Download SoftChrono, then buy or make a mic, and measure properly. SoftChrono is what I used until I could get a Chrony, and it's more than accurate enough for what your wanting.
Quote from: Big Bore Bart on June 13, 2014, 09:40:27 PM Download SoftChrono, then buy or make a mic, and measure properly. SoftChrono is what I used until I could get a Chrony, and it's more than accurate enough for what your wanting.I tried this the other night.Laptop 7' from gun, gun 17' from target, 1' below. Measured and entered everything to the inch. Either the Softchrono is off or my P17 is shooting REALLY hot. Was showing 1194FPS and just over 25fpe.
A ballistic pendulum is old school, but works. It was about the only way to chronograph before the advent of microprocessors. Using Audacity is much the same as Soft Chrono, except the calculations are done by the human operator. I also use Audacity to analyze the vibration patterns of my guns. I use the simple sound recorder that comes with Windows and put the microphone right up against the compression tube. Audacity lets you crop the resulting *.wav file down to just the firing cycle. By comparing a before and after graph of the vibrations you can examine relative amplitudes, lock time, and how quickly the vibrations ramp down at the end - stuff like that. It gives a visual confirmation that all your fussing and tuning actually accomplished something. (Audacity is a free download.)
What Bob said. The mic must be at the midpoint of the range. At 17' the mic must be 8'6" from the muzzle, and 8'6" from the impactor. The offset for chrony protection is negligible. (your 1' below the trajectory) A lot of laptops have multiple mics built in, which can throw off the program. I had problems until I went the single mic route. Radio shack has an electret mic element, speaker wire, and an 1/8" plug. Less than $20, ten minutes time, and a soldering iron and you have a mic with whatever length wire you want.
A lot of laptops have multiple mics built in, which can throw off the program.
I would assume the microphone placement is critical, since you are measuring the time between the muzzle blast and pellet impact and the speed of sound is a large factor....Bob