Hi The time of flight will be roughly a second at 800 meters. Could be out to 2 seconds won't be less than a half second. If you know it to 0.01 % that's doing pretty well compared to a commercial system.
Bob On Nov 2, 2010, at 6:00 AM, Dave Brown wrote: > Michael > Can you tell us the expected maximum and minimum time duration you want to > measure and the measurement resolution you require? At present we are just > guessing, especially re the latter. > DaveB, NZ > > ----- Original Message ----- From: "Michael Baker" <[email protected]> > To: <[email protected]> > Sent: Tuesday, November 02, 2010 1:03 PM > Subject: [time-nuts] A real world project need for timing accuracy... > > >> Timenutters-- >> I appreciate the feedback for implementing my >> ballistic field measurement project but I think >> there is some misunderstanding of what the goal is. >> For instance, it is not practical to find 800 meters >> of coax and trench it in out to the downrange target. >> This system needs to be relatively portable so it >> can be set up at any given shooting range. >> I need to determine: A) down-range velocity of the >> still super-sonic projectile, B) time of flight and >> C) shot-group size. >> Measuring down-range shot-group size with an array of >> ultrasonic sensors is pretty straightforward. I can >> do all the computation with a $6 microprocessor and >> send the X/Y coordinates back to the laptop at the >> shooting bench with a simple RF link. Down-range >> velocity is easily determined with a set of sky-screens >> and the results also sent back via an RF link. >> Time-of-flight is much more problematic to determine >> but the plan is to determine the elapsed time between >> the moment the projectile passes over the muzzle skyscreen >> and the moment of passing over the downrange skyscreen. >> This means syncing the 10 MHz clocks at both ends together. >> I guess the crux of my question to the time-nuts gang >> is what is the easiest (cheapest!!) way to do this. >> For a number of years I have been using an ultrasonic >> shot-group size measurement system made by Oehler >> Research. It can resolve individual shot placement >> to within 1 cm. Some less expensive systems that >> use fewer sensors can only resolve to +/- 2 cm. The >> Oehler Research system also determines time of flight. >> The problem is that these systems all use a cable >> to connect back to the equipment at the shooting bench. >> I am trying to find a way to synchronize/coordinate >> a downrange 10 MHz clock to the "master" 10 MHz system >> clock at the shooting bench without spending hundreds >> of $$ doing it. It is not too big a problem to process >> all of the signals from the downrange skyscreens and the >> ultrasonic shot-group sensors and telemeter the results >> back to the shooting bench. >> However, time-of-flight info (via an RF link requires >> that I sync the 10MHz clocks at both ends together. >> Use of GPS receivers seems to be the most likely way >> to do this but how do I keep the cost and complexity >> down? >> Thanks in advance for any feedback on the matter! >> Mike Baker >> --------------------- >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
