Convert analog input data, Compute the analog input signal level – Rockwell Automation 1746-FIO4V SLC 500 Fast Analog I/O/ User Manual User Manual
Page 33
Publication 1746-UM009B-EN-P - September 2007
Processor and Module Considerations 33
Convert Analog Input Data
The module converts analog input signals to 12-bit binary values for
storage in the input image table.
The decimal range, number of significant bits, and converter
resolution depend on the input range that you use for the channel.
Compute the Analog Input Signal Level
Use the following formula to determine what the analog input signal
level (sensor signal) should be for a given decimal value in the input
image table.
For voltage inputs, a full scale input of 10V dc has a full scale count of
4095 and a full scale input of 5V dc has a full scale count of 2047.
For current inputs, a full scale input of 20 mA has a full scale count of
2047.
Input Range
Decimal Range
(input image table)
Significant
Bits
Nominal Resolution
0…10V – 1LSB
0…4095
12
2.4414 mV/LSB
0…5V
0…2047
11
1…5V
409…2047
10
0…20 mA
0…2047
11
9.7656 µA/LSB
4…20 mA
409…2047
10
Full Scale Input
Full Scale Count
Sensor Signal =
x Input Image Value
Sensor Signal = 2.44 mV/count x Input Image Value
Sensor Signal = 0.00977 mA/count x Input Image Value