Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 171)

Section 4B
Connecting the 3-axis Servo Module
4B-25
A touch probe can be interfaced with the digital servo module through
connector CN9. Refer to Figure 4B.5 for the location of connector CN9
on the digital servo module. Touch probe cable information can be found
on page 7A-38.
The time delay between the servo module receiving the touch probe trigger
and latching the current axis position is considered negligible. However,
you should take into account any external delays that can introduce
position “staleness” in the probing operation, especially at high probing
speeds.
It is a good idea to establish an offset for the distance between the actual
location, as sensed by the touch probe at a very low speed, and the location
sensed by the touch probe at the intended probing speed. The offset can
then be added or subtracted to any future values obtained through probing.
This helps insure that if there are any external delays in the trigger signal,
the position staleness shows up as a constant position offset error and is
removed from the measurement (assuming the external delay is
repeatable).
The motion controller touch probe interface is intended for use with units
that offer 5V dc compatible solid state relay outputs (see Figure 4B.23).
Other configurations can be supported as long as the user operates within
the published electrical specifications.
The touch probe circuitry resident on the servo module only responds to
the trigger probe edge changes. Polarity transition (high to low or low to
high) is programmable through the AMP parameter Probe Transition
Specify the probe transition in AMP as rising edge or falling edge. Once
the active edge occurs, position data is captured by the module, and
additional occurrences of the trigger signal have no effect until the probe is
reenabled under program control.
Refer to the 9/Series CNC 9/230, 9/260 and 9/290 AMP Reference
Manual, publication 8520-6.4, for more information.
ATTENTION: It is preferred, from a safety standpoint, that the
touch probe relay be closed at rest and open when the touch
probe stylus deflects. Then, if a wire breaks or shorts to ground,
it will appear to the system as a probe fired and the probing
cycle in process will stop commanding motion towards the part.
The user should make every effort to insure fail-safe operation
of the touch probe. Not all vendors of touch probe control
units conform to this safety consideration.
4B.4
Wiring a Touch Probe to the
Digital Servo Module