Rockwell Automation 1769-IT6 Compact I/O 1769-IT6 Thermocouple/mV Input Module - Manual (Page 72)

72 Rockwell Automation Publication 1769-UM004B-EN-P - March 2010
Chapter 4 Module Data, Status, and Channel Configuration
EXAMPLE 3. Three Channels Enabled for Different Inputs with Cyclic
Calibration Enabled
Channel 0 Input: Type T Thermocouple with 60 Hz Filter
Channel 1 Input: Type T Thermocouple with 60 Hz Filter
Channel 2 Input: Type J Thermocouple with 60 Hz Filter
From Channel Update Time, on
page 42 .
Module Update Time ‘without’ an Autocalibration Cycle
= Ch 0 Update Time + Ch 1 Update Time
+ Ch 2 Update Time + CJC Update Time (uses lowest
thermocouple filter selected)
= 53 ms + 53 ms + 53 ms + 53 ms = 212 ms
Module Update Time ‘during’ an Autocalibration Cycle
Channel 0 Scan 1 (Module Scan 1)
= Ch 0 Update Time + Ch 1 Update Time
+ Ch 2 Update Time + CJC Update Time + ‘Ch 0 Gain Time’
= 53 ms + 53 ms + 53 ms + 53 ms + ‘112 ms’ = 324 ms
Channel 0 Scan 3 (Module Scan 2)
= Ch 0 Update Time + Ch 1 Update Time
+ Ch 2 Update Time + CJC Update Time + ‘Ch 0 Offset Time’
= 53 ms + 53 ms + 53 ms + 53 ms + ‘71 ms’ = 283 ms
Channel 1 Scan 1 (no scan impact)
No autocalibration cycle is required because Channel 1 is the same Input
Class as Channel 0. Data is updated in scan 3.
Channel 2 Scan 1 (Module Scan 3)
= Ch 0 Update Time + Ch 1 Update Time
+ Ch 2 Update Time + CJC Update Time + ‘Ch 2 Gain Time’
= 53 ms + 53 ms + 53 ms + 53 ms + ‘112 ms’ = 324 ms
Channel 2 Scan 2 (Module Scan 4)
= Ch 0 Update Time + Ch 1 Update Time
+ Ch 2 Update Time + CJC Update Time + ‘Ch 2 Offset Time’
= 53 ms + 53 ms + 53 ms + 53 ms + ‘71 ms’ = 283 ms
CJC Scan 1 (Module Scan 5)
= Ch 0 Update Time + Ch 1 Update Time
+ Ch 2 Update Time + CJC Update Time + ‘CJC Gain Time’
= 53 ms + 53 ms + 53 ms + 53 ms + ‘112 ms’ = 324 ms
CJC Scan 2 (Module Scan 6)
= Ch 0 Update Time + Ch 1 Update Time
+ Ch 2 Update Time + CJC Update Time + ‘CJC Offset Time’
= 53 ms + 53 ms + 53 ms + 53 ms + ‘71 ms’ = 283 ms
After the above cycles are complete, the module returns to scans without
autocalibration for approximately 5 minutes. At that time, the
autocalibration cycle repeats.