Rockwell Automation 1746-NR4 SLC RTD/Resistance Input Module User Manual - Manual (Page 58)

Publication 1746-UM008B-EN-P - December 2006
58 Preliminary Operating Considerations
Scanning Process and
Channel Timing This section shows how to determine the channel update time and
channel autocalibration time. In addition, the scanning process is
briefly described.
The RTD module channel update time is defined as the time required
for the module to sample and convert (scan) the input signal of an
enabled input channel and make the resulting data value available to
the SLC processor for update.
Channel Autocalibration
Upon entry into the channel enabled state, the corresponding channel
is calibrated and configured according to the channel configuration
word information. Channel calibration takes precedence over channel
scanning and is a function of the selected notch filter.
Update Time and Scanning Process
Scanning Cycle on page 60 shows the scanning process for the RTD
module assuming that the module is running normally and more than
one channel is enabled.
The scanning cycle is shown for the situation where channels 0 and 1
are enabled and channels 2 and 3 are not used.
Channel Calibration Time
Filter Frequency Channel Calibration Time
10 Hz 7300 ms
50 Hz 1540 ms
60 Hz 1300 ms
250 Hz 388 ms
IMPORTANT
The scanning process shown on is similar for any number of
enabled channels.