Siemens sinumerik 840D sl Function Manual page 554

3.1.3 External smoothing filters
If an external filter is to be interconnected to smooth the output voltage of the clearance
sensor before the A/D conversion of the output voltage by the I/O module, please ensure
that the resulting time constant is small in relation to the NC position controller cycle.
Note
It is better for the control if electromagnetic shielding is used to ensure a large signal-noise
ratio than if smoothing filters are used in the signal path.
3.2 Function-specific boundary conditions
NC stop from PLC
If, in addition to the programmed path motion, the traversing movement of the clearance-
controlled axes is also to be stopped in connection with an NC stop, the "NC stop axes and
spindles" interface signal must also be set in addition to the "NC stop" interface signal:
• DB21, ... DBX7.3 (NC stop)
• DB21, ... DBX7.4 (NC stop axes and spindles)
Followup
If a clearance-controlled axis is to be switched as an alarm response or via the
corresponding interface signal from the PLC in "follow-up" mode, setpoint output will cease
for clearance control on this axis.
Travel without software limit switches
If the clearance-controlled axes are to travel without referencing (travel without software limit
switches), values outside the traversing range used must be entered in the corresponding
machine data for the axis-specific software limit switches:
• MD36100 $MA_POS_LIMIT_MINUS (1st software limit switch minus)
• MD36110 $MA_POS_LIMIT_PLUS (1st software limit switch plus)
• MD36120 $MA_POS_LIMIT_MINUS2 (2nd software limit switch minus)
• MD36130 $MA_POS_LIMIT_PLUS2 (2nd software limit switch plus)
Clearance control takes the machine data into account even if an axis is not being
referenced.
Special functions: Clearance Control (TE1)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0
Boundary conditions
3.2 Function-specific boundary conditions
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