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FB MON Bit 1

Monitoring Discrepancy Error - Input Group 2

Beckhoff · TwinSAFE Logic FB

¿Qué significa FB MON Bit 1 ?

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.

Causas comunes

  • 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.

Pasos de reparación & Lista de verificación

Haga clic en los pasos para seguir su progreso.

  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.

Ver todos los códigos en este manual (60)
Datos técnicos verificados. Última actualización: March 2026

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Fuente: Beckhoff TwinSAFE Logic FB