D1-N Series Servo Drive User Manual Operation Principles
3-4 HIWIN MIKROSYSTEM Corp.
(1) Digital type
Digital encoder (or incremental encoder) normally outputs TTL RS422 differential signals. TTL
RS422 differential signal includes two digital pulses with 90 degrees phase difference. Its resolution
definition is shown in figure 3.2.1. The resolution of linear optical scale is usually 1 um.
Figure 3.2.1
(2) Analog type
Analog encoder outputs signals with two phases, sin and cos. The output signals are usually 1 Vpp
differential signals. 1 Vpp differential signal consists of two sinusoidal signals with 90 degrees phase
difference. The specification of analog encoder is usually displayed by grating period. For instance,
the grating period of commonly-used linear analog optical scale is 40 um. The grating period can be
finer by adjusting multiplier factor in D1-N servo drive to have better resolution than nanometer.
Figure 3.2.2
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