Because field conditions can change rapidly, accuracy guidelines must be considered in terms of “ranges”, not absolute number. Claims of accuracy should be taken with caution, because it is unlikely that such claims can be consistent: the results are often affected by the method of sampling, environments, speciments size and human errors; Several Standard procedures define for accuracy tests any “difference between two test results for the same material, obtained by the same operator using the same equipment on the same day in the same laboratory”. Although we have established some calibration procedures following ISO and ASTM standards, there is no certain reference to control measures and inter-laboratory data. However our systems, are provided with a function that allows you to align the measured values with the values derived from offline devices, by simply pressing a button.