Introduction
V
Introduction
The
TT302
is from the first generation of FIELDBUS devices. It is a transmitter mainly
intended for measurement of temperature using RTDs or thermocouples, but can also
accept other sensors with resistance or mV output such as: pyrometers, load cells,
resistance position indicators, etc. The digital technology used in the
TT302
enables a
single model to accept several types of sensors, an easy interface between the field and
the control room and several others features that considerably reduces the installation,
operation and maintenance costs.
FIELDBUS is not only a replacement for 4-20 mA or intelligent/smart transmitter
protocols. It contains much more. FIELDBUS is a complete system enabling distribution
of the control function to equipment in the field.
Some advantages of bi-directional digital communications are known from existing smart
transmitter protocols: higher accuracy, multivariable access, remote configuration and
diagnostics and multi-dropping of several devices on a single pair of wires. These
protocols were not intended to transfer control data, but maintain information. Therefore
they were slow and not efficient enough to be used.
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 minimum communication overhead. Using scheduling, the system
controls the variable sampling, the algorithm execution and the communication to
optimize the usage of the network, thus achieving high closed loop performance.
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 and overview complex
control strategies. Another advantage is adding flexibility, the control strategy may be
edited without having to rewire or change any hardware.
Now, thanks to Fieldbus, the transmitter accepts two channels, i.e., two measurements.
This reduces the cost per channel. Other function blocks are also available. They allow
flexibility in control strategy implementation.
The need for Fieldbus implementation 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.
Get the best result of the TT302 by carefully reading these instructions.
Summary of Contents for TT302
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Page 11: ...Installation 1 5 Figure 1 5 Tree Topology TT2EM105 CDR ...
Page 12: ...TT302 Fieldbus Temperature Transmitter 1 6 ...
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Page 38: ...TT302 Fieldbus Temperature Transmitter 4 6 ...