ASTM E251-92(2014)

1.1 The purpose of these test methods are to provide uniform test methods for the determination of strain gage performance characteristics. Suggested testing equipment designs are included.

1.2 Test Methods E251 describes methods and procedures for determining five strain gage parameters:...

1.3 Strain gages are very sensitive devices with essentially infinite resolution. Their response to strain, however, is low and great care must be exercised in their use. The performance characteristics identified by these test methods must be known to an acceptable accuracy to obtain meaningful results in field applications.

1.4 Bonded resistance strain gages differ from extensometers in that they measure average unit elongation (ΔL/L) over a nominal gage length rather than total elongation between definite gauge points. Practice E83 is not applicable to these gages.

1.5 These test methods do not apply to transducers, such as load cells and extensometers, that use bonded resistance strain gages as sensing elements.

1.6 strain gages are part of a complex system that includes structure, adhesive, gage, lead wires, instrumentation, and (often) environmental protection. As a result, many things affect the performance of strain gages, including user technique. A further complication is that strain gages once installed normally cannot be reinstalled in another location. Therefore, gage characteristics can be stated only on a statistical basis.

1.7 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.