Extensometer

An extensometer is a device that is used to measure changes in the length of an object.[1] It is useful for stress-strain measurements and tensile tests. Its name comes from "extension-meter". It was invented by Dr. Charles Huston who described it in an article in the Journal of the Franklin Institute in 1879. Huston later gave the rights to Fairbanks & Ewing, a major manufacturer of testing machines and scales.