Vector type magnetic sensor.For determinationgeomagnetic fieldThe magnitude and direction of, that is, to determine the component of the geomagnetic field intensity vector in the system where the spacecraft is located.
The magnetometer is a measurementMagnetic inductionInstrument.It is made according to the principle that small magnetic needle can deflect or vibrate under the action of magnetic field.And fromLaw of electromagnetic inductionIt can be inferred that for a closed circuit with a given resistance R, as long as the charge q flowing through the circuit is measured, the change of magnetic flux in the circuit can be known.This is also the design principle of the magnetometer. One of its purposes is to detect the change of the geomagnetic field.
utilizeMagnetic sensorTo determine the direction has been used for a long time in ancient times. According to data, Chinese people began to use it more than 2000 years agoNatural magnetTo indicate the direction.The magnetometer can be traced back to the compass, one of the four great inventions in ancient China[1]。In recent centuries, magnetometers have been widely used in the field of navigation.
application
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magnetometer
Magnetometer is a sensor used to measure the magnetic induction intensity, which is widely used in industry, agriculture, transportation, national defense, aerospace, marine, meteorological, medical and health fields.In the field of geological exploration, it can be used to monitor the change of geomagnetic field and detect the geological age;In the medical and health field, it is often used to detect human magnetic field and assist in disease diagnosis;In national defense, it can be used in magnetic minesweeping, bomb detection, magnetic wave communication, magnetic probe and magnetic navigation;In outer space exploration, it is used to detect the magnetic field of celestial body movement and evolution;In satellite attitude measurement and control, satellite attitude information can be provided by measuring space magnetic field with magnetometer[2]。
Precision magnetometer
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At present, there are two types of precision magnetometers commonly used in scientific research: one is used to measure the magnetism of small samples or weak magnetic materials, such as vibrating sample magnetometers, superconducting quantum interference device magnetometers, alternating gradient magnetometers, and lift sample magnetometers;The other type is used to measure the weak magnetic field in space or the magnetic field on the surface of objects, such as fluxgate magnetometer, film resistance magnetometer, etc. The superconducting quantum interference device magnetometer can also be used to measure the space magnetic field or the magnetic field on the surface of samples[3]。
Vibrating sample magnetometer
Using the principle of electromagnetic induction, the magnetic moment of a sample that vibrates slightly at a fixed frequency and amplitude in the center of a group of detection coils is measured.For a sample small enough, the induced voltage generated by its vibration in the detection coil and the magnetic moment of the sampleamplitudeThe vibration frequency is proportional.On the basis of keeping the amplitude and vibration frequency unchanged, the magnetic moment of the sample to be measured can be calculated by measuring the voltage with a lock-in amplifier.
It is an instrument based on the concept of magnetic flux quantization and the principle of superconducting Josephson tunneling effect.It also has many important applications in biomedicine, such as measuring cardiac magnetic field, pulmonary magnetic field, and biological tissue magnetic susceptibility.
Alternating gradient magnetometer
In fact, it is a kind of magnetic balance method with high sensitivity.Like other magnetic balance instruments, it determines the magnetic moment of a magnetic sample by measuring its force in a non-uniform magnetic field.The difference is: the generation of gradient field and the method of force measurement.
Pull sample magnetometer
The pulling sample magnetometer is also based on the principle of electromagnetic induction.In the superconducting magnet, there are two detection coils in series with the same geometric factor. When the step motor pulls the sample rod to make the sample move between the two detection coilsInduced electromotive forceThe integral of the movement time is proportional to the magnetic moment of the sample.With a larger time constantDigital voltmeterThe magnetic moment of the sample can be calculated by direct measurement.
Magneto-optical Kerr effect magnetometer
Very high sensitivity.When the thickness of the film is only nanometer, the magnetic signal changes generated in the small grinding area of the laser spot can be detected, which should be more sensitive than the above magnetometers.
Their common feature is thatsensitivity, mainly used to measure static magnetism, including technical magnetization curve, hysteresis loop, demagnetization curve, magnetocaloric curve, and various parameters defined therein.asSaturation magnetizationMa,Residual magnetization Mr, coercive force Hc, Curie temperature Tc, various susceptibility or permeability,Maximum magnetic energy product, rectangular ratio, etc.These instruments can not only measureFerromagnetismFerromagnetic samples, as well as diamagnetic and paramagnetic samples, can be measured not only for large samples, but also for thin films and other micro samplesMagnetic functional materialsSuperconducting materials, structural chemistry, geological exploration, biophysics and other research fields have a very wide range of applications.
