Geometrics Memory-Mag G-856AX, Руководство по эксплуатации

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Geometrics, Inc
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G-856AX Operation Manual
1
Introduction
This manual provides operating instructions for Geometrics G-856AX portable proton-
precession magnetometer. It includes step-by-step instructions on magnetometer set-up,
survey usage, measurement data retrieval, and maintenance.
What is a total field magnetometer?
A total magnetometer is an instrument that measures the scalar intensity of the local
magnetic field. The G-856AX relies upon the proton-precession measurement technique.
This technique makes use of an induction coil to create a strong magnetic field around a
hydrogen-rich fluid such as Kerosene. This causes the hydrogen protons to align or
polarize their spin axis with the newly applied magnetic field. When the current
producing the polarizing field is interrupted, the protons begin to align themselves with
Earth's magnetic field but in doing so will momentairly precess abou the earth’s field at a
specific frequency that is proportional to the ambient magnetic field intensity. This
precession generates a small magnetic field that induces an alternating voltage in the
induction coil that was previously used to generate the polarization field. The
relationship between the precession frequency of the induced voltage and the strength of
Earth's magnetic field is called the proton gyromagnetic ratio and is equal to 0.042576
hertz per nanotesla (Hz/nT).
Magnetometer applications
Most rocks contain some magnetite, hematite or other magnetic material and will produce
disturbances in the local magnetic field. Because of this, most soils and many man made
objects that contain iron or nickel have magnetic properties detectable by a sensitive
magnetometer because they create local or regional anomalies in the Earth’s main field.
Anomalies are revealed by systematic measurement of the variation in magnetic field
strength with position.
Interpretation of magnetometer readings allows the surveyor to make inferences about
what exists beneath the Earth’s surface. Based on experience with the survey area, the
surveyor might interpret the measurements to indicate to location of a pipeline, fired
pottery or bricks, a piece of ordnance, a particular mineral, or geologic structure. The
interpretation of magnetic survey results is sometimes a difficult task, made even more
complex by constant changes in the earth's overall magnetic field, the size and distance of
objects from the magnetometer, the amount of magnetic material the object contains, as
well as the magnetic susceptibility of the object and the host material. On the other hand,
in many applications, simple interpretations of anomalous magnetic fields will lead to a
straight forward understanding of the source of the anomaly.
The proton precession magnetometer is one of the principal instruments for magnetic
surveys because it combines high accuracy and ease of use. The Applications Manual for
Portable Magnetometers, supplied with this instrument and available for download from