Rockwell Automation 1762-IR4 RTD/Resistance Input Module - Manual (Page 52)

Publication 1762-UM003A-EN-P - February 2003
3-18 Module Data, Status, and Channel Configuration
the channel filter. The channel step response is calculated by a settling
time of 3 x (1 / filter frequency).
Channel Cutoff Frequency
The channel cutoff frequency (-3 dB) is the point on the input channel
frequency response curve where frequency components of the input
signal are passed with 3 dB of attenuation. The following table shows
cutoff frequencies for the supported filters.
All frequency components at or below the cutoff frequency are passed
by the digital filter with less than 3 dB of attenuation. All frequency
components above the cutoff frequency are increasingly attenuated,
as shown in the graphs below for several of the input filter
frequencies.
Table 3.7 Filter Frequency vs. Channel Step Response
Filter Frequency Step Response Filter Frequency Step Response
10 Hz 300 ms 250 Hz 12 ms
50 Hz 60 ms 500 Hz 6 ms
60 Hz 50 ms 1 kHz 3 ms
Table 3.8 Filter Frequency vs. Channel Cutoff Frequency
Filter Frequency Channel Cutoff Frequency
10 Hz 2.62 Hz
50 Hz 13.1 Hz
60 Hz 15.7 Hz
250 Hz 65.5 Hz
500 Hz 131 Hz
1 kHz 262 Hz
TIP
Channel cutoff frequency should not be confused
with channel update time. The cutoff frequency
simply determines how the digital filter attenuates
frequency components of the input signal. See
Determining Module Update Time on page 3-27.