Baker Hughes Masoneilan SVI II AP, Быстрый старт

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. Masoneilan SVI II AP Digital Positioner Quick Start Guide
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Wiring Guidelines
Guidelines for a successful implementation of DC current signal, DC power, and HART
®
commu-
nication 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
103.
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.