| 摘要 |
A control unit (1) interacting with a strip packaging material to which are applied, to close respective openings (3) in the packaging material, a number of patch elements (5) and a number of tear-off tongues (6) heat sealed to respective patch elements (5). To determine the integrity of the patch elements (5), the unit has at least one contact surface (21) at an operating electric potential (Va) and cooperating with the side of the packaging material (4) having the patch elements (5) to define one plate of a capacitor (23), the other plate of which is defined by an aluminium film (4a) of the packaging material (4), and the dielectric of which is defined by the heat-seal plastic material interposed between the plates; and a detecting circuit (26) connected to the contact surface (21) and to the aluminium film (4a) to detect an electric quantity related to variations in the dielectric strength of the dielectric of the capacitor (23) and so determine the presence of any microholes in the patch elements (5).
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