7.2 Calibration
The sensor calibration occurs automatically and consists in adjusting the quantity of light emitted to match the degree of
whiteness of the paper used and the degree of black of the mark printed on paper.
The device automatically performs the self-calibration during the Setup procedure only if the “Black Mark Position” param-
eter is set to a value other than “Disabled” (see
chapter 6).
When self-calibration starts, the device performs some paper feeds and then it prints the calibration result and the value of
the PWM duty-cicle (also expressed as a percentage) of the alignment sensor driver so that it can be perform an optimal
black mark detection:
Autosetting Black Mark : OK
PWM Duty Cycle : 2.7 V [82%]
successful, NOT OK will appear if the procedure has failed.
After the printing of the procedure result, the device offers the execution of the function of paper characterization “Char-
acterize Paper” and the change of the “Black Mark Threshold” parameter which represents the detection threshold of the
black mark.
Choosing the “Yes” value for the “Characterize Paper” parameter, the device prints a graphic representation (see following
This graphic representation is useful to set the most suitable value to assign to the “Black Mark Threshold” parameter
and then to better identify the optimal threshold value which takes into account the variations of the signal and the small
oscillations around zero.
is constant while passing the white paper between two black marks and presents a peak at each black mark.
In this case, the optimal value for the “Black Mark Threshold” parameter is placed about half of the peak.
Peak
“Black Mark
Threshold”
NON-THERMAL SIDE
THERMAL SIDE
82
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