Rockwell Automation 1756-OF8I ControlLogix Eight-channel Isolated Analog I/O Modules - Manual (Page 69)

Rockwell Automation Publication 1756-UM540A-EN-P - May 2014 69
1756-IRT8I Combined Temperature-sensing Isolated Analog Module Chapter 4
For example, if your application requires a Notch Filter setting of 50 Hz, the
module’s minimum RPI rate is 20.1 ms. In this case, sampling speed is more
important than noise rejection. The module automatically uses a SINC^1 filter.
If your application requires a Notch Filter setting of 50 Hz and the greater level of
noise rejection provided by a SINC^3 filter, the minimum RPI rate is 60.1 ms.
The module automatically uses a SINC^3 filter.
The RPI must be > 1/Notch Filter plus some small scan time for the ADC to
sample properly. The SINC^3 filter takes 3 times as long and thus requires RPI >
3/Notch plus some small scan time. The module rejects combinations which
violate that relationship.
The table below lists the available notch filter settings and the RPI values for the
two types of filters.
To see where to set the Notch Filter, see page 127 .
Notch Filter Fastest Available RPI Fastest RPI for a SINC^3 Filter
5 Hz 200.1 ms 600.1 ms
10 Hz 100.1 ms 300.1 ms
15 Hz 66.7 ms 200.1 ms
20 Hz 50.1 ms 150.1 ms
50 Hz 20.1 ms 60.1 ms
60 Hz (default) 16.7 ms 50.1 ms
100 Hz 10.1 ms 30.1 ms
500 Hz 2.1 ms 6.1 ms
1000 Hz 1.1 ms 3.1 ms
5000 Hz 1.0 ms 1.0 ms