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CT 9000 ® ADV
DISPLAY
POWER SUPPLIES
Refer to schematics LF P/N 800569 and LF P/N 800563 at the end
of this chapter. The Display PCB is connected to the Powerhead
PCB via the ribbon cable J8. Cable J8 also provides the connec-
tion to the keyboard.
The microconiroller communicates to the
display controller through a four wire serial bus. The Display is
divided into two sections: the three digit "Syringe Size" indictor,
and the three digit "Remaining Volume/ AutoFill Volume" indicator.
The backlit symbol indicates the active function of this Powerhead
(i.e., Remaining Volume or AutoFill Volume).
The Power Pack supplies +12VDC to the powerhead.
A voitage
regulator, VR2, is used to generate +5VDC.
The linear potentiom-
eter, used for position sensing, does not travei fully to its opposite
limit (ie. OV), a voltage divider circuit consisting of R1, R4 and R18,
is used to generate reference voltages for the microcontrollers A/D.
This divider circuit produces a usable range of approximately 4.9V
(Vrh) to 0.21V (Vn). This corresponds to the range of the linear
potentiometer using the 5.0V supply. By using the linear potenti-
ometer supply to generate the A/D reference voltages the two
devices will track each other in case of voitage fluctuations.
800961-C
Nov, 2000
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