Extensometer

An extensometer is a device that is used to measure changes in the length of an object. It is useful for stress-strain measurements and tensile tests. Its name comes from 'extension-meter'. It was invented by 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 malnufacturer of testing machines and scales.There are two main types of extensometers: contact and non-contact.In the mining environment, extensometers are used to measure displacements on batters/highwalls. Plotting displacement vs time enables Geotechnical engineers to determine if wall failures are imminent. For complicated failures, further equipment such as radar or laser scans are used enabling 3-dimensional and ultimately 4-dimensional analysis.