ASTM E1237-93(2003)
(Guide)Standard Guide for Installing Bonded Resistance Strain Gages
Standard Guide for Installing Bonded Resistance Strain Gages
SIGNIFICANCE AND USE
Methods and procedures used in installing bonded resistance strain gages can have significant effects upon the performance of those sensors. Optimum and reproducible detection of surface deformation requires appropriate and consistent surface preparation, mounting procedures, and verification techniques.
SCOPE
1.1 This document provides guidelines for installing bonded resistance strain gages. It is not intended to be used for bulk or diffused semiconductor gages. This document pertains only to adhesively bonded strain gages.
1.2 This standard does not purport to address all of the safety problems, 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: E 1237 – 93 (Reapproved 2003)
Standard Guide for
Installing Bonded Resistance Strain Gages
This standard is issued under the fixed designation E1237; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope
1.1 Thisdocumentprovidesguidelinesforinstallingbonded
resistance strain gages. It is not intended to be used for bulk or
diffused semiconductor gages. This document pertains only to
adhesively bonded strain gages.
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-
FIG. 1 Designation of Strain Gage Bridge and Color Code of Lead
bility of regulatory limitations prior to use.
Wires (Full Bridge)
2. Referenced Documents
3.2.1 bonded resistance strain gage—a resistive element
2.1 ASTM Standards:
with a carrier that is attached by bonding to the base material
E251 Test Methods for Performance Characteristics of
so that the resistance of the element will vary as the surface of
Metallic Bonded Resistance Strain Gages
the base material to which it is attached is deformed. (For a
2.2 Other Standards:
complete definition of this term see Test Methods E251.)
ANSI/SEM 1-1984; Standard for Portable Strain-Indicating
4. Significance and Use
Instruments—Designation of Strain Gage Bridge and
Color Code of Terminal Connections; August 16, 1984.
4.1 Methods and procedures used in installing bonded
resistance strain gages can have significant effects upon the
3. Terminology
performance of those sensors. Optimum and reproducible
3.1 Definitions:
detection of surface deformation requires appropriate and
3.1.1 lead wire—an electrical conductor used to connect a
consistent surface preparation, mounting procedures, and veri-
sensor to its instrumentation.
fication techniques.
3.1.2 resistance strain gage bridge—a common
5. Gage Selection
Wheatsone bridge made up of strain gages used for the
measurement of small changes of resistance produced by a
5.1 Careful consideration must be given to the intended use
strain gage, where the gages may be wired in the following
when selecting an appropriate gage. Installation and operating
configuration (see also Fig. 1 and Fig. 2):
characteristics of a gage are affected by many factors such as
Arm 1 between+excitation and−signal
resistive element alloy, carrier material, gage length, gage and
Arm 2 between−excitation and−signal
Arm 3 between+signal and−excitation
Arm 4 between+signal and+excitation
3.2 Definitions of Terms Specific to This Standard:
This guide is under the jurisdiction of ASTM Committee E28 on Mechanical
Testing and is the direct responsibility of Subcommittee E28.01 on Calibration of
Mechanical Testing Machines and Apparatus.
Current edition approved Nov. 15, 2005. Published January 2004. Originally
approved in 1993. Last previous edition approved in 1998 as E1237–93(1998).
Annual Book of ASTM Standards, Vol 03.01.
Available from American National Standards Institute, 11 W. 42nd St., 13th FIG. 2 Designations of Strain Gage Bridge and Color Code of
floor, New York, NY 10036. Lead Wires ( ⁄4 Bridge)
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1237 – 93 (2003)
resistive element pattern, solder tab type and configuration, 7.2 Erroneous gage readings may be caused by poor bond-
temperature compensation characteristics, resistance of active ing of strain gages, which could be due to unremoved coatings
elements, gage factor, and options desired. suchaspaint,scale,rust,andoils.Poorbondingmayalsoresult
5.2 Factors that should also be considered include type of from applying gages to improperly prepared surfaces, such as
testorapplication,operatingtemperaturerange,environmental mirror smooth finishes or surfaces containing deep pits and
conditions,accuracyrequirements,stability,maximumelonga- gouges.
tion, test conditions (static or dynamic) and duration, and 7.3 Strain gage manufacturers supply surface preparation
simplicity and ease of installation. Dissipation of self- suggestions and recommendations.This information should be
generated heat to the carrier should be considered in selecting reviewed and considered when preparing base material sur-
gage resistance and size of grid. faces for the particular gages selected.
5.3 To minimize errors due to strain gradients over the gage
area, gage size should normally be small with respect to the 8. Gage Installation—General
dimensions of an immediately adjacent geometric irregularity
8.1 Allworkmustbeperformedwithcleanhandsandtools.
(hole, fillet, etc.). However, the gage size should generally be
Allmaterialsneededshouldbeassembledandreadilyavailable
large relative to the underlying material structure (grain size,
at the gage installation location.
fabric-reinforced composite weave pattern, etc.).
8.2 Thespecificsurfacepreparationproceduresshouldbein
5.4 A two- or three-element rosette gage should be used
accordancewiththeinstructionssuppliedforthebondingagent
unless the strain state is unquestionably uniaxial. A single
selected. Bonding agent handling and safety precautions
element gage may be selected to measure the strain due to a
should be reviewed and carefully followed.
uniaxial strain state if the principal directions are known.
8.3 Thedetailedgageinstallationproceduresavailablefrom
5.5 Temperature compensation of the gage should be se-
the strain gage manufacturer for the particular gage/bonding
lectedtomatchthethermalcoefficientofexpansionofthebase
technique system selected should be carefully reviewed and
material, where possible. As a note of caution, for extreme
rigorously followed. Deviations from these procedures, if any,
temperaturechanges,nominalorhandbookdataonthethermal
should be documented and verified to ensure that the installa-
expansion characteristics of the base material may not be
tion will yield suitably accurate results.
sufficiently accurate, and actual calibration may be required.
8.4 Gage handling and alignment procedures should be
5.6 Strain gage manufacturers provide detailed critiques of
rigorouslyfollowed.Deviations,ifany,shouldbedocumented.
the various factors which affect gage selection (1).
5.7 For nonroutine applications, the advice of experienced
9. Gage Installation—Adhesive
users and of strain gage manufacturers should be sought.
9.1 Ensure that the proper adhesive is selected for a given
Specific verification tests may be required to ensure accurate
gage type. Follow gage manufacturer’s recommendations for
results.
selecting an adhesive.
9.2 The environment to which a gage is to be subjected and
6. Bonding Technique Selection
test duration should be considered when selecting an adhesive.
6.1 Selection of the proper bonding technique and agent is
9.3 Ensure that the adhesive to be used is not out-of-date
important. Because the bonding agent becomes part of the
with regard to storage and shelf life requirements.
strain gage system, many of the gage selection factors should
9.4 Ensure that test material temperature range and gage/
be considered in bonding technique or agent selection.
bonding system temperature range are compatible.
6.2 Additional selection factors include compatibility of the
9.5 Temperatures and times should be monitored to ensure
bonding materials used in the selected gage construction with
that the adhesive temperature and pot life requirements, if
thematerialundertest,environmentalconditions,andavailable
applicable, are not exceeded.
installation time.
9.6 Adhesive curing methods and schedules should be
6.3 Strain gages from different manufacturers may differ.
rigorouslyfollowed.Deviations,ifany,shouldbedocumented.
Generally, each manufacturer will supply instructions and
9.7 If curing with pressure is required, take special care to
recommendations for bonding. These instructions should be
make sure the pressure is proper and is distributed uniformly
considered when making a selection.
over the entire gage. Nonuniform pressure may result in an
irregular bond line. Care should be taken to ensure that the
7. Surface Preparation
gage position does not shift as a result of applying this
7.1 The surface must be properly prepared to ensure good
pressure.
bonding. Surface preparation includes solvent degreasing,
cleaning, mechanical preparation, and chemical preparation.
10. Lead Wire Connection
The surface should be smooth, but not highly polished.
10.1 Care must be exercised in attaching the lead wires. In
Preparation of this surface must be compatible with the gage,
ordertopreventleadwireforcesfromdamagingthestraingage
bonding method, and base material.
or degrading its performance, the use of gages with integ
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