Rosemount Model 3144 and 3244MV Smart Temperature Transmitters
3-10
7. Select
1 Device Setup, 4 Detailed Setup, 1 Sensors, 1 Process
Sensor, 4 Sensor Setup, 5 Misc Config, 4 Avg Units
to set the
desired average temperature units.
8. Select
HOME
to return to the Home screen.
9. Select
1 Device Setup, 4 Detailed Setup, 1 Sensors, 1 Process
Sensor, 4 Sensor Setup, 1 Snsr 1 Config, 1 Snsr 1 Conn
to set the
sensor type and number of wires for Sensor 1. Repeat for
Sensor 2.
If using a meter for local indication, configure the meter to read the
appropriate variables (see “Meter Settings” on page 3-6).
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. When Hot Backup is enabled while PV is
Sensor Average, if a sensor failed occurs, three scenarios could result.
First, if Sensor 1 fails, Hot Backup is activated, and Sensor 2 replaces
Sensor Average as PV. In the second case, if Sensor 2 fails, PV will
remain mapped as Sensor Average. However, it will only be reading
from Sensor 1, the working sensor. In both of the above cases where Hot
Backup is enabled with Sensor Average as the PV the 4-20 mA signal is
not disrupted, and a message is sent to the control system, via HART,
specifying which sensor has failed. In the last case where both
transmitters fail simultaneously, the transmitter will go into alarm and
a message will be sent, via HART, stating that both Sensor 1 and
Sensor 2 have failed.
Hot Backup
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 Sensor 1
or Sensor Average
(1)
(see “Average Temperature” on page 3-9 for details
on using Hot Backup when PV is Sensor Average). You can map Sensor
2 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 message is sent to the control
system, via HART, that Sensor 1 has failed. An LCD meter, if attached,
also displays the failed sensor signal. If Hot Backup is used and the PV
is Sensor Average a Sensor 1 failure would result in Sensor 2 being
remapped as the PV. However, if Sensor 2 fails, no re-mapping will take
place, but the Sensor Average reading will only include Sensor 1—the
working sensor.
While configured to Hot Backup, if Sensor 2 fails while Sensor 1 is still
operating properly, the transmitter continues to report the PV 4–20 mA
analog output signal while sending a HART signal to the control system
that Sensor 2 has failed. Once entering the active Hot Backup mode,
the transmitter will not use the original PV (Sensor 1 or Sensor
Average) to control the 4–20 mA analog output until the Hot Backup
mode is reset. Reset Hot Backup either by re-enabling via HART or by
briefly powering down the transmitter.
Model 3244MV
HART Fast Keys
1,4,1,1,3,3
(1)
Sensor Average is not available in previous versions of the Model 3244MV transmitter.
