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Chapter 4
What You Need to Know about Moves
NI-Motion User Manual
You can calculate this minimum velocity increment in RPM with the
following formula:
minimum RPM
where
Vmin = 1/65,536 counts/sample or steps/sample
Ts = sample period in seconds per sample
60 = number of seconds in a minute
R = counts or steps per revolution
or
You also can calculate the minimum velocity using the formula shown in
the
Calculation Based on Units
For a typical servo axis with 2,000 counts per revolution operating at a
250 µs update rate, the minimum RPM increment is
1
×
--------------- -
--------------- -
250 µs
65,536
or
3.662109
You can calculate the maximum velocity in RPM with the following
equation:
maximum RPM
where
Vmax = 20 MHz for servos
8 MHz for steppers on a NI 7350 controller
4 MHz for steppers on a NI 7330, NI 7340, or NI 7390
motion controller
R = counts/steps per revolution
×
Vmin
=
minimum RPM
MIN
=
column in Table 4-1.
1
1
×
×
60
----------- -
2000
1
×
0.00183105 RPM
----------- -
=
2000
Vmax
=
4-6
1
1
×
×
60
---- -
-- -
Ts
R
1
×
-- -
R
0.00183105 RPM
=
1
×
×
60
-- -
R
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