- 行业: Mining
- Number of terms: 33118
- Number of blossaries: 0
- Company Profile:
The U.S. Bureau of Mines (USBM) was the primary United States Government agency conducting scientific research and disseminating information on the extraction, processing, use, and conservation of mineral resources.
Founded on May 16, 1910, through the Organic Act (Public Law 179), USBM's missions ...
An instrument used for detailed studies of the Earth's magnetic field on a local basis that uses the flux-gate, which consists of two identical saturable cores of high permeability, with identical, but oppositely wound, coils. An alternating current in these coils magnetizes them first with one polarity, then in the opposite sense. If an additional field is present, such as the Earth's field, it will add to the flux in one coil while decreasing that in the other, resulting in different voltage drops across the two coils. This difference is proportional to the unvarying field, which can be measured by noting the average voltage difference between the two halves of the flux gate. In use, a part of the Earth's field is balanced out by an additional winding surrounding both cores and carrying direct current. In airborne use, the recording flux gate is kept aligned with the magnetic field by the use of two additional flux gates. When these are at right angles to the Earth's field, they generate no voltage, but if they depart from this position, they can generate voltages which operate motors returning them to proper alignment. In this fashion, the recording element is held always parallel to the total field.
Industry:Mining
An instrument used for determining the density or specific gravity of fluids, such as drilling mud or oil, by the principle of buoyancy.
Industry:Mining
An instrument used for routine gas analysis for the determination of methane and other gases. The results are accurate to 0.1%.
Industry:Mining
An instrument used in a borehole for fishing operations, for reducing the length of the box, or for coupling lost tools.
Industry:Mining
An instrument used in aerial geophysical prospecting for the direct detection of conducting ores. An alternating electromagnetic field is transmitted from an aircraft. This field is received by the conducting body in the Earth and reradiated with some change in phase. The resultant field is picked up by the device, towed behind the aircraft, and compared with the transmitted field. The phase shift is measured automatically and recorded as a profile during flight.
Industry:Mining
An instrument used in borehole surveying, which marks the core to show its position in space.
Industry:Mining
An instrument used in bridge testing to measure any outward spread of an abutment under load.
Industry:Mining
An instrument used in drawing and plotting, designed for laying out or measuring angles on a flat or curved surface, and consisting of a plate marked with units of circular measure.
Industry:Mining
