Emerson Rosemount 644 Reference Manual page 30

Configuration
March 2021
2.7.3 Hot Backup configuration
The Hot Backup
primary sensor if Sensor 1 fails. With Hot Backup enabled, the primary variable (PV) must
either be first good or average. See the
is set to 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 Hot Backup 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
has failed. An LCD display, if attached, displays the failed sensor status.
While configured to Hot Backup, 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 that Sensor 2 has failed.
Resetting Hot Backup
In Hot Backup
not revert back to Sensor 1 to control the 4–20 mA analog output until the Hot Backup
mode is reset by re-enabling through HART
powering down the transmitter.
Configure Hot Backup using Field Communicator
The Field Communicator will walk you through a method to correctly configure the
necessary elements of the Hot Backup feature.
From the HOME screen, enter the Fast Key sequence.
Device Dashboard Fast Keys
Configure Hot Backup using AMS Device Manager
Procedure
1. Right click on the device and select Configure.
2. In the left navigation pane select Manual Setup.
3. On the Diagnostics Tab find the Hot Backup group box.
4. Choose the button Configure Hot Backup or Reset Hot Backup depending on the
5. Select Apply when complete.
Configure Hot Backup using LOI
To configure Hot Backup
Figure 2-12
30
™
feature configures the transmitter to automatically use Sensor 2 as the
™
mode, if Sensor 1 does fail and Hot Backup is initiated, the transmitter will
desired function and walk through the guided steps.
™
on the LOI, enable the mode and set the PV values. Reference
for where to find these in the menu.
Note for details on using Hot Backup when the PV
®
, re-setting it through the LOI or by briefly
2, 1, 5
Reference Manual
00809-0200-4728
®
that Sensor 1
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