F31131 — Encoder 1: Deviation position incremental/absolute too large

F31131 is reported by Encoder 1 when the positions obtained from the incremental and the absolute evaluation drift apart too far. The manuals print the condition under two titles — “Encoder 1: Deviation position incremental/absolute too large” and “Encoder 1: Position deviation incremental/absolute too high” — and describe it identically, so this page covers both wordings. On an absolute encoder the drive reads the absolute position cyclically; if it differs excessively from the incremental position, the absolute position that was just read is rejected. On an incremental encoder the check runs whenever the zero pulse is passed. The drive stores the measured deviation in r0949, in quadrants. Depending on the drive configuration, the same condition can also be output as an alarm (A) or with no reaction (N); in both cases the manual specifies neither a reaction nor an acknowledgement.

• Absolute encoder: while the absolute position is being read cyclically, an excessively high difference to the incremental position is detected, and the absolute position that was read is rejected.
• The permissible deviation depends on the encoder: an EnDat encoder supplies the limit itself, as a minimum of 2 quadrants (e.g. EQI 1325 > 2 quadrants, EQN 1325 > 50 quadrants); for other encoders the limit is 15 pulses = 60 quadrants.
• Incremental encoder with equidistant zero marks: a deviation in the incremental position is detected when the zero pulse is passed. The first zero mark passed supplies the reference point for all subsequent checks, and every further zero mark must lie at n times the distance from the first one.
• Incremental encoder with distance-coded zero marks: the first zero mark pair supplies the reference point for all subsequent checks, and every further zero mark pair must keep the expected distance to the first pair.

1. Check that the encoder cables are routed in compliance with EMC.
2. Check the plug connections.
3. Replace the encoder or the encoder cable.
4. Check whether the coding disk is dirty or strong ambient magnetic fields are present.
5. Adapt the parameter for the clearance between the zero marks (p0425).
6. If the message is output above a speed threshold, reduce the filter time if necessary (p0438).

• The message value %1 is the fault value, which the drive writes to r0949; interpret it as a decimal number.
• The value is the measured deviation in quadrants, where 1 pulse corresponds to 4 quadrants.

• r0949 (fault value): for this message it contains the deviation in quadrants — interpret decimal, 1 pulse = 4 quadrants.
• p0425 (Encoder rotary zero mark distance): the clearance between the zero marks; adapt it when the checks at the zero marks keep raising the message.
• p0438 (Square-wave encoder filter time): reduce this filter time if the message occurs above a speed threshold.
• p0491 (Motor encoder fault response ENCODER): the manual cross-refers to this parameter; it holds the encoder fault response the drive applies when the fault is raised.

The fault is acknowledged with pulse inhibit: the acknowledgement is accepted once the drive's pulses are inhibited, and after acknowledgement the drive can be restarted. Where the same condition is configured as an alarm (A) or with no reaction (N), no reaction and no acknowledgement take place.