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Author Topic: Accelerometer Calibrations  (Read 2372 times)

Offline Hawaii596

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Accelerometer Calibrations
« on: 12-19-2016 -- 21:13:44 »
Basic question about calibrating accelerometers.  When calibrating accelerometers of various maximum g force ranges, are they calibrated at differing amounts of applied g force based on range, or are they calibrated at a standard amount of g force and a mV/g measured?  I am spec'ing hardware, and there are some portable vibration calibrators on the market that apparently just generate a standard amount of g force, and it seems that even for (as example) 5000 or 10000 g accelerometers, the calibration amplitude applied may only be 5 or 10 g's, then a mV/g is measured against spec, etc.

Any inputs?
"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind."
Lord Kelvin (1824-1907)
from lecture to the Institute of Civil Engineers, 3 May 1883

Offline HalAC

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Re: Accelerometer Calibrations
« Reply #1 on: 12-24-2016 -- 23:28:01 »
I performed calibrations for a year or two on accelerometers when I worked at Arnold AFB's PMEL. We used one specific amplitude for an accelerometer and would sweep through a set of frequencies to check it's response against a known standard accerlerometer.

Hope this helps.
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Offline CalMachine

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Re: Accelerometer Calibrations
« Reply #2 on: 12-31-2016 -- 20:55:13 »
Here at ENI Labs, we start at 1 g-rms @ Whatever the stated reference frequency of the accelerometer is (generally 100 Hz, but sometimes 159 Hz) and sweep up and down in frequency to provide a frequency response curve @ 1 g-rms.  Provided data points are in "deviation from nominal" form from the reference frequency sensitivity value found at the start.

Offline Hawaii596

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Re: Accelerometer Calibrations
« Reply #3 on: 01-02-2017 -- 17:41:12 »
This is pretty much what I have found.  To keep this from being commercial, I am looking into one of the new accelerometer calibrators, and that seems to be the norm.  I also looked at a few USAF T.O. procedures, and they say the same.  The new type standards are pretty nice, and not too expensive. One model has a USB where you attache a thumb drive, and semi-automatically store each reading into a CSV file, then transfer the thumb drive when finished.
"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind."
Lord Kelvin (1824-1907)
from lecture to the Institute of Civil Engineers, 3 May 1883

Offline briansalomon

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Re: Accelerometer Calibrations
« Reply #4 on: 03-29-2019 -- 22:12:02 »
I got the Vibration Research Accelerometer calibration system last year and am just about ready to proceed with the accreditation process.

I like the system fine and have noticed the software allows me to configure quite a few parameters such as dwell time at the selected frequencies, input filter parameters and response time parameters that can affect the measurement quite a bit.

The manual is quite good but I am wondering if anyone knows of a good handbook or text book that will help me understand how to configure these parameters for best (truest) response to my reference accelerometer.
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Offline lonewolf

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Re: Accelerometer Calibrations
« Reply #5 on: 04-08-2019 -- 04:26:11 »
my equipment is older Bruel & Kjaer I use an 8305 for my standard mounter on a 4809 shaker, using the 2626 conditioning Amp on the 8305, I have an old 2706 Power Amp to drive the shaker.

my test subject mounts on top of the 8305, and I sweep thru the range that I plan to use the Test Subject to make sure my curve matches my Standard and the datasheet that comes with the test subject.

All I really mess with is the Piezo types, I have several other bruel&kjaer instruments also like the 2511,1405, and a bunch of Misc adapters and standard accelerometers.

 

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