ADXL05 OR ADXL202 measuring gravity

[Randy Seden]

Carl,

I saw in the Goldmine Electronics catalog a "Gravity" sensor kit for $7.95 that uses what I believe to be a Analog Devices ADXL05 to produce differant sounds as you rotate the axis of the circuit board.
So I did some looking around on the Accelerometer pages and found in Analog Dialogue what would be the logical circuit for this kit entitled "Single Supply Acceleration-to-Frequency Circuits".
Question: Would this have a low enough noise level to measure the changes in gravity to say locate an ancient channel in bedrock? Would this be of ANY use in gold prospecting? What about the ADXL202?

Thanks,

Randy Seden

[simeon webber]

Re: ADXL05 OR ADXL202 measuring gravity

i think that is a good idea

esp if there is a river system associated with it turns up nuggets and flakes

so yes if you start with a known source to find a seem maybe gravimetrics will prob be better than deep sources

try a gravimetric graviton particle procession device
it will see quite deep

.... i think it would work

[Robert Hoolko]

Re: ADXL05 OR ADXL202 measuring gravity

Randy

Local gravity variations are measured in milligals or microgals. A milligal is about 10-6 g, so I would think you would need to be able to detect changes of less than 1 part per million.

Robert

[Carl]

Re: ADXL05 OR ADXL202 measuring gravity

It appears that the ADXL05 (5g) is being phased out. The ADXL202 would do the job for gravity measurement, but like Robert said, I don't know if it would have enough resolution.

The '202 has 500ug/rtHz noise, so if you can live with a 1Hz bandwidth, then you get sub-mg resolution. Converting to gals, nominal gravity is 980 gals, so you would only get sub-gal resolution. I suspect you need way, way better than that.

- Carl

[simeon webber]

Re: ADXL05 OR ADXL202 measuring gravity

i refer back to this link for this type of field measurements esp bed rock



Click Here

[Randy Seden]

Re: GRAVITON-M SYSTEM

Simeon,

I looked at the Russian Graviton-M Aeroborne system and to be honest it's slightly beyond my finances! Nice thought though.

Randy Seden

[Randy Seden]

Re:ADXL202 measuring gravity

Carl,

Could you help me on this design? I really need this to work especially with the price tag in my reach (especially if I can convince the sales dept. to send me a sample!). The 1 hz would be no problem with the spectrum analyzer software I have on my computer and it does averages too (audio spectrum analyzer good from 0hz-3000hz).

What I'm working on is the pedimont slopes of the Rand Mountains in the NW Mojave Desert with Author/retired Geologist Jim Straight (ever seen his best selling book follow the drywashers?). Neat guy and he's in his 70's now and been combing these slopes since 1963 trying to locate the ancient river channels. He's a die hard metal detectorist and I would kinda like to use something with more depth and precision. I'm also designing a new improved version of the PLL detector using the #3 detector of a 74HC4046 as it gives you a +/-180 degree voltage output to operate at the same 1KHZ freq. with something like a 12-15" coil for the sole purpose of detecting the variations of magnetic sand. I'm kinda hoping that it may help me find the ancient channel as it would have the highest concentration of black sand. It will be fun and with 1KHZ and a big coil I should have no problem achieving some serious depth (going to use LITZ wire for the coil that has the equivalent circumference of 4'-large and expensive, but worth it).

Randy Seden

[Randy Seden]

Correction to my post above

should read: LITZ wire with an equivelent Circumverance of 4 inches,not feet! I'm tired as I had to work today and getting up at 4:30am for me is hard plus driving 45 miles to downtown Los Angeles makes it worse.

Oh well, keeps food on the table :>)

Randy Seden

[simeon webber]

Re: GRAVITON-M SYSTEM

hi

i still think a magetometer setup making many passes then average the results to get a higher resolution is prob the best way even in rock

other methods are net the area with sensor's then use a thumper to get results
or an explosive charge


as for gravity

here in glasgow uni
the guys made a graviton meter

it runs from the usual mad guys array of bits

and they lug around the liquid nitrogen

but it worked and won a prize

used to detect minute variations over time in the area it is located

[Carl]

Re:ADXL202 measuring gravity

Getting a couple of samples is not a problem. However, I'm pretty sure this solution is still 3 or 4 (or more) orders of magnitude from what you will need.

You should first determine what kind of gravity variation to expect, then see if the 202 will do the job. You should also check out the ADI iMEMS page, see if they have an apps email. I'll betcha the apps guys (I don't know any of them) have run across gravity measurement before, and can point you closer to a solution.

- Carl

[Randy Seden]

Good Idea,Thanks! N/T

N/T