THEORY GUIDE Scan/Erase
10DEC05
TG4825-1
Page
77 of 120
ENCODER
The ENCODER monitors the speed and position of the MAGNET in during rotation to provide
smooth operation and continual speed.
The signals of the SENSORS are 90 degrees out of phase with each other in a “quadrature
relationship.” One DETECTOR detects the edge of a line and the other detects the middle of
the line.
The ENCODER determines:
• speed of the SLOW SCAN MOTOR by measuring the frequency of the signals
• direction of rotation of the SLOW SCAN MOTOR by determining the sequence in which
the signals change
Component Description
ENCODER WHEEL A clear disk that has 5000 lines leading from the center to the
outside edge.
2 OPTICAL
SENSORS -
EMITTER/
DETECTORS
Placed at the edge of the ENCODER WHEEL. Each beam from the
EMITTER/DETECTOR is blocked by the lines of the WHEEL when
the WHEEL rotates.
H194_5031BC
Signal from DETECTOR 2
Signal from DETECTOR 1
LIGHT EMITTER
LIGHT DETECTOR 1
LIGHT EMITTER
LIGHT DETECTOR 2
ENCODER WHEEL
( 5000 Lines )
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