<https://geotechnical-equipment.com/product/extensometer/#webpage>
<http://schema.org/description>
"Extensometers used for measuring the extension of specimens in traction, particularly in the case of steel and brittle materials, are only able to detect strain during the first stage of the test, or rather, while the brittle materials conserve their elasticity as they have to be disconnected before failure."
<https://geotechnical-equipment.com/product/extensometer/>