[time-nuts] A real-world precision timing need....

Brooke Clarke brooke95482 at att.net
Sun Oct 31 16:58:42 EDT 2010

Hi Mike:

Are you looking into the Pejsa Ballistics computations?

Have Fun,

Brooke Clarke

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!!
>     Thanks!!
>     Mike Baker
>     Gainesville, Florida, USA
>     ---------------------------------
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Have Fun,

Brooke Clarke

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