F32118 — Encoder 2: Speed change not plausible

F32118 is raised when the speed actual value of Encoder 2 changes faster than the drive considers plausible. The S120/S150 manual titles the message “Encoder 2: Speed change not plausible”, the G130/G150 manual “Encoder 2: Speed difference outside the tolerance range” — both describe the same condition: for an HTL/TTL encoder, the speed change (speed difference) has exceeded the value in p0492 over several sampling cycles. Where an averaged speed actual value is used, its change is additionally monitored in the current controller sampling time. Depending on how the drive is configured, the same condition can also be output only as an alarm or without any reaction.

• For the connected HTL/TTL encoder, the speed change — worded as speed difference on the G130/G150 — has exceeded the value in p0492 over several sampling cycles.
• If applicable, the change of the averaged speed actual value is monitored in the current controller sampling time and contributed to the detection.

1. Check the tachometer feeder cable for interruptions.
2. Check the grounding of the tachometer shielding.
3. If required, increase the maximum speed difference per sampling cycle in p0492.

• The drive stores the fault value in r0949, to be interpreted as a decimal number. The manual states that this value is only for internal Siemens troubleshooting, so it carries no diagnostic information for the on-site technician.

• p0492 — maximum velocity difference per sampling cycle for a square-wave (HTL/TTL) encoder; this is the threshold that the monitored speed change of Encoder 2 may not exceed, and the value the remedy tells you to increase if required.
• r0949 — fault value of this message; read it as a decimal number, but its content is reserved for internal Siemens troubleshooting.

The drive responds with an OFF1 rundown (where configured, braking via IASC/DCBRK; alternatives are shown in the table), so the drive coasts to a controlled stop. The fault may only be acknowledged while the pulses are inhibited; once acknowledged, the drive can be switched on again. When the same condition is configured as an alarm or without reaction, no acknowledgment is required.