Feedback process channel error (1Vss)

What does FA49 mean?

This diagnostic message signals an error in the analog signal provided by a 1Vss feedback system. The amplitude of the sine/cosine analog signal is detected as too small, falling outside the specified tolerance range (typically 0.53 Vss to 1.34 Vss), leading to unreliable or inaccurate position feedback. This can be caused by faulty wiring, loose connections, or incorrect monitoring parameters. The drive will switch off to prevent uncontrolled operation and ensure safety.

• Damaged or poorly shielded 1Vss encoder cable, leading to signal attenuation or noise interference.
• Faulty 1Vss incremental encoder with a weak output signal amplitude (e.g., below 0.8Vpp or 0.6Vpp).
• Improper termination impedance setting (e.g., P-0-0015) for the 1Vss feedback input.
• Loose connection or corrosion at the drive's feedback connector (e.g., X10) or the encoder's connector.
• Long feedback cable runs without proper amplification or a differential receiver, causing significant signal drop.

Click steps to track your progress.

1. 1

   Using an oscilloscope, measure the sine and cosine signals at the drive's feedback input connector (e.g., X10). Verify peak-to-peak amplitude (expecting 1Vpp ± 10%).

2. 2

   Inspect the 1Vss encoder cable for any physical damage, kinks, or inadequate shielding. Replace if necessary.

3. 3

   Verify the feedback termination resistor parameter (e.g., P-0-0015) is correctly set for 1Vss feedback (typically 120 Ohms).

4. 4

   Check for continuity of all signal wires (sin+, sin-, cos+, cos-, Z+, Z-, VCC, GND) from the drive to the encoder.

5. 5

   Temporarily connect a known good 1Vss encoder with a short cable to the drive to determine if the encoder or the cabling is at fault.