Rockwell Automation 1746-NT8 SLC 500 Thermocouple/mV Analog Input Module User Manual - Manual (Page 39)

Publication 1746-UM022B-EN-P - January 2005
Considerations Before Using Your Module 3-9
CJC sensors are acquired at 60 Hz to maximize the trade-off between
resolution and update rate. For example, if some channels are
acquired at 250 Hz and some are acquired at 50 Hz, then the total
auto-calibration time would be:
During auto-calibration, input values are not updated.
Response to Slot Disabling By writing to the status file in the modular SLC processor, you can
disable any chassis slot. Refer to your SLC programming manual for
the slot disable/enable procedure.
Input Response
When a thermocouple slot is disabled, the thermocouple module
continues to update its input image table. However, the SLC processor
does not read input from a module that is disabled. Therefore, when
the processor disables the thermocouple module slot, the module
inputs appearing in the processor image table remain in their last
state, and the module’s updated image table is not read. When the
processor re-enables the module slot, the current state of the module
inputs are read by the processor during the subsequent scan.
Output Response
The SLC processor may change the thermocouple module output data
(configuration) as it appears in the processor output image. However,
this data is not transferred to the thermocouple module. The outputs
are held in their last state. When the slot is re-enabled, the data in the
processor image is transferred to the thermocouple module.
Frequency Auto-Calibration
250 Hz 325 ms
60 Hz 525 ms
50 Hz 585 ms
1.435 s Total
ATTENTION
Possible Equipment Operation
Always understand the implications of disabling a
module before using the slot disable feature.
Failure to observe this precaution can cause
unintended equipment operation.