Emerson Rosemount 644, Reference Manual

Page: 34 / 182

24
Reference Manual
00809-0200-4728, Rev RA
Section 2: Configuration
April 2015
Configuration
Figure 2-11. Configuring Hot Backup with LOI
* Available only if option code (S) or (D) is ordered.
** Available only if option codes (S) and (DC) are both ordered, or if option codes (D) and (DC) are both ordered.
For information on using Hot Backup in conjunction with the HART Tri-Loop
™
see “Using the
transmitter with the HART Tri-Loop” on page 42 .
2.7.4 Sensor drift alert configuration
The sensor drift alert command allows the transmitter to set a warning flag (through HART), or
go into analog alarm when the temperature difference between sensor 1 and sensor 2 exceeds a
user-defined limit.
This feature is useful when measuring the same process temperature with two sensors, ideally
when using a dual-element sensor. When sensor drift alert mode is enabled, the user sets the
maximum allowable difference, in engineering units, between sensor 1 and sensor 2. If this
maximum difference is exceeded, a sensor drift alert warning flag will be set.
Though it defaults to WARNING, when configuring the transmitter for sensor drift alert, the user
also has the option of specifying the analog output of the transmitter go into ALARM when
sensor drifting is detected.
Note
Using dual sensor configuration in the 644, the temperature transmitter supports the
configuration and simultaneous use of Hot Backup and sensor drift alert. If one sensor fails, the
transmitter switches output to use the remaining good sensor. Should the difference between
the two sensor readings exceed the configured threshold, the AO will go to alarm indicating the
sensor drift condition. The combination of sensor drift alert and Hot Backup improves sensor
diagnostic coverage while maintaining a high level of availability. Refer to the 644 FMEDA report
for the impact on safety.
Sensor drift alert configuration with a Field Communicator
The Field Communicator will walk you through a method to correctly configure the necessary
elements of a sensor drift alert feature.
From the HOME screen, enter the Fast Key sequence.
Device Dashboard Fast Keys
2, 1, 6
CALIBRAT
DAMPING
VARIABLE MAP
TAG
ALM SAT VALUES
PASSWORD
SIMULATE
HART REV
HOT BACK CONFIG** HOT BACK CONFIG**
DRIFT ALERT**
....
HOT BACK MODE
HOT BACK PV
HOT BACK RESET
BACK TO MENU
EXIT MENU
VIEW CONFIG
SENSOR CONFIG
UNITS
RERANGE
LOOP TEST
DISPLAY
EXTENDED MENU EXTENDED MENU
EXIT MENU