Siemens alarm 25011: Axis %1 pollution of passive encoder

What it means

Same contamination-type degradation as alarm 25010, but detected on the passive (second) measuring system. The active position control continues, yet the redundant monitoring quality is impaired and a later changeover to this encoder would be unsafe.

Likely causes

• dirt/coolant on the second measuring system
• failing illumination source of the scale
• moisture ingress in scale housing
• shielding defects on the passive encoder cable

Replacement parts

We supply the following units for this alarm — tested, warranty-backed:

• linear/direct measuring system (per machine spec)

  encoder · Common cause

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