F33131 — Encoder 3: Deviation position incremental/absolute too large

F33131 is reported for Encoder 3. The drive checks the position the encoder provides in two ways and raises this message when they do not agree: on an absolute encoder it reads the absolute position cyclically and compares it with the incremental position — if the difference is excessively high, the absolute position that was read is rejected. On an incremental encoder the check takes place each time the zero pulse is passed, and a deviation in the incremental position there triggers the message. The manuals print the title as "Encoder 3: Deviation position incremental/absolute too large" (G130/G150) and "Encoder 3: Position deviation incremental/absolute too high" (S120/S150); the behaviour described behind both titles is identical. Depending on how the drive is configured, the same condition can also be output as an alarm (A) or with no reaction (N).

• Absolute encoder: while the absolute position is being read cyclically, an excessively high difference to the incremental position was detected, and the absolute position that was read is rejected. The limit for this deviation depends on the encoder: for an EnDat encoder it is supplied by the encoder itself and is a minimum of 2 quadrants (e.g. EQI 1325 > 2 quadrants, EQN 1325 > 50 quadrants); for other encoders it is 15 pulses, i.e. 60 quadrants.
• Incremental encoder with equidistant zero marks: a deviation in the incremental position was detected when the zero pulse was passed. The first zero mark passed supplies the reference point for all subsequent checks; every further zero mark must lie at n times that distance referred to the first zero mark.
• Incremental encoder with distance-coded zero marks: a deviation in the incremental position was detected when the zero pulse was passed. The first zero mark pair supplies the reference point for all subsequent checks; every further zero mark pair must have the expected distance to the first zero mark 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 whether strong ambient magnetic fields are present.
5. Adapt the parameter for the clearance between zero marks (p0425).
6. If the message is output above a speed threshold, reduce the filter time if necessary (p0438).

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

• r0949 — fault value: read the size of the deviation here, interpreted as a decimal number and given in quadrants (1 pulse = 4 quadrants).
• p0425 — encoder rotary zero mark distance (Enc rot dist ZM): adapt this parameter to the actual clearance between the zero marks of the encoder.
• p0438 — square-wave encoder filter time (Enc t_filt): reduce this filter time if the message is only output above a speed threshold.

When the message comes as a fault, the drive performs an OFF1 stop (alternative reactions can be configured) and the fault must be acknowledged with PULSE INHIBIT: after eliminating the cause, inhibit the pulses and acknowledge; the drive can then be restarted. If the same condition is configured as an alarm (A) or without any reaction (N), the manual gives reaction NONE and acknowledgement NONE for both variants — there is then nothing to acknowledge.