Omron NE1A-SCPU01 - 2006 Operation Manual page 149

Function Block Editing
Discrepancy Time
114
If the function block input type is set to Dual Channel Equivalent or Dual
Channel Complementary, the discrepancy time (i.e., the time between
changes in the inputs) can be evaluated.
The time between when one of the dual-channel inputs changes until the
other one changes is monitored. If the second dual-channel input does not
change before the discrepancy time expires, an error will occur and the Out-
put Enable output from the function block will not turn ON.
Dual channel mode
Dual Channel Equivalent
• Input 1: NC
• Input 2: NC
Dual Channel Complementary
• Input 1: NC
• Input 2: NO
The dual channel modes can be used to detect faults in safety devices and
safety device wiring monitored by the function block.
The time between changes in the inputs will not be monitored if the discrep-
ancy time is set to 0.
The discrepancy time is evaluated both when the input signals go from active
to inactive and from inactive to active.
Normal Operation Example for Dual Channel Equivalent Setting
Input 1
Input 2
Discrepancy time
Output
Enable
Discrepancy Normal
Error
Input signals Input signal status
Input Input
1 2
0 0 Inactive
0 1 Discrepant
1 0 Discrepant
1 1 Active
0 0 Discrepant
0 1 Inactive
1 0 Active
1 1 Discrepant
Discrepancy time
Section 6-3