What it means
F31126 reports that the signal level of Encoder 1 — the amplitude of the two incremental tracks A and B — exceeds the permissible limit. The G130/G150 manual titles the condition “Encoder 1: Amplitude AB too high”, the S120/S150 manual “Encoder 1: Signal level track A or B too high”; both describe the same monitoring of the encoder signals.
The nominal signal level of the encoder must lie in the range 375 mV to 600 mV (500 mV -25/+20 %). The drive raises the fault when the sum (|A| + |B|) exceeds 1120 mV or the root of (A^2 + B^2) exceeds 955 mV. Depending on the drive configuration, the same condition can also be output as an alarm or with no reaction at all.
The manual notes that the analog values of the amplitude error are not measured at the same time with the hardware fault output by the Sensor Module.
Why it appears
- The signal level (|A| + |B|) or the amplitude (root of A^2 + B^2) of Encoder 1 exceeds the permissible limit value.
What to check
- Check that the encoder cables and the shielding are routed in compliance with EMC.
- Replace the encoder or the encoder cable.
Reading the message value
- The drive stores the fault value in r0949, to be interpreted in hexadecimal as yyyyxxxx: yyyy is the angle, xxxx is the amplitude, i.e. the root of A^2 + B^2 (16 bits without sign).
- The angle 0 … FFFF hex corresponds to 0 … 360 degrees of the fine position; zero degrees is present at the negative zero crossover of track B.
- For the amplitude: a signal level of 500 mV peak value corresponds to the numerical value 299A hex = 10650 dec.
Parameters the manual names
- r0949 — fault value: read it in hexadecimal to obtain the amplitude and the angle that were measured when F31126 was raised.
- p0491 — motor encoder fault response (ENCODER): this is where the drive's response to a fault of this encoder is set; the entry for this code refers to it.
Acknowledging and restarting
The fault is acknowledged with pulse inhibit: once the cause has been remedied, switch off the pulses of the power stage and switch them on again, and the drive can restart. Where the drive is configured to output this condition as an alarm or with no reaction, neither a reaction nor an acknowledgement follows.
What differs between the drive families
Straight from the manuals' own fields — F31126 is not described identically everywhere.
| Drive family | Reaction | Acknowledge | Message class | Component | Manual |
|---|---|---|---|---|---|
| S120, S150 | Infeed: NONE Servo: ENCODER (IASC/DCBRK, NONE) Vector: ENCODER (IASC/DCBRK, NONE) Hla: ENCODER (NONE) | PULSE INHIBIT | Actual position/speed value incorrect or not available (11) | Encoder 1 | SINAMICS S120, S150 List Manual · p. 3036 |
| G130, G150 | Vector: ENCODER (IASC/DCBRK, NONE) Infeed: NONE | PULSE INHIBIT | Actual position/speed value incorrect or not available (11) | Encoder 1 | SINAMICS G130, G150 List Manual · p. 1725 |
The drives this code lives on
F31126 is described for G130, G150, S120, S150. These are the converters of those families in our catalogue — price on request.
Questions technicians ask
What does fault F31126 mean on a SINAMICS drive?
The signal level of Encoder 1, tracks A and B, is above the permissible limit: the nominal level is 375 mV to 600 mV, and the fault trips when (|A| + |B|) exceeds 1120 mV or the root of (A^2 + B^2) exceeds 955 mV.
How do I fix fault F31126?
Check that the encoder cables and shielding are routed in compliance with EMC, and replace the encoder or the encoder cable. Afterwards the fault is acknowledged via pulse inhibit and the drive restarts.
What does the F31126 fault value in r0949 tell me?
Interpreted in hexadecimal, yyyyxxxx contains the angle (yyyy: 0 … FFFF hex corresponds to 0 … 360 degrees of the fine position) and the amplitude (xxxx); 500 mV peak corresponds to 299A hex = 10650 dec.
Can F31126 also appear as an alarm?
Yes. Depending on the drive configuration, the same condition can be issued as an alarm or with no reaction, and in those cases neither a reaction nor an acknowledgement applies.
Codes next to this one
Source
Written from Siemens' own List Manuals and operating instructions; every number, designation and parameter on this page is checked against them before publication.
All SINAMICS codes: fault and alarm codes · the F31xxx group · SINAMICS manuals · Siemens manuals