Sinumerik Alarm 25100 Axis %1 measuring system switchover not possible

Sinumerik Alarm 25100 Axis %1 measuring system switchover not possible

%1 = Axis name, spindle number

The prerequisites are not satisfied for the required encoder switchover: 1. The newly selected encoder must be in the active state (DB 31 – 48, DBX 1.5 or 1.6 = 1 “Position measuring system 1/2”) 2. The actual value difference between the two encoders is greater than the value in the axis-specific MD 36500 ENC_CHANGE_TOL (“Maximum tolerance for position actual value switchover”). Activation of the measuring system concerned takes place in accordance with the inter- face signals: “Position measuring system 1” (DB 31 – 48, DBX 1.5) and “Position measuring system 2” (DB 31 – 48, DBX 1.6), i.e. the position control is now operated with this measuring system. The other measuring system is switched over to follow-up mode. If both interface signals are set to “1”, then only the 1st measuring system is active; if both interface signals are set to “0”, the axis is parked. Changeover takes place as soon as the interface signals have changed, even if the axis is in motion!

– If the axis is a single axis when this alarm is triggered, the alarm is only effective for this axis (not effective for e.g. the channel or mode group)
– NC Stop on alarm.
– NC Start disable in this channel.
– Alarm display.
– Interface signals are set.

Please inform the authorized personnel/service department. When referencing the active position actual value encoder, the actual value system of the inactive encoder is set to the same reference point value as soon as phase 3 has been concluded. A later positional difference between the 2 actual value systems can have occurred only as the result of an encoded defect or a mechanical displacement between the encoders.
• Check the encoder signals, actual value cable, connectors.
• Check the mechanical fastenings (displacement of the measuring head, mechanical twisting possible).
• Increase the axis-specific MD 36500 ENC_CHANGE_TOL.Program continuation is not possible. The program must be aborted with “Reset”, then program execution can be reinitiated with NC Start, if necessary at the interruption point after “Block search with/without calculation”.

Program Continuation:
Clear alarm with the RESET key. Restart part program


  1. Siemens Diagnostics Guide by Siemens
Sinumerik Alarm 25100 Axis %1 measuring system switchover not possible