CPC B65H 7/125 (2013.01) [B65H 7/18 (2013.01); B65H 2511/416 (2013.01); B65H 2511/524 (2013.01); B65H 2553/30 (2013.01); B65H 2557/63 (2013.01)] | 18 Claims |
1. A medium conveying apparatus comprising:
a conveying roller to convey a medium; and
a processor to
detect transmission information of an ultrasonic wave transmitted through the medium or thickness information of the medium at a plurality of positions in the conveyed medium,
calculate a size of an area in which the transmission information or the thickness information is within a predetermined range in the conveyed medium,
determine whether a multi-feed of the medium has occurred, by comparing a value based on the transmission information or the thickness information with a threshold, and
execute an abnormality processing when it is determined that the multi-feed of the medium has occurred, wherein
the processor changes the threshold according to the size.
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