F31101 — Encoder 1: Zero mark failed

F31101 is reported as Encoder 1: Zero mark failed: the zero mark monitoring for encoder 1 has tripped because the drive travelled a greater distance without a recognised zero mark than 1.5 times the parameterised zero mark distance. That expected distance is stored in p0425 for a rotary encoder and in p0424 for a linear encoder. Depending on how the drive is configured, the very same condition can also be issued only as an alarm (A) or with no reaction (N) rather than as a fault.

• The distance covered since POWER ON or since the last detected zero mark exceeded 1.5 times the parameterised zero mark distance, so the zero mark monitoring tripped.
• The expected clearance between zero marks comes from p0425 (rotary encoder) or p0424 (linear encoder); a value that does not match the encoder actually fitted leads to the same message.

1. Lay out and inspect the encoder cables so that their routing complies with EMC requirements.
2. Check the plug connections of the encoder.
3. Verify the encoder type — the encoder used must deliver equidistant zero marks.
4. Adapt p0425, the parameter for the clearance between zero marks, to the encoder actually in use.
5. If the message is only output above a speed threshold, reduce the filter time in p0438 where necessary.
6. When bit 1 of p0437 is active, also check p4686.
7. If the fault persists despite all this, replace the encoder or the encoder cable.

• Message value %1: r0949, interpreted as a decimal number, contains the number of increments the drive has counted after POWER ON or since it last detected a zero mark.
• 4 increments correspond to one encoder pulse, so the value tells you how many increments were counted without a fresh zero mark.

• p0425 — zero mark distance of the rotary encoder; adapt it to the actual clearance between the zero marks when F31101 occurs.
• p0424 — zero mark distance of the linear encoder; the monitoring compares against it when encoder 1 is linear, just as against p0425 for a rotary encoder.
• r0949 — read the fault value here (interpret it as decimal) to see how many increments were counted since POWER ON or the last detected zero mark.
• p0491 — the motor encoder fault response (ENCODER) that the manual cross-references for this fault; it governs how the drive responds when encoder monitoring trips.
• p0438 — square-wave encoder filter time; reduce it when the message appears only above a speed threshold.
• p0437 — extended Sensor Module configuration (SM); if its bit 1 is active, p4686 must be checked for this fault.
• p4686 — zero mark minimum length; examine this setting whenever bit 1 of p0437 is set.

Acknowledging this fault requires pulse inhibit: inhibit the drive pulses, acknowledge the fault, then re-enable the drive and restart. If the cause has not been removed — for example a p0425 setting that does not match the encoder fitted, or a faulty encoder cable — the monitoring trips again as soon as the counted increments exceed the permitted distance once more.