Rockwell Automation Allen-Bradley 1769-IF4, Руководство пользователя

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Publication 1769-UM002B-EN-P - July 2005
Module Data, Status, and Channel Configuration for the Input Modules 3-31
Alarm Deadband
You may configure an Alarm Deadband to work with the process alarms.
The deadband lets the process alarm status bit to remain set, despite the alarm
condition disappearing, as long as the input data remains within the deadband
of the process alarm.
Figure 3.6 shows input data that sets each of the two alarms at some point
during module operation. In this example, Latching is disabled; therefore, each
alarms turns OFF when the condition that caused it to set ceases to exist.
Figure 3.6 Alarm Deadbands
The value entered for a channel’s alarm deadband value must be within the
normal operating data range as set by the Input Data Format selected for that
channel. If an alarm deadband value is entered that is outside the normal
operating data range set for a channel, the module indicates a configuration
error.
The module also checks for an alarm deadband value that is less than 0 or large
enough to exceed one or both of the channel’s full range limits. When one of
these conditions occurs, the module changes the alarm deadband value that is
in violation to one that is allowed. A deadband value less than 0 is set at 0. A
deadband value that when added to the process alarm low data value or
subtracted from the process alarm high data value results in a value that
exceeds the full range limits of the channel is adjusted to the first, smaller value
that eliminates this full range violation.
43153
Low
High
Alarm deadbands
Normal input range
High alarm turns OFF
Low alarms turns OFF Low alarms turns ON
High alarm
turns ON