Extensometers for material testing machines - Zwick - #19

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19 9. Non-contact Measuring Systems The rapid pace of innovation in digital imaging systems, with ever-higher resolution levels from digital cameras, has been paralleled by an enormous increase in the power of today’s processors with a simultaneous fall in costs. This has enabled non-contact extensometers to be developed with performance data comparable to that of established mechanical systems or even superior to them in many areas. Zwick Roell has been active in this field for many years and supplies non-contact systems based on various principles: from mechanically driven optical trackers to full-screen video systems with complex digital image processing. Advantages of non-contact measuring systems • Test results are not distorted by the specimen being affected by mechanical contact with knife-edges or weight / drag forces of the mechanical measuring system. • Non-dimensionally stable specimens, such as thin foils, textiles, and non-wovens, where mechanical attachment is not possible, can be measured. • Specimens made of notch-sensitive material can be tested, for example thin elastomers. • The systems are practically wear-free and have very high life expectancy. • Non-contact measuring systems are suitable for testing specimens which release very high energies at specimen break and cause wear to mechanical systems due to the immense acceleration. • They are also suitable for specimens such as elastomers, ropes and wires which display a whiplash effect and can destroy mechanical systems. • No thermal bridges are created during tests in extended temperature ranges, as measurement takes place through a heated glass window, minimizing influences on extension measurement and reducing energy costs. • Required accuracy classes are achieved or in some cases exceeded. • Free choice of gage length - either by applying gage marks or via freely positionable measurement head in laser speckle systems. • Many different options are available for videoXtens and laserXtens to enable significant expansion of the ranges of application, for example measuring transverse strain in parallel or recording of several separate strain stages. • Some systems allow live images of the test to be recorded and used for evaluation and documentation. Technology exclusively available from Zwick: testing with laser speckle sensors – patented and standard-compliant