7—In all cases, use the smallest non-zero standard deviation for
all machines. evaluations.
E1856–97 (2002)
6.2.2.9 Investigate, identify, and correct, if necessary, the 7.2 Adifferenceinthestandarddeviationbetweenmachines
cause of any standard deviations of the results obtained by the may be due to one or more of the following:
computerwhicharemorethantwotimesthestandarddeviation
7.2.1 Differences in Resolution—Poor resolution can show
of results obtained manually. up in two forms. A standard deviation of zero may indicate
poor resolution. Alternatively, if two or more discrete numeric
7. Test Result Evaluation results (derived data) occur with a difference between them
which is large relative to the result being measured, poor
7.1 A bias in average results between machines or readouts
resolution may be the cause. Example: 206, 206, 210, 206, 210
may be due to one or more of the following:
(see Appendix X3).
7.1.1 Calibration Differences—A bias in all of the force
7.2.2 Specimen Dimension Precision—If derived-data force
results observed is usually indicative of a difference in calibra-
standard deviations agree and derived-data stress standard
tion. If maximum forces disagree between the manual and
deviations differ, the difference is probably due to imprecise
computerizedresults,itmaybeduetodifferencesincalibration
measurements of cross sectional area.
between parts of the machine (see Appendix X1). If force
7.2.3 Differences in the Speed of Testing—Testing at speeds
results are in agreement and stress results vary, the difference
thataretoofastmaygiveeitherhighorlowstandarddeviations
may be due to cross-sectional area or other measurements such
due to one or more of the transducer-channel bandwidths (see
as span in a flexure test. If maximum force results agree and
Appendix X2).
other force results differ, the difference is probably not due to
7.2.4 Unstable Control of Test Speed— Unstable control of
differences in force calibration.
the testing machine speed may increase the standard deviation
7.1.2 Differences in the Speed of Testing—Dependingonthe
of derived data in strain-rate sensitive materials and cause
strain rate sensitivity of the material being tested, a difference
poorly formed stress-strain curves and measurement errors in
in derived data may or may not be observed if there is a
extreme cases.
difference in the speed of testing. A simple way to check the
7.2.5 Electrical Noise Being Picked Up By One or More of
speed of testing is to measure the elapsed time between two
theTransducerChannels—Electricalnoisecancausecomputer
points during the tests.
algorithms to perform poorly. This may be observed in the
7.1.3 Incorrect Inputs to the Computer Algorithms—If the
graphic record or in the basic data. This problem may be
results calculated by manual methods from the graphic record
detected by capturing data at a fixed force or strain. The
agree with the other machines but the results from the
standard deviation of this data should be comparable to the
computer disagree, the difference may be due to incorrect
resolution.
inputs to the computer algorithms.
7.2.6 Differences in Gripping and Other Apparatus in Con-
7.1.4 Algorithms Used—If the results calculated by manual
tact with the Specimen—Some devices in contact with the
methodsfromthegraphicrecordagreewiththeothermachines
specimenmayonlycauseanoccasionalprematurefailure.This
but the results from the computer disagree, the difference may
will show up as a high standard deviation.
be due to algorithms used by the computer system.
7.2.7 Alignment of the Test Piece—Poor alignment is often
7.1.5 Algorithms That Are Not Working Properly—If the
not repeatable and leads to high standard deviations (see
results calculated by manual methods from the graphic record
Practice E 1012).
agree with the other machines but the results from the
7.2.8 Insufficient band width in one or more of the trans-
computer disagree, the difference may be due to algorithms
ducer channels (see Appendix X2).
that are not working properly.
7.1.6 Ambiguity in the Interpretation of the Test Method—
8. Report
The writer(s) of the algorithms used, or the user, or both, may
8.1 For each testing machine evaluated, report the following
be interpreting the test method differently or incorrectly.
information:
7.1.7 Differences in Gripping and Other Apparatus in Con-
8.1.1 Name of reporting agency,
tact with the Specimen—Differences in gripping and other
8.1.2 Date of report,
apparatus in contact with the specimen may cause premature
8.1.3 Complete testing machine description(s) including the
failure of the specimen or act as a heat sink and cause
serialnumber(s)ofthemachine(s),andallinstrumentation,and
differences in elongation related results.
the location(s),
7.1.8 Alignment of the Test Piece—Poor alignment can
8.1.4 Software version(s) identification,
cause lower than normal test results or poorly formed stress-
8.1.5 Graphic data and manually calculated test results, if
strain curves, or both, in the elastic region of the curve (see
available,
Practice E 1012).
8.1.5.1 Computer test report(s),
7.1.9 Insufficient bandwidth in one or more of the trans-
8.1.5.2 Averages and standard deviations for each test
ducer channels (see Appendix X2).
result,
8.1.5.3 Tabulation of the differences observed, and
NOTE 8—Differences are just as likely to be due to problems with the
8.1.6 Name(s) of reporting personnel.
manually calculated results as they are to problems with the computer
8.2 This report need only be performed once and need not
generated results.
be repeated unless changes are made to the system which
NOTE 9—For additional information, see the appendix on Factors
Affecting Tension Test Results in Test Methods E 8. would significantly affect the report.
E1856–97 (2002)
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