Rockwell Automation 1756-XXXX ControlLogix Analog I/O Modules - Manual (Page 61)

Publication 1756-UM009C-EN-P - December 2010 61
Non-isolated Analog Voltage/Current Input Modules (1756-IF16, 1756-IF8) Chapter 4
Real Time Sampling
This parameter instructs the module how often to scan its input channels and
obtain all available data. After the channels are scanned, the module multicasts
that data. This feature is applied on a module-wide basis.
During module configuration, you specify a real time sampling (RTS) period
and a requested packet interval (RPI) period. Both of these features instruct
the module to multicast data, but only the RTS feature instructs the module to
scan its channels before multicasting.
Underrange/Overrange Detection
This alarm feature detects when the non-isolated input module is operating
beyond limits set by the input range. For example, if you are using the
1756-IF16 module in the 0V…10V input range and the module voltage
increases to 11V, the overrange detects this condition.
The table shows the input ranges of non-isolated input modules and the
lowest/highest signal available in each range before the module detects an
underrange/overrange condition.
Input Module Available Range Lowest Signal
in Range Highest Signal
in Range
1756-IF16 and
1756-IF8 +/- 10V
0V…10V
0V…5V
0 mA…20 mA
-10.25V
0V
0V
0 mA
10.25V
10.25V
5.125V
20.58 mA
IMPORTANT
Be careful when ‘disabling all alarms’ on the channel because it
also disables the underrange/overrange detection feature. If
alarms are disabled, overrange/underrange is zero and the only
way you can discover a wire-off detection is from the input
value itself. If you need to detect a wire-off status, do not
‘disable all alarms’.
We recommend that you disable only unused channels so
extraneous alarm bits are not set.