Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 67)

Publication 1762-UM002A-EN-P - July 2002
Module Data, Status, and Channel Configuration 3-37
Impact of Autocalibration on Module Startup During Mode
Change
Regardless of the selection of the Enable/Disable Cyclic Calibration
function, an autocalibration cycle occurs automatically on a mode
change from Program-to-Run and on subsequent module
startups/initialization for all configured channels. During module
startup, input data is not updated by the module and the General
Status bits (S0 to S5) are set to 1, indicating a Data Not Valid condition.
The amount of time it takes the module to startup is dependent on
channel filter frequency selections as indicated in Table 3.5, Channel
Update Time, on page 3-34. The following is an example calculation
of module startup time.
EXAMPLE
1.Two Channels Enabled for Different Inputs
Channel 0 Input: Type T Thermocouple with 60 Hz filter
Channel 1 Input: Type J Thermocouple with 60 Hz filter
Module Startup Time
= Ch 0ADC Self-Calibration Time + Ch 0 Offset Time
+ CJC Self-Calibration Time
= 103 ms + 53 ms + 103 ms = 259 ms
2.Three Channels Enabled; Two with Different Inputs
Channel 0 Input: Type T Thermocouple with 60 Hz filter
Channel 1 Input: Type J Thermocouple with 60 Hz filter
Channel 2 Input: T
ype K Thermocouple with 50 Hz filter
Module Startup Time
= Channel 0 ADC Self-Calibration Time + Channel 0 Offset Time
+ Channel 2 ADC Self-Calibration Time + Channel 2 Offset Time
+ CJC Self-Calibration Time
= 103 ms + 53 ms + 123 ms + 63 ms + 103 ms = 445 ms