Proposed are a method and a device for consolidation of a number n of items, whose weight varies within predefined limits, in a container to a single unit with a predefined target weight. A control unit controls a flow of current between the first energy storage unit and the second energy storage unit in both directions. The second side is engagable with a process void and at least one vent void such that when the process pressure is below the fluid pressure the diaphragm is engaged with the vent void. The sensing elements identify the location where the reflected signal is received, and based on this identified location, the location of the cavity wall is determined. The first side wall may be fixed to the cam engagement surface and may include first and second portions. The optical film comprises a substrate and an anti-static layer disposed thereon.