Fisher FIELDVUEDVC6200f Instruction Manual page 164

DVC6200f Digital Valve Controller
Principle of Operation
February 2017
As the setpoint increases, the drive signal to the I/P converter increases, increasing the I/P output pressure. The I/P
output pressure is routed to the pneumatic relay submodule. The relay is also connected to supply pressure and
amplifies the small pneumatic signal from the I/P converter. The relay accepts the amplified pneumatic signal and
provides two output pressures. With relay A, an increasing setpoint will produce increasing pressure at output A and
decreasing pressure at output B. With relay B an increasing setpoint will produce decreasing pressure at output B
(output A is not available). With relay C an increasing setpoint will produce an increasing pressure on output A (output
B is not available). 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.
Figure A‐2. FIELDVUE DVC6200f Digital Valve Controller Assembly
HOUSING
TERMINAL BOX
WITH COVER
W9925‐1
As shown in figure A‐1, the increased output A pressure causes the actuator stem to move upward. The stem position
is sensed by the travel sensor. The stem continues to move upward until the correct stem position is attained. At this
point the printed wiring board assembly stabilizes the I/P drive signal. This prevents any further increase in the
pneumatic signal from the I/P converter.
As the digital setpoint 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
downward until the correct position is attained. At this point the printed wiring board assembly stabilizes the I/P drive
signal. This prevents any decrease in the pneumatic signal from the I/P converter.
164
PRINTED WIRING
BOARD ASSEMBLY
MODULE BASE ASSEMBLY
PNEUMATIC
RELAY
I/P CONVERTER
Instruction Manual
D103412X012
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