Siemens SINUMERIK 840Di Function Manual page 92

Detailed Description
2.2 Encoder monitoring
Passive measuring system
The following occurs when the zero mark monitoring is initiated:
• Alarm: " 25020 Axis <
Restrictions
Absolute encoder
The monitoring of the deviation between the absolute and incremental encoder track:
MD36310 $MA_ENC_ZERO_MONITORING > 0
MD30240 $MA_ENC_TYPE == 4
only detects deviations due to contamination of the absolute track. Corruptions of the
incremental track are not recognized. This type of monitoring is therefore intended only as a
supplementary monitoring that can be used when disturbances of the absolute position are
suspected.
Notice
Errors in the incremental track that cannot be detected with amplitude monitoring can cause
position deviations in the millimeter range. The deviation depends on the lattice pitch/line
count and the traversing velocity of the axis when the error occurs.
Complete position monitoring is only possible through redundancy, i.e., through comparison
with an independent second measuring system.
2-20
Axis identifier
The alarm is only displayed.
Note
Absolute encoders
In the event of a fault, the adjustment of the absolute encoder is lost and the axis is no
longer referenced. The absolute encoder must be readjusted. For information about
adjusting absolute encoders, refer to:
References:
/FB/ Description of Functions Basic Machine; Reference Point Approach (R1);
Section: Referencing with absolute encoders
> Zero mark monitoring of passive encoders"
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Axis Monitoring, Protection Zones (A3)