Ni 73Xx Time Base - National Instruments NI-Motion User Manual

Update Rate
62.5 µs 14.648438 counts/min
125 µs 7.324219 counts/min
187.5 µs 4.882813 counts/min
250 µs 3.662109 counts/min
312.5 µs 2.929688 counts/min
375 µs 2.441406 counts/min
437.5 µs 2.092634 counts/min
500 µs 1.831055 counts/min
© National Instruments Corporation

NI 73xx Time Base

Velocity and acceleration values are loaded in counts/s, RPM, RPS/s,
steps/s, and so on, which are all functions of seconds or minutes. However,
the trajectory generator updates target position at the Trajectory Update
Rate, which is programmable with the Enable Axes function. This means
that the range for these parameters depends on the update rate selected, as
shown in the following examples.
Table 4-1 lists minimum and maximum update rates for acceleration and
velocity in various units.
NI 73xx
Velocity in RPM
Velocity values in RPM are converted to an internal 16.16 fixed-point
format in units of counts (steps) per sample period (update period) before
being used by the trajectory generator. NI-Motion can control velocity to
1/65,536 of a count or step per sample.
Table 4-1 shows the minimum and maximum velocity in counts/min. Use
the formula shown in the Calculation Based on Units column to determine
the counts/min value to RPM.
Table 4-1. Velocity in Counts/Min
MIN
For servo motors, the
maximum counts/min is
1.2 billion independent
of the update rate.
For stepper motors, the
maximum counts/min
value is dependent on the
controller:
• 480 million
counts/min for 7350
• 240 million
counts/min for 7330,
7340, and 7390
Chapter 4
MAX
4-5
What You Need to Know about Moves
Calculation Based
on Units
±RPM = MAX×1/r
max
where r = counts/revolution
±RPM = MIN×1/r
min
where r = counts/revolution
NI-Motion User Manual