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Hardware reference
3.13.8 Incremental encoder
An incremental encoder has this phase definition:
•
An advanced phase A for forward rotation.
•
An advanced phase B for reverse rotation.
By monitoring the relative phase of the 2 signals, you can easily detect the
rotation direction. If signal A leads signal B, the movement is clockwise and
the counter increments. If channel B leads channel A, the movement is
counterclockwise and the counter decrements.
Most rotary encodes also provide an additional Z marker. This Z marker is a
reference pulse within each revolution. With these 3 signals, you can
determine the direction, the speed and the relative position.
Encoder input
The pulse ratio of the TJ2-MC__ is 1: every encoder edge (i.e., a pulse edge
for either phase A or B) is equal to one internal count.
The figure shows phase A (A), phase B (B) and the number of counts (C)
for forward or clockwise rotation (D) and reverse or counterclockwise
rotation (E).
The signals A, B and Z appear physically as A+ and A-, B+ and B- and Z+
and Z-. They appear as differential signals on twisted-pair wire inputs. This
makes sure that common mode noise is rejected.
When you use an encoder from other manufacturers, check the encoder
specification for the phase advancement carefully. If the phase definition is
different from the phase definition of the standard OMRON equipment,
reverse the B-phase wiring between the TJ2-MC__ and the encoder.
Note
The TJ2-KS02 does not have a termination inside. In case of long
distances or disturbed communication, add an external termina-
tion to the TJ2-KS02.
HARDWARE REFERENCE MANUAL
fig. 144
D
A
B
0
1
2
3
4
5
6
7
7
6
C
E
5
4
3
2
1
0
266
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