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Reference mark selector and limit magnet installation
IMPORTANT: Allow 24 hours after the scale application before fitting the magnets.
For accuracy and ease of positioning of the reference mark selector and limit magnets, the
applicator tool should be used. The magnet should be attached to the applicator tool as shown.
Limit magnets can be positioned at any user defined location along the scale, but the reference
mark selector magnet should be positioned adjacent to the selected IN-TRAC reference mark
as shown.
As the TONiC FS readhead passes the reference mark selector magnet or limit switch magnet,
a force of up to 0.2 N is generated between the magnet and the concentrators on the readhead.
The design of the bracket should be sufficiently stiff so that it is able to tolerate such force
without distorting.
Following the datum clamping instructions will prevent this magnetic force from disturbing
the scale (see
'Fitting the datum clamp'
on page 30).
Limit trigger point
The limit output is nominally asserted when the readhead limit switch sensor passes the limit
magnet leading edge, but can trigger up to 3 mm before that edge (see
installation drawing'
on page 26).
NOTES:
•
The reference and limit magnets may creep when influenced by magnetic materials in close
proximity. In such cases, they should be held in place using an additional fillet of epoxy glue
or similar along the outer edge of the magnet assembly. Optional bolted reference and limit
magnets are available (see
'RTLC20-S scale installation drawing'
•
The reference mark selector and limit actuator locations are correct for the readhead
orientation shown.
•
The reference mark selector magnet is only required for 'Customer selectable reference mark'
readheads. For more information refer to TONiC
part no. L-9517-9878).
•
External magnetic fields greater than 6 mT, in the vicinity of the readhead, may cause false
activation of the limit and reference sensors.
Original instructions
'RTLC20-S scale
on page 26).
FS encoder system data sheet (Renishaw
™
Magnet applicator tool
P limit magnet
Remove self-adhesive
backing paper
Reference mark
selector magnet
Selected IN-TRAC
reference mark
Q limit magnet
www.renishaw.com
31
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