user manual

Chapter 5 Signal Connections
NI 7350 User Manual 5-10 ni.com
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 strongly recommends you use encoders with
differential line drive outputs for all applications. You must use differential
encoders if the encoder cable length is longer than 3.05 m (10 ft). Shielded,
24 AWG wire is the minimum recommended size for the encoder cable.
Cables with twisted pairs and an overall shield are recommended for
optimized noise immunity.
All National Instruments power drives and UMI accessories provide
built-in circuitry that converts differential encoder signals to single-ended
encoder signals.
Caution Unshielded cables can cause noise to corrupt the encoder signals, resulting in lost
or additional counts and reduced motion system accuracy.
Encoder Input Circuit
The Phase A, Phase B, and Index encoder inputs all have an onboard
pull-up resistor, and are interpreted as high logic level if left floating.
Both phases A and B are required for proper encoder counter operation,
and the signals must support the 90° phase difference within system
tolerance. The encoder and Index signals are conditioned by a
software-programmable digital filter inside the FPGA. The Index signal
is optional but highly recommended and is required for initialization
functionality with the Find Reference function.
Trigger Inputs, Shutdown Input, and Breakpoint Outputs
The NI 7350 controller offers additional high-performance encoder
features. The encoder channels have high-speed position capture trigger
inputs and position breakpoint outputs. These signals are useful for
high-speed synchronization of motion with actuators, sensors, and other
parts of the complete motion system.
• Trigger Input <1..8>—When enabled, an active transition on a
high-speed position capture input causes instantaneous position
capture of the corresponding encoder count value. You can use this
high-speed position capture functionality for applications ranging
from simple position tagging of sensor data to complex camming
systems with advance/retard positioning and registration. An available
NI 7350 controller position mode is to move an axis relative to a
captured position.