Rockwell Automation Publication 1734-UM013N-EN-P - September 2017 101
Configure the Module in a GuardLogix Controller System Chapter 5
Configure the Safety Analog Input Channel Operation
To configure the safety analog input channels, follow this procedure.
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 measurement is the amount of time the two channels can differ 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. This setting would effectively eliminate 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.
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.
Configure a deadband value for applications that use two sensors to
measure the same variable; otherwise, spurious trips can occur.
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