Emerson Rosemount 56, Instruction Manual

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Section 11: HART Communications Instruction Manual
April 2017 LIQ-MAN-56
88 HART Communications
11.2 Physical Installation and Configuration
11.2.1 HART Wiring and Output Configuration
HART communications is superimposed on Analog Output 1 for all of the measurements and
parameters of the 56. The 4-20 mA current of Analog Output 1 can be configured by the
keypad display to be powered by the 56 (Output 1 power: Internal), or by an external 24 VDC
power supply, or an I/O that provides power (Output 1 power: External).
11.2.2 HART Multidrop (Bus) Configuration
The HART Polling Address should be left at its default value of “0”, unless the 56 is used in a
Multidrop configuration with up to 14 other transmitters. When the Polling Address is
greater than “0”, the 4-20 mA output is held at 4 mA or below, and does not change in
response to changes in the measurement in HART 5.
In HART 7, Loop Current Mode should be set to “On” to hold the current output to a
minimum value. In both HART 5 and HART 7, Output Power should be set to “External” so that
an external 24 VDC power supply can be used to power the multidrop bus.
11.2.3 HART Configuration
To access the HART Configuration screens, press the “HART” button in the Main Menu. The
following controls are available:
HART Configuration Screen 1: Basic Definitions
• Host HART mode – toggles between HART version 5 and HART version 7. If the HART
host being used can accommodate HART 7, HART 7 should be chosen due to its larger
feature set. If the host can only use HART 5, then HART 5 must be chosen.
NOTE: If the 56 is connected to a HART host and the HART version is changed, the host
will likely detect the transmitter as a new transmitter with a different device revision
number.
• Tag – The traditional 8 character HART tag number
• Long tag – HART tag number of up to 32 characters (HART 7 only).
• Polling address – Choose “0” unless Multidrop is being used. If Multidrop is being
used, each transmitter should have its own polling address of from 1 to 15.
• Loop current mode – Set Output 1 current to a minimum value for multidrop applica-
tions (HART 7 only).