Underflow (InValue below the envelope)

What does FB ENVELOPE Value 1 mean?

The input value (InValue) has fallen below the defined lower limit of the envelope in the FB Envelope function block. This indicates a deviation from the expected operating range, potentially causing the safety function to trip or behave unpredictably, leading to an unsafe state.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Review the FB Envelope parameters, specifically 'Target Value' and 'Offset', in the TwinSAFE configuration to ensure they match the application's actual requirements.

2. 4

   Monitor the 'InValue' in real-time using diagnostic tools (e.g., TwinCAT Scope) to observe its behavior and confirm the underflow condition.