Masoneilan SVI II AP Digital Positioner Quick Start Guide
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Connecting to the Control Loop
The SVI II AP digital valve positioner
MUST BE
grounded according to local regulations. It is im-
portant to maintain correct polarity at all times, otherwise the positioner may not operate prop-
erly. Physically connect the SVI II AP to the HART
®
loop using a cable specified by the HART
®
Communication Foundation. A shielded cable is recommended. To connect the Control Loop to
the SVI II AP:
1. Connect one end of the cable to the control loop's 4 - 20mA output
2. Remove the threaded wiring covers on the positioner.
3. Connect the other end of the cable to the SVI II AP. There are two threaded
openings on the positioner. Use the opening with the red plastic insert.
4. Maintain po and - respectively.
Wiring Guidelines
This list contains guidelines for a successful implementation of DC current signal, DC power, po-
sition Retransmit and HART
®
communication to the SVI II AP:
Compliance voltage at the SVI II AP must be 9 V at the maximum current of
20 mA.
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.
Frequency range of the HART
®
tones 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.
Capacitance of the signaling circuit must not exceed 0.26 microfarads or
0.10 microfarads with high series resistance.
Cabling must be shielded to prevent electrical noise that would interfere with
the HART
®
tones, with the shield grounded.
Signal must be properly grounded in only one place.
Position Retransmit: when wiring this feature:
Wire using the same gauge wire as for the 4-20 mA control loop.
In general, ensure that it is connected to the control system’s analog systems
card.
Ensure the control loop is powered when using a meter to make any
measurements.
NOTE
For details and calculation methods for wiring resistance, and
capacitance and for calculation of cable characteristics, refer to
the HART
®
FSK Physical Layer Specification.