Rockwell Automation 1746-XXXX SLC 500 4-Channel Analog I/O Modules User Manual - Manual (Page 53)

Publication 1746-UM005B-EN-P - June 2004
Module Operation and System Considerations 4-15
If power line noise is coupling into the input signal through the input
cable, the proper use of differential inputs reduces the effect of noise.
With differential inputs, noise couples into both the plus (+) and
minus (-) inputs where it is attenuated by over 105 dB (60 Hz
common mode rejection).
The affect of the filter with respect to time can be seen by examining
the step response of the input channel. The following illustration
shows the response of the input value versus time when a step
change is made in the voltage or current at the input terminal. The
response of the filter demonstrates no overshoot and rapid settling
time. The input value settles to within 95% of the final value in 60
milliseconds, independent of the input magnitude.
EXAMPLE
If the input instantaneously changes from 0 to 10
volts, the value converted by the analog module after
60 milliseconds is 9.5 volts. Within this time the
analog module updates the input data value in
memory with an intermediate response every 512
microseconds.
120 80 40
100
80
60
40
20
0
0
Percentage (%) of Final V
alue
Time (ms)
60
95