| The German company Zwick GmbH has recently developed a new extensometer, model optiXtens, designed for the contact-free measurement of the specimen deformation under quasi-static load application. This is a completely new method of extension measurement, which allows a precise, contact-free and standard-conforming determination of the deformation of specimens. The new system supplies very accurate and high-resolution test results over a total measuring range of 500mm. In the fine measuring range (10mm), quick processes are recorded with an acquisition rate of 250Hz without being impaired by mass inertias of the measuring system. The concept and design of optiXtens makes it a perfect device for precise measurements in temperature chambers.
The extensometer applies the method of the Laser-Speckle-Interferometry. It consists of two optical measuring heads with evaluation units. Each measuring head illuminates the specimen surface with laser light lines. Due to the specimen�s micro-roughness an unambigious signal is created during the irradiation of the surface by coherent laser light. From the developing interference pattern, a point of the surface is selected by the evaluation unit in dependence on the selected initial gauge length L0. This point is then tracked in real time during specimen deformation. So the extension between both measuring points can be determined in accordance to the standard.
In addition to highest precision in the fine- and long-stroke measuring range the method distinguishes itself by a unique ergonomics. Functions such as the automatic test area measurement and centering, automatic setting of the initial gauge length and integration into the testing system via a Can-Bus-System allow a reliable and safe operation and a precisely controlled test sequence.
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