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Need A Little Electronics Help To Measure Barrel Vibration

What kind of data collector do you have? To measure vibrations you will need to take samples at around 20ms or so. Piezotronics is the company i use. You can use a variety of sensors and combine to get different readings. I learned when i was an engineer for GE doing shaft positioning and vibration analysis on gas turbines
 
The Data Sheet stresses the importance of the attachment method, and as AllthingsAI, mentioned, the device itself, when attached to the barrel, is likely to affect the results. As far as for power supply, since the current draw is so small, I would use batteries.
Keep us posted.
Alex
 
I'll try to get some info but it might take a bit, as Mom is still in the hospital and doc says itll be another week to 10 days or so.
 
Details follow since it sounds like I can thankfully get some good help here!

Eventhough the ADXL only weighs 41grains, there is certainly a possibility it will affect barrel harmonics. So I will shoot a charge ladder while it is attached such that the harmonics and point of impact are measured under identical conditions. The objective is to correlate the two for my personal understanding, and of course others as well.

Power will be supplied and data will be captured using an Arduino connected to my laptop, which while very inexpensive will read 20,000 times per second! Its amazing how inexpensive capability is these days.

The ADXL can digitize 10,000 times per second and provide a voltage analog output. The following schematic is the only info supplied with the unit:

a. I am supplying 5V to VDD P1-1, and the ground is connected to GND P1-2 via the Arduino board

b. Output from the ADXL, Vout P2-1 is connected to the voltage input on the Arduino board.

In this configuration I read a constant 2.55 volts with no response to moving the ADXL. I confirmed using a volt meter as well.

There are pins on the ADXL for self test (ST) and standby (STBY), and I wonder if this should be used as a trigger to initiate operation? But the tech reps I talked to at Analog Device don't seem to know either.
 

Attachments

Boyd, could you tune for vertical dispersion with different powder loads ?
There are a lot of things that can influence vertical, and powder is one of them.
Years back, I was running one of the first model Hoehn windage tops on my Hart rest, with the thin bag that folds up to make the sides. It is a cordura bag and was not filled tight, with the result that tracking was not all that I wanted. I added sand, and tracking improved, but with it came a couple of bullets of vertical. Since there is no tracking trophy, I took the sand back out.
http://bulletin.accurateshooter.com/2018/11/how-to-tame-vertical-stringing-tips-from-speedy/
 
To your last question (Charlie), no.

The device has a response of 0.4mV for each g of force. https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL1001-1002.pdf It is also very sensitive to noise on the supply and so you need to feed it with a very good voltage source decoupled as described in the data sheet. (I'm not sure if this decoupling is on the evaluation board. From the pic at Mouser's website it looks like the eval board is merely the chip with decoupling on Vdd and a low pass filter on the output.) A voltmeter is highly unlikely to detect the response on the output pin. Couple it to a good oscilloscope and see what you're getting. Vdd/2 is correct as the zero point. Note the guidance in the data sheet re driving capacitive loads.

Note the chip taps out at 50g. What sort of g forces do you expect on a rifle barrel when fired?
 
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Personally I just do not see this happening by using a vibration transducer. There are only two other people in this thread that have an idea of what goes on while taking vibration readings. All vibrations occur at some resonant harmonic generated by the rotating or source part. When you attach the transducer to your barrel your are affecting that harmonic. Even if you managed to attach the Xducer to the receiver, what would it be telling you? IF this is something worth pursueing someone would have already done it. That is just my opinion.
 
The guy is interested in his experiment. He's asking for help getting it into an operable, observable state.

The shockwave on a barrel on firing isn't a small vibration. I highly doubt the movement is massively distorted by a tiny, lightweight board affixed to the barrel. In any event, that's a second order problem.
 
To your last question (Charlie), no.

The device has a response of 0.4mV for each g of force. https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL1001-1002.pdf It is also very sensitive to noise on the supply and so you need to feed it with a very good voltage source decoupled as described in the data sheet. (I'm not sure if this decoupling is on the evaluation board. From the pic at Mouser's website it looks like the eval board is merely the chip with decoupling on Vdd and a low pass filter on the output.) A voltmeter is highly unlikely to detect the response on the output pin. Couple it to a good oscilloscope and see what you're getting. Vdd/2 is correct as the zero point. Note the guidance in the data sheet re driving capacitive loads.

Note the chip taps out at 50g. What sort of g forces do you expect on a rifle barrel when fired?

The Arduino supposedly has a very stable 5 volt output to drive devices. Voltage reading is 5mv resolution. If my memory is correct I think Vaughn reported something like 20g vibration, using a similar setup to what I am trying to emulate.

It's good to hear the 2.55 volt output baseline is normal. When I shake it vigorously or tap on a table I don't see any voltage change from 2.55 on the Arduino. This is where I am stuck.
 
Attach an oscilloscope. A voltmeter won't cut it. At least then you can narrow down the issue to the eval board or, more likely, your data capture. (I can't help you on the Arduino side of things except to note that it's a poor substitute for an oscilloscope.)
 
Attach an oscilloscope. A voltmeter won't cut it. At least then you can narrow down the issue to the eval board or, more likely, your data capture. (I can't help you on the Arduino side of things except to note that it's a poor substitute for an oscilloscope.)

I don't have a scope.But if the Arduino samples twice as fast as the AD can output, why do you suspect the board would be the problem? I have confirmed the board operability by reading other voltage inputs.
 
FWIW, we used a laser accelerometer and I dont recall anything having to be in direct contact with the bbl. But the equipment and using it is above my pay grade.
 
It's one or the other. It could be lots of issues. Note the limitations on ability to drive a capacitive load for one. Can't help you with Arduino - I would use my oscilloscope. It would at least narrow things down.
 
You can find “relatively” inexpensive scopes that would probably be sufficient for what you are doing. A scope would be very beneficial.
 
Experimenting to learn is a great endeavor and I wish you success! With respect to vibration, software to transform the signal into frequency domains will be needed to determine a barrel’s natural frequency and related harmonics. I’m not aware of any that exist that are inexpensive and/or exist as “shareware.” As combustion continues along the barrel’s length, and is non-repeating forcing function, traditional vibration analysis techniques will not easily be applied.
 
Experimenting to learn is a great endeavor and I wish you success! With respect to vibration, software to transform the signal into frequency domains will be needed to determine a barrel’s natural frequency and related harmonics. I’m not aware of any that exist that are inexpensive and/or exist as “shareware.” As combustion continues along the barrel’s length, and is non-repeating forcing function, traditional vibration analysis techniques will not easily be applied.

Thanks. Fortunately I have a good statistics package and even an old Fortran program from the 70s for frequency analysis once I can get a data string.
 
Ive been using proximity sensors for these type measurements. A seismic sensor (measuring in g force) will possibly tell you how fast it moves (inches/second) but youre not going to get any meaningful data. GE bently is who i was working for when i was doing it for a living. Here is a link to the type sensors to do what is needed on measuring barrel vibrations and the pattern it moves in. You could see a 3d rendition in 4k of the movement
https://www.bakerhughesds.com/bently-nevada/sensors/proximity-sensors
 

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