Delta Tau Acc-51E, Руководство пользователя

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Accessory 51E
12 Encoder Connections
ENCODER CONNECTIONS
1. Be sure to use shielded, twisted pair cabling for sinusoidal encoder wiring. Double insulated is the
best. The sinusoidal signals are very small and must be kept as noise free as possible. Avoid cable
routing near noisy motor or driver wiring. Refer to the appendix for tips on encoder wiring.
2. The use of single-ended output style sinusoidal encoders at very slow speeds has been shown to
provide large amounts of velocity-ripple. When very slow speeds are desired, it is best to use
differential output style sinusoidal encoders. The 3-line encoder table entry (which is available with
Turbo PMAC models) has been designed to help adjust the offsets that may be present with single-
ended encoders.
3. The Acc-51E uses voltage mode 1Vp-p encoders only.
4. It is possible to reduce noise in the encoder lines of a motor-based system by the use of inductors that
are placed between the motor and the amplifier. Improper grounding techniques may also contribute
to noisy encoder signals.
Sinusoidal Encoder Wiring
Sinusoidal encoders operate on the concept that there are two analog signal outputs 90 degrees out of
phase. They are available with different drive characteristics, some of which are described below.
Differential Format
The differential format provides a means of using twisted pair wiring that allows for better noise
immunity when wired into machinery.
There are two common output types available with differential style sinusoidal encoders. They are
current mode and voltage mode style encoder outputs.
The current mode encoder output uses a high
impedance 11

A pk-pk output. The voltage mode
output encoder uses a low impedance 1 V pk-pk
output.
The voltage mode encoder type is connected to the
interpolator as shown. Usually, termination is
selected by using jumpers on the interpolator
board.
SN+
SN-
COS+
COS-
NDX+
NDX-
ENC
PWR
GND
Sinusoidal
Encoder
Differential Encoder Connection
Note:
Voltage mode encoders are becoming the more popular choice for machine designs
due to their lower impedance outputs. Lower impedance outputs represent better
noise immunity, and therefore more reliable encoder interfaces.
The Acc-51P uses only voltage mode encoders.
Single-Ended Format
The single-ended formats provide a simpler means of using a sinusoidal encoder. Typically, fewer wires
are needed and the encoders are always of the lower impedance voltage output type.
It should be noted that all the single-ended encoder formats shown here might have velocity-ripple effects
at very slow speeds due to the effects of op-amp V
io
offsets. These offsets cause the sinusoidal signal to
be centered at a value that is slightly different from the reference or servo ground.