412LXR Series Product Manual
Chapter 3 - How to Use the 412LXR
26
Setting Home Sensor
The 412LXR is equipped with a “home” position reference sensor. This is located on the same PCB as
the limit sensors and the target is located between the limit targets. This sensor is typically used in
conjunction with the encoder “Z” marker (refer to “Z” channel reference below). If the unit is equipped
with this option it will be set at the “Z” channel location. If another home location is desired the home
target can be adjusted by loosening the screws on the target and sliding it along the track. Note: If the
home sensor is used without “Z” channel, the home position repeatability is reduced to +/-5 microns.
Z Channel Position Reference
The Z channel is an output on the encoder. Many servo controllers support this input. The Z channel on
the 412LXR is located in one of three positions, (positive end, mid travel, or negative end). The location
depends on how the unit was ordered (See Chapter 2, Order Number Nomenclature). The Z channel is a
unidirectional device. This means that the final homing direction must occur in one direction. The
412LXR is set that the final home direction is to be toward the positive end of the table (See Chapter 2,
Dimensional Drawing, for positive direction definition). The repeatability of the Z channel is equal to +/- 2
resolution counts of the encoder (except for 0.1 micron scales which have a repeatability of +/-1
microns). Thus the repeatability of the “Z” channel equals:
Encoder Resolution Z Channel Repeatability
5 micron
+/- 10 micron
1 micron
+/- 2 micron
0.5 micron
+/- 1 micron
0.1 micron
+/- 1 micron
NOTE: Home repeatability is also very dependent on controller input speed and homing algorithms. The
above repeatability does not include possible controller tolerance. Additionally, to achieve the highest
repeatability the final homing speed must be slow. Slower final speed usually results in higher
repeatability.
NOTE: The “Z” channel output is only one resolution count wide. Thus the on-time may be very brief.
Due to this some controllers may have difficulty reading the signal. If you are experiencing the positioner
not finding the “Z” channel during homing, try reducing final homing speed; also refer to your controller
manual for frequency rates of the “Z” channel input.
Grounding / Shielding
All cables are shielded. These shields are to be grounded to a good earth ground. Failure to ground
shields properly may cause electrical noise problems. These noise problems may result in positioning
errors and possible run away conditions.
