Eggtimer Rocketry Eggtimer User Manual page 19

This value is also used for the pre-launch sampling which occurs prior to Launch Detect, while
the rocket is either sitting on the pad or is approaching LDA. Values are 4,5,10, 15, 20, 25, and
33 samples per second.
Note that there is a finite amount of memory available for each flight, and using higher sample
rates will consume more memory and may not necessarily produce a more "accurate" flight
graph. In fact, if you have a rocket with a relatively low thrust-to-weight ratio, you are much
better with a lower sample rate, i.e. 4, 5, or 8 samples per second. If you have a mid-power
rocket with a thrust-to-weight ratio of 10+, a sample rate of 10, 15, or 20 will give you the best
graph. If you have a screamer with a 20+ thrust-to-weight ratio, then it's OK to use 25 or 33,
and you will get the best mach-transition detection with those rates for such a beast (assuming
that it will go to Mach 1+...)
Be careful not set the sample rate too high. Besides wasting memory, the noise due to variations
in air pressure will be proportionately higher for smaller interval sizes. If you choose too high a
sample rate, you will most likely see a lot of noise in the velocity graph.
We recommend that you set this value near the average thrust/weight ratio of your rocket. For
example, if you have a rocket that weighs 18 oz, that's 5N (3.6 oz = 1 N). If you are flying on a
G77 motor, the thrust/weight ration would be 77N/5N, or about 15/1. In this case, you should
use the 15 samples/second setting to produce a good graph and enough samples to produce an
accurate burnout detection.
Thrust-to-Weight Calculation:
A Weight in oz............................
B Divide A by 3.6 (Weight in N)........
C Average thrust of Motor (N)..........
Thrust/Weight Ratio (C/B)...........
Ascent Interval (ms.)
This is the amount of time, in milliseconds (1/1000 sec.) represented by the Ascent Sample
setting. For example, if you set the Ascent Sample setting to 10 samples/sec, each sample will
be 100 ms. You cannot change this setting, it is automatically populated when you change the
Bur/Coast Sample rate.
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