Reference Manual
00809-0100-4021, Rev FB
August 2011
Rosemount 3144P
3-16
HART
Hot Backup 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 Hot Backup
enabled, the primary variable (PV) must either be First Good or Sensor
Average. See “Average Temperature” on page 3-14 for details on using
Hot Backup 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 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. In Hot Backup mode, 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 either re-enabling through
HART or by briefly powering down the transmitter.
To set up and enable the Hot Backup feature for the 3144P transmitter with
the Traditional Fast Key sequence:
1. Attach any two sensors to the transmitter as shown in Figure 2-12 on
page 2-13.
2. From the Home screen, select 1 Device Setup, 3 Configuration, 1
Variable Mapping, 5 Variable Re-map to set primary, secondary, tertiary,
and quaternary variables. The communicator displays the PV, SV, TV,
and QV menus in succession.
3. Set PV as First Good or Sensor Average; set secondary, tertiary, and
quaternary variables as desired.
4. After verifying the variable settings from the Variable Mapping menu
select OK.
5. To return the control loop to automatic control select OK. Select HOME
to return to the Home screen.
6. From the Home screen, select 1 Device Setup, 3 Configuration, 2
Sensor Configuration, 1 Change Type and Conn, 3 Sensor 1 Setup to
configure Sensor 1.
7. Set the sensor type, number of wires, damping, and units for Sensor 1.
8. Select SEND to download the new data to the transmitter. Select HOME
to return to the Home screen.
9. Repeat Steps 5, 6, and 7 for Sensor 2 using 4 Sensor 2 Setup.
Traditional Fast Keys 1, 3, 3, 4
Device Dashboard Fast Keys 2, 2, 4, 1, 3
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