Low Cutoff; Process Alarms; Alarm Priority - Emerson Rosemount 3051S Series Reference Manual

Configuration
October 2016
Note
The AI Block has it's own filtering parameter called PV_FTIME. For simplicity, it is better to do filtering in
the Transducer Block as damping will be applied to primary value on every sensor update. If filtering is
done in AI block, damping will be applied to output every macrocycle.
3.7.5

Low cutoff

When the converted input value is below the limit specified by the LOW_CUT parameter, and the Low
Cutoff I/O option (IO_OPTS) is enabled (True), a value of zero is used for the converted value (PV). This
option is useful to eliminate false readings when the differential pressure measurement is close to zero,
and it may also be useful with zero-based measurement devices such as flowmeters.
Note
Low cutoff is the only I/O option supported by the AI Block. Set the I/O option in Manual or Out of Service
mode only.
3.7.6

Process alarms

Process alarm detection is based on the OUT value. Configure the alarm limits of the following standard
alarms:
High (HI_LIM)

High high (HI_HI_LIM)

Low (LO_LIM)

Low low (LO_LO_LIM)

In order to avoid alarm chattering when the variable is oscillating around the alarm limit, an alarm
hysteresis in percent of the PV span can be set using the ALARM_HYS parameter. The priority of each
alarm is set in the following parameters:
HI_PRI

HI_HI_PRI

LO_PRI

LO_LO_PRI

3.7.7

Alarm priority

Alarms are grouped into five levels of priority:
Priority number
38
Description
0 The alarm condition is not used.
1 An alarm condition with a priority of 1 is recognized by the system, but is not
reported to the operator.
2 An alarm condition with a priority of 2 is reported to the operator.
3-7 Alarm conditions of priority 3 to 7 are advisory alarms of increasing priority.
8-15 Alarm conditions of priority 8 to 15 are critical alarms of increasing priority.
Reference Manual
00809-0200-4801, Rev DA
Configuration