Fanuc alarm SV0448: UNMATCHED FEEDBACK ALARM
αi/βi Servo (SV0xxx) · Fanuc 0i-D
What it means
The sign of feedback from the separate detector is opposite to that from the built-in pulse coder, meaning the two loops disagree in polarity. With dual feedback the axis will servo against itself and rapidly exceed deviation limits. Correct the polarity via the direction parameter for the separate detector (parameter No. 2019#7 / related configuration) or fix mis-wiring of the external detector.
Likely causes
- Separate detector wired with reversed polarity
- External detector direction parameter set incorrectly
- Wrong detector mounted relative to motor rotation direction
- Configuration error after retrofit/rebuild
Need the part urgently?
Send us alarm SV0448 with your machine details — typical RFQ turnaround is 24–48h.