NI 73xx Acceleration in Counts/s2
Acceleration and deceleration values are converted to an internal 16.16 fixed-point format in units of counts/s2 before being used by the trajectory generator.
The following table shows the minimum and maximum acceleration update rates in counts/sec2.
| Update Rate | MAX | MIN | Calculation Based on Units |
|---|---|---|---|
| 62.5 µs | 2,048,000,000 counts/sec2 | 3906 counts/sec2 | Accelmax = MAX |
| 125 µs | 2,048,000,000 counts/sec2 | 977 counts/sec2 | |
| 187.5 µs | 910,222,222 counts/sec2 | 434 counts/sec2 | |
| 250 µs | 512,000,000 counts/sec2 | 244 counts/sec2 | |
| 312.5 µs | 327,680,000 counts/sec2 | 156 counts/sec2 | Accelmin = MIN |
| 375 µs | 227,555,556 counts/sec2 | 109 counts/sec2 | |
| 437.5 µs | 167,183,673 counts/sec2 | 80 counts/sec2 | |
| 500 µs | 128,000,000 counts/sec2 | 61 counts/sec2 |
You can calculate the minimum acceleration increment with the following formula:
minimum acceleration/deceleration = Amin × (
)2
where
Amin = 1/65,536 counts/sample2 or steps/sample2
Ts = sample period in seconds per sample
For a typical servo axis with 2,000 counts per revolution operating at the 250 µs update rate, calculate the minimum acceleration/deceleration increment using the following equation:
(
) × (
)2 = 244 counts/second2
You can calculate the maximum acceleration/deceleration using the following equation:
maximum acceleration/deceleration = Amax × ()2
where
Amax = 32 counts/sample2
Ts = sample period in seconds per sample
and is constrained according to the following equations:
acceleration 256 
deceleration
deceleration 65536 acceleration