SM-Encoder Plus User Guide
13
Issue Number: 3
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4.4.1
Encoder with galvanic isolation from motor
When galvanically isolated the encoder device is mounted to the motor with isolation
fitted between the motor housing / shaft and encoder as shown in Figure 4-5.
Figure 4-5 Galvanic Isolation from motor
An example of this is the Unimotor where isolation from the motor is achieved by
inserting a plastic mounting plate between the motor housing and encoder housing and
a plastic insert fitted in the motor shaft for encoder mounting to the motor shaft. With this
preferred method of mounting noise current is prevented from passing from the motor
housing into the encoder housing, and hence into the encoder cable. The ground
connection of the cable shield is optional, this may be required to comply with safety
measures or to reduce radiated radio frequency emissions from either the drive or
encoder.
4.4.2
Encoder circuit with galvanic isolation from encoder body
In this case the encoder device is mounted directly on the motor housing with contact
being made between the motor housing/shaft and encoder. With this mounting method
the encoder internal circuits are exposed to electrical noise from the motor housing
through the stray capacitance, and they must be designed to withstand this situation.
However this arrangement still prevents large noise currents from flowing from the
motor body into the encoder cable. The ground connection of the cable shield is
optional, this may be required to comply with safety measures or to reduce radiated
radio frequency emissions from either the drive or encoder.
0V
+5V
0V
+5V
0V
+5V
B
B
Z
Z
A
A
Motor
Shaft
Motor
Housing
Encoder
Housing
Isolation
between motor housing
and encoder housing
Encoder
Body
Isolation
between motor shaft
and encoder
Encoder
Connection
Encoder
Circuit
