Monitoring Discrepancy Error - Input Group 2

What does FB MON Bit 1 mean?

A discrepancy has been detected between the channels of input group 2 in the FB MON function block. This means the redundant inputs are not switching in sync or are reporting different states, indicating a potential sensor fault, wiring issue, or incorrect timing that could compromise the monitoring function, leading to a safety stop.

• One channel of the redundant safety input device for Group 2 is experiencing an intermittent connection or contact failure.
• Damaged insulation or a short to an adjacent wire on one input channel (e.g., MonIn_CH2_2) of the monitored device.
• Physical obstruction or wear preventing proper actuation of the safety device's redundant contacts.
• Safety controller's internal input filtering for Group 2 is inadequate, allowing noise to be interpreted as a discrepancy.
• Parameter (e.g., P_MON_CONFIG_G2) setting for input logic (e.g., NO/NC) for Group 2 is incorrect.

Click steps to track your progress.

1. 1

   Observe the diagnostic status of both Input Group 2 channels (e.g., via software or LEDs IN_G2_A, IN_G2_B) while actuating the monitored safety device.

2. 2

   Measure the voltage potential on both input terminals (e.g., X11.1 and X11.2) of the safety controller for Group 2, relative to ground.

3. 3

   Verify the wiring integrity from the monitored device's output contacts to the safety controller's Input Group 2 terminals.

4. 4

   Adjust the discrepancy monitoring time (e.g., P_MON_DISCREPANCY_WINDOW_G2) in the safety controller to accommodate slight timing differences.

5. 5

   Inspect the monitored safety device itself (e.g., safety light barrier, gate switch) for physical damage, misalignment, or contamination.