1-8 One-Way Positional accuracy
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Repeatability (CG type)
The repeatability is measured by moving to a given theoretical position seven times, each time approaching from the same
direction. The actual position of the output shaft is measured each time and repeatability is calculated as the 1/2 of the
maximum difference of the seven data points. Measured values are indicated in angles (arc-sec) prefixed with "±".
.
CG type
(Unit: arc-sec)
Model
Reduction ratio
SHA20A
SHA25A
SHA32A
SHA40A
Ratio to full speed
±
5
±
5
±
4
±
4
Bi-directional repeatability (CG type)
For the "bi-directional repeatability", the shaft is rotated beforehand in the forward (or reverse) direction and the stop position
for that rotation is set as the reference position. An instruction is given to rotate the shaft in the same direction and from the
stopped position, the same instruction is given in the reverse (or forward) direction and the difference between the stop
position after this rotation and the reference position is measured. The average value from repeating this 7 times in each
direction is shown and the maximum value measured at the 4 locations on the output shaft is shown.
CG type
(Unit: arc-sec)
Model
Reduction ratio
SHA20A
SHA25A
SHA32A
SHA40A
50:1
75
60
60
50
80:1 of more
30
25
25
20
P1
P2
＊
P1
～
P7
：
Stop position
X
：
Maximum error
P7
X
Repeatability
：±
X/2
P1
P1’
＊
P1
～
P7
：
Stop position after forward rotation
P1’
～
P7’
：
Stop position after reverse rotation
X1
～
X7
：
Difference between the stop positions
after forward and reverse rotations
Reverse positional accuracy
：
|X1+X2+
・・・
+X7|/7
X1
X2
P2
P2’
P7’
P7
X7
