Siemens alarm F31115: Encoder 1: amplitude error track A or B (A^2+B^2)
SINAMICS S120 encoder fault (Sensor Module / DRIVE-CLiQ encoder) · SINAMICS S120
What it means
Amplitude of incremental A/B signals outside allowed range (software monitoring); one resolver winding may be broken.
Likely causes
- resolver/encoder winding break or weak signal
- encoder cable damage / poor EMC routing
- SMC/SME evaluation module marginal
- connector contamination
Triage note: Companion faults F31116/F31120 narrow to hardware-vs-supply-voltage causes; F31120 points at cable/supply rather than encoder element.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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motor resolver/encoder (1FK7/1FT6 built-in)
encoder/resolver · Primary suspect
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6FX5002-2E… / 6SL3066-0BA00-…
signal/DRIVE-CLiQ cable · Common cause
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6SL3055-0AA00-… (SMC20)
sensor evaluation module (external encoders) · Check if others ruled out
Need the part urgently?
Send us alarm F31115 with your machine details — typical RFQ turnaround is 24–48h.