Rockwell Automation 1756-OF8I ControlLogix Eight-channel Isolated Analog I/O Modules - Manual (Page 75)

Rockwell Automation Publication 1756-UM540A-EN-P - May 2014 75
1756-IRT8I Combined Temperature-sensing Isolated Analog Module Chapter 4
10 Ohm Copper Offset
With this feature, you can compensate for a small offset error in a 10 ohm copper
RTD. The channel must be connected to the 10 Ohm CU 427 Sensor Type to
use this feature. The offset value is indicated in units of 0.01 Ohms.
You can set the 10 Ohm copper offset in either of the following ways:
• On the Configuration tab of the Module Properties dialog box. In this
case, valid values are from -0.99…0.99.
• Directly in the channel’s C.Ch[x].TenOhmOffset tag. In this case, valid
values are -99…99
For example, if the resistance of a copper RTD used with a channel is 9.74 Ω at
25 °C, you account for error by setting the 10 Ohm Copper Offset field on the
Configuration tab to -0.26 or by setting the
C.Ch[x].TenOhmOffset to -26.
To see where to set the 10 Ohm Copper Offset on the Configuration tab, see
page 127 .
Wire Off Detection
The 1756-IRT8I module alerts you when one or more wires have been
disconnected from a channel.
When a wire off condition occurs, the following events occur:
• Input data for the channel changes to a specific scaled value.
• A fault bit is set in the owner-controller indicating the presence of a wire
off condition.
For more information on module behavior when a wire off condition occurs, see
Table 10 on page 76 .
IMPORTANT Be aware that the Disable All Alarms feature, does not disable the wire off
detection feature. The Disable All Alarms feature disables all alarms on the
module.
The wire off detection feature is not an alarm. It is an indicator that a wire
has been disconnected from the channel but does not trigger an alarm.
To disable the wire off detection feature, you must disable the channel.