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Air Gun Home Forum Index » General Air Gun Questions and Topics » Homemade audio chrony Goto page 1, 2  Next    View previous topic :: View next topic  Homemade audio chrony   Posted: Sat May 01, 2010 4:11 pm AlphaCent New Member Joined: 01 May 2010 Posts: 10 Hi everyone, I've got a RWS Panther 34 with an original spring which is about 2 years old, light to moderate shooting. Because i'm too much of a cheapstake to spend the 100$ on a chrony but i still wanted to know in which ballpark my pellets were flying. So i've made an audio chrony using two piezo elements one at the muzzle and one at the target, spaced apart about 3.5m. Used my PC to record waveforms of the shots. Here they are: The red marks is where i measured. Can anyone with a Panther 34 and a chrony (or anyone who tested their P34) confirm these numbers? I also tried using a program called SoftChrony but it didn't work because the program wouldn't sense the low voltage of the piezzo elements. Thanks   Posted: Sat May 01, 2010 4:28 pm fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2442 Location: New Jersey- outside of Philadelphia Could you explain how you measured the velocity using the sound? I would guess you set up the mics and synchronized them, and measured the time it took for the pellet flight sound to pass between the two devices. Of course that would be an over-simplification, and I can see it wouldn't work because the flight noise would travel faster than the pellet itself. _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Sat May 01, 2010 4:49 pm AlphaCent New Member Joined: 01 May 2010 Posts: 10 fritz wrote: Could you explain how you measured the velocity using the sound? I would guess you set up the mics and synchronized them, and measured the time it took for the pellet flight sound to pass between the two devices. Of course that would be an over-simplification, and I can see it wouldn't work because the flight noise would travel faster than the pellet itself. I've put a piezzo element right next to the muzzle and another directly on the target. They are connected parallel so that they send signals simultaneously. Being so close to the audio source negates any delay due to the speed of sound. If i were to use just one microphone then it must be centered right in the middle otherwise it would be off.   Posted: Sat May 01, 2010 5:23 pm fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2442 Location: New Jersey- outside of Philadelphia So in between the first bar and the second, you are hearing the flight noise coming. Then as the pellet passes, the peaks just after the second bar are the pellet going past the device. And the initial peak after the first line would be the muzzle noise? You can tell I have no experience measuring velocity using sound. By the way, noticed you are new here. Welcome to AGH. _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Sat May 01, 2010 6:08 pm AlphaCent New Member Joined: 01 May 2010 Posts: 10 fritz wrote: So in between the first bar and the second, you are hearing the flight noise coming. Then as the pellet passes, the peaks just after the second bar are the pellet going past the device. And the initial peak after the first line would be the muzzle noise? You can tell I have no experience measuring velocity using sound. By the way, noticed you are new here. Welcome to AGH. As long as the pellet remains sub-sonic and if the mics are set properly to negate delay then the speed of sound is fast enough to make accurate readings on the mics. When the pellet reaches the first mic (first bar) is make a noise that is quickly captured on a very short distance, so you don't have to worry about the sound catching up. The second bar is the second mic which is at the target, and once that is struck then it quickly sends sound to the other mic. I'm still trying to tweak the system to produce even more precise readings. You can see the second bar is clear and crisp, making no problems to accurately mark when the pellet hit. The first is a bit tricky because some air gets out of the muzzle before the pellet making a false reading, but when the pellet flies by it makes a louder sound thus creating the first bar. However i'll try to perfect it so it only reads the pellet. All in all i think these results are quite accurate for such a device. I can't confirm yet until someone tries it with a chrony, but i can't be that far off. I think the accuracy is +/- 25FPS, however the margin of error (in the current setup) is probably somewhat the same, so in the worst case scenario i could be 50 or more FPS off. After further refining i think i could get some really decent results. I'm pretty sure my P34 isn't shooting 900+ FPS pellets of 8.3gr, especially considering how used the spring is. Maybe with hobby pellets i could get 920, but that's stretching it. If anyone ever tested their 34 with the same pellets, i'd be very grateful for the results.   Posted: Sat May 01, 2010 6:11 pm broommaster2000 Moderator Joined: 10 Mar 2007 Posts: 5714 Location: City of Groningen, Groningen, The Netherlands Welcome aboard! 25 to 50 fps is a bit much of a spread, but if it's constant then technically it would tell a lot about your rifle. _________________ BIG GAP   Posted: Sat May 01, 2010 6:21 pm AlphaCent New Member Joined: 01 May 2010 Posts: 10 broommaster2000 wrote: Welcome aboard! 25 to 50 fps is a bit much of a spread, but if it's constant then technically it would tell a lot about your rifle. It can't compete against optical chronographs, but for such a crude device i was quite surprised. Cost me almost nothing. I'm quite interested how far can i get it to work, it's just a shame i can't calibrate it with some precise measurements. I was really surprised it showed the difference between different pellets...i'd like to believe that the results were quite tempting.   Posted: Sat May 01, 2010 6:38 pm fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2442 Location: New Jersey- outside of Philadelphia Move your first mic a couple feet from the muzzle. The same thing occurs with optical chronographs, and it is far more pronounced with high-powered 'burners, because of the massive muzzle blasts. Sometimes the reading (for 'burners) need to be taken over 10 yards from the muzzle. Again with more questions... so you are distinguishing the pellet passing the device by its louder signature than the background noise of its flight? Using sound to measure velocity of projectiles is very interesting, never heard of it before. I do think if you use a good setup (couldn't tell you what would define "good"), very accurate measures could be obtained. The high SD readings you are getting, are likely due to the muzzle "blast", so again move your first device further from the muzzle. _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Sat May 01, 2010 6:54 pm AlphaCent New Member Joined: 01 May 2010 Posts: 10 fritz wrote: Move your first mic a couple feet from the muzzle. The same thing occurs with optical chronographs, and it is far more pronounced with high-powered 'burners, because of the massive muzzle blasts. Sometimes the reading (for 'burners) need to be taken over 10 yards from the muzzle. Again with more questions... so you are distinguishing the pellet passing the device by its louder signature than the background noise of its flight? Using sound to measure velocity of projectiles is very interesting, never heard of it before. I do think if you use a good setup (couldn't tell you what would define "good"), very accurate measures could be obtained. The high SD readings you are getting, are likely due to the muzzle "blast", so again move your first device further from the muzzle. Well, i think i am distinguishing both, but i'm not 100% certain. I'll probably do as you suggested and move away from the muzzle. In theory it should register only the pellet and not the air, but the trick is place the mic as close as possible to the flight trajectory, because if it's too far away it won't register anything. But i have some ideas on how to achieve that. Tomorrow i'll experiment with as much variations as i can. I must be sure what i'm reading is really the pellet and not air.   Posted: Sat May 01, 2010 7:10 pm fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2442 Location: New Jersey- outside of Philadelphia At say 5 feet from the muzzle, I would assume nearly any projectile except a lead balloon would still be going "straight". And having the second device at the target, as long as you hit the target, it's good. Of course I could be totally wrong, not knowing anything but what you have explained about this means of measure. _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Sat May 01, 2010 11:04 pm rsterne Moderator Joined: 15 Jan 2008 Posts: 2998 Location: Coalmont, BC Your estimates for the RWS-34 in .177 are a bit high but not totally out to lunch.... Typically you get about 850 fps with 7.9 gr pellets in that gun.... Bob _________________ Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! Airsonal: Too many to count!   Posted: Sun May 02, 2010 7:58 am fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2442 Location: New Jersey- outside of Philadelphia They do seem a tad high, but that may just be from poor positioning of his first device. ^ Wow that was perverted.... ^ _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Sun May 02, 2010 4:23 pm broommaster2000 Moderator Joined: 10 Mar 2007 Posts: 5714 Location: City of Groningen, Groningen, The Netherlands fritz wrote: They do seem a tad high, but that may just be from poor positioning of his first device. ^ Wow that was perverted.... ^ Only because you said so. _________________ BIG GAP   Posted: Mon May 03, 2010 10:23 am AlphaCent New Member Joined: 01 May 2010 Posts: 10 I've redesigned the chrony, did some improvements. And i did get some pretty consistent results. I've tried different settings I tried a distance of 3.77m: ->0 inches from mic, gave me 880FPS ->5 inches from mic, gave me also 880FPS Distance of 3.41m: ->0 inches from mic, game me also around 880 FPS Is to be noted that it has an inherit up to 30FPS error because i can't measure the waveforms more precisely than 0.001s. Any additional error is because of inaccurate distance. There is still the issue of the air registering before the pellet, i've tried different distances from the muzzle...it seems at 5 inches from muzzle i can get a decent spike. It just might be that the difference between the air and bullet is to small to register with this device. It might seem that the FPS are a tad high but i've noticed i do get some dieseling because the smell in some shots is pretty noticeable. Not long ago i did re lube the internal parts, so it's quite possible i'm getting some additional FPS. In conclusion i'm pretty confident to say i'm within 50 FPS of error with this device. I haven't yet tried different pellets with this new design. I guess it's accurate enough to detect a seal leak or some moderate malfunction...if that's really the case than i'm very content.   Posted: Mon May 03, 2010 10:52 am AlphaCent New Member Joined: 01 May 2010 Posts: 10 I just did the different pellets again, i think it's clearly defined 1: 10.5gr->771 FPS 2: 9.56gr->820FPS 3: 8.3fr->880FPS P.S. If anyone is wondering why the waveforms seem cut, that's because they are, i fired them in a row so i had to dissect the track to compare them side by side. However i did cut them at the exact place where i took measurements. This is the original unzoomed track And zoomed (i think it's the TS 10) If i did place on the correct distance i should be in +/- 30FPS Homemade audio chrony     Air Gun Home Forum Index » General Air Gun Questions and Topics You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum All times are GMT - 5 Hours   Page 1 of 2   Goto page 1, 2  Next All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First  Select a forum Main Forums----------------AirGunHome Q&AGeneral Air Gun Questions and TopicsPicture GalleryTarget Shooting: Casual, Fun and CompetitionHunting, Pest Control, Varminting People/Events/Airgun Issue Discussion----------------Introduce YourselfThe BS TopicClubs/Events/Regional/Political Airgun Issues Maintenance, Modification and Reviews----------------RiflesPistolsAntique, Collector and Novelty AirgunsBB GunsPellets/AmmoOpticsAccessoriesAirgun Smithing Buy, Sell or Trade Forums----------------For SaleWant to Buy   Note: If you are seeing "Please enter your username and password to log in." 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