Flowserve 2000 Series Digital Positioner - Manual (Page 3)

42-3
Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611
Electronics Module
with Keypad and
Local Display
Air Lines to
Cylinder Actuator
User Access
Terminal
Behind
Lower Door
Temperature
Sensor
Process Pressure Sensors
Electronics
Conduit
Position
Feedback
Arm
Figure 2: StarPac II / Logix 2000 Intelligent Control System Components
only at the source. The input power is isolated within the
unit and may be referenced to whatever level is neces-
sary.
The 24 VDC power supply should not be
connected to earth ground.
RS-485 Communication
RS-485 wiring requires the use of a shielded twisted
pair cable, which is grounded only at the source and not
in the unit. (For maximum performance, wire should
have a characteristic impedance of 120 ohms.) The
RS-485 input is fully isolated, using opto-isolators.
The RS-485 allows only a 7 to 12 V common mode
voltage differential between stations. Valtek's RS-232
to RS-485 converter is not a grounded connection.
PC's with internal RS-485 cards, on the other hand, are
often grounded. If another ground communication
device is on the network, a fault condition will almost
certainly exist due to transient and steady state differ-
ences in ground potential.
4 - 20 mA Command Input, Auxiliary Input, and
Feedback Output
These signals are isolated but shielded twisted pair wire
should be used to reduce crosstalk from other signals.
The shield should be connected only at the source.
Discrete Inputs and Outputs
These signals are isolated, but because they are fre-
quently used to switch high voltage (120 VAC), they
should be run in separate shielded wire paths away
from the other StarPac II / Logix 2000 signals.
AIB and RS-232 to RS-485 Converter Connection
When connecting a StarPac II / Logix 2000 unit to a
communication device, no shield or ground connec-
tions exist. Hence, the 24 VDC power and RS-485
communication shield drain wires must be connected to
a convenient ground near the AIB or converter.
Wiring The StarPac II / Logix 2000 System
All electrical connections must be done according to
local and industry electrical codes. Valtek recommends
a shielded cable be used for the RS-485 command
signal wire (e.g., Belden 9841 or equivalent).
When connecting multiple StarPac II / Logix 2000 units,
a parallel daisy-chain wiring pattern is used. Connect
unit's branch lines to main line, keeping branch lines as
short as possible. The total length of wiring should not
exceed 4,000 feet (1,200 meters) without use of repeaters.
Avoid devices producing electrical 'noise' while install-
ing the cable.
CAUTION: The following procedure should be per-
formed on the bench or with the unit isolated so that
unexpected valve stroking will not adversely affect
the process.
WARNING: The following procedures may cause
the valve to stroke, causing pressures and tem-
peratures to vary from their norms. Notify appropri-
ate personnel that the valve may stroke unexpect-
edly. Valtek suggests that the system be isolated
from the process, if installed in line.