Overflow (InValue above the envelope)

What does FB ENVELOPE Value 2 mean?

The input value (InValue) has exceeded the defined upper 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.

• Analog sensor (e.g., pressure, flow, temperature) reading above its expected operating range due to calibration drift or process upset.
• Incorrect upper limit parameter (e.g., P1-06) set too low within the FB Envelope function block configuration.
• Signal conditioning error causing the input value to be amplified above the envelope's upper threshold (e.g., faulty amplifier).
• Sensor failure mode where the output is stuck at its maximum value or an open circuit on a voltage input (e.g., 10V pull-up).

Click steps to track your progress.

1. 1

   1. Measure the actual process variable (PV) and compare it to the 'InValue' displayed in the safety logic.

2. 2

   2. Verify the analog sensor's output (e.g., 4-20mA, 0-10V) directly at the input terminals of the safety module (e.g., EL3xxx terminal X2).

3. 3

   3. Check the 'Upper Limit' parameter (e.g., P1-06) within the FB Envelope configuration for correct scaling and value.

4. 4

   4. Calibrate the associated analog sensor according to manufacturer specifications.

5. 5

   5. Inspect the signal wiring from the sensor to the safety module for damage or short circuits to an external voltage source.