ABB 691HT Operating Instructions Manual Download Page 5

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Multidrop connection
The Hand Held Communicator can be connected via its
leads at any point of the current loop : the connection
shall be made in parallel to the multidrop connected-
transmitters, as shown in the figure below, and is
polarity indipendent. Also in this case, a resistor of
250 ohm minimum must be present in the loop,
between the Communicator and the power supply
for communication purpose.

The power supply should provide a minimum voltage of
12 Volt at the transmitters terminals and supply a
current of 4 mA for each transmitter connected. A
maximum of 15 transmitters can be connected in
multidrop mode.

- broadcasting : connection to several transmitters

using a suitable interface that provides a separation
between the analog signals coming from the different
transmitters and the HART digital communication.
Also in this case the access to an individual transmitter
is possible using the TAG. With this type of connection
each transmitter maintains it's analog output and the
full functionality of the transmission loop is maintained.
The operations on transmitters are the same as
indicated for the direct connection.

Broadcasting connection
In the broadcasting configuration the connection can be
made in any point of the common Bell 202 link between
the interface modules and the modem module.
This connection being not directly branched with a low
impedance power supply, no additional resistors are
required.

This manual covers the use of the Hand Held Commu-
nicator in direct, multidrop or broadcasting mode and
gives general information for the use in serial and
modem modes. In these two modes the Communicator
is in slave mode with all the operations performed by the
Personal Computer. The operations that can be
performed using a Personal Computer have still to be
defined. The Software that is going to be adopted will be
probably the SMART VISION! Please refer also to the
Operating Instructions of the Smart ABB pressure and
temperature transmitters for the general and specific
informations on this products.

The Communicator can be used in several different
ways to fullfill the needs of commissioning and mainta-
nance of a HART transmitter:

- direct : the Communicator is directly connected to

the transmitter, either in the field or on the laboratory
bench and the plant engineer may use it to configure,
calibrate or check the connected instrument. Up to 32
different configurations can be saved in the
Communicator memory: you can use a personal com-
puter based software (e.g. the SMART VISION) for
database management.

Transmitter direct connection
The Hand Held Communicator can be connected via its
leads at any point of the current loop : the connection
shall be made in parallel to the transmitter and is
polarity independent. Do not connect the Communica-
tor in series in the current loop: this will not damage the
instrument but the current loop will be interrupted.

NOTE - A resistor of 250 ohm minimum must be
present in the loop, between the Communicator and
the power supply for communication purpose.
If the resistor is represented by the intrinsic safety
barrier and the connection is made in the hazardous
area side of the barrier, any possible precaution must
be taken to avoid hazard via the leads or operator.
The insertion or the removal of the Communicator does
not disturb the operation of the loop, whether the instru-
ment is working ( ON ) or not ( OFF ).

- multidrop : the Communicator is multidrop connected

to several transmitters and the access to each
transmitter is possible using the TAG name.
The operation on transmitters are the same indicated
for the direct connection. Note that in multidrop
connection the analog output of each transmitter is
locked to 4 mA and the process value is transmitted
through digital signal.

Power
Supply

≥

250 Ohm

Control Room Field

691HT

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