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44
Reference Manual
00809-0100-4021, Rev JA
HART Commissioning
April 2017
HART Commissioning
First good configuration
Field Communicator
The first good
device variable is useful for applications where dual-sensors (or a single dual element
sensor) are used in a single process. The first good variable will report the sensor 1 value, unless sensor 1
fails. When sensor 1 fails, the sensor 2 value will be reported as the first good variable. Once the first
good variable has switched to sensor 2, it will not revert back to sensor 1 until a master reset occurs or
“Suspend Non-PV alarms” is disabled. When the PV is mapped to first good variable and either sensor 1
or sensor 2 fails, the analog output will go to the alarm level, but the digital PV value read through the
HART Protocol interface will still report the proper first good sensor value.
If the user does not want the transmitter to go into analog output alarm when the PV is mapped to first
good and Sensor 1 fails, enable “Suspend Non-PV Alarm” mode. This combination prevents the analog
output from going to the alarm level unless BOTH sensors fail.
Hot Backup feature configuration
Field Communicator
The
config hot BU command configures the transmitter to automatically use sensor 2 as the primary
sensor if sensor 1 fails. With the Hot Backup feature enabled, the primary variable (PV) must either be
first good or sensor average. See
“Average temperature” on page 43
for details on using the Hot Backup
feature when PV is sensor average. Sensors 1 or 2 can be mapped as the secondary variable (SV), tertiary
variable (TV), or quaternary variable (QV). In the event of a primary variable (Sensor 1) failure, the
transmitter enters the Hot Backup feature mode and sensor 2 becomes the PV. The 4–20 mA signal is
not disrupted, and a status is available to the control system through HART Protocol that sensor 1 has
failed. An LCD display, if attached, displays the failed sensor status.
While configured to the Hot Backup feature, if sensor 2 fails but sensor 1 is still operating properly, the
transmitter continues to report the PV 4–20 mA analog output signal, while a status is available to the
control system through HART Protocol that sensor 2 has failed. In the Hot Backup feature mode, the
transmitter will not revert back to sensor 1 to control the 4–20 mA analog output, until the Hot Backup
feature mode is reset by either re-enabling through HART Protocol or by briefly powering down the
transmitter.
For information on using the Hot Backup feature in conjunction with the HART Tri-Loop
Problem description: The unexpected failure of a critical temperature measurement can cause safety
issues, environmental or regulatory concerns, and process shutdowns.
Our solution: The Hot Backup feature allows the transmitter to automatically switch the transmitter
input from the primary sensor to the secondary sensor should the primary sensor fail. This prevents a
process disruption due to the failure of the primary sensor. A maintenance alert is also generated to
notify operators that a sensor has failed and the Hot Backup feature is active.
HART 5 Fast Keys
2, 2, 3, 2
HART 7 Fast Keys
2, 2, 3, 2
HART 5 Fast Keys
2, 2, 4, 1, 3
HART 7 Fast Keys
2, 2, 4, 1, 3
Содержание Rosemount 3144P
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