Rockwell Automation 1756-OF8H ControlLogix HART Analog I/O Modules - Manual (Page 100)

100 Rockwell Automation Publication 1756-UM533C-EN-P - February 2011
Chapter 7 Configure the Modules with RSLogix 5000 Software
This sets up a relationship between the electrical signal generated by your tank
gauge and the number sent to the Logix Controller for use in your control system.
Graphically, this relationship looks like this:
Note that the module can measure signals slightly higher and lower than the
sensor will provide for this tank. Setting the High or Low Engineering Units will
not limit the values to within that range. The module will still measure signals all
the way from 4…20 mA. In this example, if the module senses 20 mA, it will
report the tank is 124% full. A signal of 0 mA will be reported as -4% full, or
‘less than empty’.
To have the tank level reported in liters instead of percent, put the capacity of the
tank as the High Engineering value. If you have a 750 liter tank, in the example
above put 750 instead of 100, and you will get the scaling relationship shown by
this graph: