User`s manual

Strobe Accuracy Calculations
GFK-1742A Appendix G Strobe Accuracy Calculations G-3
G
0
6
.25
1
0
5
1
.25
1
0
4
1
.875 10
4
2.5
1
0
4
T
ime (sec)
Position (deg)
0.4
0.3
0.2
0.1
0
-0.1
-0.2
Estimated assuming
constant velocity
Actual
Error
Figure G-1: Example axis position capture error due to acceleration
Since the initial velocity is equal to 0, the formula for calculating P
act
can be manipulated
to determine the time that the count actually occurred at (T
act
) as follows:
T
act
=
2
P
act
A
Likewise, the formula for estimating the strobe position (P
est
) can be solved for time (T
est
)
as well (assuming that the initial velocity is 0):
T
est
= P
est
/ V
avg
Using these formulas, the difference in time between when the strobe occurred and when
the reported count occurred (i.e. the effective delay) can be calculated as follows:
Effective Delay = T
est
- T
act
The effective delay for the maximum strobe position error (i.e. at 125 microseconds) is
equal to -62.5 microsecond. This value is negative because the estimated/reported strobe
position occurred prior to the actual position when the strobe event happened. The graph