[time-nuts] A real-world precision timing need....
brooke95482 at att.net
Sun Oct 31 16:58:42 EDT 2010
Are you looking into the Pejsa Ballistics computations?
Michael Baker wrote:
> Hello, Time-Nutters--
> A real-world precision timing need:
> As a dedicated long-range rifle shooter and
> ballistics enthusiast, I am in the early stages
> of a project I am getting started on...
> The object is to measure the velocity of a
> rifle bullet both at the muzzle and downrange at
> various distances up to 800 yards/meters or so.
> Conventional optical sky-screens will will be
> used for measuring the velocity at both ends.
> However, I also need time-of-flight and this
> requires knowing the timing relationship between
> the time the bullet crosses the muzzle sky-screen
> and the downrange sky-screen. Bullet muzzle velocities
> will be between 1900 to 3200 feet-per-second.
> Additionally, I will be using the output from an
> array of 4 ultrasonic sensors located on the
> corners of a 4-foot PVC pipe square to determine
> the size of the shot group at the far end and
> telemeter this info back to a laptop at the
> shooting bench.
> I can use a 10-MHz crystal for the sky-screen clocks
> and the for the 4 ultrasonic bullet shot location
> sensors. However, determining the time-of-flight is
> a more difficult task as this requires syncing clocks
> together at both ends to a moderate degree of accuracy.
> Out to 100 yards I can send the time-of-flight
> far-end pulse back by wire and compare it to the
> muzzle-end sky-screen pulse but this is not practical
> to do by wire out at 800 yards.
> This project is on a tight budget-- namely, MY
> wallet, so cost is a major concern. Suggestions
> will be most welcome!!
> Mike Baker
> Gainesville, Florida, USA
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