Hi Michael, I have a couple of Trimble Palisade receivers (replaced by the Accutime). These have a timestamp input. you could use a pair, one at each end with the timestamp trigger connected to the skyscreen. log the data locally (PIC or what ever) and then post process the time stamps. I''ll have to check the resolution of the Palisade. You could do something similar with a simple GPS, external TIC and logger. Robert. G8RPI
--- On Tue, 2/11/10, Michael Baker <[email protected]> wrote: From: Michael Baker <[email protected]> Subject: [time-nuts] A real world project need for timing accuracy... To: [email protected] Date: Tuesday, 2 November, 2010, 0:03 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.
