Manufacturing method of magnetic measurement device and magnetic measurement device

Abstract

To provide a manufacturing method of a magnetic measurement device and a magnetic measurement device capable of improving sensing performance.SOLUTION: According to one aspect of the present invention, a manufacturing method of a magnetic measurement device is provided. The manufacturing method includes: a preparation step of preparing a sensing wire with magnetic anisotropy, a sensing pickup coil wrapped around the sensing wire, a pulse generating circuit configured to supply a pulsed current to the sensing wire, and a sensing circuit configured to measure induced electromotive force for sensing, which is generated in the sensing pickup coil by the pulse current at a timing when a set sensing delay time has elapsed from the start of supplying the pulse current; and a setting step of setting the sensing delay time so as to eliminate a specific period in which the S / N ratio of the induced electromotive force for sensing becomes small after the start of supplying the pulse current.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a magnetic measurement device and a magnetic measurement device. [Background technology]

[0002] As disclosed in Patent Document 1, Non-Patent Document 1, and Non-Patent Document 2, a magnetic measurement device is known that includes a wire having magnetic anisotropy, a pickup coil wound around the wire, a pulse generating circuit that supplies a pulse current to the wire, and a sensing circuit that measures the induced electromotive force generated in the pickup coil.

[0003] In Patent Document 1, Non-Patent Document 1, and Non-Patent Document 2, the peak-to-peak detection or gradiometer method is used to improve the S / N ratio and / or reduce low frequency noise. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-190774 [Non-patent literature]

[0005] [Non-Patent Document 1] J. Ma and T. Uchiyama, "High Performance Single Element MI Magnetometer With Peak-to-Peak Voltage Detector by Synchronized Switching", in IEEE Transactions on Magnetics, vol.53, no.11, pp.1-4, Nov.2017, Art no.4003404 [Non-patent document 2] J. Ma and T. Uchiyama, "Development of Peak-to-Peak Voltage Detector-Type MI Gradiometer for Magnetocardiography", in IEEE Transactions on Magnetics, vol.54, no.11, pp.1-5, Nov.2018, Art no.5000605 Summary of the Invention [Problem to be solved by the invention]

[0006] In magnetic measurement devices using the above-mentioned wires, noise occurs during the magnetization process of the wire due to pinning sites such as scratches and impurities on the wire surface. Near the peak of the induced electromotive force, there is a singular point where this noise reduces the S / N ratio. Therefore, if the induced electromotive force is measured at this singular point, the sensing performance will be reduced.

[0007] In view of the above circumstances, the present invention provides a method for manufacturing a magnetic measurement device and a magnetic measurement device that can improve sensing performance. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a method for manufacturing a magnetic measurement device. The manufacturing method includes the following steps: a preparation step includes preparing a sensing wire having magnetic anisotropy, a sensing pickup coil wound around the sensing wire, a pulse generation circuit configured to supply a pulse current to the sensing wire, and a sensing circuit configured to measure a sensing induced electromotive force generated in the sensing pickup coil by the pulse current at a timing when a set sensing delay time has elapsed since the start of supply of the pulse current. In the setting step, the sensing delay time is set so as to exclude a specific period during which the S / N ratio of the sensing induced electromotive force becomes small after the start of supply of the pulse current.

[0009] According to this aspect, since the induced electromotive force for sensing is measured after the lapse of the singular period in which the singular point is measured, a magnetic measurement device capable of outputting a signal with a high S / N ratio can be obtained, thereby improving the sensing performance of the magnetic measurement device. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic circuit diagram of a magnetic measurement device 1A according to a first embodiment. [Figure 2] 1 is a graph showing the waveform of the induced electromotive force in sensing pickup coil 3 (upper part) and the waveform of the exciting pulse current supplied to sensing wire 2 (lower part). [Figure 3] 10 is a graph showing an example of a relationship between an external magnetic field and a first peak value in an excitation stage and a second peak value in a recovery stage. [Figure 4] FIG. 2 is a schematic circuit diagram of a manufacturing apparatus 200 for a magnetic measurement device. [Figure 5] 10 is a graph showing an example of an S / N ratio in the measurement results of an induced electromotive force generated in sensing pickup coil 3. [Figure 6] FIG. 10 is a schematic circuit diagram of a magnetic measurement device 1B according to a second embodiment. [Figure 7] 10 is a graph comparing noise spectra of a conventional magnetic measurement device and the magnetic measurement device 1B. [Figure 8] 10 is a graph showing an example of an S / N ratio in the magnetic measurement device 1B. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. Various features shown in the following embodiments can be combined with each other.

[0012] First Embodiment 1 is a schematic circuit diagram of a magnetic measurement device 1A according to a first embodiment. The magnetic measurement device 1A includes a sensing wire 2, a sensing pickup coil 3, a pulse generating circuit 4, a sensing circuit 5, and a time difference circuit 6.

[0013] <Sensing wire 2> The sensing wire 2 is an element having magnetic anisotropy. The sensing wire 2 is configured so that its impedance changes due to the skin effect caused by a pulse current and an external magnetic field. For example, an amorphous wire having a three-layer domain structure can be used as the sensing wire 2.

[0014] <Sensing pickup coil 3> The sensing pickup coil 3 is wound around the sensing wire 2. Specifically, the sensing pickup coil 3 is a solenoid coil that detects the magnetic field around the sensing wire 2. An induced electromotive force is generated in the sensing pickup coil 3 due to the skin effect of the sensing wire 2.

[0015] <Pulse generation circuit 4> The pulse generating circuit 4 is configured to supply a pulse current to the sensing wire 2 to excite the sensing wire 2. The pulse generating circuit 4 includes a differentiation / delay circuit 101, a timer clock 102, and a differentiation circuit 103.

[0016] <Sensing circuit 5> The sensing circuit 5 is configured to measure the sensing induced electromotive force generated in the sensing pickup coil 3 by the pulse current when a set sensing delay time has elapsed since the start of supply of the pulse current through the sensing wire 2. The sensing delay time is set so as to exclude a specific period after the start of supply of the pulse current in which the S / N ratio of the sensing induced electromotive force becomes small.

[0017] The sensing circuit 5 has a first detection circuit including a first sample-and-hold circuit 104A, and a second detection circuit including a second sample-and-hold circuit 104B.

[0018] The first detection circuit is configured to measure the sensing induced electromotive force generated in the sensing pickup coil 3 by the pulse current at a timing when a preset first delay time has elapsed since the start of supply of the pulse current.

[0019] The second detection circuit is configured to measure the sensing induced electromotive force generated in the sensing pickup coil 3 by the pulse current at a timing when a preset second delay time, which is longer than the first delay time, has elapsed from the start of supply of the pulse current. In other words, the second detection circuit measures the sensing induced electromotive force at a timing later than that of the first detection circuit.

[0020] Here, the induced electromotive force generated in the sensing pickup coil 3 will be explained. Figure 2 is a graph showing the waveform of the induced electromotive force in the sensing pickup coil 3 (top row) and the waveform of the excitation pulse current supplied to the sensing wire 2 (bottom row). The induced electromotive force has peak values ​​in the excitation stage, where the sensing pickup coil 3 is induced by the rising edge of the pulse current, and in the recovery stage, where the sensing pickup coil 3 is induced by the falling edge of the pulse current. The first peak value in the excitation stage (circled number 1 on the graph) and the second peak value in the recovery stage (circled number 2 on the graph) have opposite voltage polarities.

[0021] The first delay time is set in accordance with the excitation stage. That is, the first delay time is set so that the first detection circuit measures the induced electromotive force in the excitation stage. The second delay time is set in accordance with the recovery stage. That is, the second delay time is set so that the second detection circuit measures the induced electromotive force in the recovery stage. The first delay time and the second delay time are each on the order of ns (nanoseconds).

[0022] As shown in FIG. 1, a sampling pulse current SP1 whose peak timing has been adjusted by a first delay time is input to a first detection circuit (first sample-and-hold circuit 104A). That is, the first detection circuit samples and holds a signal at the peak timing of the sampling pulse current SP1. A sampling pulse current SP2 whose peak timing has been adjusted by a second delay time is input to a second detection circuit (second sample-and-hold circuit 104B). That is, the second detection circuit samples and holds a signal at the peak timing of the sampling pulse current SP2.

[0023] The first and second detection circuits receive sampling pulse currents SP1 and SP2 from the differentiation / delay circuit 101 and acquire sample values ​​(i.e., sensing induced electromotive forces). The differentiation / delay circuit 101 (specifically, the circuit's memory area) stores sensing delay times (i.e., first and second delay times) and singular periods (i.e., timings at which singular points occur) set using procedures described below. The differentiation / delay circuit 101 outputs sampling pulse currents SP1 and SP2 that have peaks immediately after the sensing delay time has elapsed.

[0024] A signal due to the induced electromotive force generated in the sensing pickup coil 3 is sent to the first detection circuit and second detection circuit via high-speed voltage buffer 109. High-speed voltage buffer 109 is provided to block interference between the sensing pickup coil 3 and pulse generating circuit 4 and the sensing circuit 5. A reference potential circuit 110 is also connected to the sensing pickup coil 3.

[0025] <Time difference circuit 6> The time difference circuit 6 is configured to calculate the difference between the sensing induced electromotive force measured by the first detection circuit and the sensing induced electromotive force measured by the second detection circuit. The time difference circuit 6 detects the time difference by correlated double sampling (CDS). The time difference circuit 6 has a first balance buffer 111A, a second balance buffer 111B, and an instrumentation amplifier 112.

[0026] The induced electromotive force for sensing in the excitation stage output by the first detection circuit (first sample-and-hold circuit 104A) and the induced electromotive force for sensing in the recovery stage output by the second detection circuit (second sample-and-hold circuit 104B) are input to the instrumentation amplifier 112 via the first balance buffer 111A or the second balance buffer 111B, respectively.

[0027] The instrumentation amplifier 112 outputs the difference between the induced electromotive force for sensing in the excitation stage and the induced electromotive force for sensing in the recovery stage. The output of the instrumentation amplifier 112 is input to the function circuit 113. The function circuit 113 performs processing such as AGC (automatic gain control), filtering, offset correction, and ADC (analog-to-digital conversion), and outputs a voltage value (measurement signal) corresponding to the magnetism sensed by the sensing wire 2.

[0028] FIG. 3 is a graph showing an example of the relationship between the external magnetic field and the first peak value of the excitation stage and the second peak value of the recovery stage. The first peak value (triangle dot on the graph) detected by the first detection circuit and the second peak value (star dot on the graph) detected by the second detection circuit are differential mode signal values ​​that depend on the magnitude of the external magnetic field. The difference between the first peak value and the second peak value (circle dot on the graph) has a strong linear relationship with the external magnetic field. Therefore, by taking the time difference of the induced electromotive force for sensing using the time difference circuit 6, the accuracy of magnetic measurement can be improved.

[0029] <Manufacturing Method of Magnetic Measurement Device 1A> The manufacturing method of the magnetic measurement device 1A includes a preparation step, a setting step, and an assembly step.

[0030] In the preparation step, the sensing wire 2, the sensing pickup coil 3, the pulse generating circuit 4, the sensing circuit 5, and the time difference circuit 6 are prepared.

[0031] In the setting step, the sensing delay time is set so as to exclude a singular period in which the S / N ratio of the induced electromotive force for sensing measured by the sensing circuit 5 becomes small after the pulse generating circuit 4 starts supplying the pulse current. As a result, the induced electromotive force for sensing is measured after the singular period in which the singular point is measured has passed, and therefore the magnetic measuring device 1A can output a signal with a high S / N ratio. As a result, the sensing performance of the magnetic measuring device 1A is improved.

[0032] 4 is a schematic circuit diagram of a manufacturing apparatus 200 for a magnetic measuring device. The manufacturing apparatus 200 is an apparatus that automatically tunes the sensing delay time (i.e., detection timing) of the magnetic measuring device 1A. The manufacturing apparatus 200 incorporates a sensing wire 2, a sensing pickup coil 3, a pulse generating circuit 4, and an adjustment sensing circuit 5A. The sensing wire 2, the sensing pickup coil 3, and the pulse generating circuit 4 are used in the magnetic measuring device 1A (i.e., prepared in the preparation step).

[0033] The adjustment sensing circuit 5A includes a sample-and-hold circuit 104 and an operational amplifier 105. The adjustment sensing circuit 5A receives the sampling pulse current SP1 from the differentiation / delay circuit 101 and acquires the sample value (i.e., the sensing induced electromotive force). The differentiation / delay circuit 101 reads the adjustment measurement time stored in the memory 108 and outputs the sampling pulse current SP1 that has a peak immediately after the adjustment measurement time has elapsed.

[0034] The sample-and-hold circuit 104 samples and holds a signal at the peak timing of the sampling pulse current SP1. The sample-and-hold signal is input to the non-inverting input of the operational amplifier 105, and a signal from a reference potential circuit 110 connected to the sensing pickup coil 3 is input to the inverting input. The output signal amplified by the operational amplifier 105 is input to an analog-to-digital conversion circuit 106.

[0035] The signal digitized by the analog-to-digital conversion circuit 106 is input to the data processing unit 107. The data processing unit 107 calculates the S / N ratio (ratio of signal to noise) of the sample value. The data processing unit 107 determines the sensing delay time using a search procedure described below. The data processing unit 107 also writes the set sensing delay time into the memory 108. The memory 108 stores the sensing delay time as well as the anomalous period used to determine the sensing delay time.

[0036] Here, we will explain the specific period when the S / N ratio becomes small in the measurement of induced electromotive force. Figure 5 is a graph showing an example of the S / N ratio in the measurement results of the induced electromotive force generated in the sensing pickup coil 3. The graph in Figure 5A shows the measurement results in the excitation stage, and the graph in Figure 5B shows the measurement results in the recovery stage.

[0037] Each graph shows the measurement results for samples S1 and S2 of the two sensing wires 2. The horizontal axis of each graph is the time axis (unit: ns), with 0 ns being the time when the first peak value or the second peak value is observed. The vertical axis is the S / N ratio (unit: dB), with the S / N ratio at 0 ns being 0 dB. When the S / N ratio is positive, the detection sensitivity is higher than the sensitivity at the peak value, and when the S / N ratio is negative, the detection sensitivity is lower than the sensitivity at the peak value.

[0038] The S / N ratios in each graph include singular points with low S / N ratios. If a signal is measured at such a singular point, the accuracy of the magnetic measurement will decrease. Therefore, in the setting step, a "sensing delay time" is set to avoid measurements during a "singular period" where a singular point may occur. Note that a "singular point" refers to a point where the S / N ratio is 90% or less of the average S / N ratio measured during the search period for the sensing delay time in the setting step (until the measurement start time of the dielectric electromotive force is determined).

[0039] In the setting step, the sensing delay time is determined by measuring the S / N ratio while varying the time from the start of supplying the pulse current to the measurement of the induced electromotive force for sensing in an environment where a constant magnetic field is applied to the sensing wire 2. Specifically, the manufacturing apparatus 200 repeatedly acquires a voltage based on the shape of the sampling pulse current (i.e., the delay time) adjusted by the differentiation / delay circuit 101 and calculates the S / N ratio of the acquired voltage until a delay time that does not include a singular point is found. In other words, the manufacturing apparatus 200 searches for a measurement start time of the induced electromotive force that does not have a singular point nearby. This allows for an appropriate setting of a sensing delay time that avoids a decrease in measurement accuracy.

[0040] Furthermore, in the setting step, the S / N ratio is measured for a search period that includes the timing at which the peak value of the sensing induced electromotive force is observed and during which the sensing induced electromotive force having an absolute value equal to or greater than a predetermined threshold value can be observed. The threshold value can be, for example, 50%, 45%, 40%, 35%, or 30% of the peak value. The "search period" is a period predicted from the timing at which the peak value is observed and the characteristics of the sensing wire 2. By presetting the search period for measuring the S / N ratio in this manner, the search period for the sensing delay time by the manufacturing apparatus 200 is reduced. As a result, the manufacturing cost of the magnetic measuring device 1A is reduced.

[0041] Furthermore, in the setting step, the sensing delay time is set so that the timing for measuring the sensing induced electromotive force is 10 nsec or more after the timing at which an S / N ratio below a certain value is measured. For example, if a low S / N ratio (singular point) is measured during the search for the sensing delay time, the timing for measuring the next S / N ratio is set to 10 nsec or more later. This reduces the search period for the sensing delay time and reduces the manufacturing cost of the magnetic measuring device 1A.

[0042] The manufacturing apparatus 200 writes the sensing delay time determined by the above-described procedure into the memory 108. The sensing delay time stored in the memory 108 is incorporated into the differentiation / delay circuit 101, thereby completing the magnetic measuring apparatus 1A.

[0043] In the setting step, a first delay time and a second delay time are set as the sensing delay time. That is, the manufacturing apparatus 200 independently determines the first delay time in the excitation stage and the second delay time in the recovery stage. For example, after searching for the first delay time for the sensing pickup coil 3, it searches for the second delay time.

[0044] In the assembly step, after the sensing delay time is set, the circuit constituting the magnetic measurement device 1A is assembled. Two mutually independent parameters, a first delay time and a second delay time, are incorporated into the magnetic measurement device 1A as sensing delay times. This results in a magnetic measurement device 1A with improved accuracy due to singularity avoidance and correlated double sampling.

[0045] Specifically, because the outputs of the excitation stage and recovery stage are common-mode signals, correlated double sampling can significantly reduce common-mode noise such as thermal noise (kTC noise) due to the capacitance of the detection node, sample hold, etc., and magneto-thermal noise from magnetic elements. Furthermore, time differential measurement at the nanosecond level can significantly suppress low-frequency noise such as 1 / f noise, voltage fluctuation noise at the coil termination, and electromagnetic interference noise.

[0046] Second Embodiment 6 is a schematic circuit diagram of a magnetic measurement device 1B according to a second embodiment. The magnetic measurement device 1B includes a sensing wire 2, a sensing pickup coil 3, a pulse generating circuit 4, a sensing circuit 5, a first time differencing circuit 6A, a second time differencing circuit 6B, a reference wire 7, a reference pickup coil 8, a reference circuit 9, and an output differencing circuit 10.

[0047] The magnetic measurement device 1B is a gradiometer-type measurement device that includes a pair of sensor elements and a circuit that outputs the spatial difference between the output signals of these elements. The sensing wire 2, sensing pickup coil 3, pulse generating circuit 4, and sensing circuit 5 of the magnetic measurement device 1B are the same as those of the magnetic measurement device 1A of the first embodiment, so their description will be omitted.

[0048] <Time difference circuits 6A and 6B> The first time difference circuit 6A is the same as the time difference circuit 6 of the magnetic measurement device 1A of the first embodiment. The second time difference circuit 6B is configured to calculate the difference between the reference induced electromotive force measured by the third detection circuit (third sample-and-hold circuit 104C) of the reference circuit 9 and the reference induced electromotive force measured by the fourth detection circuit (fourth sample-and-hold circuit 104D). The principle and configuration of the second time difference circuit 6B are the same as those of the first time difference circuit 6A.

[0049] <Reference wire 7> The reference wire 7 is an element having magnetic anisotropy. The reference wire 7 is equivalent to the sensing wire 2. The reference wire 7 is connected in series with the sensing wire 2. Therefore, the excitation pulse current generated by the pulse generating circuit 4 is also supplied to the reference wire 7 via the sensing wire 2.

[0050] <Reference pickup coil 8> The reference pickup coil 8 is wound around the reference wire 7. The reference pickup coil 8 is the same as the sensing pickup coil 3.

[0051] <Reference Circuit 9> The reference circuit 9 is configured to measure the reference induced electromotive force generated in the reference pickup coil 8 by the pulse current when a set reference delay time has elapsed since the start of supplying the pulse current to excite the sensing wire 2 and the reference wire 7.

[0052] The reference circuit 9 has a third detection circuit including a third sample-and-hold circuit 104C, and a fourth detection circuit including a fourth sample-and-hold circuit 104D.

[0053] The third detection circuit is configured to measure the reference induced electromotive force generated in the reference pickup coil 8 by the pulse current when a preset third delay time has elapsed since the start of supply of the pulse current. The third delay time in the reference circuit 9 is different from the first delay time in the sensing circuit 5. In other words, the first delay time and the third delay time are independent of each other.

[0054] The fourth detection circuit is configured to measure the sensing induced electromotive force generated in the reference pickup coil 8 by the pulse current at a timing when a preset fourth delay time, which is longer than the third delay time, has elapsed from the start of supply of the pulse current. In other words, the fourth detection circuit measures the reference induced electromotive force at a timing later than that of the third detection circuit. Note that the fourth delay time in the reference circuit 9 is different from the second delay time in the sensing circuit 5. In other words, the second delay time and the fourth delay time are independent of each other.

[0055] The third delay time in the reference circuit 9 is set so that the third detection circuit measures the induced electromotive force in the excitation stage, and the fourth delay time in the reference circuit 9 is set so that the fourth detection circuit measures the induced electromotive force in the recovery stage.

[0056] The sampling pulse current SP3, the peak timing of which is adjusted by a third delay time, is input to the third detection circuit (third sample-and-hold circuit 104C) of the reference circuit 9. The sampling pulse current SP4, the peak timing of which is adjusted by a fourth delay time, is input to the fourth detection circuit (fourth sample-and-hold circuit 104D) of the reference circuit 9.

[0057] <Output differential circuit 10> The output difference circuit 10 is configured to calculate the difference between the sensing induced electromotive force and the reference induced electromotive force.

[0058] Specifically, output difference circuit 10 is a differential amplifier having the output of first time difference circuit 6A (time difference in sensing circuit 5) as its non-inverting input and the output of second time difference circuit 6B (time difference in reference circuit 9) as its inverting input. Output difference circuit 10 includes an analog filter and an offset compensation circuit. The output of output difference circuit 10 is input to function circuit 113.

[0059] <Manufacturing Method of Magnetic Measurement Device 1B> The manufacturing method of the magnetic measurement device 1B includes a preparation step, a setting step, and an assembly step.

[0060] In the preparation step, a sensing wire 2, a sensing pickup coil 3, a pulse generating circuit 4, a sensing circuit 5, a first time difference circuit 6A, a second time difference circuit 6B, a reference wire 7, a reference pickup coil 8, a reference circuit 9, and an output difference circuit 10 are prepared.

[0061] The setting step is the same as the setting step in the manufacturing method of the magnetic measurement device 1A, except for the following point: In the setting step in the manufacturing method of the magnetic measurement device 1B, in addition to the sensing delay time, a reference delay time is set so as to exclude a specific period in which the S / N ratio of the reference induced electromotive force becomes small after the start of supply of the pulse current.

[0062] As described above, the reference delay time includes the third delay time in the third detection circuit and the fourth delay time in the fourth detection circuit of reference circuit 9. The reference delay time is determined by replacing sensing wire 2 and sensing pickup coil 3 of manufacturing apparatus 200 with reference wire 7 and reference pickup coil 8.

[0063] Similar to the sensing delay time, the third and fourth delay times of the reference delay time are determined independently of each other. Therefore, in the setting step, four time parameters are set: the first and second delay times as the sensing delay times, and the third and fourth delay times as the reference delay times.

[0064] In the assembly step, after setting the sensing delay time and the reference delay time, the circuits that make up the magnetic measurement device 1A are assembled. This results in a magnetic measurement device 1B with improved accuracy due to singularity avoidance, correlated double sampling, and cancellation of environmental magnetic noise.

[0065] FIG. 7 is a graph comparing the noise spectrum of a conventional magnetic measurement device and the magnetic measurement device 1B. The horizontal axis of FIG. 7 is the noise frequency, and the vertical axis is the density of the magnetic spectrum detected by the device. The conventional device has a noise density of about 10 pT / Hz at 1 Hz. 1 / 2 , approximately 8 pT / Hz at 10 Hz 1 / 2 On the other hand, the magnetic measurement device 1B has a frequency of about 3 pT / Hz at 1 Hz. 1 / 2 , approximately 3 pT / Hz at 10 Hz 1 / 2 The effect of reducing low frequency noise is remarkable.

[0066] FIG. 8 is a graph showing an example of the S / N ratio in the magnetic measurement device 1B. A target signal (65 nT, 10 Hz) was applied using a Helmholtz coil to measure the S / N ratio. The noise floor of the magnetic measurement device 1B for the target signal is approximately -90 dB (for 65 nT, -90 dB is approximately 2 pT). Therefore, the magnetic measurement device 1B can also be applied to measuring biomagnetism at the pT level.

[0067] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention.

[0068] The magnetic measurement device of the present invention does not necessarily have to include a time difference circuit. For example, the magnetic measurement device may acquire only the induced electromotive force in the excitation stage. That is, the magnetic measurement device of the present invention may have a configuration in which the functional circuit 113 is directly connected to the sensing circuit 5 and / or the reference circuit 9.

[0069] The magnetic measurement device of the present invention may be configured so that the user can rewrite (reset) each delay time.

[0070] It may be provided in the following manner.

[0071] (1) A method for manufacturing a magnetic measurement device, comprising the following steps: in the preparation step, a sensing wire having magnetic anisotropy, a sensing pickup coil wound around the sensing wire, a pulse generating circuit configured to supply a pulse current to the sensing wire, and a sensing circuit configured to measure a sensing induced electromotive force generated in the sensing pickup coil by the pulse current at a timing when a set sensing delay time has elapsed since the start of supply of the pulse current; and in the setting step, the sensing delay time is set so as to exclude a specific period in which the S / N ratio of the sensing induced electromotive force becomes small after the start of supply of the pulse current.

[0072] (2) In the method for manufacturing a magnetic measuring device described in (1) above, in the setting step, the sensing delay time is determined by measuring the S / N ratio while changing the time from the start of supplying the pulse current to the measurement of the sensing induced electromotive force in an environment in which a constant magnetic field is applied to the sensing wire.

[0073] (3) In the method for manufacturing a magnetic measuring device described in (2) above, the setting step includes measuring the S / N ratio for a period that includes the timing at which a peak value of the sensing induced electromotive force is observed and in which the sensing induced electromotive force whose absolute value is equal to or greater than a predetermined threshold value can be observed.

[0074] (4) In the method for manufacturing a magnetic measuring device described in (2) or (3) above, in the setting step, the sensing delay time is set so that the timing for measuring the sensing induced electromotive force is 10 nsec or more after the timing at which the S / N ratio is measured to be equal to or less than a certain value.

[0075] (5) In a method for manufacturing a magnetic measuring device described in any one of (1) to (4) above, the sensing circuit has a first detection circuit that measures the sensing induced electromotive force at a timing when a first delay time has elapsed, and a second detection circuit that measures the sensing induced electromotive force at a timing when a second delay time longer than the first delay time has elapsed, and the preparation step further provides a time difference circuit configured to calculate the difference between the sensing induced electromotive force measured by the first detection circuit and the sensing induced electromotive force measured by the second detection circuit, and the setting step sets the first delay time and the second delay time as the sensing delay time.

[0076] (6) In the method for manufacturing a magnetic measuring device described in any one of (1) to (5) above, the preparing step further includes preparing a reference wire having magnetic anisotropy, a reference pickup coil wound around the reference wire, a reference circuit configured to measure a reference induced electromotive force generated in the reference pickup coil by the pulse current at a timing when a set reference delay time has elapsed since the start of supply of the pulse current, and an output differential circuit configured to calculate the difference between the sensing induced electromotive force and the reference induced electromotive force, and the setting step further includes setting the reference delay time so as to exclude a specific period in which the S / N ratio of the reference induced electromotive force becomes small after the start of supply of the pulse current.

[0077] (7) A magnetic measurement device comprising: a sensing wire having magnetic anisotropy; a sensing pickup coil wound around the sensing wire; a pulse generating circuit configured to supply a pulse current to the sensing wire; and a sensing circuit configured to measure a sensing induced electromotive force generated in the sensing pickup coil by the pulse current at a timing when a set sensing delay time has elapsed since the start of supply of the pulse current, wherein the sensing delay time is set so as to exclude a specific period in which the S / N ratio of the sensing induced electromotive force becomes small after the start of supply of the pulse current.

[0078] (8) In the magnetic measuring device described in (7) above, the peculiar period is stored. Of course, this is not the case.

[0079] Finally, while various embodiments of the present disclosure have been described, they are presented as examples and are not intended to limit the scope of the invention. The novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. Such embodiments and modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0080] 1A: Magnetic measurement device 1B: Magnetic measurement device 2: Sensing wire 3: Sensing pickup coil 4: Pulse generation circuit 5: Sensing circuit 5A: Adjustment sensing circuit 6: Time difference circuit 6A: 1st time difference circuit 6B: Second time difference circuit 7: Reference wire 8: Reference pickup coil 9: Reference circuit 10: Output differential circuit 101: Delay circuit 102: Timer clock 103: Differential circuit 104: Sample and hold circuit 104A: First sample and hold circuit 104B: Second sample and hold circuit 104C: Third sample and hold circuit 104D: 4th sample and hold circuit 105: Operational amplifier 106: Analog-to-digital conversion circuit 107: Data processing section 108: Memory 109: High-speed voltage buffer 110:Reference potential circuit 111A: First balance buffer 111B: Second balance buffer 112: Instrumentation amplifier 113: Functional circuit 200: Manufacturing equipment

Claims

1. A method for manufacturing a magnetic measurement device, comprising: It includes the following steps: In the preparation step, a sensing wire having magnetic anisotropy; a sensing pickup coil wound around the sensing wire; a pulse generating circuit configured to supply a pulsed current to the sensing wire; a sensing circuit configured to measure a sensing induced electromotive force generated in the sensing pickup coil by the pulse current at a timing when a set sensing delay time has elapsed since the start of supply of the pulse current; In the setting step, the sensing delay time is set based on a measurement start time of the induced electromotive force for sensing, which is searched so as to exclude a specific period in which the S / N ratio of the induced electromotive force for sensing becomes small after the start of supply of the pulse current; Here, the specific period is a period during which a specific point may occur in which the S / N ratio is 90% or less of the average value of the S / N ratios measured up until the measurement start time is determined.

2. 2. The method for manufacturing a magnetic measurement device according to claim 1, In the setting step, the sensing delay time is determined by measuring the S / N ratio while changing the time from the start of supplying the pulse current to the measurement of the sensing induced electromotive force in an environment in which a constant magnetic field is applied to the sensing wire.

3. 3. The method for manufacturing a magnetic measurement device according to claim 2, In the setting step, the S / N ratio is measured for a period that includes the timing when the peak value of the sensing induced electromotive force is observed and in which the sensing induced electromotive force whose absolute value is equal to or greater than a predetermined threshold value can be observed.

4. 3. The method for manufacturing a magnetic measurement device according to claim 2, In the setting step, the sensing delay time is set so that the timing for measuring the sensing induced electromotive force is 10 nsec or more after the timing at which the S / N ratio is measured to be equal to or less than a certain value.

5. 2. The method for manufacturing a magnetic measurement device according to claim 1, The sensing circuit includes: a first detection circuit that measures the induced electromotive force for sensing at a timing when a first delay time has elapsed; a second detection circuit that measures the induced electromotive force for sensing at a timing when a second delay time longer than the first delay time has elapsed; The preparing step further includes preparing a time difference circuit configured to calculate a difference between the induced electromotive force for sensing measured by the first detection circuit and the induced electromotive force for sensing measured by the second detection circuit; In the setting step, the first delay time and the second delay time are set as the sensing delay time.

6. 2. The method for manufacturing a magnetic measurement device according to claim 1, In the preparation step, a reference wire having magnetic anisotropy; a reference pickup coil wound around the reference wire; a reference circuit configured to measure a reference induced electromotive force generated in the reference pickup coil by the pulse current at a timing when a set reference delay time has elapsed since the start of supply of the pulse current; and an output difference circuit configured to calculate a difference between the sensing induced electromotive force and the reference induced electromotive force; In the setting step, the reference delay time is set so as to exclude the specific period in which the S / N ratio of the reference induced electromotive force becomes small after the start of supply of the pulse current.

Images