Calculating The Software Calibration - Allen-Bradley SLC 500 User Manual

C-2 Optional Analog Input Software Calibration
Publication 1746-UM005B-EN-P - June 2004
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20 mA = 16384
(scale Hi)
Scaled
Value
4 mA = 3277
(scale low)

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.
3267
Low Value from card Hi Value from card
Input Value
Scaled Value vs. Input Value
16396