Epson DFX-9000 Service Manual page 80

Epson DFX-9000
2.2.5.1 Head gap detection
The Figure 2-15 shows the components of the DFX-9000 platen-gap
measurement. As illustrated, the platen-gap is divided into two sections:
the Media-gap and the Paper thickness. Both of these gaps are calibrated
in terms of APTC Motor drive steps.
The paper thickness is physically measured by the APTC mechanism.
The media-gap is a calculated space using a predefined formula based
on the paper thickness value.
Figure 2-15. Platen gap components
Figure 2-16 shows how the printer measures the paper thickness with the
APTC mechanism.
Operating Principles
The printer counts the number of drive pulses applied to the APTC
Motor while monitoring the width of (time between) the pulses output
from the APTC Sensor-encoder. A change in encoder pulse width is
interpreted as an increase of the APTC Motor load due to the printhead
contacting the surface of the platen or paper.
Figure 2-16. Paper thickness measurement process
Printer mechanism
Revision B
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