THEORY OF OPERATION
4-21
Versapulse Select Service Manual
0621-499-01 01/94
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4.4.9 Fiber and Blast Shield Position Sense Circuits
Refer to the Fiber and Blast Shield Position Sense Simplified Diagram (figure 4.7) and to the associated
schematics in Section 8. The Versapulse Selectwill not allow treatment delivery if it senses that the blast shield
is not inserted or that a fiber is not properly attached.
The blast shield position is sensed by a microswitch that closes when the blast shield is properly inserted. A
ground from the Shutter PCB is applied through the microswitch, back through the Shutter PCB and on to the
main processor digital I/O through U98-2 on the CPU PCB (BLST SHLD). The BLST SHLD signal is high
when the blast shield is properly inserted.
Correct fiber attachment is important to insure proper Z position of the focusing lens in relation to the end of
the fiber. As the fiber is screwed onto the SMA connector, it forces a spring loaded cover plate inwards
towards the fiber focus assembly. Whenthe fiber is completely screwed down it provides two separate
electrical indications:
The cover plate activates a microswitch, causing the switch to open. The switch open removes ground
from the FIBER SW N.C.. The FIBER SW N.C. line goes through the Shutter PCB to the CPU PCB ((J1-
15) where it is inverted to become the /FBRSNC/ signal, a main processor digital I/O input.
The cover plate physically contacts the SMA connector and fiber focus assembly housing, completing
an electrical connection to ground for the FIBER NO line. The FIBER NO line is inverted to become /
FBRSNO/, a main processor digital I/O input.
P/O CPU PCB
Fiber Focus
Assembly
FBR SW N.C.
FBR SW N.O.
BLST SHLD
BLAST SHIELD
COVER PLATE
MµP
DIO
FIBER
P/O Shutter PCB
FIGURE 4.7 FIBER & BLAST SHIELD POSITION SENSE SIMPLIFED DIAGRAM
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