Rockwell Automation 1746-XXXX SLC 500 4-Channel Analog I/O Modules User Manual - Manual (Page 44)

Publication 1746-UM005B-EN-P - June 2004
4-6 Module Operation and System Considerations
If you are using the Hand-Held Terminal (HHT) or the Data Table
Access Module
™ (DTAM) to monitor input and output data, the binary
radix is the only available option. To view the analog input and
output data in decimal radix, the data must be moved to an integer
data file.
Converting Analog Input Data
Analog inputs convert current and voltage signals into 16 bit two’s
complement binary values.
The table below identifies the current and voltage input ranges for the
input channels, the number of significant bits for the applications
using input ranges less than full scale, and their resolution
To determine an approximate voltage that an input value represents,
use one of the following equations:
Voltage/Current Range Decimal Representation Number of Significant Bits Resolution per LSB
-10V dc to +10V dc - 1LSB -32,768 to +32,767 16 bits 305.176 µ V
0 to 10V dc - 1LSB 0 to 32,767 15 bits
0 to 5V dc 0 to 16,384 14 bits
1 to 5V dc 3,277 to 16,384 13.67 bits
-20 mA to +20 mA -16,384 to +16,384 15 bits 1.22070 µ A
0 to +20 mA 0 to 16,384 14 bits
4 to +20 mA 3,277 to 16,384 13.67 bits
×
input value
=
input voltage(V)
10V
32,768
The Input Value is the decimal value of the word in the
input image for the corresponding analog input.
For example, if an input value of ±16,021 is in the input
image, the calculated input voltage is:
10V
32,768
×
±16,201
=
±4.889221(V)
It should be noted that this is the calculated value. The
actual value may vary within the accuracy limitations of the
module.