Excessive PID Feedback

What does FbH mean?

The PID feedback input signal has continuously exceeded the threshold set in parameter b5-36 for a duration longer than specified in b5-37. This fault occurs when PID fault detection (parameter b5-12) is enabled (e.g., set to 1, 2, 4, or 5). Common causes include incorrect PID parameter tuning, faulty feedback wiring, or a malfunctioning feedback sensor, leading to unstable process control.

• Process variable (PV) exceeding the upper limit (b5-36) due to an actual overproduction or overpressure condition in the controlled process.
• Incorrect scaling of the PID feedback input (e.g., from an analog sensor), causing the drive to interpret a normal process value as excessive.
• Sensor failure or incorrect calibration, providing a falsely high feedback signal to the drive's analog input terminal (e.g., A1, A2).
• Electrical noise or ground loop affecting the analog feedback signal wiring, causing intermittent spikes above the b5-36 threshold.
• Incorrect setting of parameter b5-36 (PID feedback upper limit) or b5-37 (PID feedback fault delay time), triggering the fault too sensitively.

Click steps to track your progress.

1. 1

   Verify the actual process variable (e.g., pressure, flow, temperature) at the sensor's physical location using a calibrated external gauge or instrument.

2. 2

   Measure the analog voltage or current signal directly at the drive's feedback input terminals (e.g., A1-AC) using a multimeter and compare to the expected scaled value.

3. 3

   Check the scaling parameters for the analog input (e.g., C3-01, C3-02 for 0-10V or 4-20mA) to ensure they match the sensor's output range and the desired engineering units.

4. 4

   Review parameter b5-36 (PID Feedback Upper Limit) and b5-37 (PID Feedback Fault Delay Time) and adjust them to match the process's normal operating range and acceptable transient excursions.

5. 5

   Inspect the feedback signal wiring for proper shielding, grounding, and absence of physical damage or proximity to high-current power cables.

6. 6

   Temporarily disable PID fault detection (b5-12 = 0) and monitor the PID feedback value (e.g., U1-07) to understand its behavior under varying process conditions.