Rockwell Automation 1746-NT8 SLC 500 Thermocouple/mV Analog Input Module User Manual - Manual (Page 37)

Publication 1746-UM022B-EN-P - January 2005
Considerations Before Using Your Module 3-7
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 sum of all enabled
sample times, plus a CJC update time.
The following table shows the channel sampling time for each filter
frequency. It also gives the CJC update time.
Channel Sampling Time
The times above include a settling time necessary between input
channel readings. The sampling times for filter frequencies listed do
not include a 45 ms open-circuit detection time utilized when the
channel is configured for open-circuit detection. CJC open-circuit
detection does not require the additional 45 ms settling time.
The fastest module update time occurs when only one channel with a
250 Hz filter frequency is enabled.
Module update time = 290 ms + 66 ms = 356 ms
The slowest module update time occurs when eight channels, each
using a 10 Hz filter frequency, are enabled.
Module update time = 290 ms + 470 ms + 470 ms + 470 ms + 470
ms + 470 ms + 470 ms + 470 ms + 470 ms = 4.05 s
Enabled Enabled Enabled Enabled
Calculate
Previous Calculate
Previous Calculate
Previous Calculate
Previous
Sample
Channel 0
Update CJC
Sample
Channel 1
Sample
Channel 2
Sample
Channel 7
Sample
CJC
Channel
Channel 0 Disabled Channel 1 Disabled Channel 2 Disabled Channel 7 Disabled
Channel Sampling Time for Each Filter Frequency (all values ±1 ms)
CJC Update Time 250 Hz Filter 60 Hz Filter 50 Hz Filter 10 Hz Filter
290 ms 66 ms 125 ms 140 ms 470 ms