Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 117)

Chapter 7
Using Analog
7–3
Update Time Examples
Example 1 – All (4) channels enabled with 60 Hz filter selected (default
settings).
Maximum Update Time = (4) x ladder scan time
+ (4) x 16.67 ms
+ (4) x 66.67 ms
= 333.36 ms + (4) x ladder scan times
( Each channel is updated approximately three times per second.)
Example 2 – 1 channel enabled with 250 Hz filter selected.
Maximum Update Time = ladder scan time + 4 ms
Input Channel Filtering
The analog input channels incorporate on-board signal conditioning. The
purpose of this conditioning is to reject the AC power line noise that can
couple into an analog input signal while passing the normal variations of the
input signal.
Frequency components of the input signal at the filter frequency are rejected.
Frequency components below the filter bandwidth (–3 dB frequency) are
passed with under 3 dB of attenuation. This pass band allows the normal
variation of sensor inputs such as temperature, pressure and flow transducers
to be input data to the processor.
Noise signals coupled in at frequencies above the pass band are sharply
rejected. An area of particular concern is the 50/60 Hz region, where pick-up
from power lines can occur.