ABB ACS880 Fault 7121 — Analog Input Supervision

What This Fault Means

Fault 7121 triggers when an analog input (4-20mA or 0-10V) drops below the configured minimum supervision level. This typically means the sensor or transmitter has failed or lost its wiring.

Common Causes

• Broken wire to the 4-20mA transmitter
• Transmitter power supply failure
• Sensor failure causing signal to drop below 4mA
• Loose terminal connection at the drive or transmitter

Recommended Fix

1. Measure the current at the drive's analog input terminal with a clamp meter (should be 4-20mA in normal operation).
2. If <4mA, trace the wiring back to the transmitter.
3. Verify 24VDC power at the transmitter.
4. If the transmitter and wiring are healthy, check the analog input supervision parameters (12.03, 12.04).
5. To temporarily bypass, set the AI supervision mode to 'Warning' instead of 'Fault' (parameter 30.06).