turn
1
8
Readhead mounting and alignment
Mounting brackets
The bracket must have a fl at mounting surface, ensure conformance to the installation tolerances,
allow adjustment to the rideheight of the readhead, and be suffi ciently stiff to prevent defl ection or
vibration of the readhead during operation.
Readhead set-up
Ensure that the scale surface, readhead optical
window and mounting face are clean and free
from obstructions. To set nominal rideheight,
position readhead spacer with the ‘ L’ shaped
aperture under the optical centre to allow
normal LED function during set-up procedure.
Adjust the readhead to maximise the signal
strength. On RGH20 direct output you
should achieve a Green LED on the
readhead over the full rotation.
For RGH20F/REF systems the SETUP
LED on the interface should be at least
Green, ideally Blue or Purple over the
full rotation.
NOTE:
When using REF system ensure
that Automatic Gain Control
(AGC) is switched off.
(CAL/AGC LED on the interface is off).
NOTE:
Ensure readhead
fi xing screws are tightened
to 0.5 Nm to 0.7 Nm.
Limit switch
A limit switch signal is output when the readhead sensor passes over the magnetic actuator.
Reference mark set-up
To ensure unidirectional repeatability, the reference mark requires phasing with the scale in the
direction of normal datuming operation. A reference pulse is output in both directions, but repeatability
is guaranteed only in the phased direction. Ensure readhead is set-up correctly with a Green LED
indication over the full rotation and that the reference mark actuator is fitted correctly.
NOTE:
It is recommended that a datum procedure is performed as part of any power-up sequence to
ensure the correct datum position is recorded.
Phasing procedure
The readhead must be moved over the reference mark in the direction to be used for the datuming
operation. The reference mark is phased correctly when the set-up LED on the readhead or interface
fl ashes red for 0.25 seconds. If it fl ashes Orange or goes Blank, the reference mark adjuster screw
should be turned anti-clockwise by
1
8
turn and the procedure repeated until a red fl ash is obtained.
Orange Blank
Red
RGH20
LED colour, except at
reference mark position.
RGH20
LED colour, except at
reference mark position.
Green Orange Red
Yaw
0°±0.5°
Roll
0°±1°
Pitch
0°±1°
0.8 ±0.08 mm
Rideheight
RGH20F/REF
SETUP LED colour, except at reference mark position.
Red Orange Blank
NOTE:
Reference mark fl ashes only
occur up to 100 mm/s traverse speed.
RGH20F/REF
SETUP LED colour, except at
reference mark position.
Green Orange Red
Blue
Purple
NOTE:
The RGH20F readhead does not have an LED.
NOTE:
The RGH20F readhead does not have an LED.