18
Reference Manual
00809-0200-4728, Rev SA
Configuration
July 2018
Configuration
Note
If Sensor 1 and/or Sensor 2 should fail while PV is configured for average temperature and Hot Backup is
not enabled, the transmitter will go into alarm. For this reason, it is recommended when PV is Sensor
Average, that Hot Backup be enabled when dual-element sensors are used, or when two temperature
measurements are taken from the same point in the process. If a sensor failure occurs when Hot Backup
is enabled, while PV is Sensor Average, three scenarios could result:
If Sensor 1 fails, the average will only be reading from Sensor 2, the working sensor
If Sensor 2 fails, the average will only be reading from Sensor 1, the working sensor
If both sensors fail simultaneously, the transmitter will go into alarm and the status available (via
HART) states that both Sensor 1 and Sensor 2 have failed
In the first two scenarios, the 4–20 mA signal is not disrupted and the status available to the control
system (via HART) specifies which sensor has failed.
2.7.3 Hot Backup configuration
The Hot Backup feature configures the transmitter to automatically use Sensor 2 as the primary sensor if
Sensor 1 fails. With Hot Backup enabled, the primary variable (PV) must either be first good or average.
See the “NOTE” directly above for details on using Hot Backup when the PV is set to 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 that Sensor 1 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 mode, if Sensor 1 does fail and Hot Backup is initiated, the transmitter will 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, re-setting it through the LOI or by briefly powering down the transmitter.
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.
AMS Device Manager
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 desired function
and walk through the guided steps.
5. Select Apply when complete.
Device Dashboard Fast Keys
2, 1, 5
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