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Sigma II User's Manual
Note: The number of bits representing the resolution of the applicable encoder is not the same as the num-
ber of encoder signal pulses (A and B phase) output from the servo amplifier.
3. Determine the reference unit used.
A reference unit is the minimum position data unit used to move a load. (Mini-
mum unit of reference from the host controller).
Examples (in mm):
•
Reference unit can be0.1in., or 0.01in., or 0.01mm, or 0.001mm, etc.
A reference unit of one pulse moves the load by one reference unit.
•
When the reference unit is 1µm
If a reference of 50000 units is input, the load moves 50mm (1.97in.)
(50000 × 0.001mm = 50mm).
4. Determine the load travel distance per load shaft revolution in reference units.
Travel distance per load shaft revolution = Travel distance per load shaft revolution
•
When the ball screw pitch is 0.20in. (5mm) and the reference unit is
0.00004in. (0.001mm),
Ball Screw
Load shaft
P
P: Pitch
P
1 revolution =
reference unit
To move a table in 0.001mm units
Reference unit: 0.001mm
Determine the reference unit according to
equipment specifications and positioning accuracy.
0.20
------------------ -
=
5000
(reference units)
0.00004
Disc Table
Load shaft
360°
1 revolution =
reference unit
5-29
Chapter 5: Parameter Settings and Functions
Reference Unit
Belt and Pulley
Load shaft
D: Pulley
1 revolution =
reference unit
π∆
D
D: Pulley
πD
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