Introduction
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. This simple and economic system fully satisfy these requirements because:

• it is applied directly to the specimen
• it remains connected until breakage
• it measures extensions with high precision of both elastic and plastic stage and with the appropriate simple adjustment, it is connectable to almost all testing machines

Description
The extensometers are basically made by 2 clamping devices and a middle tubolar steel part determining the gauge length of 200 mm.