Control Techniques SM-encoder plus User Manual page 14

4.4.3 No isolation
As shown in Figure 4-7 the encoder 0V connection may be permanently connected to
the housing. This has the advantage that the encoder body can form a shield for its
internal circuits. However it permits noise current from the motor body to flow into the
encoder cable shield. A good quality shielded cable correctly terminated protects the
data against this noise current, but much more care is needed in ensuring correct cable
management than for the isolated cases.
14
Figure 4-6 Encoder galvanically isolated from encoder body
No Isolation
between motor shaft
and encoder
Motor
Housing
Motor
Shaft
No Isolation
between motor housing
and encoder housing
Figure 4-7 No isolation
between motor shaft
Motor
Housing
Motor
Shaft
No Isolation
between motor housing
and encoder housing
www.controltechniques.com
0V
A
A
+5V
0V
B
B
+5V
0V
Z
Z
+5V
Encoder
Galvanic
Housing
Isolation
No Isolation
and encoder
0V
A
A
+5V
0V
B
B
+5V
0V
Z
Z
+5V
Encoder
Encoder
Body
Housing
Encoder
Circuit
Stray
Capacitance
Encoder
Connection
Encoder
Body
Encoder
Circuit
Stray
Capacitance
Encoder
Connection
0V
connected
to encoder
housing
SM-Encoder Plus User Guide
Issue Number: 3