Rockwell Automation Allen-Bradley 1734-IB8S, User Manual

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94 Rockwell Automation Publication 1734-UM013J-EN-P - July 2014
Chapter 5 Configure the Module in a GuardLogix Controller System
Configure the Safety Analog Input Channel Operation
Follow this procedure to configure the safety analog input channels.
1. From the Module Properties dialog box, click the Safety Input
Configuration tab.
2. Assign the Operation Type.
3. If you chose Equivalent, you must also assign a Discrepancy Time, from
0…65,530 ms in 10 ms increments.
This is the amount of time the two channels can be different from each
other (larger than the Deadband value) before a discrepancy error is
declared. A discrepancy time setting of 0 ms means that the channels in a
dual configuration can be discrepant for an infinite amount of time
without a fault being declared, effectively eliminating the usefulness of
dual channel mode.
4. Configure a Deadband for the paired safety analog inputs.
The deadband can be any value from 0…32767 (engineering units) in
increments of 1. When the paired input values exceed the deadband
tolerance for longer than the Discrepancy Time, a discrepancy fault
occurs.
5. If desired, configure a Channel Offset for the paired safety analog inputs.
Choose Description
Single Inputs are treated as single channels. Dual-channel safety inputs can be configured as two
individual, single channels.
IMPORTANT: Use single-channel mode when you intend to use the GuardLogix safety
application instructions.
Equivalent Inputs are treated as a dual-channel equivalent pair. The channels must match within the
discrepancy time or an error is generated.
IMPORTANT
If you are using a Dual-channel Analog (DCA) safety instruction in
your application program, you must configure the 1734-IE4S module
for single-channel operation. Analog input pairs are then evaluated
as pairs and compared to each other in the application logic.
TIP
Configure a deadband value for applications that use two sensors to
measure the same variable; otherwise, spurious trips may occur.