Instruction Manual

Principle of Operation
September 2013
A-3
Figure A-3. FIELDVUE DVC6000 SIS Digital Valve Controller Block Diagram
E0408
INPUT SIGNAL
4−20 mA
+
HART
SUPPLY PRESSURE
PRINTED
WIRING BOARD
PNEUMATIC
RELAY
I/P
CONVERTER
OUTPUT A
OUTPUT B
AUXILIARY
TERMINALS
TERMINAL BOX
DRIVE
SIGNAL
VALVE AND ACTUATOR
VALVE TRAVEL FEEDBACK
double-acting and single-acting reverse applications.
For single-acting actuators, unused ports can also be
used to monitor the actuator pressure if any
accessories are used in the output of the digital valve
controller. As shown in figure A-3 the increased output
A pressure causes the actuator stem to move
downward. Stem position is sensed through the
feedback linkage by the travel sensor which is
electrically connected to the printed wiring board
assembly submodule. 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 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.
Safety Instrumented System
Applications
The principle of operation of the DVC6000 SIS is the
same for safety instrumented system applications as
for process applications. However, when used in a
safety instrumented system application the DVC6000
SIS can be configured for two output positions.
Depending on relay action (direct or reverse) the
DVC6000 SIS can be configured for full pneumatic
output during normal operation and minimum output
during trip condition, or vice versa.
A