This article aims to identify the appropriate sampling duration for a tribocharging process on a vibratory feeder device in order to compute the capability indexes and set up a statistical control procedure. The outcome of the process is evaluated as the ratio between the charge and the mass of the granules that exit the tribocharging device during a given laps of time. A virtual instrument developed in LabWiew was used in conjunction with a Faraday cage connected to an electrometer and with an electronic scale, to simultaneously measure the charge and the mass of tribocharged granular plastics, for fixed sampling durations.