Chapter 5
Signal Connections
NI PCI-7342 Hardware User Manual
5-10
ni.com
Figure 5-6 shows the quadrature encoder phasing diagram when
interfacing directly to the PCI-7342 without using a UMI or drive
accessory.
Figure 5-6.
Quadrature Encoder Phasing without a UMI or Drive Accessory
Wiring Concerns
The encoder inputs are connected to quadrature decoder/counter circuits.
It is very important to minimize noise at this interface. Excessive noise on
these encoder input signals may result in loss of counts or extra counts and
erroneous closed-loop motion operation. Verify the encoder connections
before powering up the system.
Caution
Wire encoder signals and their ground connections separately from all other
connections. Wiring these signals near the motor drive/amplifier or other signals can cause
positioning errors and faulty operation.
National Instruments recommends using encoders with differential line
driver outputs for all applications. If the encoder cable length is longer than
3.05 m (10 ft), you must use encoders with differential line driver outputs.
Shielded 24 AWG wire is the minimum recommended size for the encoder
cable. For optimized noise immunity, use cables with twisted pairs and an
overall shield.
All National Instruments power drives and UMI accessories provide
built-in circuitry that converts differential encoder signals to single-ended
encoder signals.
Caution
Unshielded cable can cause noise to corrupt the encoder signals, resulting in lost
counts and reduced motion system accuracy.
Phase A
Phase B
Index
