Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 66)

Publication 1762-UM002A-EN-P - July 2002
3-36 Module Data, Status, and Channel Configuration
EXAMPLE
2.Three Channels Enabled for Different Inputs
Channel 0 Input: Type J Thermocouple with 10 Hz filter
Channel 1 Input: Type J Thermocouple with 60 Hz filter
Channel 2 Input: ±100 mV with 250 Hz filter
From Table 3.5, Channel Update Time, on page 3-34:
Module Update Time
= Ch 0 Update Time + Ch 1 Update Time
+ Ch 2 Update Time + CJC Update Time (uses lowest
thermocouple filter selected)
= 303 ms + 53 ms + 15 ms + 303 ms
= 674 ms
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 Table 3.5, Channel Update Time, on page 3-34:
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
Module Scan 1
= Ch 0 Update Time + Ch 1 Update Time + Ch 2 Update Time
+ CJC Update Time + Ch 0 ADC Self-Calibration Time
= 53 ms + 53 ms + 53 ms + 53 ms + 103 ms = 315 ms
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 + 53 ms = 265 ms
Channel 1 and Channel 2: (no scan impact)
No autocalibration cycle is required for Channels 1 and 2 because they are
configured to use the same Input Filter as Channel 0.
Module Scan 3
= Ch 0 Update Time + Ch 1 Update Time + Ch 2 Update Time
+ CJC Update Time + CJC ADC Self-Calibration Time
= 53 ms + 53 ms + 53 ms + 53 ms + 103 ms = 315 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.