ASTM E1856-97e1
(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
SCOPE
1.1 This guide is intended to assist the user in the evaluation and documentation of computerized 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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e1
Designation: E 1856 – 97
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.
e NOTE— Editorial corrections were made throughout in November 1997.
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 for Tension Testing 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-
ware algorithms, such as a peak force or a modulus value.
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
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
design of the system, but the 3 dB bandwidth (expressed in
Hertz) is a simple single measure of responsiveness (see Fig.
This guide is under the jurisdiction of ASTM Committee E-28 on Mechanical
Testing and is the direct responsibility of Subcommittee E28.15 on Automated
2).
Testing.
3.1.6 computerized data acquisition system—for the pur-
Current edition approved Jan. 10, 1997. Published March 1997.
2 pose of this guide, a computerized data acquisition system is a
Annual Book of ASTM Standards, Vol 03.01.
Annual Book of ASTM Standards, Vol 14.02. device which collects basic data from a universal testing
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 1856
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,
machine during a test and calculates and presents derived data
whichever is greater.
based on the basic data collected.
NOTE 5—In all cases, use the smallest non-zero standard deviation for
4. Summary of Guide
evaluations.
4.1 Comparative tests are performed to determine if the
6.2.1.9 Investigate, identify, and correct, if necessary, the
derived data acquired with a computerized universal testing
cause of any standard deviations of the results obtained by the
machine agree with results acquired on the same machine from
computer which are more than two times the standard deviation
graphical records or with results acquired on other testing
obtained manually or by the other machines.
machines to ensure that the materials being tested are correctly
characterized. NOTE 6—Differences in averages and standard deviations of these
magnitudes are quite often due to variations in the material being tested,
5. Significance and Use
and a complete statistical evaluation of the data using methods such as
Practice E 691 may be necessary.
5.1 This guide is recommended to be used by anyone
acquiring data from a universal testing machine using a
6.2.2 Single Machine Procedure:
computerized data acquisition system.
6.2.2.1 This procedure may be used for testing machines
with the capability of producing graphic records from which
6. Procedure
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 Ascertain that all readout and recording devices used
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
conformance with the applicable test methods or established
NOTE 3—It is preferable to use testing machines of varying types so
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.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 1856
6.2.2.9 Investigate, identify, and correct, if necessary, the 7.2.1 Differences in Resolution—Poor resolution can show
cause of any standard deviations of the results obtained by the up in two forms. A standard deviation of zero may indicate
computer which are more than two times the standard deviation poor resolution. Alternatively, if two or more discrete numeric
of results obtained manually. results (derived data) occur with a difference between them
which is large relative to the result being measured, poor
7. Test Result Evaluation
resolution may be the cause. Example: 206, 206, 210, 206, 210
7.1 A bias in average results between machines or readouts
(see Appendix X3).
may be due to one or more of the following:
7.2.2 Specimen Dimension Precision—If derived-data force
7.1.1 Calibration Differences—A bias in all of the force
standard deviations agree and derived-data stress standard
results observed is usually indicative of a difference in calibra-
deviations differ, the difference is probably due to imprecise
tion. If maximum forces disagree between the manual and
measurements of cross sectional area.
computerized results, it may be due to differences in calibration
7.2.3 Differences in the Speed of Testing—Testing at speeds
between parts of the machine (see Appendix X1). If force
that are too fast may give either high or low standard deviations
results are in agreement and stress results vary, the difference
due to one or more of the transducer-channel bandwidths (see
may be due to cross-sectional area or other measurements such
Appendix X2).
as span in a flexure test. If maximum force results agree and
7.2.4 Unstable Control of Test Speed— Unstable control of
other force results differ, the difference is probably not due to
the testing machine speed may increase the standard deviation
differences in force calibration.
of derived data in strain-rate sensitive materials and cause
7.1.2 Differences in the Speed of Testing—Depending on the
poorly formed stress-strain curves and measurement errors in
strain rate sensitivity of the material being tested, a difference
extreme cases.
in derived data may or may not be observed if there is a
7.2.5 Electrical Noise Being Picked Up By One or More of
difference in the speed of testing. A simple way to check the
the Transducer Channels—Electrical noise can cause computer
speed of testing is to measure the elapsed time between two
algorithms to perform poorly. This may be observed in the
points during the tests.
graphic record or in the basic data. This problem may be
7.1.3 Incorrect Inputs to the Computer Algorithms—If the
detected by capturing data at a fixed force or strain. The
results calculated by manual methods from the graphic record
standard deviation of this data should be comparable to the
agree with the other machines but the results from the
resolution.
computer disagree, the difference may be due to incorrect
7.2.6 Differences in Gripping and Other Apparatus in Con-
inputs to the computer algorithms.
tact with the Specimen—Some devices in contact with the
7.1.4 Algorithms Used—If the results calculated by manual
specimen may only cause an occasional premature failure. This
methods from the graphic record agree with the other machines
will show up as a high standard deviation.
but the results from the computer disagree, the difference may
7.2.7 Alignment of the Test Piece—Poor alignment is often
be due to algorithms used by the computer system.
not repeatable and leads to high standard deviations (see
7.1.5 Algorithms That Are Not Working Properly—If the
Practice E 1012).
results calculated by manual methods from the graphic record
7.2.8 Insufficient band width in one or more of the trans-
agree with the other machines but the results from the
ducer channels (see Appendix X2).
computer disagree, the difference may be due to algorithms
that are not working properly.
8. Report
7.1.6 Ambiguity in the Interpretation of the Test Method—
8.1 For each testing machine evaluated, report the following
The writer(s) of the algorithms used, or the user, or both, may
information:
be interpreting the test method differently or incorrectly.
8.1.1 Name of reporting agency,
7.1.7 Differences in Gripping and Other Apparatus in Con-
8.1.2 Date of report,
tact with the Specimen—Differences in gripping and other
8.1.3 Complete testing machine description(s) including the
apparatus in contact with the specimen may cause premature
serial number(s) of the machine(s), and all instrumentation, and
failure of the specimen or act as a heat sink and cause
the location(s),
differences in elongation related results.
8.1.4 Software version(s) identification,
7.1.8 Alignment of the Test Piece—Poor alignment can
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
gener
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