Rockwell Automation 1762-IR4 RTD/Resistance Input Module - Manual (Page 66)

Publication 1762-UM003A-EN-P - February 2003
3-32 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, a 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 to S3) 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
Four Channels Enabled with 10 Hz Filters (worst-case startup time)
All 4 Channels: 100
Ω
Platinum 385 RTD, 1.0 mA current source with 10 Hz filter
Module Startup Time
= (4-step Calibration Time x 4 channels) + (Lead Wire Compensation Time x 4 Channels) +
(4-Channel Data Acquisition Time)
= (2139 ms x 4) + (408 ms x 4) + (303 ms x 4)
= 8556 ms + 1632 ms + 1212 ms = 114700 ms = 11.4 seconds