Alarm Measurement Definition - Allen-Bradley 1444-TSCX02-02RB User Manual

Alarm Measurement Definition

Each Measurement Alarm can be uniquely defined to compare any of the
measured values in the module. The measurement is not necessary in the
controller input assembly. (See
However, the module must be configured to measure the value before it can be
selected as input to a Measurement Alarm.
Alarm Limit Definition
Each Measurement Alarm can be uniquely defined to apply limits that are
either entered as static values that are part of the measurement alarm
definition. Each Measurement Alarm can also be passed to the module as I/O
in the controller output table.
IMPORTANT When using profile alarms, so the alarm limits are provided on controller
output, there can be some short period of time after the module begins
measurements, and before the controller updates the output alarm limit
values. To accommodate this, the module does not apply the alarm limits
from the controller output until the limit is made non-zero. Until then the
module uses the Static Limits configured for the alarm. You must set the
Static Limits for the alarms at appropriate initial values.
Static Alarm Limits
Limits for high and low alert and danger levels can be entered. When used, the
module compares the measured value with the limits each time the
measurement is updated. The limits can also be multiplied, either by a set limit
multiplier, or by any of up to five 'Adaptive Multipliers' .
Limit Multiplier
Typically an alarm limit multiplier is used for alarms that are applied to
machines that operate above their first critical (natural) frequency. During
startup, these machines experience vibration excursions that can exceed the
(normal) alarm limits, as the speed of the machine traverses the critical
frequency. Without applying this multiplier, the vibration levels can exceed
danger setpoints, which can force a machine trip, during a normal machine
startup.
Control of the limit multiplier (on/off ) is provided through the Setpoint
Multiplier (SPM) function. A bit on the controller output assembly or by a
physical input (switch) to the module manages the SPM. SPM is defined as
part of any voted alarm definition that uses the measurement alarm (See
Alarms Page on page 222).
Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Configure Alarms
Select Input Data for Input Tag on page
Chapter 8
106).
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