Research And Design On The Residence Times Difference Fluxgate Sensor

Magnetic field measurement techniques has been widely used in the field ofgeophysical such as geological exploration，earthquake prediction，and geomagneticforecast so on，in the military field，for example，inertial navigation systems，militaryweapons research，flying body heading the attitude control system，etc.，and spacetechnology， industrial， medical， biology， archeology other fields. Fluxgatemagnetometer with high sensitivity and can measure the space vector field andsingle-component magnetic field and total field，as well as a large measurement rangein the magnetic field measuring instruments，therefore，the fluxgate magnetometer hasbroad application prospects.The fluxgate sensor is the structure of a transformer. With the periodic modulationof the alternating current，it transform magnetic field signal into electrical signals，which through a characteristic electrical parameters of the extraction of the signalmeasured magnetic field. Able to measure the magnetic field，resolution up to1nT. Atpresent，most of the fluxgate magnetometer are based on the even harmonicscharacterization of the measured magnetic field. Because traditional fluxgate sensorare affected by the core material properties，the probe structure and probe productionprocess，so the improvement of sensitivity is restricted. Therefore，the need to researcha new detection means to break the bottleneck to improve sensitivity.The residence times difference fluxgate principle is that during the core to bemagnetized to saturation，due to the presence of weak magnetic field，their stay in thepositive and negative saturation，the measured magnetic field characterized by the timedifference between the two. Such detection methods，as opposed to traditional fluxgatesensor that does not require strict symmetrical dual-core probe，do not need thecomplexity of the detection circuit，to improve the stability of the system. The timedifference fluxgate sensor by the induced voltage signal time difference，it can use the FPGA and DSP digital circuit to obtain the required time difference， therebyincreasing the temperature stability of the systems of the fluxgate，reducing thevolume of the instrument，and enhancing the portability of the system，and thus canachieve a digital fluxgate sensor.Based on the principle of the time difference fluxgate sensor，establish a model ofthe time difference fluxgate sensor. Then，simulate and analysis the time differencefluxgate character，such as the relationship between the time difference and themeasured magnetic field，the relationship between the time difference and theamplitude of excitation signal，the frequency，and the relationship between fluxgatesensor sensitivity and the amplitude and frequency of the excitation signal. Andcomparative analysis of two cases of the sine wave signal excitation and triangularwave signals incentives.By analyzing the impact of the probe structure，the core material and windings onthe induced voltage signal of the fluxgate sensor，and experimental comparativeanalysis to determine the production program of the fluxgate sensor probe. The core ofthe fluxgate sensor use1K107stripe with a high initial permeability, high squarenessratio, low coercivity; the probe is made into,”said”-shaped structure; the windingsusing symmetrical structure,using the induction coil of1200turns and with a matchingresistor to prevent the coil underdamped state. According to the detection principle ofthe fluxgate sensor，design and complete the detection circuit of the fluxgate sensor.The detection circuit is simple，with low noise，high stability. Fluxgate sensorresolution60nT. The time difference fluxgate sensor detection of the time difference,you can use digital signal processing, such as DSP，achieve digital sensor.Experimental analysis， the sensitivity of the fluxgate sensor relate to corecharacteristics，the probe core characteristics is not easy to change and difficult to get，so the improvement of the fluxgate sensitivity is restricted. The “residence timesdifference” fluxgate has stochastic resonance phenomenon，according to the principleof stochastic resonance，the paper established a fluxgate sensor model with feedbackstructure，this feedback structure can change the parameters of the core，so as toenhance the fluxgate sensitivity. Simulation analysis to adjust the feedback coefficient can change the optimal noise intensity，and core coercivity. By adjusting the feedbackcoefficients and with changing the incentives of the signal amplitude，the fluxgatesensitivity can be enhanced.