Rockwell Automation 1769-IR6 Compact I/O 1769-IR6 RTD/Resistance Input Module - Manual (Page 76)

76 Rockwell Automation Publication 1769-UM005B-EN-P - March 2012
Chapter 4 Module Data, Status, and Channel Configuration
Effects of Cyclic Lead Wire Compensation on Module Update
Time
The 1769-IR6 module provides the option to enable lead wire compensation
for each channel. This feature improves measurement accuracy for 3- and 4-
wire RTDs by compensating for the resistance of the RTD lead wire. Lead wire
compensation occurs automatically on a mode change from Program-to-Run
for all configured channels or if any online
(1)
configuration change is made to a
channel regardless of the type of RTD being used. In addition, you can either
configure the module to perform a lead wire compensation cycle every 5
minutes during normal operation or disable this feature using the Enable/
Disable Cyclic Lead Wire function (default: Enable). You can also implement a
lead wire compensation cycle anytime, using your control program to enable
and then disable this function.
(1)
If you enable the cyclic lead wire compensation function, the module update
time will increase when the lead wire compensation cycle occurs. To limit its
impact on module update time, the lead wire compensation function is divided
over 3 module scans. The amount of time added for lead wire compensation
per module scan depends on the filter frequency (channel update time)
selected for that channel.
(1) Not all controllers allow online configuration changes. Refer to your controller’s user manual for details. During
an online configuration change, input data for that channel is not updated by the module.