Rockwell Automation 1756-OF8H ControlLogix HART Analog I/O Modules - Manual (Page 102)

102 Rockwell Automation Publication 1756-UM533C-EN-P - February 2011
Chapter 7 Configure the Modules with RSLogix 5000 Software
Module Resolution
Resolution is the smallest amount of change that the module can detect.
Resolution is sometimes expressed in bits. If 16 bits of resolution are available, the
module can detect 65536 different signal values. If configured for 4 …20 mA, it
could discern the difference between 10 mA and 10.0003 mA, but it would not
distinguish 10 mA from 10.0002 mA.
Resolution affects how the module measures analog signals and scaling converts
that to an Engineering Unit for convenience in your control system. In the 16 bit
example above and the 750 liter tank example in the previous section, you would
have a resulting resolution of 0.0146 liters. As the tank fills, you might see the
volume jump from a reading of 250 liters to 250.015 liters without seeing any
values between. Note that because of sampling, filtering, and RPI, you might see
intermediate values or it might jump over even more values, depending on the fill
rate.
The resolution of analog input modules depends on the module and the filter
configuration. To measure a rapidly changing signal, a configuration with less
resolution is used. For information about the resolution available, see the
following locations.
For this Module’s Available Resolution Page
1756-IF8H 55
1756-IF16H 69
1756-OF8H 80
IMPORTANT Because these modules must provide for possible calibration
inaccuracies, resolution values represent the available analog-to-digital
or digital-to-analog counts over the selected range, including a small
amount of Overrange and Underrange.