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Chapter 4
What You Need to Know about Moves
Update Rate
62.5 µs
2,048,000,000 counts/sec
125 µs
2,048,000,000 counts/sec
187.5 µs
910,222,222 counts/sec
250 µs
512,000,000 counts/sec
312.5 µs
327,680,000 counts/sec
375 µs
227,555,556 counts/sec
437.5 µs
167,183,673 counts/sec
500 µs
128,000,000 counts/sec
NI-Motion User Manual
Table 4-3. Acceleration Update Rate in RPS/s
MAX
2
3906 counts/sec
2
977 counts/sec
2
434 counts/sec
2
244 counts/sec
2
156 counts/sec
2
109 counts/sec
2
80 counts/sec
2
61 counts/sec
You can calculate the minimum acceleration increment in RPS/s with the
following formula:
where
Amin = 1/65,536 counts/sample
Ts = sample period in seconds per sample
R = counts or steps per revolution
or
For a typical servo axis with 2,000 counts or steps per revolution operating
at the 250 µs update rate, calculate the minimum RPS/s increment using the
following equation:
1
--------------- -
65,536
or
MIN
2
2
2
2
2
2
2
2
1
×
RPS/s
Amin
---- -
=
Ts
RPM/s
MIN
=
2
1
1
×
×
-------------- -
----------- -
250µs
2000
1
×
244
0.122
----------- -
=
2000
4-10
Calculation Based
on Units
±RPS/s
= MAX×1/r
max
where r = counts/revolution
±RPS/s
= MIN×1/r
min
where r = counts/revolution
2
1
×
-- -
R
2
2
or steps/sample
1
×
-- -
R
0.122070 RPS/s
=
ni.com
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