Rockwell Automation 1756-OF8H ControlLogix HART Analog I/O Modules - Manual (Page 56)

56 Rockwell Automation Publication 1756-UM533C-EN-P - February 2011
Chapter 4 1756-IF8H HART Analog Input Module
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.
For more RTS information, see Real Time Sample (RTS) on page 41 .
Underrange and Overrange Detection
The module detects when it is operating beyond limits of the input range. This
status indication tells you that the input signal is not being measured accurately
because the signal is beyond the measuring capability of the module. For example,
the module cannot distinguish between 10.25V and 20V.
The following table shows the input ranges of the 1756-IF8H module and the
lowest and highest signal available in each range before the module detects an
underrange and overrange condition.
Table 3 - Low and High Signal Limits on the 1756-IF8H Module
Input Module Available Range Lowest Signal in
Range Highest Signal in
Range
1756-IF8H -10…10V
0…10V
0…5V
0…20 mA
4…20 mA -10.25V
0V
0V
0 mA
3.42 mA 10.25V
10.25V
5.125V
20.58 mA
20.58 mA