Research On The Digital Technology Of Residence Times Difference Fluxgate

Magnetic phenomena go with our life, so people started to research magneticmeasurements as well as some magnetic phenomena earlier. As electromagneticphenomena are studied in-depth in modern physics, the technology of magnetic fieldmeasurement is developing rapidly and has appeared as a separate discipline. After thetechnology combined with other different disciplines, a range of other disciplinesformations come into being, such as magnetic chemical, magnetic prospecting,magnetic testing science and magnetic medical science et al. Currently, the technologyof magnetic field measurement has been widely used in the field of geological, such asgeomagnetic field observation, space magnetic field measurements and geologicalexploration, and in the fields of military, industrial and medical, such as inertialnavigation, submarine detection, pipeline inspection and magnetic resonance imaging.There is a wide range of magnetic field sensor, some of which can measure themagnetic vector are mainly Induction magnetic sensors, Hall Effect magnetic sensors,Magnetoresistive sensors, SQUID and fluxgate magnetometers. Compared with othermagnetic measurement equipments and integrated all kinds of indicators, fluxgatemagnetometers with high sensitivity, large measurement range, can measure a single ora total magnetic field of the magnetic vector space, low cost, good stability, low powerconsumption, integration, miniaturization and high degree of intelligence features,those features make the range of application more widely.Although the odd harmonics of the output signal have been reduced bydifferential structure of conventional Even-harmonics-fluxgate sensor to some extent,odd harmonic noise will be generated again, when the coil size or the core structuresize of fluxgate asymmetry. The changing temperature around the measured targetmagnetic field, the heats of fluxgate sensor in the work, the magnetic noise and the DCbias voltage produced by the detection part will cause the drift of the output signal. These situations are the reasons of the zero signal, which is the output signal of thefluxgate sensor caused by the noise when the external magnetic field is zero, presentsin an actual application of sensor. When measuring a weak magnetic field, the smallsignals of the sensor are submerged due to the presence of noise which is notconducive to signal detection., Especially the part of the phase-sensitive detector in thecomplex circuit structure, the phase of the input signal and the fundamental signal isvery difficult to keep them same exactly. This phenomenon affects the detectingefficiency of phase-sensitive detector. In order to improve the performance of fluxgate,besides improvement of the sensing element structure and research of new materials, anew study about fluxgate in detection theory of magnetic field need to be started.As the reasons above, the purpose of this research is to study a digital outputfluxgate magnetometer based on the residence times difference of fluxgate core whenworking to detect magnetic field. As the different magnetic fields are measured by thecorresponding output pulse signals which is undisturbed by the odd harmonic noise inRTD-fluxgate sensor, therefore the design of the sensing element requires a simplestructure. The time difference can be measured by a single magnetic core structure ofsensor. In addition, the simple circuit configuration and the digital output provide abasis for the development of magnetic field sensors which based on Micro ElectroMechanical System (MEMS) technology. In summary, the meaning of researching theRTD-fluxgate sensor as follows: exploring a new measurement methods for fluxgate;simplifying the production process; cutting down the detection circuit links; reducingthe noise on the output signal to increase the sensitivity; decreasing powerconsumption; minimizing the volume; realizing the digital output of magnetic fieldmeasurements; providing a basis for the development of magnetic field sensors basedon MEMS technology.In this paper, after the author deeply researched the points of domestic and foreignscholars in RTD-fluxgate technology, the digital RTD-fluxgate sensor has beenprimarily realized. The text mainly adopts the method of combining bistablecharacteristics with incentive magnetic deviation to detail introduce the measurementtheory of magnetic field of RTD-fluxgate sensor as well as its output response mathematical model in the two driving waves of sine and triangular are introduced; byanalyzing dynamic arctangent hysteresis model, the effects of hysteresis characteristicsof the core to the output response of RTD-fluxgate is analyzed; the relationshipbetween the different frequencies currents excitation signals and hysteresischaracteristics is given; by comparison and analysis, the core structure ofRTD-fluxgate sensor, winding way, selection of magnetic core material and productionof the shield are described; by combining direct digital frequency synthesizer DDSwith voltage-controlled current source, the controllable excitation device is designed toachieve high-precision driving signal; by using digital coding quantization, the workfor changing an analog signal into a digital signal is completed; the performance ofsingle component RTD-fluxgate sensor is tested and analyzed in the electromagneticshielding room. The full-text provides a theoretical basis for the next research work ofRTD-fluxgate sensor.