Filter
Top Products
Reference Manual
00809-0100-4021, Rev DA
November 2004
3-11
Rosemount 3144P
HART
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, when PV is Sensor Average it is recommended 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, where Hot Backup is enabled with PV set to Sensor
Average, the 4-20 mA signal is not disrupted and the status available to the
control system (via HART) specifies which sensor has failed.
AMS
For AMS, configure each sensor as indicated above.
Right click on the device and select “Configuration Properties” from the
menu. Select the Dual Sensor tab to configure the Average
Temperature.In the Average Temperature box, Set the Ave Units to the
desired output. Set damping if applicable.
Apply changes made (see “Apply AMS Changes” on page 3-5).
First-Good Configuration
The First Good device variable is useful for applications in which
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 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 it is desired that the transmitter not go into analog output alarm while
having the PV mapped to first good and Sensor 1 fails, enable “Suspend
Non-PV Alarm” mode. This combination will prevent the analog output
from going to the alarm level unless BOTH sensors fail.
AMS
For AMS, configure each sensor as indicated above.
Right click on the device and select “Configuration Properties” from the
menu. Select the Dual Sensor tab to configure the 1st Good. In the 1st
Good box, set the 1st Good Units to the desired output. Set damping if
applicable.
HART Fast Keys 1, 3, 1, 5, 5