Saturday, May 23, 2015

ACOUSTIC CHRONOGRAPH FROM ADAM MACDONALD

From Adam MacDonald
Hi everyone,

I brought my acoustic chrono to the match in St Gabriel and there was some interest in people wanting their own. So here is what it is and if you would like one please let me know. (e-mail: adamjmac@gmail.com) Pass on the word to anyone else you think might be interested.


And then replace the optical light sensors with microphones - the same circuit board that is in the (Silver Mountain) electronic target microphones. The conversion process takes a few hours. It uses the same timing circuitry and display - this is not modified. The chronograph can talk to a phone/tablet through a cable which will record all the readings as you shoot.

The main advantage over a standard chronograph is precision. I measured a Chrony to have an SD of 15 fps (over 50 shots). I measured two of the converted acoustic chronos to have an SD of 4 fps. This data was measured using a system that has an SD of 1 fps. These numbers may vary based on your setup, but the acoustic chrono is much more capable of telling the difference between a good load and bad load (6-10 fps SD) making it much for useful for our purposes.

The acoustic sensors are not affected by light or rain. The sunshades are not needed. You can shoot anywhere around it but it's best if you shoot 2-3 feet over top. It is more affected by alignment error than an optical - it needs to be parallel to your bore. If you have a misalignment, it will report the wrong absolute value but the deviations will be right. You should use it to measure your velocity SD and use scope elevations at different distances to figure out your actual velocity. You should also have a sturdy tripod or place it on a wooden board on the ground so it does not move around in the wind.

The price is $200 each for these. I want to place one order for a number of these and convert them all at once. If I already told you it would be a lower price then it is what I already told you.

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