[0030] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0031] The power consumption of the fluxgate magnetometer is mainly distributed in the excitation unit, the amplifying detection integration circuit and the feedback circuit; the key to reducing the detection power consumption of the fluxgate magnetometer is to reduce the power consumption of the excitation unit; the present invention reduces the excitation power consumption The specific measure is to use the bipolar intermittent pulse voltage excitation method, with a narrow rectangular pulse, through a low on-resistance switch, control a constant voltage source to excite the fluxgate iron core, and the iron core is periodically excited to saturation Status, to ensure that the magnetometer has sufficient resolution, while greatly improving the energy utilization efficiency of the excitation unit.
[0032] figure 1 Shown is a functional block diagram of the first axis zero point measurement circuit of the low-power three-axis decoupling self-zeroing fluxgate magnetometer provided by the embodiment; including an excitation unit, an excitation coil, a signal coil, a feedback circuit, and a zero point measurement The control circuit, synchronous detection control circuit, amplification detection integration circuit and micro-processing unit; the zero point measurement circuit of the remaining two axes is the same.
[0033] figure 2 Shown is a schematic diagram of the excitation unit in the embodiment; in the embodiment, the excitation unit includes a square wave signal generating unit, a counting decoding circuit, a first energy storage unit and a second energy storage unit;
[0034] Wherein, the input terminal of the counting and decoding circuit is connected with the output terminal of the square wave signal generating unit; the first terminal of the first energy storage unit is connected with the first output terminal of the counting and decoding circuit, and the power terminal is used to connect an external constant voltage source ;
[0035] The first end of the second energy storage unit is connected to the second output end of the counting and decoding circuit, the second end is connected to the second end of the first energy storage unit, the third end is connected to the third end of the first energy storage unit, The fourth end is grounded, and the fifth end is connected to the excitation coil.
[0036] image 3 As shown, it is a schematic diagram of the excitation waveform generated by the excitation unit in the embodiment; during the high level of the excitation pulse Q2, the switch K1 of the first energy storage unit is turned on, and the switch K2 of the second energy storage unit is turned off. The on-resistance is much smaller than the excitation coil impedance, and the voltage across the switch can be ignored; the reverse voltage charged on the capacitor C of the second energy storage unit and most of the power supply voltage Vs fall on both ends of the excitation coil, and the energy utilization rate Very high; the excitation unit slowly increases the excitation current with a stable voltage amplitude to drive the iron core to saturation to ensure that the magnetometer has a strong enough signal output;
[0037] When the fluxgate core is excited to saturation, the instantaneous inductance L of the excitation coil is small, the excitation current increases rapidly, and the capacitor is quickly charged. After a period of time, the capacitor is charged to close to the power supply voltage, so that the voltage across the excitation coil is very high. Small, the excitation current no longer increases, limiting the saturation depth of the iron core and reducing power consumption;
[0038] When the excitation pulse Q2 turns to a low level, the switch K1 of the first energy storage unit is turned off, and the excitation coil loop current continues to charge the capacitor C through the diode D2 under the action of inertial inertia, and the remaining energy on the excitation coil inductance is stored in the capacitor on;
[0039] In the second half of the excitation cycle, during the high level of pulse Q7, the switch K2 of the second energy storage unit is turned on, the switch K1 of the first energy storage unit is turned off, and the voltage stored on the capacitor C is applied to both ends of the excitation coil , Reverse excitation of the fluxgate core, the time waveform of the excitation voltage is basically symmetrical with the first half cycle, and the magnetometer has similar signal output with the first half cycle;
[0040] When the excitation pulse Q7 turns to a low level, the switch K2 of the second energy storage unit is turned off, and the excitation coil loop current continues to charge the capacitor C through the diode D1 under the action of inertial inertia, and the remaining energy in the excitation coil inductance is also Stored on the capacitor;
[0041] During the entire excitation cycle, only when Q2 is at high level, can the power supply supplement the excitation energy, and the pulse width of Q2 is very narrow, so the energy consumption is very low; moreover, through the energy storage of the diode, the flux gate will be ironed every time After the core is excited to saturation, the remaining energy in the excitation coil inductance L is converted into capacitor energy and stored, so that the energy consumed in each excitation cycle is mainly the core hysteresis loss and the heat loss on the coil internal resistance. Therefore, The excitation unit in the embodiment has a high energy utilization rate, and the average power supply current of the circuit can be conveniently controlled below 0.3 mA.
[0042] In order to improve the accuracy and resolution of the three-axis fluxgate magnetometer, as well as the long-term zero point stability; in the embodiment, a temperature-controlled crystal oscillator circuit with high stability and low power consumption is used to generate intermittent pulse voltage waveforms with stable frequency and width, and pass low Resistance switch, turn on the constant voltage source to excite the iron core, the excitation signal waveform is positive and negative, and the frequency, width, and amplitude are all stable measures, thus ensuring the stability of the magnetometer zero point; and, due to the high excitation energy utilization rate, Under the condition of low power consumption, the iron core can still be excited to deep saturation, which ensures the stability and high resolution of the magnetometer.
[0043] Figure 4 It is a schematic diagram of the matching of the zero point measurement control circuit and other components in the embodiment; the zero point measurement control circuit includes two sets of switches; under the control of the micro-processing unit, the two output ends of the probe signal coil are switched to reverse , Measure the output voltage value backwards and backwards, and obtain the zero point of the circuit according to the output voltage value; this zero point measurement method can be accurately performed on-line and eliminated, which reduces the impact of zero point drift on the measurement results.
[0044] Figure 5 It is a schematic diagram of the three-axis fluxgate weak coupling installation method in the embodiment; among them, the three-axis probe is orthogonal and the three-axis probe has a symmetry axis on a straight line; the two-axis probe is not coplanar and orthogonal to this The line connecting the center points of the two-axis probe cores is vertical, and the other axis probe is installed on the extension line of the line connecting the center points of the first two-axis probe cores. This installation method ensures that the feedback magnetic field and excitation magnetic field of any axis in the magnetometer have little effect on other axes, thereby reducing the three-axis coupling error.
[0045] Those skilled in the art can easily understand that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement and improvement, etc. made within the spirit and principle of the present invention, All should be included in the protection scope of the present invention.
