Reference Manual
00809-0100-4021, Rev FB
August 2011
3-15
Rosemount 3144P
HAR
T
5. Select
OK
to return the control loop to automatic control.
6. Select
HOME
to return to the Online menu.
7. Select
1 Device Setup, 3 Configuration, 3 dual sensor configuration, 2
average, 1 avg units
to set the desired average temperature units.
8. Select
HOME
to return to the Home screen.
If using an LCD display, configure it to read the appropriate variables using
“LCD Display Options” on page 3-21.
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.
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
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.
Traditional Fast Keys
1, 3, 1, 5, 5
Device Dashboard Fast Keys
2, 2, 3, 3
Aotewell Ltd
www.aotewell.com
Industry Automation
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