Fisher® FIELDVUE DVC6200 Digital Valve Controller
Fisher® FIELDVUE DVC6200 Digital Valve Controller
Fisher® FIELDVUE DVC6200 Digital Valve Controller
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Principle of Operation<br />
July 2012<br />
Instruction Manual<br />
D103605X012<br />
Figure A‐2. Typical <strong>FIELDVUE</strong> Instrument to Personal Computer Connections for <strong>Valve</strong>Link Software<br />
CONTROL SYSTEM<br />
HART MODEM<br />
FIELD TERM.<br />
E1362<br />
<strong>DVC6200</strong> digital valve controllers are loop‐powered instruments that provide a control valve position proportional to<br />
an input signal from the control room. The following describes a double‐acting digital valve controller mounted on a<br />
piston actuator.<br />
The input signal is routed into the terminal box through a single twisted pair of wires and then to the printed wiring<br />
board assembly submodule where it is read by the microprocessor, processed by a digital algorithm, and converted<br />
into an analog I/P drive signal.<br />
As the input signal increases, the drive signal to the I/P converter increases, increasing the I/P output pressure. The I/P<br />
output pressure is routed to the pneumatic relay submodule. The relay is also connected to supply pressure and<br />
amplifies the small pneumatic signal from the I/P converter. The relay accepts the amplified pneumatic signal and<br />
provides two output pressures. With increasing input (4 to 20 mA signal), the output A pressure always increases and<br />
the output B pressure decreases. The output A pressure is used for double‐acting and single‐acting direct applications.<br />
The output B pressure is used for double‐acting and single‐acting reverse applications. As shown in figure A‐3 the<br />
increased output A pressure causes the actuator stem to move downward. Stem position is sensed by the non‐contact<br />
travel feedback sensor. The stem continues to move downward until the correct stem position is attained. At this point<br />
the printed wiring board assembly stabilizes the I/P drive signal. This positions the flapper to prevent any further<br />
increase in nozzle pressure.<br />
As the input signal decreases, the drive signal to the I/P converter submodule decreases, decreasing the I/P output<br />
pressure. The pneumatic relay decreases the output A pressure and increases the output B pressure. The stem moves<br />
upward until the correct position is attained. At this point the printed wiring board assembly stabilizes the I/P drive<br />
signal. This positions the flapper to prevent any further decrease in nozzle pressure.<br />
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