Rockwell Automation 1746-XXXX SLC 500 4-Channel Analog I/O Modules User Manual - Manual (Page 102)

Publication 1746-UM005B-EN-P - June 2004
C-2 Optional Analog Input Software Calibration
Calculating the Software Calibration
Use the following equation to perform the software calibration:
Scaled Value = (input value x slope) + offset
Slope = (scaled max. - scaled min.) / (input max. - input min.)
Offset = Scaled min. - (input min. x slope)
Procedure
1. Place your SLC 500 system in the normal operating temperature.
Ensure that adjacent I/O modules in your system do not cause
temperature fluctuations. For example, place high power and
random load I/O modules away from your analog input module.
2. Determine the scaled high and low values you wish to use in
your application. In this example, scaled high is 16384 and
scaled low is 3277.
3. Using an analog input calibration source or your system’s input
device placed at the 4 mA position, capture the low value by
energizing the calibrate low input. Ensure that your low value
lies within the conversion range of your analog input.
Scaled
Value
Input Value
20 mA = 16384
(scale Hi)
4 mA = 3277
(scale low)
Low Value from card Hi Value from card
3267 16396
Scaled Value vs. Input Value