An extensometer measures the change in distance between two specimen points. Its gauge length defines the reference length used to calculate engineering strain.
The gauge length is the initial separation of the points whose extension defines a reported engineering strain. It need not equal the full deforming length between grips.
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An extensometer is an electronic or mechanical device used to measure the extension or deformation of a material or specimen under load. It is commonly employed in material testing, structural monitoring, and other applications where precise measurements of displacement or strain are required. Extensometers can be used in various settings, including laboratories and field environments, and can measure elongation, compression, or changes in diameter.