The machine for continuous automatic weight control essentially consists of: A base which has the task of supporting the balance and the device for transporting objects. A high sensitivity and readiness comparison scale, equipped with an electromagnetic detector that transforms the position of the scale plate into an electrical signal, burdened by the weight passing on it. A belt conveyor, and a projector unit - photocell that signals the instant when the object is about to leave the weighing pan.

The scale is inserted into a transport line of objects to be checked of any nature and shape. The passing object takes some time to traverse the entire weighing pan; this time, although small, is sufficient for the scale to settle in a position proportional to the weight of the object. When the object is about to leave the weighing pan, it intercepts a light beam that crosses the conveyor. The phototransistor receiver, thus obscured, provides the electronic circuit with the command to carry out the reading of the weight at that precise moment. This weight value is immediately compared with the two values, lower and upper, set as limits of the allowed tolerance. From this comparison arises the decision of the machine to accept or not the weighing, i.e. whether to let the object go on undisturbed, or to deviate it or expel it to the right or left of its path, depending on whether its weight was in excess or in lack of respect to the predetermined tolerance.