Instruction Manual

DVC6000 SIS
September 2013
A-2
Figure A-1. HART Frequency Shift Keying Technique
−0.5 V
+0.5 V
1200 Hz
“1”
2200 Hz
“0”
AVERAGE CURRENT CHANGE DURING COMMUNICATION = 0
ANALOG
SIGNAL
0
A6174
HART Communication
The HART (Highway Addressable Remote
Transducer) protocol gives field devices the capability
of communicating instrument and process data
digitally. This digital communication occurs over the
same two-wire loop that provides the 4-20 mA process
control signal, without disrupting the process signal. In
this way, the analog process signal, with its faster
update rate, can be used for control. At the same time,
the HART protocol allows access to digital diagnostic,
maintenance, and additional process data. The
protocol provides total system integration via a host
device.
The HART protocol uses frequency shift keying (FSK).
Two individual frequencies of 1200 and 2200 Hz are
superimposed over the 4-20 mA current signal. These
frequencies represent the digits 1 and 0 (see figure
A-1). By superimposing a frequency signal over the
4-20 mA current, digital communication is attained.
The average value of the HART signal is zero,
therefore no DC value is added to the 4-20 mA signal.
Thus, true simultaneous communication is achieved
without interrupting the process signal.
The HART protocol allows the capability of
multi-dropping, i.e., networking several devices to a
single communications line. This process is well suited
for monitoring remote applications such as pipelines,
custody transfer sites, and tank farms. See table 7-2
for instructions on changing the printed wiring board
DIP switch configuration to multi-drop.
Digital Valve Controller Operation
The DVC6000 SIS digital valve controller housing
contains the travel sensor, terminal box, pneumatic
input and output connections and a module base that
may be easily replaced in the field without
disconnecting field wiring or tubing. This master
module contains the following submodules: I/P
Figure A-2. Typical FIELDVUE Instrument to Personal
Computer Connections for ValveLink Software
FIELD
TERM.
CONTROL SYSTEM
HART
MODEM
A6761
converter, printed wiring board (pwb) assembly, and
pneumatic relay. The module base can be rebuilt by
replacing the submodules. See figures A-3 and A-4.
Process Applications
DVC6000 SIS digital valve controllers are
loop-powered instruments that provide a control valve
position proportional to an input signal from the control
room. The following describes a double-acting
DVC6010 SIS digital valve controller mounted on a
piston actuator.
The input signal is routed into the terminal box through
a single twisted pair of wires and then to the printed
wiring board assembly submodule where it is read by
the microprocessor, processed by a digital algorithm,
and converted into an analog I/P drive signal.
As the input signal 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 increasing input (4 to 20
mA signal), the output A pressure always increases
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
A