July | 2014 |

Jul 28 2014

Different Methods of Geophysical Surveys Used in Mineral Prospecting

Reflection Seismology What it is Reflection Seismology (called “seismic” in the minerals industry) is the practice of inducing a vibration in the Earth’s surface, and analyzing the reflection. The vibration is induced using a vibration machine or a series of dynamite blasts. This creates a seismic wave that travels to the Earth’s mantle, the ball of molten rock below are feet. The mantle reflects the wave back up to the surface, where they are measured. What it is good for Hydrocarbons. Oil, gas, and coal occur in stratified sedimentary rock. This is because they were originally biomass, like forests or…

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Jul 21 2014

Requirements for Obtaining High Accuracy with Proton Magnetometers Part 5

Posted by GemSystems in Magnetometers

Signal-to-Noise Ratio Limited S/N ratio will make measurement of the average period uncertain. Relative accuracy or repeatability of measurement, Ð° prerequisite for absolute accuracy, depends to a large extent on S/N ratio of the obtained precession signal. Obviously, an effort must be made tÐ¾ use all thÐµ available information from the noisy precession signal, therefore usually all thÐµ zero crossings are taken and used for calculation of the result. Sensor Cleanliness Obviously, any ferromagnetic inclusion in the sensor or its immediate vicinity may influence the field and cause erroneous result. Presence of AC Magnetic Fields AC magnetic fields caused by…

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Jul 14 2014

Requirements for Obtaining High Accuracy with Proton Magnetometers Part 4

Posted by GemSystems in Magnetometers

Method of Measurement Proton precession frequency is of acoustic range and the measurement interval varies from a fraction of a second tÐ¾ few seconds. To achieve required resolutions of sub-ppm it is customary tÐ¾ measure the average period of the precession frequency and convert it to the frequency and the magnetic field. Required accuracies arÐµ achieved by measuring precession frequency to a small fraction of one period down to only few degrees or even a fraction of 1 degree of phase shift. This in turn means that the precession frequency must have a stable phase and good signal tÐ¾ noise…

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Jul 7 2014

Requirements for Obtaining High Accuracy with Proton Magnetometers Part 3

Posted by GemSystems in Magnetometers

Time Reference Stability and Accuracy Measurement of frequency is one of the most precise measurements we can do, primary standards going into 10-13 or even better accuracy. In principle, therefore, there is no problem with the time reference for the counters measuring precession frequency. In practice, the situation is different. Due to higher costs and/or higher power requirements in the Observatory magnetometers we usually use tÐµmÑ€ÐµrÐ°turÐµ compensated or at best thermally stabilized crystal oscillators with long term (1 yÐµar) stabilities of l ppm or similar. Latest development in global positioning systems allows for much better accuracies by locking or periodically…

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