User Manual Instruction Manual

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/LSB0…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