Ricoh PRIPORT VT 2000 Series Service Manual page 145

28 February '91
(
1) Standard Generation
Pulse
(
2) Detecting Pulse
(
3) Output of CN902-2
(
LED 102)
(1) The standard pulse is output from OUTPUT 1. The pulse length (T
can be adjusted by adjusting VR901.
(2) OUTPUT 2 is the detection pulse. The time constant is determined by
C908 and the ink. The detection pulse is triggered by the rising edge of
the standard pulse.
When ink is present, the electrostatic capacity increases and the pulse
length (T
sent, the pulse length (T
ity decreases.
(3) The pulse length (T
When the time constant (T
pulse (T
Ink is present
T0
T1
) becomes longer. On the other hand, when ink is not pre-
1
or T
1
), the output of CN902-2 goes low.
0
) becomes shorter as the electrostatic capac-
2
) is compared with the standard pulse (T
2
= No ink) is shorter than the standard
2
2-118
No ink is present
T0
T2
)
0
).
0