CN109407157B - Induction type magnetic sensor and electromagnetic exploration equipment - Google Patents
Induction type magnetic sensor and electromagnetic exploration equipment Download PDFInfo
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- CN109407157B CN109407157B CN201811480299.XA CN201811480299A CN109407157B CN 109407157 B CN109407157 B CN 109407157B CN 201811480299 A CN201811480299 A CN 201811480299A CN 109407157 B CN109407157 B CN 109407157B
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- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
- G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils
- G01V3/104—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils
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Abstract
The invention provides an induction type magnetic sensor which comprises a signal pre-amplification measuring circuit, a feedback loop, a magnetic core, a coil, a low-noise and zero-stabilization processing circuit and an output protection module, wherein the input end of the coil is electrically connected with the signal pre-amplification measuring circuit, the signal pre-amplification measuring circuit is electrically connected with the low-noise and zero-stabilization processing circuit, the output end of the coil is electrically connected with the feedback loop, the feedback loop and the low-noise and zero-stabilization processing circuit are respectively electrically connected with the output protection module, and through the introduction of a resonance wave trap, the bandwidth can be further expanded to a low frequency, the low-frequency characteristic of the magnetic sensor is expanded, and a better low-frequency magnetic sensor is obtained. The invention also provides electromagnetic exploration equipment.
Description
Technical Field
The invention relates to the field of exploration geophysics, in particular to an induction type magnetic sensor and electromagnetic exploration equipment.
Background
An induction type magnetic sensor (hereinafter referred to as a magnetic sensor) is a device for indirectly measuring a magnetic field by measuring an output voltage of a coil based on a faraday's law of electromagnetic induction by using a relationship that the output voltage of the coil is proportional to a variation amount of a magnetic flux passing through the coil. The MT magnetic sensor is characterized in that a low-frequency and ultralow-frequency magnetic field signal is obtained, a magnetic field is converted into a measuring voltage by winding tens of thousands of turns of coils on a magnetic core with high magnetic conductivity, and adopting a magnetic flux negative feedback structure by utilizing a low-noise amplifying circuit.
As shown in fig. 1, there is shown an equivalent circuit diagram of an inductive magnetic sensor, in which,
b is the external magnetic field to be detected;
Cpto measure coil parasitic capacitance;
Lpto measure the coil self-inductance;
Rpto measure coil resistance;
Lsself-inductance of the feedback coil;
Rsis a feedback coil resistance;
Rfbis a feedback resistor;
m is the mutual inductance between the feedback coil and the measuring coil;
Npand NsThe number of turns of the measuring coil and the number of turns of the feedback coil are respectively;
a is the amplification factor of the amplifying circuit;
viis the input of the amplifying circuit;
voutis the output of the amplifying circuit;
and e is the induced electromotive force of the measuring coil.
From the circuit model of fig. 1, the transfer function of the magnetic sensor can be obtained as:
wherein, muaIs the effective permeability and S is the effective cross-sectional area of the magnetic circuit.
As the application of the magnetic sensor is very wide, many people develop research on the inductive magnetic sensor at home and abroad, and in the field of electromagnetic prospecting, typical products applied to the magnetic sensor with the MT method comprise MFS-06e of Metronix corporation in Germany, MTC-80 of Pheonix corporation in Canada and the like. In China, the units for researching MT magnetic sensors, such as the university of China and south China, the university of Jilin, the institute of electronics of the Chinese academy, and the like, are mainly used.
Although there are many units for studying MT magnetic sensors, the method adopted by these units or tissues is usually to determine the number of turns of the coil within the allowable range of volume and weight, then to adopt the method of increasing the effective permeability of the magnetic core to increase the sensitivity of the magnetic sensor, and to suppress the low-frequency 1/f noise effect by the chopper-stabilized zero amplifying circuit. According to the initial permeability parameter and demagnetization factor formula of the magnetic core material, the length of the magnetic core is required to reach more than 1.0m, so that the length-diameter ratio is larger than 40:1, and the effective permeability is large enough, which brings certain inconvenience to field construction. In recent years, there have been some units or organizations that employ a Flux Concentrator (Flux Concentrator) technology to make the effective permeability of a shorter core comparable to the conventional slender permeability, thereby achieving miniaturization of magnetic field sensors.
In fact, by increasing the length-diameter ratio of the magnetic core and increasing the magnetic flux collector, the effective magnetic permeability can be effectively increased, but the low-frequency bandwidth cannot be expanded, and the optimization of the magnetic sensor is limited.
For system stability, the resonance frequency of the coil must be higher than the measured passband frequency and the quality factor of the magnetic sensor at the resonance frequency point is suppressed by introducing flux feedback. This concept is not problematic in itself, and it is a prerequisite for system design that sufficient stability of the system must be ensured. However, this causes a problem that when measuring a very low frequency, the sensitivity of the very low frequency signal is very low, so that the signal cannot be picked up normally, and on the other hand, the noise of the high frequency is very large, so that the signal-to-noise ratio of the low frequency measurement is very low.
Disclosure of Invention
In view of the above, the present invention provides an inductive magnetic sensor and an electromagnetic surveying apparatus. Further, the low-frequency characteristics of the magnetic sensor are expanded, and a more excellent low-frequency magnetic sensor is obtained.
In a first aspect, the present invention provides an inductive magnetic sensor, including a signal pre-amplification measuring circuit, a feedback loop, a magnetic core and a coil, a low-noise and zero-stabilization processing circuit, and an output protection module, where an input end of the coil is electrically connected to the signal pre-amplification measuring circuit, the signal pre-amplification measuring circuit is electrically connected to the low-noise and zero-stabilization processing circuit, an output end of the coil is electrically connected to the feedback loop, and the feedback loop and the low-noise and zero-stabilization processing circuit are electrically connected to the output protection module, respectively.
As an optional scheme, the signal pre-amplification measuring circuit is provided with a pre-amplification unit and a resonance trap, when the frequency of the measuring magnetic field is lower than 100Hz, the input end of the pre-amplification unit is connected in parallel with a capacitor, and the resonance trap is electrically connected with the low-noise zero-stabilizing processing circuit.
As an alternative, the signal pre-amplification measuring circuit has a pre-amplification unit when the measuring magnetic field frequency is higher than 100 Hz.
As an alternative, the coil includes a feedback coil and a measurement coil, the feedback coil and the measurement coil are coupled, the measurement coil is connected in parallel with the capacitor, and the feedback coil is electrically connected to the feedback loop.
As an optional scheme, the signal pre-amplification measuring circuit includes two groups of pre-amplification units and a resonance trap, which are respectively a first pre-amplification unit, a second pre-amplification unit, a first resonance trap and a second resonance trap, the first resonance trap and the second resonance trap are connected together by a first resistor and output as an output end, and the output end is connected with a grounding capacitor to a reference ground.
As an alternative, the feedback loop switch is opened when the measuring magnetic field frequency is below 100 Hz.
As an alternative, the low-noise zero-stabilizing processing circuit adopts a switch zero-stabilizing circuit.
In a second aspect, the invention provides an electromagnetic surveying apparatus having an inductive magnetic sensor as described above.
According to the technical scheme, the embodiment of the invention has the following advantages:
the invention provides an induction type magnetic sensor and electromagnetic exploration equipment, which comprise a signal pre-amplification measuring circuit, a feedback loop, a magnetic core, a coil, a low-noise and zero-stabilization processing circuit and an output protection module, wherein the input end of the coil is electrically connected with the signal pre-amplification measuring circuit, the signal pre-amplification measuring circuit is electrically connected with the low-noise and zero-stabilization processing circuit, the output end of the coil is electrically connected with the feedback loop, the feedback loop and the low-noise and zero-stabilization processing circuit are respectively and electrically connected with the output protection module, and through the introduction of a resonance wave trap, the bandwidth can be further expanded to a low frequency, the low-frequency characteristic of the magnetic sensor is expanded, and the excellent low-frequency sensor magnetic field is obtained.
Drawings
FIG. 1 is an equivalent circuit diagram of an inductive magnetic sensor in a prior art arrangement;
FIG. 2 is a block circuit diagram of one embodiment of an inductive magnetic sensor provided by the present invention;
FIG. 3 is a block diagram of a signal pre-amplification measurement circuit in an embodiment of the inductive magnetic sensor provided in the present invention;
FIG. 4 is a schematic illustration of the switching characteristics in one embodiment of an inductive magnetic sensor provided in accordance with the present invention;
FIG. 5 is a schematic diagram of an inductive magnetic sensor provided in accordance with an embodiment of the present invention incorporating a capacitor;
FIG. 6 is a circuit diagram of a de-noising circuit in an embodiment of the inductive magnetic sensor provided by the present invention;
FIG. 7 is a schematic diagram of a signal under test and circuit noise in an embodiment of an inductive magnetic sensor provided in accordance with the present invention;
FIG. 8 is a schematic diagram of the input and output signals of the de-noising circuit in one embodiment of the inductive magnetic sensor provided by the present invention;
FIG. 9 is a schematic illustration of a low signal-to-noise ratio input in one embodiment of an inductive magnetic sensor provided in accordance with the present invention;
FIG. 10 is a schematic diagram of the processing results of a low signal-to-noise ratio circuit in one embodiment of an inductive magnetic sensor provided in accordance with the present invention;
FIG. 11 is a schematic diagram of an output power spectrum of a denoising circuit in an embodiment of the inductive magnetic sensor provided by the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
With reference to fig. 2, an embodiment of the present invention provides an inductive magnetic sensor, including a signal pre-amplification measuring circuit, a feedback loop, a magnetic core, a coil, a low-noise and zero-stable processing circuit, and an output protection module, where an input end of the coil is electrically connected to the signal pre-amplification measuring circuit, the signal pre-amplification measuring circuit is electrically connected to the low-noise and zero-stable processing circuit, an output end of the coil is electrically connected to the feedback loop, the feedback loop and the low-noise and zero-stable processing circuit are respectively electrically connected to the output protection module, and by introducing a resonator trap, a bandwidth can be further extended to a low frequency, a low-frequency characteristic of the magnetic sensor is extended, and a better low-frequency magnetic sensor is obtained.
The signal preamplification measuring circuit is provided with a preamplification unit and a resonance trap, the resonance trap is used for measuring resonance frequency points of a coil to trap, when the frequency of a measuring magnetic field is lower than 100Hz, the input end of the preamplification unit is connected with a capacitor in parallel, and the resonance trap is electrically connected with the low-noise zero-stabilizing processing circuit. The signal preamplification measurement circuit has a preamplification unit when the measurement magnetic field frequency is higher than 100 Hz.
The coil comprises a feedback coil and a measuring coil, the feedback coil is coupled with the measuring coil, the measuring coil is connected with the capacitor in parallel, and the feedback coil is electrically connected with the feedback loop.
The signal preamplification measuring circuit comprises two groups of preamplification units and a resonance trap, wherein the preamplification units are respectively a first preamplification unit, a second preamplification unit, a first resonance trap and a second resonance trap, the first resonance trap and the second resonance trap are connected together by a first resistor and output as an output end, and the output end is connected with a grounding capacitor to a reference ground.
In this embodiment, the low-noise zero-stabilizing processing circuit adopts a switch zero-stabilizing circuit or a chopper zero-stabilizing operational amplifier, which can be flexibly selected in the field and is not limited thereto.
On the premise of optimizing a magnetic core, when extremely low frequency is measured, the induction type magnetic sensor provided by the invention is combined with a capacitor at the input end, and because the magnetic field conversion capability of the magnetic sensor is hardly influenced by magnetic flux negative feedback and the closed loop is opened after the magnetic flux negative feedback is combined with the capacitor, the unstable problem of self-oscillation does not exist. By the introduction of the wave trap, the bandwidth can be further expanded to low frequencies. In order to avoid the artifact problem of the traditional chopper-stabilized amplifying circuit, a new zero-stabilized magnetic sensor processing circuit is provided, so that the low-frequency characteristic of a magnetic sensor is expanded, and a better low-frequency magnetic sensor is obtained.
The inductive magnetic sensor provided by the invention provides a solution for measuring magnetic field signals below 100Hz, and the magnetic field measurement above 100Hz needs to remove the input capacitor and the resonance wave trap and close the feedback loop at the same time.
As shown in fig. 2, the magnetic sensor of the present invention may include a magnetic core with high magnetic permeability, a coil, a low-noise amplifier circuit, and a feedback loop, except that two capacitors are added at the input end of the measuring coil during low-frequency measurement, and the low-noise amplifier circuit does not use a commonly used chopper amplifier, but a low-noise zero-stabilizing processing circuit specially designed for expanding the low-frequency characteristics of the magnetic sensor.
The capacitor is added in the preamplifier, so that the resonant frequency of the magnetic sensor moves to a low frequency, and the magnetic flux negative feedback does not work any more after the resonant frequency is transferred, so that the magnetic sensor can perform open-loop measurement, and the stability problem of self-oscillation does not exist. Meanwhile, the capacitor can inhibit high-frequency noise, and can further increase the gain of the amplifier without saturation, so that the frequency characteristic passband of the magnetic sensor moves towards the low-frequency direction, and the purpose of frequency spreading is achieved.
Different from the design of chopping amplification, the low-noise zero-stabilizing technology adopts three-level processing of pre-amplification, filtering and zero-stabilizing. The circuit has excellent zero-stabilizing characteristic, and particularly has very good performance on 1/f noise, offset voltage temperature drift, offset current and inhibition of offset current temperature drift.
When the measured magnetic field frequency is lower than 100Hz, a capacitor Ci needs to be connected in parallel from the coil to the input end of the preamplifier, and then the capacitor Ci is matched with a subsequent resonance wave trap, so that the pass band of the system is ensured to further move towards low frequency, and the action of a feedback loop can be ignored; when the measured magnetic field frequency is higher than 100Hz, the parallel capacitance of the input end needs to be removed, the resonance wave trap cannot be used, the wave trap is short-circuited to avoid damaging the normal measurement, and a magnetic flux negative feedback loop needs to be used to ensure that the system gain can be larger than 1 and can be stable. In addition, when the measuring frequency is higher than 100Hz, the resonance trap can be replaced by a low-pass filter, and the measuring frequency must be ensured to be in the pass band range, so that the influence of high-frequency noise can be reduced.
The signal pre-amplification measuring circuit is shown in fig. 3, and the signal pre-amplification measuring circuit has two identical circuits, and the two circuits are connected together through Ro and output, and are connected with a capacitor Co to the reference ground in parallel at the output end. The method is characterized in that a certain processing circuit is taken as an example for introduction, N is a middle tap of a measuring coil from the left side, A and B are an upper tap and a lower tap of the coil respectively and are sent to a double-input single-output preamplifier, and a resonance wave trap is connected to the rear of the preamplifier and is mainly used for further expanding the movement of a pass band to low frequency and strengthening low frequency components. The resonance trapped wave is sent to a denoising core circuit of the circuit, the circuit works in two modes through a switch control circuit, and an upper circuit and a lower circuit in the figure 3 respectively show the two states: one is to track the noise and store the noise signal on a capacitor C, as in the lower part of fig. 3; the other is to subtract the circuit noise signal stored on capacitor C from the input signal, as shown in the lower half of fig. 3.
The upper and lower circuits in fig. 3 are operated complementarily, when one circuit is operated in a noise tracking state, the other circuit is operated in a measuring state, and outputs a measuring signal, and the measuring signal is filtered by Ro and a capacitor Co to be used as an output signal. Ro and Co must be chosen to ensure that the cut-off frequency is above the upper limit frequency of the measurement passband.
The invention can realize the goal that the frequency domain electromagnetic method exploration method uses one magnetic sensor together, can greatly reduce the volume and the weight of the magnetic sensor, and brings great convenience to field construction.
The embodiment of the invention provides an application scenario of an inductive magnetic sensor and explains the application scenario.
The magnetic sensor with resonant frequency up to 20kHz is arranged in a laboratory, can be applied to electromagnetic source controlled audio frequency (CSAMT) detection, and has the advantages that the self-inductance of a measuring coil is 0.3459H, the parasitic capacitance is 170pF, the resistance of the measuring coil is 1934 omega, and the equivalent area of the coil is S-112.903 mm2The number of turns of the measuring coil is 10000, the feedback resistance Rf is 1k Ω, the number of turns of the feedback coil is 35, the effective permeability is 705, and the amplification factor is 1, and then the conversion relation of the magnetic sensor with or without feedback magnetic flux is shown in fig. 4.
Fig. 4 shows the switching characteristics of the magnetic sensor, and it can be seen that the resonant frequency of the magnetic sensor is 20kHz, and the quality factor at the resonant point is greatly reduced by adding the closed-loop magnetic flux negative feedback, so that the system can stably operate. When the measuring frequency is a low frequency less than 100Hz, obviously, the high resonant frequency is not beneficial to the measurement, after a 2uF capacitor is incorporated at the input end of the preamplifier, the resonant point of the magnetic sensor is moved to the low frequency to 170Hz, and in order to further expand the system passband to the low frequency and improve the system gain, a wave trap is added at the new resonant point. The magnetic field switching characteristics under different conditions after the incorporation of the capacitance are shown in fig. 5.
As can be seen from fig. 5, in the conversion characteristic of the magnetic sensor after the capacitor is incorporated, when the resonance shifts to a low frequency, the closed loop basically does not work, and no magnetic flux negative feedback has no effect on the magnetic sensor, so that the effect of the magnetic flux negative feedback can be ignored after the capacitor is incorporated. If no wave trap is introduced, the system has high conversion performance near 170Hz, so that low-frequency measurement is influenced, and after the wave trap is introduced, the magnetic sensor is forced to be pressed down at the conversion performance of 170Hz, so that the frequency band of the magnetic sensor is further expanded to low frequency, and the magnetic sensor can obtain a low-frequency signal by further increasing the gain of the system without entering saturation.
Regarding the problem of noise removal, a half of the circuit is cut out for illustration, as shown in FIG. 6, the noise removal circuit is SWWhen 1 is closed, the preamplifier input is 0 and the preamplifier output is its noise voltage vnoise1The pre-amplified noise voltage is sent to the next-stage in-phase input voltage follower, and the total noise of the pre-amplification circuit and the post-stage operational amplifier is obtained on the sampling capacitor C. Let the noise voltage of the rear-stage operational amplifier be vnoise2The voltage on the capacitor is:
vc＝vnoise1+vnoise2 (2)；
when SW1 is turned on, the measured signal v is amplified by the pre-amplifier circuit and the total noise of the operational amplifieriAfter input, the voltage output to the subsequent stage is:
because the circuit is mainly 1/f noise, offset voltage temperature drift, offset current and offset current temperature drift, the frequency of the noise is very low, and under the condition of high enough switching frequency, the noise is considered to be unchanged before and after switching. Then equation (2) can be substituted into equation (3) to obtain the output voltage of the rear stage operational amplifier as:
it can be seen that the output has removed the noise, leaving the signal under test.
There is a 200uV sinusoidal signal at 50Hz, and there is a 1/f noise in the circuit with a peak-to-peak value of 400uV, as shown in FIG. 7, the measured signal and the circuit noise.
The processing is performed by using the circuit shown in fig. 3, the input signal is the measured signal added with the circuit noise, the output signal is the output processed by the circuit shown in fig. 3, the input and output waveforms of the circuit are shown in fig. 8, and the input and output signals of the denoising circuit are shown in fig. 8.
As can be seen from fig. 8, the denoising circuit well eliminates circuit noise, and effectively suppresses low-frequency noise caused by the circuit itself, which provides a favorable guarantee for expanding the detection capability of the low-frequency magnetic sensor.
The circuit has the advantages that the noise is basically unchanged before and after the switching, and is relative to the measurement signal, when the measurement signal is very low, the change of the noise before and after the switching cannot be ignored relative to the measurement signal, the effect of the processing circuit is poor, the switching frequency can be further improved, the effect of the circuit is better because the change amplitude of the noise is smaller in a smaller time, and the high-frequency noise can be filtered firstly under the condition that the frequency of the measured signal is not high, so that the better effect is obtained.
If the measurement signal is still at 50Hz, the input signal-to-noise ratio is lower, the input noise is unchanged, the measurement signal is reduced by a factor of 10 to 20uV, and the low signal-to-noise ratio input is shown in fig. 9:
the amplification factor of the system is adjusted to 10 times, and the processing result of the input and output waveform to the circuit with low signal-to-noise ratio shown in figure 10 is obtained:
the power spectrum of the output signal (about 8 measurement signal periods) with a measurement time of 0.16s is shown in fig. 11:
fig. 11 shows the output power spectrum of the denoising circuit, as can be seen from fig. 11, the signal peak value is 40uV, when the noise peak value reaches 400uV, the system amplification factor reaches 10 times, and the output signal of the denoising circuit can still obtain a relatively ideal noise processing effect. And the circuit eliminates 1/f noise well.
Accordingly, the present invention provides an electromagnetic surveying apparatus having an inductive magnetic sensor as described above.
The invention provides electromagnetic exploration equipment, which aims to realize the aim that the frequency domain electromagnetic exploration method commonly uses one magnetic sensor, can greatly reduce the volume and the weight of the magnetic sensor, and brings great convenience to field construction.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
Those skilled in the art will appreciate that all or part of the steps in the methods of the above embodiments may be implemented by associated hardware instructed by a program, which may be stored in a computer-readable storage medium, and the storage medium may include: read Only Memory (ROM), Random Access Memory (RAM), magnetic or optical disks, and the like.
While the present invention has been particularly shown and described with reference to an inductive magnetic sensor and electromagnetic surveying apparatus, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (4)
1. An induction type magnetic sensor is characterized by comprising a signal preamplification measuring circuit, a feedback loop, a magnetic core and coil, a low-noise and zero-stabilization processing circuit and an output protection module, wherein the coil comprises a feedback coil and a measuring coil, the feedback coil is coupled with the measuring coil, and the feedback coil is electrically connected with the feedback loop;
the output end of the measuring coil is electrically connected with the signal pre-amplification measuring circuit, the signal pre-amplification measuring circuit is electrically connected with the low-noise zero-stabilizing processing circuit, the output end of the feedback coil is electrically connected with the feedback loop, and the feedback loop and the low-noise zero-stabilizing processing circuit are respectively electrically connected with the output protection module;
the signal preamplification measuring circuit is provided with a preamplification unit and a resonance trap, when the frequency of a measuring magnetic field is lower than 100Hz, the input end of the preamplification unit is connected with a capacitor in parallel, and the resonance trap is electrically connected with the low-noise zero-stabilizing processing circuit;
when the measured magnetic field frequency is higher than 100Hz, the parallel capacitance of the input end is removed, and the resonance wave trap can not be used;
the signal preamplification measurement circuit comprises two groups of preamplification units and a resonance trap, and the preamplification units are respectively a first preamplification unit, a second preamplification unit, a first resonance trap and a second resonance trap, the first resonance trap and the second resonance trap are connected together by a first resistor and output as an output end, and the output end is connected with a grounding capacitor to a reference ground.
2. Inductive magnetic sensor according to claim 1, characterized in that the feedback loop switch is opened when the measuring magnetic field frequency is below 100 Hz.
3. The inductive magnetic sensor of claim 1, wherein the low noise zero stabilization processing circuit employs a switching zero stabilization circuit.
4. Electromagnetic surveying apparatus having an inductive magnetic sensor as claimed in any one of claims 1 to 3.
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| CN101033983A (en) * | 2007-01-18 | 2007-09-12 | 武汉天任光电互感器有限公司 | High anti-interference alternating-current/magnetic field sensor |
| CN201477199U (en) * | 2009-09-03 | 2010-05-19 | 曹宜 | Direct-current and low-frequency magnetic field signal detection device |
| CN101964591A (en) * | 2010-08-05 | 2011-02-02 | 成都飞机工业集团电子科技有限公司 | Single-phase static inverter |
| CN102854535A (en) * | 2012-08-24 | 2013-01-02 | 中国船舶重工集团公司第七二二研究所 | Broadband magnetic sensor |
| CN106504581A (en) * | 2017-01-03 | 2017-03-15 | 安徽嘉盛位联网络科技有限公司 | A kind of Vehicle berth vehicle checker and detection method |
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