Chapter 5 Signal Connections
© National Instruments Corporation 5-5 NI 7350 User Manual
Motion Axis Signals
The following signals control the servo amplifier or stepper drive.
•Analog Output <1..8>—These 16-bit DAC outputs are typically
the servo command outputs for each axis. They can drive the
industry-standard ±10 V output, and can be software limited to
anyp ositive or negative vol tage range desired. These outputs also
feature a software-programmable voltage offset.
Although typically used as the command output of an axis control
loop, unused DACs also can function as independent analog outputs
for general-purpose control.
•Analog Reference—For convenience, a 7.5 V (nominal) analog
reference voltage is available. You can use this output as a low-current
supply to sensors that require a stable reference.
Note The analog reference output is an output signal only and must not be connected to
an external reference voltage. Connect the common of the external reference to the Analog
Input Ground pin for proper A/D reference and improved voltage measurement.
•Analog Output Ground—To help keep digital noise separate from
the analog DAC outputs, there is a separate return connection. Use this
analog ground connection as the reference for the DAC outputs when
connecting to servo amplifiers instead of the Digital Ground
(digital I/O reference).
•Axis <1..8> Step (CW) and Dir (CCW)—These signals are the
stepper command outputs for each axis. The NI 7350 controller
supports both industry standards for stepper command signals—step
and direction, or independent clockwise (CW) and counterclockwise
(CCW) pulse outputs.
The output configuration and signal polarity is software programmable
for compatibility with various third-party drives, as follows:
– When step and direction mode is configured, each commanded
step (or microstep) produces a pulse on the step output. The
direction output signal level indicates the command direction
ofm otion, either forward or reverse.
– CW and CCW modes produce pulses (steps) on the CW output for
forward-commanded motion and pulses on the CCW output for
reverse-commanded motion.
In either case, you can set the active polarity of both outputs to
activelow or active high. For example, with step and direction, you can
make a logic high correspond to either forward or reverse direction.