Rockwell Automation 1746-NT4 Series B,D17466.6.1 SLC 500 4-Channel Thermocouple/mV Input Module User Manual - Manual (Page 46)

Publication 1746-UM007C-EN-P - July 2004
4-4 Preliminary Operating Considerations
Channel Filter Frequency
Selection The thermocouple module uses a digital filter that provides high
frequency noise rejection for the input signals. The digital filter is
programmable, allowing you to select from four filter frequencies for
each channel. The digital filter provides the highest noise rejection at
the selected filter frequency.
Selecting a low value (i.e. 10 Hz) for the channel filter frequency
provides the best noise rejection for a channel, but it also increases
the channel update time. Selecting a high value for the channel filter
frequency provides lower noise rejection, but decreases the channel
update time.
The following table shows the available filter frequencies, associated
minimum normal mode rejection (NMR), cut-off frequency, and step
response for each filter frequency.
Effective Resolution
The effective resolution for an input channel depends upon the filter
frequency selected for that channel. Graphs that shows actual bit
resolution for the thermocouple types at all filter frequencies are
provided in Appendix A.
Filter
Frequency 50Hz NMR 60Hz NMR Cut-Off
Frequency Step
Response
10 Hz 100 dB 100 dB 2.62 Hz 300 msec
50 Hz 100 dB - 13.1 Hz 60 msec
60 Hz - 100 dB 15.72 Hz 50 msec
250 Hz - - 65.5 Hz 12 msec