The Laser Extensometers of the company Fiedler Optoelektronik GmbH can be classified conforming with the accuracy classes of the different standards (DIN EN 10002-4, ISO 9513). The classes 2, 1, 0.5 and 0.2 exisit.
The figure on the right hand side shows the setup of a Laser Extensometer P-50 for calibration in our laboratory. [1].

The accuracy classes describe the amount of deviation between the measured elongation and the real elongation [2]. The accuracy class X (X = 2, 1, 0.5, 0.2) defines for the standard DIN EN 10002-4 b resp. ISO 9513 a maximum deviation of ± X % or ± 3 X µm - whichever is larger.
Description of the Accuracy Class 0.5

1. [1] The company Fiedler is able to provide factory calibration as well as calibrations conforming with the DKD in cooperation with an accredited laboratory.
2. [2] More accurate: The deviation of the determined elongation measured by the Laser Extensometer to the elongation measured by the Calibration Gauge.