| 摘要 |
Defective objects can be retrospectively rejected by passing objects ( 9, 10 ) sequentially past at least one sensor ( 20 ) which generates a signal representative of a property of each object. The sensor is first calibrated and a set point is established in dependence upon the signal generated by the sensor in respect of at least the first such object to pass the sensor. The at least first object is presumed not to be defective. A sensor signal is generated in respect of a subsequent object and, in the event of a signal which varies from the set point by at least a predetermined threshold in a predetermined direction, a number of actions are taken. The set point is re-established in dependence upon the signal generated in respect of the subsequent object. In addition an indication ( 23 ) is provided that at least the preceding object was defective and is to be rejected.
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