Rockwell Automation 1769-IR6 Compact I/O 1769-IR6 RTD/Resistance Input Module - Manual (Page 78)

78 Rockwell Automation Publication 1769-UM005B-EN-P - March 2012
Chapter 4 Module Data, Status, and Channel Configuration
Impact of Autocalibration and Lead Wire Compensation on
Module Startup
Regardless of the selection of the Enable/Disable Cyclic Calibration and
Enable/Disable Cyclic Lead Calibration functions, an cycle of both of these
functions 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 until the
calibration and compensation cycles are complete. During this time the
General Status bits (S0…S5) are set to 1, indicating a Data Not Valid
condition. The time it takes the module to startup is dependent on channel
filter frequency selections and other items defined in the previous sections.
The following examples show how to calculate the module startup time.
EXAMPLE 1. Six Channels Enabled with Same Configurations
All 6 Channels: 100
Ω Platinum 385 RTD, 1.0 mA current source, 60 Hz filter
Module Startup Time
= (6-step Calibration Time + Current Source Calibration Time)
+ (Lead Wire Compensation Time x 6 channels)
+ (Channel 0…5 Data Acquisition Time)
= (504 ms + 482 ms) + (53 ms x 6) + (53 ms x 6)
= 986 ms + 318 ms + 318 ms = 1622 ms = 1.622 seconds
2. Six Channels Enabled with Different Configurations (worst-case startup time)
All 6 Channels: 100
Ω Platinum 385 RTD, 1.0 mA current source, 60 Hz filter
Module Startup Time
= [(6-step Calibration Time x 6 channels) + Current Source
Calibration Time] + (Lead Wire Compensation Time for
Ch 0 to 5 x 3) + (Channel 0 to 5 Data Acquisition Time)
= [(504 ms x 6) + 482 ms] + (449 ms x 3)
+ (303 ms + 63 ms + 53 ms + 15 ms + 9 ms + 6 ms)
= 3506 ms + 1347 ms + 449 ms = 5302 ms = 5.302 seconds