Incremental Encoder - Omron TJ1-DRT Hardware Reference Manual

Hardware reference
3.8.5

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 TJ1-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 TJ1-MC__ and the encoder.
The TJ1-FL02 does not have a termination inside. In case
of long distances or disturbed communication, add an
external termination to the TJ1-FL02.
HARDWARE REFERENCE MANUAL
fig. 90
D
A
B
0 1 2 3 4 5 6 7 7 6
C
E
5 4 3 2 1 0
147