ASTM E1237-93(1998)
(Guide)Standard Guide for Installing Bonded Resistance Strain Gages
Standard Guide for Installing Bonded Resistance Strain Gages
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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 1237 – 93 (Reapproved 1998)
Standard Guide for
Installing Bonded Resistance Strain Gages
This standard is issued under the fixed designation E 1237; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. 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 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
the base material to which it is attached is deformed. (For a
complete definition of this term see Test Methods E 251.)
2.1 ASTM Standards:
E 251 Test Methods for Performance Characteristics of
4. Significance and Use
Metallic Bonded Resistance Strain Gages
4.1 Methods and procedures used in installing bonded
2.2 Other Standards:
resistance strain gages can have significant effects upon the
ANSI/SEM 1-1984; Standard for Portable Strain-Indicating
performance of those sensors. Optimum and reproducible
Instruments—Designation of Strain Gage Bridge and
detection of surface deformation requires appropriate and
Color Code of Terminal Connections; August 16, 1984.
consistent surface preparation, mounting procedures, and veri-
3. Terminology
fication techniques.
3.1 Definitions:
5. Gage Selection
3.1.1 lead wire—an electrical conductor used to connect a
5.1 Careful consideration must be given to the intended use
sensor to its instrumentation.
when selecting an appropriate gage. Installation and operating
3.1.2 resistance strain gage bridge—a common
characteristics of a gage are affected by many factors such as
Wheatsone bridge made up of strain gages used for the
resistive element alloy, carrier material, gage length, gage and
measurement of small changes of resistance produced by a
resistive element pattern, solder tab type and configuration,
strain gage, where the gages may be wired in the following
temperature compensation characteristics, resistance of active
configuration (see also Fig. 1 and Fig. 2):
elements, gage factor, and options desired.
Arm 1 between + excitation and − signal
5.2 Factors that should also be considered include type of
Arm 2 between − excitation and − signal
test or application, operating temperature range, environmental
Arm 3 between + signal and − excitation
Arm 4 between + signal and + excitation
3.2 Definitions of Terms Specific to This Standard:
3.2.1 bonded resistance strain gage—a resistive element
with a carrier that is attached by bonding to the base material
so that the resistance of the element will vary as the surface of
This guide is under the jurisdiction of ASTM Committee E-28 on Mechanical
Testing and is the direct responsibility of Subcommittee E28.14 on Strain Gages.
Current edition approved Feb. 15, 1993. Published April 1993.
Annual Book of ASTM Standards, Vol 03.01.
FIG. 2 Designations of Strain Gage Bridge and Color Code of
Available from American National Standards Institute, 11 W. 42nd St., 13th
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.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 1237
conditions, accuracy requirements, stability, maximum elonga- 7.3 Strain gage manufacturers supply surface preparation
tion, test conditions (static or dynamic) and duration, and suggestions and recommendations. This information should be
simplicity and ease of installation. Dissipation of self- reviewed and considered when preparing base material sur-
generated heat to the carrier should be considered in selecting faces for the particular gages selected.
gage resistance and size of grid.
8. Gage Installation—General
5.3 To minimize errors due to strain gradients over the gage
8.1 All work must be performed with clean hands and tools.
area, gage size should normally be small with respect to the
dimensions of an immediately adjacent geometric irregularity All materials needed should be assembled and readily available
at the gage installation location.
(hole, fillet, etc.). However, the gage size should generally be
large relative to the underlying material structure (grain size, 8.2 The specific surface preparation procedures should be in
accordance with the instructions supplied for the bonding agent
fabric-reinforced composite weave pattern, etc.).
5.4 A two- or three-element rosette gage should be used selected. Bonding agent handling and safety precautions
should be reviewed and carefully followed.
unless the strain state is unquestionably uniaxial. A single
element gage may be selected to measure the strain due to a 8.3 The detailed gage installation procedures available from
the strain gage manufacturer for the particular gage/bonding
uniaxial strain state if the principal directions are known.
5.5 Temperature compensation of the gage should be se- technique system selected should be carefully reviewed and
rigorously followed. Deviations from these procedures, if any,
lected to match the thermal coefficient of expansion of the base
material, where possible. As a note of caution, for extreme should be documented and verified to ensure that the installa-
tion will yield suitably accurate results.
temperature changes, nominal or handbook data on the thermal
8.4 Gage handling and alignment procedures should be
expansion characteristics of the base material may not be
sufficiently accurate, and actual calibration may be required. rigorously followed. Deviations, if any, should be documented.
5.6 Strain gage manufacturers provide detailed critiques of
9. Gage Installation—Adhesive
the various factors which affect gage selection (1).
9.1 Ensure that the proper adhesive is selected for a given
5.7 For nonroutine applications, the advice of experienced
gage type. Follow gage manufacturer’s recommendations for
users and of strain gage manufacturers should be sought.
selecting an adhesive.
Specific verification tests may be required to ensure accurate
9.2 The environment to which a gage is to be subjected and
results.
test duration should be considered when selecting an adhesive.
6. Bonding Technique Selection
9.3 Ensure that the adhesive to be used is not out-of-date
with regard to storage and shelf life requirements.
6.1 Selection of the proper bonding technique and agent is
9.4 Ensure that test material temperature range and gage/
important. Because the bonding agent becomes part of the
bonding system temperature range are compatible.
strain gage system, many of the gage selection factors should
9.5 Temperatures and times should be monitored to ensure
be considered in bonding technique or agent selection.
that the adhesive temperature and pot life requirements, if
6.2 Additional selection factors include compatibility of the
applicable, are not exceeded.
bonding materials used in the selected gage construction with
9.6 Adhesive curing methods and schedules should be
the material under test, environmental conditions, and available
rigorously followed. Deviations, if any, should be documented.
installation time.
9.7 If curing with pressure is required, take special care to
6.3 Strain gages from different manufacturers may differ.
make sure the pressure is proper and is distributed uniformly
Generally, each manufacturer will supply instructions and
over the entire gage. Nonuniform pressure may result in an
recommendations for bonding. These instructions should be
irregular bond line. Care should be taken to ensure that the
considered when making a selection.
gage position does not shift as a result of applying this
7. Surface Preparation
pressure.
7.1 The surface must be properly prepared to ensure good
10. Lead Wire Connection
bonding. Surface preparation includes solvent degreasing,
10.1 Care must be exercised in attaching the lead wires. In
cleaning, mechanical preparation, and chemical preparation.
order to prevent lead wire forces from damaging the strain gage
The surface should be smooth, but not highly polished.
or degrading its performance, the use of gages with integral
Preparation of this surface must be compatible with the gage,
copper terminals or bonded terminals is recommended. Bond-
bonding method, and base material.
able terminals are recommended where extended use of the test
7.2 Erroneous gage readings may be caused by poor bond-
piece is expected. References (2), (3), and (4) provide supple-
ing of strain gages, which could be due to unremoved coatings
mental information on these subjects.
such as paint, scale, rust, and oils. Poor bonding may also result
10.2 Wire splices should be avoided, but if a splice is
from applying gages to
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.