Rockwell Automation 1756-XXXX ControlLogix Analog I/O Modules - Manual (Page 50)

50 Publication 1756-UM009C-EN-P - December 2010
Chapter 3 ControlLogix Analog I/O Module Features
Scaling
With scaling, you change a quantity from one notation to another. For
ControlLogix analog I/O modules, scaling is only available with the
floating point data format.
When you scale a channel, you must choose two points along the module’s
operating range and apply low and high values to those points. For example, if
you are using the 1756-IF6I module in current mode, the module maintains a
0…21 mA range capability. But your application may use a 4…20 mA
transmitter. You can scale the module to represent 4 mA as the low signal and
20 mA as the high signal.
Scaling lets you configure the module to return data to the controller so that 4
mA returns a value of 0% in engineering units and 20 mA returns a value of
100% in engineering units.
Module Resolution Compared to Module Scaling
Module resolution
65,536 counts
0 mA 21 mA
4 mA 20 mA
0% in
engineering units
100% in
engineering units
Module scaling
Module scaling represents
the data returned from the
module to the controller
IMPORTANT
In choosing two points for the low and high value of your
application, you do not limit the range of the module. The
module’s range and its resolution remain constant regardless of
how you scale it for your application.