Fisher FIELDVUE DVC6200 Instruction Manual page 97

INPUT SIGNAL
4−20 mA
+
HART
TERMINAL BOX
AUXILIARY
TERMINALS
VENT
E1361
and the output B pressure decreases. The output A
pressure is used for double-acting and single-acting
direct applications. The output B pressure is used for
double-acting and single-acting reverse applications.
As shown in figure A-3 the increased output A
pressure causes the actuator stem to move
downward. Stem position is sensed by the non-contact
travel feedback sensor. The stem continues to move
downward until the correct stem position is attained. At
this point the printed wiring board assembly stabilizes
the I/P drive signal. This positions the flapper to
September 2010
PRINTED
WIRING BOARD
DRIVE
SIGNAL
I/P
CONVERTER
PNEUMATIC
RELAY
Figure A-3. FIELDVUE DVC6200 Digital Valve Controller Block Diagram
Principle of Operation
OUTPUT A
SUPPLY
PRESSURE
OUTPUT B
prevent any further increase in nozzle pressure.
As the input signal decreases, the drive signal to the
I/P converter submodule decreases, decreasing the
I/P output pressure. The pneumatic relay decreases
the output A pressure and increases the output B
pressure. The stem moves upward until the correct
position is attained. At this point the printed wiring
board assembly stabilizes the I/P drive signal. This
positions the flapper to prevent any further decrease in
nozzle pressure.
VALVE TRAVEL FEEDBACK
VALVE AND ACTUATOR
89
A