Hitachi HT-4139-48 Instruction Manual page 73

(2) Ultra sonic Detection type
The specifications of multiple feed detection by the Ultrasonic sensor are shown below.
The ultra sonic type checks multiple feeding by detecting air layer between papers.
Feed Direction
23
16
< Relaxation of multi-feed detection >
In case there are attachment in the area of dual feed detection, it is possible to set the
length (L5) to neglect it.
L5：25～394mm（Default is 25mm.）
As this method detects air gap between papers, condition of adhesion of heat-seal
papers, tape, and seals affects to the detection accuracy.
① Detection position
・23～39mm from left edge of sheet
② Detection area
L2
・Area L4excluding L2 and L3
（L0is about 25% of sheet length L）
（L2: about 35mm, L3: about 10mm）
L4
③Judgment
L
・Compare detected length and criteria in
area L4.
L3
affected by print nor written characters on
papers but degree of adhesion might be
cause of mis-detection.
5. Specifications
Note: This type of detection will not
５
5-9