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INTRODUCTION
The IF302 is a converter mainly intended to interface analog transmitters to a F
OUNDATION™
fieldbus network. The IF302 receives up to three current signal typically 4-20 mA or 0-20 mA, and
makes them available to Fieldbus system. The digital technology used in the IF302 enables an easy
interface between the field and the control room and it has several interesting features that reduce
considerably the installation, operation and maintenance costs.
The IF302 is part of SMAR's complete 302 line of FOUNDATION™ fieldbus devices.
F
OUNDATION™ fieldbus, is not only a replacement for 4-20 mA or intelligent/smart transmitter
protocols, it contains much more. F
OUNDATION™ fieldbus is a complete system enabling distribution
of the control function on equipment in the field.
Some of the advantages of bi-directional digital communications are known from existing smart
transmitter protocols: Higher accuracy, multi-variable access, remote configuration and diagnostics,
and multi-dropping of several devices on a single pair of wires.
Those protocols were not intended to transfer control data, but maintenance information. Therefore
they were slow and not efficient enough to be used as control network.
The main requirements for Fieldbus were to overcome these problems. Closed loop control with
performance like a 4-20 mA system requires higher speed. Since higher speed means higher power
consumption, this clashes with the need for intrinsic safety. Therefore a moderately high
communication speed was selected, and the system was designed to have a minimum of
communication overhead. Using scheduling, the system controls variable sampling, algorithm
execution and communication to optimize the usage of the network, not loosing time. Thus, high
closed loop performance is achieved.
Using Fieldbus technology, with its capability to interconnect several devices, very large control
schemes can be constructed. In order to be user friendly the function block concept was introduced
(users of SMAR CD600 should be familiar with this, since it was implemented several years ago).
The user may now easily build complex control strategies. Another advantage is added flexibility;
the control strategy may be edited without having to rewire or change any hardware.
The IF302, like the rest of the 302 family, has several Function Blocks built in, like PID controller,
Input Selector, Arithmetic, Signal Characterizer and Flow Totalization. These useful blocks eliminate
the need for separate devices and reduce communication and therefore decreasing dead-time and
making the control tighter, not to mention the reduction in cost. Other function blocks are also
available, allowing flexibility in control strategy implementation.
The need for implementation of Fieldbus in small as well as large systems was considered when
developing the entire 302 line of Fieldbus devices. They have the common features of being able to
act as a master on the network and be configured locally using a magnetic tool, eliminating the need
for a configurator or console in many basic applications.
Get the best result of the IF302 by carefully reading these instructions.
This product is protected by US patent number 5,706,007.
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