Connecting An Encoder; Table 4-26 Encoder Types - Emerson Quantum MP User Manual

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4.17

Connecting an encoder

Additional measures to prevent unwanted emission of radio frequency
noise are only required where the installation is subject to specific
requirements for radio frequency emission.
Encoder connections:
To ensure suppression of radio frequency emission, observe the
following:
• Use an encoder with the correct impedance
• Use a cable with individually shielded twisted pairs.
• Connect the cable shields to 0V at both the drive and the encoder,
using the shortest possible links (pig-tails).
• The cable should not be interrupted. If interruptions are unavoidable,
ensure the absolute minimum length of "pig-tail" in the shield
connections at each interruption. Use a connection method that
provides substantial metallic clamps for the cable shield
terminations.
The above applies where the encoder body is isolated from the motor
and where the encoder circuit is isolated from the encoder body. Where
there is no isolation between the encoder circuits and motor body, and in
case of doubt, the following additional requirements must be observed to
give the best possible noise immunity.
• The shields must be directly clamped to the encoder and to the
drives grounding bracket. This may be achieved by clamping of the
individual shields or by providing an additional overall shield that is
clamped.
NOTE
The recommendations of the encoder manufacturer should also be
adhered to for the encoder connections.
N
NOTE
In order to guarantee maximum noise immunity for any application
double shielded cable as shown should be used.
In some cases single shielding of each pair of differential signals cables,
or a single overall shield with individual shield on the thermistor
connections is sufficient. In these cases all the shields should be
connected to ground and 0V at both ends.
If the 0V is required to be left floating a cable with individual shields and
an overall shield must be used.
Figure 4-20 and Figure 4-21 illustrate the preferred construction of cable
and the method of clamping. The outer sheath of the cable should be
stripped back enough to allow the clamp to be installed. The shield must
not be broken or opened at this point. The clamps should be installed
close to the drive or feedback device, with the ground connections made
to a ground plate or similar metallic ground surface.
Figure 4-20 Feedback cable, twisted pair
54
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Figure 4-21 Feedback cable connections

Table 4-26 Encoder types

Pr 3.38
(Fb07, 0.77)
setting
Quadrature incremental encoder with or without marker
Ab (0)
pulse
Incremental encoder with frequency pulses and
Fd (1)
direction, with or without marker pulse
Incremental encoder with forward pulses and reverse
Fr (2)
pulses, with or without marker pulse
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