Rockwell Automation 1769-IT6 Compact I/O 1769-IT6 Thermocouple/mV Input Module - Manual (Page 50)

50 Rockwell Automation Publication 1769-UM004B-EN-P - March 2010
Chapter 4 Module Data, Status, and Channel Configuration
Selecting Enable/Disable Cyclic Calibration (word 6, bit 0)
Cyclic calibration functions to reduce offset and gain drift errors due to
temperature changes within the module. By setting word 6, bit 0 to 0, you can
configure the module to perform calibration on all enabled channels. Setting this
bit to 1 disables cyclic calibration.
You can program the calibration cycle to occur whenever you desire for systems
that allow modifications to the state of this bit via the ladder program. When the
calibration function is enabled (bit = 0), a calibration cycle occurs once for all
enabled channels. If the function remains enabled, a calibration cycle occurs every
five minutes thereafter. The calibration cycle of each enabled channel is staggered
over several module scan cycles within the five minute period to limit impact on
the system response speed.
See Effects of Autocalibration on Module Update Time on page 70.
Determining Effective
Resolution and Range The effective resolution for an input channel depends upon the filter frequency
selected for that channel. The following graphs provide the effective resolution
for each of the range selections at the six available frequencies. These graphs do
not include the affects of unfiltered input noise. Choose the frequency that most
closely matches your requirements.