F31123 — Encoder 1: Signal level A/B outside tolerance

Fault F31123 means that the drive is measuring a signal level on Encoder 1 that is outside the permissible tolerance: the unipolar level of the pair AP/AN or of the pair BP/BN has left the permissible window. The unipolar nominal signal level of the encoder must lie in the range 2500 mV ± 500 mV; the drive responds to levels below 1700 mV and above 3300 mV.

The signal level is only evaluated when the Sensor Module properties are available (r0459.31 = 1) and when the monitoring is active (p0437.31 = 1). Depending on the drive configuration, the same condition can also be output with no reaction (N) or as an alarm (A) instead of a fault. The S120/S150 manual titles the code Encoder 1: Signal level A/B outside tolerance, the G130/G150 manual Encoder 1: Signal level A/B unipolar outside tolerance — both describe the same monitoring of the encoder's unipolar A/B levels.

• The unipolar level (AP/AN or BP/BN) for encoder 1 lies outside the permissible tolerance.
• The nominal unipolar signal level of the encoder must lie in the range 2500 mV ± 500 mV; a level below 1700 mV or above 3300 mV exceeds the response thresholds.

1. Make sure that the encoder cables and the shielding are installed in an EMC-compliant manner.
2. Check the plug connections and the contacts of the encoder cable.
3. Check for a short-circuit of a signal cable with mass or with the operating voltage.
4. Replace the encoder cable.

• The drive stores the fault cause as a binary value in r0949 (message value: "Fault cause: %1 bin").
• Bit 0 = 1: Either AP or AN is outside the tolerance.
• Bit 16 = 1: Either BP or BN is outside the tolerance.

• r0949 — fault value: read it in binary to see which signal pair is affected (bit 0 set: AP/AN, bit 16 set: BP/BN).
• r0459 — Sensor Module properties extended: the signal level is only evaluated when bit 31 = 1, i.e. when the Sensor Module properties are available.
• p0437 — Sensor Module configuration extended: the level monitoring only runs when bit 31 = 1, i.e. when monitoring is active.
• p0491 — motor encoder fault response ENCODER: sets the response with which the drive reacts to this encoder fault.

First remedy the cause, then acknowledge the fault and restart the drive. The acknowledgement is a pulse-inhibit acknowledgement: the drive only accepts it when the pulses are inhibited. How the drive reacts while the encoder signal level is faulty follows the motor encoder fault response set in p0491.