Apparatus for detecting the passage of multiple superposed sheets along a feed path

摘要

An apparatus for detecting the passage of superposed sheets, e.g. currency notes, along a feed path (76) includes a mechanism which has a pair of cooperating rollers (12, 14) and which is arranged to generate an output voltage whose magnitude varies in response to the passage of an item (single or multiple sheet) between the rollers (12, 14). This output voltage is applied to an A/D converter whose outputs are sampled at regular intervals while an item is passing between the rollers (12, 14). A data processing means generates a first digital value representative of the sum of these outputs. From this digital value is subtracted a value representative of the sum of the outputs of the A/D converter over the corresponding part of the cycle of the rollers while no sheet is passing between them. A determination is thereby made as to whether or not said item comprises a single sheet.