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CHAPTER 2. BASIC OPERATION
C. Linear Encoder
1. Outline
A linear encoder is installed on the printer to allow checking the carriage operation and ad-
justing the dot placement position on the paper. When the carriage is returning, after the home
position sensor (PS2) turns ON and the carriage has travelled an additional 12mm, that position
is considered the home position.
2. Structure
[1] Linear scale
Slits are printed at an interval of about 1/360 inch on a polyethylene telephthalate sheet.
[2] Linear sensor
Composed of a light emitting diode and photo diode, the sensor reads the slit pattern on
the linear scale and outputs a 2-phase rectangular wave.
3. Output signal
When the linear sensor moves along the linear scale, the photo diode detects the light coming
through the slit pattern and outputs 4 signals (A, A, B, B) to the signal processing circuit. Two
comparators output rectangular waves (LSA, LSB) with a phase difference of 90°.
2–26
1/360 inch
Linear scale
Figure 2-203
LSA/LSB
Carriage
controller
Linear sensor
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