The present invention relates to a metering process of a number of granular materials comprising the steps of:a) initial calibration of a multiple metering device (DM) including the steps of:loading a number of granular materials to be metered into respective hoppers or silos (T1, T2, . . . , Tn), each equipped with a respective extractor device (DE1, DE2, . . . , DEn) making up part of the multiple metering device (DM);separately driving each of the extractor devices (DE1, DE2, . . . , DEn), each associated with a respective hopper (T1, T2, . . . , Tn), whereby carrying out a pre-established number of opening-closing steps in the time unit thereby obtaining a corresponding amount of extracted
granular material;weighing the amount of
granular material extracted by each extractor device (DE1, DE2, . . . , DEn);inserting weight data for each
granular material to be metered into a
program control unit (CPU) for the calculation of the opening-closing period (P1, P2, . . . , Pn) of each extractor device (DE1, DE2, . . . , DEn) based on desired percentages of each granular material to be metered, for the obtainment of a final mixture with desired composition; and subsequentlyb) cyclic execution of the following sequential steps:sending control signals processed by the
program control unit (CPU) as a function of said periods of extractor opening-closing (DE1, DE2, . . . , DEn ) for the extraction of an metered amount of the respective granular material to be treated by at least two extractor devices (DE1, DE2, . . . , DEn);collecting, in a holding container (CP), the metered amounts of each granular material thus extracted; anddetecting, by means of sensor means (MS), a pre-established filling threshold of the holding container (CP) thereby stopping the at least two extractor devices (DE1, DE2, . . . , DEn) upon attainment of the pre-established filling threshold.