Rockwell Automation 1746-NR8 SLC 500 RTD/Resistance Input Module User Manual - Manual (Page 41)

Publication 1746-UM003A-EN-P
Preliminary Operating Considerations 3-5
Example - To obtain the status of channel 2 (input word 6) of the RTD
module located in slot 3 in the SLC chassis, use address I:3.6.
Chapter 4 gives you detailed bit information about the content of the data
word and the status word.
Channel Filter Frequency
Selection The RTD module uses a digital filter that provides noise rejection for the input
signals. The digital filter is programmable, allowing you to select from four
filter frequencies for each channel.
Selecting a low value (for example, 28 Hz) for the channel filter frequency
provides greater noise rejection for a channel, but also increases the channel
update time. Selecting a high value for the channel filter frequency provides
lesser noise rejection, but decreases the channel update time.
The Notch Frequencies table in the next section shows the available filter
frequencies, as well as the associated minimum normal mode rejection (NMR),
cut-off frequency, and step response for each filter frequency. The graphs on
page 3-8 and page 3-9 show the input channel frequency response for each
filter frequency selection.
1746-NR8 Channel Step Response
The channel filter frequency determines the channel’s step response. The step
response is the time required for the analog input signal to reach 100% of its
expected final value. This means that if an input signal changes faster than the
channel step response, a portion of that signal is attenuated by the channel
filter. The table below shows the step response for each filter frequency.
Table 3.1 Notch Frequencies
I : 3 . 6
File Type
Slot
Word
Word Delimiter Element Delimiter
Filter Frequency 50 Hz NMR 60 Hz NMR 3 dB Cut-Off
Frequency Step Response
28 Hz 110 dB 95 dB 7.80 Hz 120 msec
50/60 Hz 65 dB 65 dB 13.65 Hz 68.6 msec
800 Hz - - 209.8 Hz 3.75 msec
6400 Hz - - 1677 Hz 1.47 msec