Products > Test Equipment
Capture Peak Strain Gage Fluctuation For Shotgun Chamber Pressure Measurement
tautech:
--- Quote from: nctnico on December 16, 2023, 04:31:43 pm ---I'm not sure what the defacto standard is for measuring pressures in guns ……
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Test guns have pressure ports and historically used an anvil to crush a metal pellet.
Shotguns used lead for a LUP measurement
Rifles used copper for CUP
Both are now outdated now PSI sensors are available and PSI data sets are still evolving/growing for the large range of different firearms available.
bdunham7:
--- Quote from: Silver_Is_Money on December 16, 2023, 03:51:28 pm ---If the Oscilloscopes (ahem) 'trigger' was set to just above the nominally zero voltage line of the balanced Wheatstone Bridge, would that 'trigger' the capture of the spike in voltage as post firing chamber pressure begins to stretch the strain gage? And is there a capture feature which can be stored and played back whereby to measure the peak voltage captured by the Oscilloscope, or better yet, observe the entire event which will end when the payload exits the barrel?
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Any reasonable modern DSO will do all of that. They will record both before and after the trigger, so you could use the slug leaving the gun to break a foil to trigger the scope as well--this might have the advantage of showing you the exact point in time the slug clears the barrel (if you care). Or, you could just have a manual trigger button that you press about the same time as the shotgun trigger. It will just take some setting up and if you are new to oscilloscopes, triggering is an art that takes a bit to learn. As far as which one, both Rigol and Siglent have inexpensive ($400-500) models with 10M+ memory points and low noise inputs. I would avoid the other cheap brands and ask here specifically about a particular model you intend to buy for this just to make sure it doesn't come up short.
tautech:
Then one wonders why the OP is wanting to undertake chamber pressure measurements when much info is available from the multitude of reloading manuals and propellant manufacturers websites. :-//
What reloading experience has SIM ?
Silver_Is_Money:
I'm 68 years old and I have been reloading metallic cartridges (rifle and pistol) and shotshells since the age of 16.
I also have a wildcat 6.5mm rifle chambered to my own design, so for that one there is no looking at manuals.
Stray Electron:
--- Quote from: Silver_Is_Money on December 17, 2023, 12:59:32 am ---I'm 68 years old and I have been reloading metallic cartridges (rifle and pistol) and shotshells since the age of 16.
I also have a wildcat 6.5mm rifle chambered to my own design, so for that one there is no looking at manuals.
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Cool! What cartridge case and what bullet weight? A gunsmithing friend of mine designed a wildcat .257 cartridge based on the .300 Win Mag case. That thing was a ripper!
If you haven't done it already, I suggest posting your question on some of the forums that deal with reloading such as Castboolits.com and TheHighRoad.org and see if anyone there has actual experience with what you're trying to do. You can also post on AR15.com, it's a larger forum but the noise level there is significantly higher.
In many modern digital scopes you can set them to start recording before the trigger event and continue until after the event so that the trigger event appears right in the middle of the recording. Or you could set the scope to trigger on the muzzle flash and have it save all of the readings prior to the trigger. Initially it might sound like both are impossible but what the scope really does is just to take readings continuously and puts them into it's memory until it fills and then it starts loading the memory at the the beginning again. It just keeps doing that until it is triggered and it then stops the recording at the selected point while the readings prior to that point are still in memory. Think it it like driving down the highway and video taping non-stop until you get to a certain mile marker and then discarding everything prior to say one minute prior to reaching the marker and everything more than one minute after the marker. With digital electronics you're basically only limited by the rate that you want to take readings, the time that you want to record and your memory size. One note though, acquisition memory and internal memory used for computing are two different things and most manufacturers advertise the computing memory size since it is always much larger and much cheaper. If you want to take say 1 million readings in real time, you need to be sure that your scope has enough acquisition memory for that.
2nd I think that finding a sensor that is capable of taking readings as fast and as with as much resolution as you desire will be the hard part of this project. IMO you need to find a sensor that will do what you want and find our how fast it can take readings and then select a scope that will keep up with the sensor.
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