Rockwell Automation 1771-IL/B , D17716.5.91 ISOLATED ANALOG INPUT Module - Manual (Page 33)

Module Configuration
Chapter 4
4-9
Alarms
Each input channel has alarm functions that provide status indication
through associated status bits in the block transfer read data returned by
the module.
Underrange alarm - This bit is set if the input falls below the minimum
range for that specific input type. This alarm is predefined and cannot be
changed by the user. In current loop inputs, this bit also indicates an
open loop.
Overrange alarm - This bit is set if the input rises above the maximum
range for that specific input type. This alarm is predefined and cannot be
changed by the user. For all voltage inputs, this bit indicates an
open channel.
Range
Underrange Bit is set
when the input signal is
less than:
Overrange Bit is set
when the input signal is
greater than:
1 to 5V/4 to 20mA 1V dc or 4mA 5V dc or 20mA
0 to 5V/0 to 20mA Zero 5V dc or 20mA
-5 to 5V/-20 to 20mA -5V dc or -20mA 5V dc or 20mA
-10 to +10V -10V dc +10V dc
User-defined alarms let the user specify a range of “good” input values. If
the input value goes outside of this range, the module will set the low or
high alarm bit for that channel. The alarm values are written to the module
in the same units as the scaling values. Valid alarm values are +9999 BCD
or +32767 binary. If you select “no alarms” you must set both the low
alarm value and the high alarm value to zero. If either the low or high
alarm for a channel is not zero, alarms for that channel are enabled.
Figure 4.3
Alarm Example
Underrange Limit
User-Defined High Alarm Limit
User-Defined Low Alarm Limit
Overrange Limit
Time
Input Channel
alarm active
alarm inactive