Measuring instruments are used to verify that products features fall within the tolerances prescribed by the technical specifications of the products themselves. According to UNI EN ISO 14253-1, the product is compliant if the measured value falls within an area obtained by reducing the area of ​​measurement uncertainty. The metrological validation, which is made after the calibration, compares the calibration results, which are the instrument errors, with the user-defined maximum permissible errors (MPEs) and a safe compliance zone can be determined.