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Reference Manual
00809-0100-4697, Rev EA
October 2011
3-3
Rosemount 848T
Alarms Use the following steps to configure the alarms, which are located in the
Resource Function Block.
1. Set the resource block to OOS.
2. Set WRITE_PRI to the appropriate alarm level (WRITE_PRI has a
selectable range of priorities from 0 to 15, see “Alarm Priority Levels”
on page 3-11. Set the other block alarm parameters at this time.
3. Set CONFIRM_TIME to the time, in
1
/32 of a millisecond, that the
device will wait for confirmation of receiving a report before trying
again (the device does not retry if CONFIRM_TIME is 0).
4. Set LIM_NOTIFY to a value between zero and MAX_NOTIFY.
LIM_NOTIFY is the maximum number of alert reports allowed before
the operator needs to acknowledge an alarm condition.
5. Enable the reports bit in FEATURES_SEL. (When Multi-bit alerts is
enabled, every active alarm is visible for any of the eight sensors,
generated by a PlantWeb alert. This is different than only viewing the
highest priority alarm.)
6. Set the resource block to AUTO.
For modifying alarms on individual function blocks (AI or ISEL blocks), refer to
Appendix D: Function Blocks.
Damping Use the following steps to configure the damping, which is located in the
Transducer Function Block.
1. Set Sensor Mode to Out of Service.
2. Change DAMPING to the desired filter rate (0.0 to 32.0 seconds).
3. Set Sensor Mode to In Service.
Configure the Differential
Sensors
Use the following steps to configure the Differential Sensors:
1. Set Dual Sensor Mode to Out of Service.
2. Set Input A and Input B to the sensor values that are to be used in the
differential equation diff = A–B. (NOTE: Unit types must be the same.)
3. Set the DUAL_SENSOR_CALC to either Not Used, Absolute, or
INPUT A minus INPUT B.
4. Set Dual Sensor Mode to In Service.
Configure Measurement
Validation
Use the following steps to configure Measurement Validation:
1. Set mode to Disabled for specific sensor.
2. Select sample rate. 1-10 sec/sample is available. 1 second/sample is
preferred for sensor degradation. The higher the number of seconds
between samples, the more emphasis put on process variation.
3. Select Deviation Limit from 0 to 10 units. If deviation limit is exceeded,
a status event will be triggered.
4. Select Increasing Limit. Sets the limit for increasing rate of change. If
limit is exceeded, a status event will be triggered.
5. Select Decreasing Limit. Sets the limit for decreasing rate of change.
If limit is exceeded, a status event will be triggered.
NOTE:
The decreasing limit selected is required to be a negative value.