F31115 — Encoder 1: Amplitude error track A or B (A^2 + B^2)

F31115 reports that the composite signal level of Encoder 1 — the root of A^2 + B^2 of the two tracks — has left the permissible range. The manuals print the condition under two slightly different titles: 'Encoder 1: Signal level track A or B too low' and 'Encoder 1: Amplitude error track A or B (A^2 + B^2)'. On S120 and S150 the drive raises it when the signal level falls below the permissible limit value; the G130/G150 manual describes it as an amplitude error that can also be tripped by a level that is too high. Depending on the drive configuration, the same condition can also be output as an alarm or with no reaction instead of a fault. The message value shows both tracks ('A track: %1, B-track: %2'); what the drive puts into %1 and %2 is decoded below. The other Encoder 1 messages (F31110, F31111, F31112, F31116, F31117, F31118, F31120, F31121) are described on their own pages.

• On S120 and S150: the signal level (root of A^2 + B^2) of the encoder falls below the permissible limit value.
• On G130 and G150: the amplitude (root of A^2 + B^2) for encoder 1 exceeds the permissible tolerance, i.e. the level leaves the window between the lower and the upper response threshold.

1. Check that the encoder cables and the shielding are routed in compliance with EMC.
2. Check the plug connections.
3. Replace the encoder or the encoder cable.
4. Check the Sensor Module (e.g. contacts).
5. For measuring systems without their own bearing system: adjust the scanning head and check the bearing system of the measuring wheel.
6. For measuring systems with their own bearing system: ensure that the encoder housing is not subject to any axial force.

• The drive stores the fault value in r0949 and it must be interpreted hexadecimal as yyyyxxxx: yyyy is the signal level of track B (16 bits with sign), xxxx the signal level of track A (16 bits with sign). The placeholders in the message value carry the same levels: %1 = track A, %2 = track B.
• Reference levels for the encoder: the nominal signal level must lie in the range 375 mV to 600 mV (500 mV -25/+20 %); a signal level of 500 mV peak value corresponds to the numerical value 5333 hex = 21299 dec.
• Response thresholds on S120/S150: the level trips the message below 170 mV at input frequencies up to 256 kHz and below 120 mV at input frequencies above 256 kHz.
• Response thresholds on G130/G150: below 170 mV (observe the frequency response of the encoder) and above 750 mV.
• For resolvers on a Sensor Module (e.g. SMC10): the nominal signal level is 2900 mV (2.0 Vrms); the response threshold is below 1070 mV (the G130/G150 manual additionally gives 3582 mV as the upper threshold); a signal level of 2900 mV peak value corresponds to the numerical value 6666 hex = 26214 dec.
• The analog values of the amplitude error are not measured at the same time with the hardware fault output by the Sensor Module. The levels you read out can therefore differ from those present at the instant the fault was raised.

• r0949 — fault value: read the stored value here (interpret hexadecimal) and split it into the two track levels as decoded above, to see how far each track is from its nominal level.
• p0491 — motor encoder fault response: this parameter sets the response the drive applies when this encoder fault occurs; the manual points to it from the fault text for the ENCODER fault response.

Rectify the cause first, then acknowledge the fault — the acknowledgement is tied to the pulse inhibit, so the message must be acknowledged with the pulses inhibited before the converter is enabled and restarted. If the condition is configured with no reaction or as an alarm, the manual specifies no reaction and no acknowledgement for those configurations.