Rockwell Automation Publication 1769-UM021I-EN-P - May 2018 199
Use I/O Modules with CompactLogix 5370 L2 Controllers Chapter 8
The filter frequency selection for the channel determines the CJC update time.
Tab le 14
shows the CJC update times that are based on filter
frequency selections.
Table 14 - Channel Update Times
Filter Frequency Selection
(1)
(1) Filter frequency selections are made on the Input Configuration tab of the Module Properties dialog box.
CJC Update Time
10 Hz 614 ms
50 Hz 134 ms
60 Hz 114 ms
250 Hz 38 ms
500 Hz 26 ms
1 kHz 22 ms
IMPORTANT Keep the following in mind when calculating the CJC update time:
• If multiple input channels are configured to use a thermocouple input
type and another filter value is selected for each, the filter frequency
selection with the slowest update time determines the CJC update time.
For example, if one input channel uses a thermocouple input with a
50 Hz filter frequency and another input channel uses a thermocouple
input with a 60 Hz filter frequency, the CJC channel update time is
134 ms.
• The CJC update time that increases overall module update time is only
used once regardless of the number of input channels on a module that
have CJC enabled to scan every other scan.
In other words, if your module uses a filter frequency selection of 250 Hz
and includes three channels with CJC enabled to scan every other scan,
you add only one instance of CJC update time to the overall equation.
Instead of including 38 ms for each channel, you include 38 ms once.
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