View Single Post
Old 9th November 2012, 08:22 AM
acrybb acrybb is offline
Join Date: Sep 2012
Member of: Bearsden R&P Club, Westfield Air Rifle club
Location: Glasgow
Posts: 30
Default Smartphone Chrono

I have seen these smartphone chronos demonstrated on youtube and if what i was seeing is true then its quite impressive. Anyway i thought i'm gonna give that a go. Except that i couldn't, because there is not an app for the iphone yet.

I set about finding out how it worked. It works by measuring the time from muzzle blast to impact using sound to identify when these event have occured then calculates it out into FPS then into muzzle energy. I found someone who was using an app called WavePad. Its a free app for i-devices. You basically start it take the shot and identify manually when the muzzle blast happened in milliseconds (500m/s). Then when the impact happened (515m/s) It then calculates the flight time (15m/s) and using Speed, distance & time formula find out FPS then using pellet weight and FPS calculates muzzle energy. Sorry i know most of you know how it all works. I seen someones calculation and they do something slightly different but i couldn't get it to work properly. They way i have calculated it seems to work OK but i can test it until i have a chrono.

Anyway i was gonna ask. If anyone has a chrono, I-device, is sitting in their pants bored and fancies trying it out. I dont have a chrono so cant check the techniques accuracy. I have made up a spreadsheet which you just put in Muzzle blast time, Impact time, Distance from target and pellet weight. It works it all out for you. Well if i have done me sums right lol

Simple instructions however you should be able to figure it out. I hope this isnt a repeat of something already posted ps:

The XLS is attached (i think lol) if not i can e-mail. Basically download the app and figure out how it works. Zoom into the bottom sound wave until the last point where the time is expressed in m/s (690ms 710 ms etc) Place your phone in the middle between the muzzle & target. Take a shot. Then analyse the wave and identify at what time these two events happen and put them into the calculator. Remember to measure the distance between the Muzzle & Target and put that into the calculator. Then add your pellet weight in grains.

Reply With Quote
Connect With Facebook to "Like" This Thread