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Introduction to a variety of magnetometers

The geomagnetic sensor is an instrument for measuring the geomagnetic inclination. It was made by scientist Weber based on the principle of electromagnetic induction. The most important component is a multi-turn coil with one shaft rotating. The coils are mounted on a horizontal shelf with a 90° cross. When the axis of rotation of the coil and the direction of the earth's magnetic field are kept in parallel, the voltage output of the rotating coil is zero. The inclination at this moment is the geomagnetic inclination. The error can be eliminated by comparing the two sets of measurement data of the coil's positive and negative rotation and horizontal and vertical dial rotation by 180°, so the accuracy can reach several seconds.
The geomagnetic theodolite is a magnetometer for measuring the horizontal strength of the earth's magnetic field. It is designed by the scientist Gauss et al. based on the interaction between two different magnetic bars and the oscillation period of the suspended magnetic bar and the strength of the earth's magnetic field. The main components are the biasing rod, the deflection magnetic system and its suspension wire, the telescope and the horizontal dial, and the magnetic rod oscillation box. Geomagnetic theodolites are mainly available in two models, Martin Magnetometer and Schmidt Magnetometer
A sinusoidal galvanometer is a magnetometer used to measure the horizontal strength of a geomagnetic field. The main components are Helmholtz coils, suspension wires and magnetic systems. The coil constant and the magnitude of the current and the eccentricity of the magnetic needle affect the measurement.
The quartz wire horizontal strength magnetometer is a magnetometer for measuring the horizontal strength of the earth's magnetic field. It is designed and manufactured by the scholar Lacour by the law of the balance between the torsional moment and the magnetic moment. The main components are quartz wire and magnetic needle. As long as the deflection angle of the magnetic needle is measured when the suspension wire is twisted by +2π to 2π, the horizontal strength of the geomagnetic field can be calculated by calculation, so the application is very extensive.
The zero-point magnetic scale is a magnetometer for measuring the vertical magnitude of the earth's magnetic field. It is based on the principle that the balance between the two magnetic needles is based on the principle of balance between the weight and the magnetic moment. The main components are the single magnetic needle and the vertical in-plane magnetic bar. The magnetic needle can be zeroed as long as the direction of the magnetic bar is changed. The strength of the magnetic field caused by the magnetic rod in the opposite direction to the magnetic needle is measured. The direction of the magnetic rod when the magnetic needle is zero can measure the vertical magnitude of the magnetic field.
The fluxgate magnetometer is a magnetometer used to measure the magnitude and direction of the earth's magnetic field. The fluxgate probe is a magnetic core of a high permeability alloy that can become saturated magnetized in a weak magnetic field. The principle is that two primary and secondary coils are wound on the magnetic cores that are kept parallel, and the two coils are connected in series to stimulate the magnetic field at a frequency of about 20 to 1000 Hz, so that the magnetic core becomes saturated, and the secondary coil Connected to the differential amplifier. When the external magnetic field is zero, the size of the negative half-cycle of the AC magnetic flux in the core of the high-permeability alloy is completely symmetrical, and the output of the two coils at this time is zero. When there is a DC magnetic field in the core shaft, the core will become saturated first in a certain half-week, and the size will be asymmetrical between positive and negative half cycles. At this time, the output voltage difference of the coil is The magnitude of the magnetic flux is proportional, and the value of the geomagnetic field can be obtained by measuring the magnitude of the voltage.
The proton precession magnetometer is a magnetometer for measuring the total strength of the earth's magnetic field. When a strong magnetic field is present, the protons in the water or hydrocarbons are polarized. When the strong magnetic field disappears, the protons move around the earth at an angular velocity ω. As long as the proton's precession frequency is measured, the total value of the geomagnetic field can be obtained, and the measurement precision can reach 0.01 nit, but the disadvantage is that it can be continuously measured. In particular, as long as a Helmholtz coil is added to the outside of the probe when measuring the magnetic field, it can be turned into a proton precession component magnetometer, which can be used to measure the component of the earth's magnetic field.
The optical pump magnetometer is a phenomenon of Zeeman splitting when the atomic energy level is in the magnetic field. It is mainly developed by a light pump and magnetic resonance technology to develop a magnetometer that measures the total intensity of the earth's magnetic field. For example, the principle of the Shuguang pump magnetometer is to use a circularly polarized light from a xenon lamp to illuminate the 铷 absorption cell and focus on the photocell, because the beam and the earth's magnetic field form an angle of approximately 45°, and the electron is pulled around the earth's magnetic field. Mohr exercise, so the intensity of light will also flash at the same time as the Larmor frequency. Since the output signal of the photovoltaic cell is amplified and connected to the external high frequency coil, it constitutes an electronic component-oscillator, since the oscillation frequency f is proportional to the total intensity T of the earth magnetic field. Therefore, as long as the magnitude of the oscillation frequency is measured, the total intensity value of the geomagnetic field can be calculated.

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