Cause: PID feedback low threshold warning comes when the feedback value used by the PID controller has dropped below a predefined low limit. This could signal potential issues with the process, the controller, or the associated sensors.

"PFAL "PID Feedback Low Threshold" warning in a Schneider ATV950 drive indicates that the feedback signal in a PID (Proportional-Integral-Derivative) control loop has fallen below the low threshold set in the drive's configuration. This means that the feedback value from the process being controlled is lower than expected, which could signify a problem with the process, the sensor, or the configuration settings.

Here are steps to address the PFAL warning:

1. Check Feedback Sensor:

   • Verify the feedback sensor (e.g., pressure sensor, temperature sensor, flow meter) to ensure it is functioning correctly and providing accurate readings. Look for any signs of damage or malfunction.

2. Inspect Sensor Wiring and Connections:

   • Ensure all wiring and connections between the sensor and the drive are secure and undamaged. Loose or corroded connections can lead to incorrect feedback readings.

3. Review PID Settings:

   • Check the PID control settings in the drive. Ensure the low threshold value is set correctly according to the process requirements. Adjust the setpoint and threshold if necessary.

4. Analyze Process Conditions:

   • Examine the current process conditions to determine if there have been any changes that could cause the feedback to fall below the low threshold. This could include changes in load, process demands, or environmental conditions.

5. Monitor Feedback Signal:

   • Use the drive’s monitoring features to track the feedback signal in real-time. Look for patterns or drops that could indicate why the feedback is below the threshold.

6. Calibrate Sensors:

   • If possible, calibrate the feedback sensor to ensure it is providing accurate measurements. Calibration may correct any drift or inaccuracy in the sensor readings.

7. Check for Interference:

   • Electrical noise or interference can affect sensor readings. Ensure that sensor cables are properly shielded and routed away from potential sources of electrical noise.