CN211557625U - Printed circuit board and magnetic field sensor - Google Patents
Printed circuit board and magnetic field sensor Download PDFInfo
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- CN211557625U CN211557625U CN202020142709.6U CN202020142709U CN211557625U CN 211557625 U CN211557625 U CN 211557625U CN 202020142709 U CN202020142709 U CN 202020142709U CN 211557625 U CN211557625 U CN 211557625U
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Abstract
The embodiment of the utility model provides a printed circuit board and magnetic field sensor relates to the magnetic field sensing field, can be accurate effectual position of ground net conductor really. The printed circuit board comprises two opposite shielding plates and a plurality of layers of insulating substrates which are positioned between the two shielding plates and are arranged in sequence; the printed circuit board is provided with a hollow area which penetrates through the two shielding plates and the multilayer insulating substrate along the thickness direction; at least one side surface of each insulating substrate is provided with a conductive coil group surrounding the hollow area; only one group of conductive coil groups is arranged between two adjacent insulating substrates; the conductive coil group consists of a plurality of coils which are formed by winding a conductive wire around the hollow area in a circle, and any two adjacent coils are insulated; the winding directions of the coils in all the conductive coil groups are the same, and all the conductive coil groups are connected in series; the shielding plate is provided with a metal shielding pattern, and the metal shielding pattern is insulated from the coil in the conductive coil group.
Description
Technical Field
The utility model relates to a magnetic field sensing field especially relates to a printed circuit board and magnetic field sensor.
Background
The grounding grid is one of necessary equipment for safe and reliable operation of a transformer substation, the grounding performance of the grounding grid is directly related to the safety of workers in the substation and the normal operation of power equipment, and therefore the conductor corrosion state of the grounding grid needs to be periodically excavated and detected after the grounding grid is specified to operate for ten years. However, the early design drawing is not properly stored or construction is not strictly carried out according to the design drawing, so that the actual position of the grounding grid conductor is unknown, and when the grounding grid conductor is excavated, the buried position cannot be accurately and effectively determined, and a large amount of manpower and material resources are wasted. Meanwhile, the grounding grid corrosion diagnosis method proposed according to the electric network principle depends on the actual position of the conductor, so the diagnosis result is limited by the accuracy of the position of the conductor of the grounding grid.
SUMMERY OF THE UTILITY MODEL
An embodiment of the utility model provides a printed circuit board and magnetic field sensor can be accurate effectual position of ground net conductor really.
In order to achieve the above object, the embodiments of the present invention adopt the following technical solutions:
the embodiment of the application provides a printed circuit board, which comprises two opposite shielding plates and a plurality of layers of insulating substrates, wherein the insulating substrates are positioned between the two shielding plates and are arranged in sequence; the printed circuit board is provided with a hollow-out area which penetrates through the two shielding plates and the multilayer insulating substrate along the thickness direction; at least one side surface of each insulating substrate is provided with a conductive coil group surrounding the hollow area; only one group of conductive coil groups is arranged between two adjacent insulating substrates; the conductive coil group consists of a plurality of coils which are formed by winding a conductive wire around the hollow area in a circle, and any two adjacent coils are insulated; the winding directions of the coils in all the conductive coil groups are the same, and all the conductive coil groups are connected in series; and a metal shielding pattern is arranged on the shielding plate and is insulated from the coil in the conductive coil group.
In some embodiments, the metal shield pattern includes shield traces that are perpendicular to the coils in the conductive coil set.
In some embodiments, the overlapping area of the two shield plates where the metallic shield pattern is disposed completely covers all of the conductive coil sets.
In some embodiments, the area of the hollowed-out area is 0.05cm2～0.15cm2。
In some embodiments, the printed circuit board comprises 4 layers of the insulating substrate.
The embodiment of the application also provides a magnetic field sensor, which comprises the printed circuit board.
In some embodiments, the magnetic field sensor further comprises a filter amplification circuit connected to the printed circuit board and formed by cascading multiple stages of band-pass filters.
In some embodiments, the band pass filter comprises an operational amplifier, a first resistor, a second resistor, a third resistor, a first capacitor, a second capacitor; the non-inverting input end of the operational amplifier is connected with a grounding end, and the inverting input end of the operational amplifier is connected with the output end through the first resistor; one end of the second resistor is used as an input end, and the other end of the second resistor is connected with the first node; one end of the second capacitor is connected with the first node, and the other end of the second capacitor is connected with the inverting input end; one end of the first capacitor is connected with the first node, and the other end of the first capacitor is connected with the output end; one end of the third resistor is connected with the first node, and the other end of the third resistor is connected with a grounding end.
In summary, the magnetic field sensor made of the PCB made of the multi-layer hollow coil assembly in series based on the present application performs magnetic field method detection for the position of the grounding grid conductor where the grounding grid drawing is missing or the actual construction does not conform to the design drawing, and generates a magnetic field signal for the interference of the background magnetic field noise of the transformer substation by using the ac excitation source with a specific frequency, the measurement accuracy of the designed magnetic field sensor can reach the nT level, and meanwhile, the magnetic field signal processing is performed by using the multi-stage band pass filter, and the position information of the grounding grid conductor is determined according to the magnetic field peak distribution, thereby providing a basis for the subsequent positioning of the grounding grid excavation and the corrosion diagnosis.
Because the interference magnetic field generated by various power equipment and power transmission lines on the site of a transformer substation is far larger than the target magnetic field to be measured, the induction magnetic field is measured by adopting the hollow coil magnetic field sensor layers manufactured on the basis of multilayer PCBs. Through analyzing and comparing the common magnetic field sensor principle, characteristics and the like, and combining the interference characteristic of background noise and the magnetic field signal size of a target to be detected under the field measurement of a transformer substation, the magnetic field sensor made based on the PCB hollow coil is adopted to carry out positioning detection on the grounding grid conductor. The principle of PCB coil magnetic field measurement is introduced, the coil cascade design based on the PCB multilayer board is completed, meanwhile, the accuracy test of a circular current-carrying conductor is carried out on the magnetic field signal extraction of specific frequency generated by an excitation source, and the feasibility of the PCB coil for measuring the magnetic field signal is proved. Meanwhile, simulation analysis is carried out on the designed multi-order band-pass filtering amplifying circuit, and the amplifying function of the circuit to specific frequency is verified.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram illustrating a principle of measuring a magnetic field of an air-core coil according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a printed circuit board according to an embodiment of the present disclosure;
FIG. 3 is a schematic cross-sectional view of the printed circuit board of FIG. 2 taken along the location O1-O2;
FIG. 4 is a schematic diagram of an intermediate layer of a printed circuit board according to an embodiment of the present disclosure;
fig. 5 is a schematic structural diagram of a shielding plate in a printed circuit board according to an embodiment of the present application;
fig. 6 is a schematic structural diagram of a PCB magnetic field sensor according to an embodiment of the present application;
FIG. 7 is a schematic diagram of a band pass filter circuit according to an embodiment of the present disclosure;
FIG. 8 is a schematic diagram of a magnetic field measurement provided by an embodiment of the present application;
fig. 9 is a schematic diagram of a Multisim simulation circuit of a bandpass filter circuit according to an embodiment of the present application;
fig. 10 is a diagram of an ac analysis result of a bandpass filter amplifier circuit according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
Unless otherwise defined, technical or scientific terms used in the embodiments of the present application should have the ordinary meaning as understood by those having ordinary skill in the art to which the present invention belongs. The use of "first," "second," and similar terms in the embodiments of the invention do not denote any order, quantity, or importance, but rather the embodiments are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. "mounted," "connected," and "coupled" are to be construed broadly and may, for example, be fixedly coupled, detachably coupled, or integrally coupled; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. "upper," "lower," "left," "right," "horizontal," and "vertical" are used merely for relative terms as to the orientation of the elements in the drawings, and these directional terms are relative terms, which are used for descriptive and clarity relative to the elements and which can vary accordingly depending on the orientation in which the elements in the drawings are placed.
Referring to fig. 1, the principle of detecting the position of a ground net conductor by using a Printed Circuit Board (PCB) of the present application will be described in detail.
The printed circuit board utilizes a magnetic field method to detect the position of a conductor of a grounding grid, and the key is to detect an induction magnetic field generated by an excitation source, inject an alternating current sinusoidal current source with specific frequency into a main body of the grounding grid through a down lead of the grounding grid, and assume that the current frequency of the excitation source is fcThe frequency f is also generated above the grounding gridcThe induced magnetic field B.
When the variable magnetic flux passes through the hollow part, corresponding induced electromotive force is generated inside the coil, and the magnetic field intensity can be calculated by measuring the magnitude of the induced electromotive force.
If a rectangular spatial coordinate system is established as shown in fig. 1, an included angle between the hollow coil and the direction of the induction magnetic field B is θ, and the amplitude of the magnetic field is B, then:
B＝Bmsim(2πfct) (1)
since the measurement coil is negligible compared to the ground grid specification, considering the flux through the coil open area as uniform, the total flux through the open coil Ψ:
Ψ＝NSBcosθ＝NSBmsim(2πfct)sinθ (2)
wherein s is the hollow area of the coil, and N is the total number of turns of the coil.
Calculating the induced electromotive force generated inside the coil according to the electromagnetic induction law:
in order to better reflect the magnitude of the induced electromotive force, the induced electromotive force generated by the coil is input into a band-pass filter with the amplification factor of A, and the amplified induced voltage is voComprises the following steps:
vo＝A＝A·2πfcNSBmcos(2πfct)sinθ (4)
suppose the output voltage amplitude is vomThe magnitude of the induced magnetic field is BmAnd vomThe relationship between them is:
Bm＝vom/(ksinθ) (5)
wherein:
k＝2πfcNSA (6)。
in the detection process, through changing the contained angle between coil and the induction magnetic field, when output voltage reaches the biggest, can confirm the magnetic field direction, theta is 90 this moment, has this moment:
Bm＝vom/k (7)。
the intensity of the induction magnetic field can be determined by measuring the maximum value of the output voltage of the band-pass filter, and the intensity and the maximum value are in a linear relation, so that the method has higher accuracy theoretically.
The printed circuit board and the magnetic field sensor provided by the embodiments of the present application are specifically described below.
The embodiment of the present application provides a printed circuit board, as shown in fig. 2 and fig. 3 (a schematic cross-sectional view taken along the position O1-O2 in fig. 2), which includes two oppositely disposed shielding plates (i.e., an upper shielding plate 1 and a lower shielding plate 2) and a multilayer insulating substrate (e.g., a1, a2, A3, a4) disposed between the two shielding plates 1, 2 and in sequence.
It should be noted here that the number of the insulating substrates provided between the two shielding plates 1 and 2 is not particularly limited in the present application; illustratively, in some embodiments, 4 insulating substrates a1, a2, A3, a 4; the following examples are each described by way of example in which 4 insulating substrates a1, a2, A3, and a4 are provided between two shield plates 1 and 2.
On this basis, as shown in fig. 2, the printed circuit board is provided with a hollow-out region C penetrating the two shield plates 1 and 2 and the multilayer insulating substrates a1, a2, A3, a4 in the thickness direction.
On the basis, referring to fig. 4, at least one side of each of the insulating substrates a1, a2, A3 and a4 is provided with conductive coil sets S1, S2, S3 and S4 surrounding the hollow area C; only one group of conductive coil groups is arranged between two adjacent insulating substrates; the conductive coil groups S1, S2, S3, and S4 are formed by winding a conductive wire around the hollow area C in a circle by circle, and any two adjacent coils are insulated.
It is understood that, for the above-mentioned conductive coil groups disposed around the hollow area C on at least one side of each of the insulating substrates a1, a2, A3 and a4, there is a portion of the insulating substrate that may be disposed around the hollow area C on both sides (upper and lower sides), for example, for the upper insulating substrate a1 and the lower insulating substrate a4, the upper and lower sides may be disposed around the hollow area C.
Of course, in consideration of the actual manufacturing process and the arrangement of other traces in the printed circuit board, in some possible implementation manners, as shown in fig. 4, the conductive coil sets S1, S2, S3 and S4 may be arranged on each of the insulating substrates a1, a2, A3 and a4 facing the same side (for example, the upper side or the lower side).
On the basis, in the printed circuit board, the winding directions of the coils in all the conductive coil sets S1, S2, S3 and S4 are the same, and all the conductive coil sets are connected in series.
It should be noted that, the winding directions of the coils in all the conductive coil sets S1, S2, S3 and S4 are the same, that is, the winding directions of the coils in each conductive coil set S1, S2, S3 and S4 are the same, for example, all the coils are clockwise or all the coils are counterclockwise, so as to ensure that the directions of the electromotive forces generated by the induced magnetic fields of all the coils are the same when the electromagnetic coil is in operation.
The shape of the coil in each conductive coil set S1, S2, S3, S4 is not specifically limited in this application. In some embodiments, the shape of the coils in each conductive coil set S1, S2, S3, S4 may be the same; for example, the shapes of the two parts can be both circular ring-like shapes and type rectangular shapes. In some embodiments, the shape of the coils in each conductive coil set S1, S2, S3, S4 may also be different; for example, part is shaped like a circular ring and part is shaped like a rectangle.
On the basis, referring to fig. 5, the shielding plates 1 and 2 in the printed circuit board of the present application are provided with metal shielding patterns, the metal shielding patterns 100 are insulated from the coils in the conductive coil set, and the metal shielding patterns themselves do not generate loops, and the metal shielding patterns are made of a material with higher magnetic permeability to reduce interference.
In order to reduce the interference to the maximum extent, in some possible implementations, the overlap area of the two shielding plates where the metal shielding pattern is disposed may be arranged to completely cover all of the conductive coil sets.
Additionally, in some possible embodiments, referring to fig. 4 and 5, the shield traces in the metal shield can be positioned perpendicular to the coils in the conductive coil set.
In an actual test, because the strength of the induced magnetic field signal to be tested is only nT level, in order to increase the magnitude of the output signal, the magnitude of the induced electromotive force is related to the frequency of the excitation current source, the number of turns of the coil, the hollow area and the like according to an induced voltage calculation formula. Since the frequency of the excitation source is increased to a limited extent, the area of the measuring coil should not be too large in order to improve the portability of the device. Because the magnetic induction intensity of the grounding grid conductor is an uneven field generated under the action of the excitation source, the area of a magnetic field passing through the coil cannot be too large, otherwise, the hollow part of the coil passing through the magnetic flux cannot be regarded as an even field, and the resolution is reduced when the current-carrying conductor is detected due to the fact that the area is too large. However, if the hollow area of the coil is too small, the induced electromotive force generated will also be reduced along with the passing area of the magnetic flux, so that the sensitivity of conductor detection is reduced, and the detection is not facilitated.
Based on this, in some embodiments, the area of the hollow-out area C may be 0.05cm2～0.15 cm2。
In actual sites, the geometric dimension of the transformer substation grounding grid conductor grid is generally 10-20 m, so that the detection requirement can be met when the hollow area of the coil is far smaller than the dimension, and in some possible implementation modes, the area of the hollow area C can be set to be 0.1cm2。
Through the analysis, the sensitivity of the measuring device can be improved by increasing the number of turns of the coil. Because the hollow coil is made of the PCB, the increase of the number of turns of the coil in one PCB can be realized by a multilayer board technology. The PCB multilayer board is characterized in that a plurality of layers of insulating base boards are arranged on one printed board, each layer of insulating base board is mutually insulated, each layer of insulating base board is provided with a conducting circuit, a plurality of PCB boards are used, and the number of turns of a coil can be increased on the premise of keeping the portability of the device as much as possible in a mutual series connection mode. The number of turns of the measuring coil can be greatly improved without reducing the convenience of the device by using the multi-layer board technology and a plurality of PCB boards in a series connection mode.
Of course, referring to fig. 4, for the multilayer printed circuit board, it further includes inter-coil fixing holes H1, and a saw-tooth structure H2, etc., which is not specifically limited in this application, and in practice, the arrangement may be made with reference to the related art.
The embodiment of the application also provides a magnetic field sensor, which comprises the printed circuit board.
It should be noted that the magnetic field sensor of the present application is not necessarily applied only to the field of measuring the position of the ground grid conductor, but may also be applied to other fields of electromagnetic induction detection.
Considering that in some detection environments, the initial induced electromotive force amplitude is small and the interference noise is large, in some embodiments, referring to fig. 6, the magnetic field sensor further includes a filtering and amplifying circuit connected to the printed circuit board and formed by cascading a plurality of stages of band-pass filters, so as to improve the signal-to-noise ratio.
In some possible implementations, as shown in fig. 7, the band pass filter may include an operational amplifier a, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, and a second capacitor C2.
The non-inverting input terminal (+) of the operational amplifier a is connected to the ground terminal DGND, and the inverting input terminal (-) is connected to the output terminal OUT through the first resistor R1. One end of the second resistor R2 is used as an input terminal, and the other end of the second resistor R2 is connected to the first node N1. One end of the second capacitor C2 is connected to the first node N1, and the other end of the second capacitor C2 is connected to the inverting input (-) of the operational amplifier a. One end of the first capacitor C1 is connected to the first node N1, and the other end of the first capacitor C1 is connected to the output terminal OUT. One end of the third resistor R3 is connected to the first node N1, and the other end of the third resistor R3 is connected to the ground terminal DGND.
Of course, the operational amplifier a is further provided with a power supply terminal, which schematically, as shown in fig. 7, may be a dual power supply terminal; but is not limited thereto and may be a single power supply terminal.
In summary, the magnetic field sensor made of the PCB made of the multi-layer hollow coil assembly in series based on the present application performs magnetic field method detection for the position of the grounding grid conductor where the grounding grid drawing is missing or the actual construction does not conform to the design drawing, and generates a magnetic field signal for the interference of the background magnetic field noise of the transformer substation by using the ac excitation source with a specific frequency, the measurement accuracy of the designed magnetic field sensor can reach the nT level, and meanwhile, the magnetic field signal processing is performed by using the multi-stage band pass filter, and the position information of the grounding grid conductor is determined according to the magnetic field peak distribution, thereby providing a basis for the subsequent positioning of the grounding grid excavation and the corrosion diagnosis.
Because the interference magnetic field generated by various power equipment and power transmission lines on the site of a transformer substation is far larger than the target magnetic field to be measured, the induction magnetic field is measured by adopting the hollow coil magnetic field sensor layers manufactured on the basis of multilayer PCBs. Through analyzing and comparing the common magnetic field sensor principle, characteristics and the like, and combining the interference characteristic of background noise and the magnetic field signal size of a target to be detected under the field measurement of a transformer substation, the magnetic field sensor made based on the PCB hollow coil is adopted to carry out positioning detection on the grounding grid conductor. The principle of PCB coil magnetic field measurement is introduced, the coil cascade design based on the PCB multilayer board is completed, meanwhile, the accuracy test of a circular current-carrying conductor is carried out on the magnetic field signal extraction of specific frequency generated by an excitation source, and the feasibility of the PCB coil for measuring the magnetic field signal is proved. Meanwhile, simulation analysis is carried out on the designed multi-order band-pass filtering amplifying circuit, and the amplifying function of the circuit to specific frequency is verified.
The performance of the magnetic field sensor, which is used as the frontmost element for the system device measurement, is directly related to the accuracy of the subsequent ground grid conductor position drawing, so that the performance test of the magnetic field sensor module is required.
The following describes simulation tests performed on the magnetic field sensor of the present application, and related test data and test results.
Firstly, due to the complexity of the magnetic field environment of the substation, a magnetic field measuring device with high anti-interference capability is required. The background magnetic field strengths of the 110kV, 220kV and 500kV substations are substantially in the order of μ T. The 1A alternating current excitation source is adopted, the induced magnetic field intensity generated by the alternating current excitation source is only in nT level, and therefore after corresponding magnetic field signals are obtained through measurement, corresponding signal processing is needed to obtain the specific induced magnetic field intensity. Meanwhile, when electromagnetic environment analysis is carried out on each grade of transformer substation, the frequency of electromagnetic environment noise is mainly power frequency and odd harmonic of the power frequency, wherein the power frequency is a main noise source, and the higher the frequency is, the smaller the amplitude is. The relation between the frequency of the excitation source and the amplitude of the induction magnetic field can be obtained, when the frequency of the excitation source is within 1kHz, no obvious correlation exists between the amplitude of the induction magnetic field and the frequency, and when the frequency of the excitation source exceeds 1kHz, the amplitude of the induction magnetic field is sharply reduced along with the increase of the frequency.
Through the analysis and the actual design of the excitation circuit, the frequency of the excitation source needs to avoid the main background noise frequency of the transformer substation, namely the power frequency and the odd harmonics thereof, and the frequency of the excitation source needs to be improved as much as possible to increase the distinctiveness from the background noise, so that the sinusoidal alternating-current power supply with the frequency of 1kHz and the amplitude of 1A is adopted as the excitation in the design. When the PCB hollow coil is used for measuring an induction magnetic field, the magnetic field signal needs to be filtered and amplified, and a 1kHz magnetic field signal is extracted.
Because the amplitude of the initial induced electromotive force is small and the interference noise is large, the design uses a multistage band-pass filter cascaded filtering amplification circuit (refer to fig. 6) to improve the signal-to-noise ratio; on the basis, an active band-pass Filter circuit (refer to fig. 7) is designed by using Filter Pro software, and a band-pass Filter amplifier consisting of ADA4841-2YRZ operational amplifier chips is used. A second-order band-pass filter is designed by using the chip, the center frequency is 1kHz, and the amplification factor is A-1 + R1/R3By adjusting R1And R3The amplification factor of the passband can be flexibly adjusted. In the design, four second-order band-pass filter circuits are adopted to carry out level filtering amplification on the induction voltage signal in series.
Referring to fig. 8, the magnetic field sensor module is subjected to accuracy testing, three circular conductors with the radius of 15cm, 20cm and 25cm are respectively used as testing objects, sinusoidal alternating currents with the output frequency of 1kHz and the amplitude of 1A are respectively injected into the three circular conductors by using an XJ-IIB excitation source, magnetic field testing is performed by using a magnetic field sensor module which is designed by 2 sections and is formed by multilayer PCB layers in series connection, and then induced voltage is input into an oscilloscope through a digital-to-analog conversion circuit for observation.
The test used was a hollow area S of 100mm2The number of turns N is 192.5, the amplification factor a of the bandpass filter amplifier is 400, and according to equation (6), k is 1.94 × 105At this time, the relationship between the induced voltage and the induced magnetic field is:
calculating the magnetic field intensity B of the center of the circular current-carrying conductor with the radius a according to the electromagnetic field as follows:
the direction of the magnetic field is perpendicular to the plane of the conductor.
The results of the comparative analysis of the induced voltage output from the PCB magnetic field sensor and the calculated theoretical value are shown in the following table.
It can be seen from the comparison data in the table above that the measurement error of the magnetic field sensor based on the hollow PCB coil is within 2%, the measurement errors of the three times are relatively close, and meanwhile, the ratio k of the induced voltage to the theoretical magnetic field also has good consistency, which indicates that the sensor has high measurement accuracy and good linearity, and proves the feasibility of using the hollow PCB coil as the theory of the magnetic field sensor.
In the actual transformer substation environment, a magnetic field signal source is complex, and a background magnetic field generated by various power equipment and wires can bring great interference to a target magnetic field, so that a band-pass filter circuit of a magnetic field sensor module needs to be tested, whether the filtering capability of the circuit to each frequency signal meets requirements or not is verified, and the method has important practical reference significance.
The method utilizes Multisim circuit simulation software to carry out simulation analysis on a band-pass filter of the magnetic field sensor, and adopts a simulation circuit diagram as shown in fig. 9 to change the resistance and capacitance of a filter circuit, so that the amplification factor is 10000 times, the center frequency is 1kHz, and the pass-band range is 0.7 kHz-1.3 kHz.
By utilizing the self-contained alternating current analysis function in Multisim software, an input point is set as a current excitation source, an output point is the output of the last stage of band-pass filtering and amplifying circuit, the scanning frequency is from 50Hz to 1.65kHz, and fig. 10 is a schematic diagram of the relationship between the amplification factor and the scanning frequency. It can be clearly seen from the figure that the center frequency of the whole band-pass filtering amplifying circuit is 1kHz, the amplification factor at the center frequency is 9810 times, when the frequency is lower than 850Hz or higher than 1130Hz, the amplification factor of the magnetic field induction voltage is less than 1000 times, and is one order of magnitude smaller than the amplification factor of the target magnetic field to be measured. The background noise of the magnetic field of the transformer substation is mostly odd harmonic waves of power frequency and the power frequency, the interference intensity of the power frequency is the maximum, and the amplitude of the frequency is smaller as the frequency is larger. Therefore, the multistage band-pass filtering amplification circuit can effectively extract the magnetic field to be measured with the frequency of 1kHz from background noise, and can meet the field measurement requirement.
The above description is only for the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (8)
1. The printed circuit board is characterized by comprising two opposite shielding plates and a plurality of layers of insulating substrates which are positioned between the two shielding plates and are arranged in sequence;
the printed circuit board is provided with a hollow-out area which penetrates through the two shielding plates and the multilayer insulating substrate along the thickness direction;
at least one side surface of each insulating substrate is provided with a conductive coil group surrounding the hollow area; only one group of conductive coil groups is arranged between two adjacent insulating substrates;
the conductive coil group consists of a plurality of coils which are formed by winding a conductive wire around the hollow area in a circle, and any two adjacent coils are insulated;
the winding directions of the coils in all the conductive coil groups are the same, and all the conductive coil groups are connected in series;
and a metal shielding pattern is arranged on the shielding plate and is insulated from the coil in the conductive coil group.
2. The printed circuit board of claim 1,
the metal shielding diagram comprises shielding wires which are perpendicular to coils in the conductive coil set.
3. A printed circuit board according to claim 1 or 2, wherein the overlapping area of the two shield plates where the metallic shield pattern is provided completely covers all of the conductive coil sets.
4. The printed circuit board of claim 1, wherein the area of the hollowed-out area is 0.05cm2~0.15cm2。
5. The printed circuit board of claim 1, wherein the printed circuit board comprises 4 layers of the insulating substrate.
6. A magnetic field sensor, characterized in that it comprises a printed circuit board according to any of claims 1-5.
7. The magnetic field sensor according to claim 6, further comprising a filter amplifier circuit connected to the printed circuit board and formed by cascading a plurality of stages of band pass filters.
8. The magnetic field sensor of claim 7, wherein the band pass filter comprises an operational amplifier, a first resistor, a second resistor, a third resistor, a first capacitor, a second capacitor;
the non-inverting input end of the operational amplifier is connected with a grounding end, and the inverting input end of the operational amplifier is connected with the output end through the first resistor;
one end of the second resistor is used as an input end, and the other end of the second resistor is connected with the first node; one end of the second capacitor is connected with the first node, and the other end of the second capacitor is connected with the inverting input end;
one end of the first capacitor is connected with the first node, and the other end of the first capacitor is connected with the output end; one end of the third resistor is connected with the first node, and the other end of the third resistor is connected with a grounding end.
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|---|---|---|---|---|
| CN114814669A (en) * | 2022-05-06 | 2022-07-29 | 中国科学院近代物理研究所 | Magnetic field ripple wave measuring method and device |
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