Appendix C. Hart® Wiring Configurations; Overview; System Connections - GE Masoneilan SVI II ESD Installation And Maintenance Manual

Appendix C. HART

Overview

The SVI II ESD is used as a current loop device drawing power and analog input signal from a
precision current source. This section describes wiring configurations using HART
communications operating in 4 - 20 mA current mode.

System Connections

All system connections must comply with the HART
For complete technical information refer to HART
Number HCF-SPEC-11 and references. The SVI II ESD is a HART
It is therefore a 4 - 20 mA receiver, and cannot have a voltage source applied to its input
terminals.
When installing the SVI II ESD in a 4 - 20 mA current loop, the engineer designing the loop must
consider a set of conflicting electrical requirements. The control signal to the positioner is a 4 -
20 mA current generated by the controller or from the DCS and transmitted to the positioner
located remotely in the field. The electrical characteristics of a current loop sending a signal to
the field device are different from the apparently similar loop bringing a signal to a controller
from a transmitter in the field.
The positioner receives its power from the current signal. It receives its control setpoint from the
value of the current and must be able to communicate bi-directionally by superimposing signal
tones upon the current signal without distorting the current signal itself. Tones are unaffected by
the electrical characteristics of the current signaling device. All these conflicting requirements
must comply with equipment manufactured by different manufacturers, and working long
cables, in a noisy hostile plant environment. Energy levels are often limited for safe installation in
explosive environments. Special engineering may be required to meet signaling requirements at
low energy levels in such an environment.
The following does not cover all cases. That is beyond the scope of this instruction manual. It
suffices to explain the requirements as a guideline to obtain necessary components from many
sources for a successful installation.
© 2016 General Electric Company. All rights reserved.
®
Wiring Configurations
Masoneilan SVI II ESD Installation and Maintenance Manual
®
Communications Protocol Specifications.
®
Communications Foundations Document
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compliant device Actuator type.
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