Rockwell Automation 1746-NT4 Series B,D17466.6.1 SLC 500 4-Channel Thermocouple/mV Input Module User Manual - Manual (Page 49)

Publication 1746-UM007C-EN-P - July 2004
Preliminary Operating Considerations 4-7
Update Time The thermocouple module update time is defined as the time required
for the module to sample and convert the input signals of all enabled
input channels and make the resulting data values available to the SLC
processor. It can be calculated by adding the the sum of all enabled
channel sample times, plus a CJC update time.
The NT4 module sequentially samples the channels in a continuous
loop.
The following table shows the channel sampling times for each filter
frequency. It also gives the CJC update time.
The fastest module update time occurs when only one channel with a
250 Hz filter frequency is enabled.
Module update time = 12 ms + 14 ms = 26 ms
The slowest module update time occurs when four channels, each
using a 10 Hz filter frequency (4 * 300 = 1200), are enabled.
Module update time = 1200 ms + 14 ms = 1.214 seconds
Channel 0 Disabled Channel 1 Disabled Channel 2 Disabled Channel 3 Disabled
Sample
Channel 0 Sample
Channel 1 Sample
Channel 2 Sample
Channel 3
Enabled Enabled Enabled Enabled
Update CJC Calculate Previous Calculate Previous Calculate Previous Calculate Previous
Sample
CJC
Channels
CJC Update
Time Channel Sampling Time
250 Hz Filter 60 Hz Filter 50 Hz Filter 10 Hz Filter
14 msec 12 msec 50 msec 60 msec 300 msec