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Thread: Gravity meter

  1. #1
    Join Date
    Nov 2005
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    128

    Default Gravity meter

    Has any one succeeded in building and using a gravity meter? for locating cavities or masses of dense material (treasure) in the ground?

    Some patents about simple gravity meters are :
    http://www.freepatentsonline.com/result.html?p=5&srch=xprtsrch&query_txt=icl/g01v7+and+abst/(gravity+or+gravitation+or+gravitational)&uspat=on &usapp=on&eupat=on&jp=on&pct=on&date_range=all&ste mming=off&sort=chron

    To get a complete copy of US patent, click on www.pat2pdf.org, fill in the patent no. from the above search (read the instructions on this site), and download the patent document in pdf format. Or log in to freepatentsonline and create an account.

  2. #2
    Join Date
    Nov 2007
    Location
    GREECE
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    5

    Default

    Very interesting.
    Thank you very much.

  3. #3
    Join Date
    Nov 2005
    Posts
    128

    Default Gravity and magnetic survey : Prospecting

    Here is a document explaining about the process and use of gravity + magnetic survey.
    http://www.em.gov.bc.ca/dl/Oilgas/CO...File2004_1.pdf (8.3 MB)

  4. #4
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    Nov 2006
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    Vicksburg, MS
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    39

    Default

    I have done some gravity surveys. We currently have an old Lacoste & Romberg gravimeter. My wish list currently includes a Scintrex CG-5 gravimeter, but since they cost $80,000 and have a one year waiting list I won't be getting it very soon, which is a relative gravimeter. There were three manufacturers of gravimeters until a few years ago. Scintrex, Micro-G and Lacoste & Romberg all merged into one company.

    Building a gravimeter is not a simple DIY project. It might be the most difficult geophysical instrument to design and build. The absolute gravimeters from Micro-G are amazing instruments that cost up to $500,000 and take almost a year to build. The gravimeters a measuring a signal that is nine orders of magnitude smaller that the values we normally use (e.g. 9.8 m/s2).

  5. #5
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    Nov 2005
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    128

    Default

    I absolutely agree about the sensitivity and design difficulty.

    However, the problem is : because a good gravity meter is expensive and takes a long time to build, its use is not very prevalent.

    So. if people can themselves make one, just sufficient for their purpose, they will start using the GM.

    And I think, present day engineering expertise available with the people, is a magnitude better than what was available to the best of the labs half a century ago.

    I am sure that with little help from experts like you, interested people will come up with a working model :-)

  6. #6
    Join Date
    Feb 2006
    Location
    California
    Posts
    381

    Default

    Quote Originally Posted by Atul Asthana
    And I think, present day DIY expertise is a magnitude better than what was available to the best labs half a century ago.
    Can Dell Winders out-perform other gravity sensing devices using methods of a half a century ago?
    Quote Originally Posted by Dell Winders
    Let me make it clear, I have NEVER claimed, or believed for a moment, that any electronic configurations, and even some non-electronic configurations can be used effeciently as a Meta-Physical Dowsing tool. A simple needle & thread is suffice to me for that purpose


    Best wishes,
    J_P

  7. #7
    Join Date
    Jun 2009
    Location
    Rhode Island
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    15

    Default

    Quote Originally Posted by Atul Asthana View Post
    I absolutely agree about the sensitivity and design difficulty.

    However, the problem is : because a good gravity meter is expensive and takes a long time to build, its use is not very prevalent.

    So. if people can themselves make one, just sufficient for their purpose, they will start using the GM.

    And I think, present day engineering expertise available with the people, is a magnitude better than what was available to the best of the labs half a century ago.

    I am sure that with little help from experts like you, interested people will come up with a working model :-)
    I think you are totally correct about the engineering expertise that is floating around, and with internet there is so much information previously difficult to come by. Also, electronics has become more integrated and practical for the part-timer.
    I recently opened up a late 1980's gravity meter and found a multi card board system of electronics for
    1-CPU, 2- ram, 3-display, 4-keypad that call ALL reside in a single modern day microcontroller. I guess the hardest part is winding the spring (assuming one wants to make a spring based one) and making the electronic readout. I reckon electronic because electronics are easier than mechanics in this day and age (or at least that is my impression). In the quartz spring ones, the setup is fairly straight forward, just hang a vertical mass (5-10 mg i think) over a plate, then use capacitance to check the displacement. Better yet, use feedback and measure the voltage required to hold the mass a specific distance from the plate, and hold it to within ~0.1 nm. Of course, you have to do this in a vacuum (minimize convective disturbances), and hold the temperature stable to a milidegree or so (opamp with thermistor or whatever). And you have to level the instrument to within about 10 arcseconds (ive seen some electrolytic tilt sensors with 0.05 arc second resolution)

  8. #8
    Join Date
    Nov 2005
    Posts
    128

    Default

    Quote Originally Posted by willemite View Post
    I think you are totally correct about the engineering expertise that is floating around, and with internet there is so much information previously difficult to come by. Also, electronics has become more integrated and practical for the part-timer.
    I recently opened up a late 1980's gravity meter and found a multi card board system of electronics for
    1-CPU, 2- ram, 3-display, 4-keypad that call ALL reside in a single modern day microcontroller. I guess the hardest part is winding the spring (assuming one wants to make a spring based one) and making the electronic readout. I reckon electronic because electronics are easier than mechanics in this day and age (or at least that is my impression). In the quartz spring ones, the setup is fairly straight forward, just hang a vertical mass (5-10 mg i think) over a plate, then use capacitance to check the displacement. Better yet, use feedback and measure the voltage required to hold the mass a specific distance from the plate, and hold it to within ~0.1 nm. Of course, you have to do this in a vacuum (minimize convective disturbances), and hold the temperature stable to a milidegree or so (opamp with thermistor or whatever). And you have to level the instrument to within about 10 arcseconds (ive seen some electrolytic tilt sensors with 0.05 arc second resolution)
    willemite, Thanks for your comments.

    As brought out by you, Electronics is much easier and more manageable.

    With a little help from experts in mechanical design and construction, GMs can be more affordable.

  9. #9
    Join Date
    Jun 2009
    Location
    Rhode Island
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    15

    Default

    Also, as per gravity meter construction, just remember the zero length spring technology was developed in the 1940's. With a decent machine shop it can likely be replicated, though I am sure it would need some research and development.

  10. #10
    Join Date
    Nov 2005
    Posts
    128

    Default Zero length spring and gravity meter

    Some text on zero length spring can be found here :

    http://physics.mercer.edu/earthwaves/zero.html

    http://large.stanford.edu/courses/2007/ph210/lee1/

    La Coste and Romberg patent is available here :
    http://www.freepatentsonline.com/2293437.pdf
    Present day technology (specially, use of electronics) can definitely improve upon the 1941/42 patent.

  11. #11
    Join Date
    Jun 2009
    Location
    Rhode Island
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    15

    Default

    some neat diagrams here showing spring arrangement:
    http://www.ukm.my/rahim/gravity%20lecture(MSc).htm

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