Rockwell Automation 440C Guardmaster 440C-CR30 Configurable Safety Relay User Manual - Manual (Page 41)

Rockwell Automation Publication 440C-UM001C-EN-P - November 2014 41
Chapter
7
Discrepancy Time
Safety Monitoring functions using dual inputs have a feature that allows the
CR30 to test for the timing of the operation of both channels. In most cases, the
outputs of dual channel safeguarding devices change state within a few
milliseconds of each other. In some cases, the second channel can change state
much later than the first.
In these later cases, you want to allow (that is, make sure that) both channels
return to their “safety” state within a specified time relative to each other. For
example, the “safety” state of dual N.C. input is when both inputs are in the
closed state. Channel A can close before Channel B or Channel B can close before
Channel A. The CR30 allows you to specify a discrepancy time in 50 ms
increments, from 0…3 seconds.
Figure 25 - Discrepancy Time
The discrepancy is set in the Advanced Settings of each safety monitoring block.
The following example shows the Gate Switch function with the discrepancy
time set to 2 (2 x 50 = 100 ms).
When the discrepancy setting is set to zero, the CR30 does not test for
discrepancy. The duration between the operation of channel one and channel
two is infinite. The default value 100 ms.
Figure 26 - Setting Discrepancy Time
Channel A
Channel B
t <= Discrepancy Time
Output
t t
1
0
0
0
1
1