Rockwell Automation 1746-NR4 SLC RTD/Resistance Input Module User Manual - Manual (Page 59)

Publication 1746-UM008B-EN-P - December 2006
Preliminary Operating Considerations 59
Channel scanning is sequential and always occurs starting with the
lowest numbered enabled channel and proceeding to the next highest
numbered channel, for example, channel 0 - channel 1 - channel 2 -
channel 3 - channel 0 - channel 1. Channel scan time is a function of
the filter frequency.
The fastest module update time occurs when only one channel with a
250 Hz filter frequency is enabled.
Module Update Time = 17 ms
The slowest module update time occurs when four channels, each
using a 10 Hz filter frequency, are enabled.
Module Update Time = 4 _ 305 ms = 1220 ms
Channel Scan Time
Filter Frequency
Channel Scan Time
(1)
(1)
The module-scan time is obtained by summing the channel-scan time for each enabled channel. For example, if
3 channels are enabled and the 50 Hz filter is selected, the module-scan time is 3 X 65 ms = 195 ms.
10 Hz 305 ms
50 Hz 65 ms
60 Hz 55 ms
250 Hz 17 ms
TIP
With 3 channels enabled, the module update time is: 3
channels_ 17 ms/channel = 51 ms