laserXtens Array HP extensometer: non-contacting, high-accuracy and unique

The strain measurement capability offered by Zwick's laserXtens Array HP extensometer is unique in the world. laserXtens Array HP provides non-contact, high-accuracy strain recording over a wide measuring-range without the use of gage marks. It is easy to operate, wear-free and has a wide range of functions which no contact-type system can offer, such as identification of break location (including determination of strain at break), strain distribution over the entire specimen length and automatic tracking of the gage length to the area of highest strain.

Strain measurement by laserXtens is based on the speckle correlation principle, making specimen markings redundant. This laser-optical measurement system enables determination of specimen strain in tensile tests with no need for prior specimen preparation. 'Virtual gage marks' are generated by illuminating the specimen with coherent light, forming a sort of 'fingerprint' whose movement is tracked in real time and in two dimensions.

laserXtens Array HP's patented array technology takes this principle further. The individual high-resolution fields of view of seven cameras are combined into a single large image, giving a very large measuring range combined with high resolution. This patented process combines the best of both worlds in measuring technology, enabling large areas of the specimen to be recorded simultaneously and in high resolution.

This technology opens up a whole range of possibilities for the expansion of measured-value acquisition beyond classical extension measurement using two-point measurement. The software can place large numbers of measuring points in any desired position on the specimen surface; following measurement, the system can (by calculation) combine the measuring point movements flexibly into measurement channels.

In this way laserXtens Array HP can automatically determine the strain distribution of a specimen, identify the break location and determine strain at break. Other functions include two-dimensional tracking of individual points and transverse strain. Strain-rate control as per ISO 6892-1 is also possible with this extensometer.

laserXtens Array HP achieves Accuracy Class 0.5 and a resolution of 0.10┬Ám in a measuring range up to 190mm. In 2013 the German Patent Office granted a patent for this unique innovation.