Emerson SI-Universal User Manual page 30

Figure 5-2 Encoder galvanically isolated from encoder body
between motor housing
and encoder housing
5.2.3 No isolation
As shown in Figure 5-3, 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
this permits noise current from the motor body to flow into the encoder cable shield. The use of high
quality shielded cable correctly terminated, will help protect the data against induced noise, but a
greater level of care must be taken to ensure good cable management than would be used for
example in isolated cases.
Figure 5-3 No isolation
between motor housing
and encoder housing
30
No Isolation
between motor shaft
and encoder
Motor
Housing
Motor
Shaft
No Isolation
No Isolation
between motor shaft
and encoder
Motor
Housing
Motor
Shaft
No Isolation
Encoder
housing
0V
A
A
+5V
0V
B
B
+5V
Galvanic
Encoder
Isolation
Housing
0V
A
A
+5V
0V
B
B
+5V
Encoder
Body
Encoder
Circuit
Stray
Capacitance
Encoder
Connection
Encoder
body
Encoder
Circuit
Stray
capacitance
Encoder
Connection
0V connected
to encoder
housing
SI-Universal Encoder User Guide
Issue: 2