Baker Hughes Masoneilan SVIII AP, Installation And Maintenance Manual, Page: 107 / 204

Masoneilan SVI II AP Installation and Maintenance Manual =
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Wiring Guidelines
Guidelines for a successful implementation of DC current signal, DC power, and HART
®
communication to the SVI II AP:
Compliance voltage at the SVI II AP is approximately 9 V at 20 mA, 11 V @ 4 mA. See
“Determining an SVI Positioner Compliance Voltage in a Control System” on page 199.
Signal to the SVI II AP must be a regulated current in the range 3.2 to 22 mA.
Controller output circuit must be unaffected by the HART
®
tones which are in the
frequency range between 1200 and 2200 Hz.
In the frequency range of the HART
®
tones, the controller must have a circuit
impedance of more than 220 Ohms, typically 250 Ohms.
HART
®
tones may be imposed by the positioner and a communication device located
anywhere on the signaling circuit.
Cabling must be shielded to prevent electrical noise that would interfere with the
HART
®
tones, with the shield grounded.
Shield must be properly grounded in only one place.
For details and calculation methods for wiring resistance, and capacitance and for
calculation of cable characteristics, refer to the HART
®
FSK Physical Layer
Specification.
For split range installations the output voltage must be sufficient to operate two
positioners (11 V @ 4 mA, 9 V @ 20 mA) and the expected voltage drop in the cable.
Use of a low impedance voltage source damages the SVI II AP. The current source must
be a true high impedance current limiting device. A proper current source explicitly
enables adjustment of the current, not the voltage.
When wiring a position retransmit:
Use the same gauge wires as the 4-20 mA control loop.
Ensure that the position retransmit signal is connected to the control system’s
analog input card.
Ensure the control loop is powered while making make measurements with a meter.