Baker Hughes Masoneilan SVI3, Инструкция по эксплуатации, Страница: 36 / 123

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3.6 Wiring the SVI3
The procedure below outlines wiring the SVI3.
3.6.1 Required Practices for Explosion Proof Installations
Please refer ES-817 Product safety manual for required practices for explosion proof
Installations. .
3.6.2 Wiring Guidelines
Guidelines for a successful implementation of DC current signal, DC power, and HART
®
communication to the SVI3:
• Compliance voltage at the SVI3 is approximately 9 V at 20 mA, 11 V @ 4 mA. See
“Split Range Applications” on page 114.
• Signal to the SVI3 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 SVI3. 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.
WARNING
• There can be unexpected valve, actuator or positioner movement at any
time during installation or operation.
• Comply with current national and local regulations for electrical installation
work.
• Comply with national and local explosive atmosphere regulations.
• Before carrying out any work on the device, power off the instrument or
make sure that the local conditions for potentially explosive atmosphere
permit the safe opening of the cover.