Sensor

Abstract

To enable reduction of restriction on an element having a color center and suppression of influence by an external magnetic field, thereby enabling a magnetic field to be highly accurately detected.SOLUTION: A sensor 1 comprises: first and second sensor units 1A and 1B detecting and outputting a magnetic field around a busbar 9; and a calculation processing unit 200 calculating difference between the outputs of the first and second sensor units 1A and 1B. The first and second sensor units 1A and 1B include: diamond elements 2A and 2B arranged around the busbar 9 and having NV centers, respectively; antennas 5A and 5B for radiating the magnetic field of a microwave to the diamond elements 2A and 2B; an optical system 8 irradiating the diamond elements 2A and 2B with green light GL, respectively; and photosensors 4A and 4B detecting and outputting the intensity of red fluorescence RL generating from the diamond elements 2A and 2B; and a control unit outputting at least one of a magnetic field and temperature around the busbar 9 on the basis of the outputs of the photosensors 4A and 4B.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sensor. [Background technology]

[0002] There is known a magnetic sensor that uses a diamond element having an NV center to measure a magnetic field based on the principle of optically detected magnetic resonance (ODMR) (see, for example, Non-Patent Document 1). In the magnetic sensor described in Non-Patent Document 1, a pair of diamond elements are arranged close to each other in order to cancel out the influence of an external magnetic field, and the difference between the magnetic fields detected by the pair of diamond elements is calculated.

[0003] Furthermore, as a magnetic sensor configured for the purpose of canceling out the influence of external magnetic fields, a pair of magnetic sensors such as Hall elements are arranged on either side of the object to be measured, and the difference between the magnetic fields detected by the pair of magnetic sensors is calculated (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 544502

[0005] [Non-Patent Document 1] Yuta Masuyama, Katsumi Suzuki, Akira Hekizono, Mitsuyasu Iwanami, Mutsuko Hatano, Takayuki Iwasaki, Takeshi Ohshima, "Gradiometer Using Separated Diamond Quantum Magnetometers", Sensors 2021,21,977. https: / / doi.org / 10.3390 / s21030977 Summary of the Invention [Problem to be solved by the invention]

[0006] In the magnetic sensor described in Non-Patent Document 1, if there is a difference in the characteristics of the pair of diamond elements, the influence of the external magnetic field cannot be canceled out by the above calculation. Therefore, there is an additional constraint that the characteristics of the pair of diamond elements must be as similar as possible.

[0007] Furthermore, when the magnetic sensor described in Patent Document 1 is used as a current sensor to measure the current flowing through the bus bar of an electric vehicle battery, the large current flowing through the bus bar causes a temperature difference between the two sides of the bus bar, and the magnetic field detected by the pair of magnetic sensors is affected by the temperature characteristics of the magnetic sensors. Therefore, unless a magnetic sensor with stable temperature characteristics is used, the effect of the external magnetic field cannot be canceled out by the above calculation, and the magnetic sensor is subject to temperature characteristic constraints.

[0008] In view of the above circumstances, an object of the present invention is to provide a sensor that reduces the restrictions on elements having color centers, suppresses the influence of external magnetic fields, and enables highly accurate detection of magnetic fields. [Means for solving the problem]

[0009] The sensor of the present invention comprises a first magnetic sensor and a second magnetic sensor that detect and output a magnetic field around a current line, and a calculation device that calculates a difference between the output of the first magnetic sensor and the output of the second magnetic sensor, wherein the first magnetic sensor and the second magnetic sensor each comprise an element that is arranged around the current line and has a color center, an antenna that radiates a microwave magnetic field to the element, an optical system that irradiates the element with excitation light, an optical sensor that detects and outputs the intensity of fluorescence generated from the element, and a control unit that oscillates the microwave, calculates at least one of the magnetic field and the temperature around the current line based on the output of the optical sensor, and outputs the calculated value to the calculation device. the control unit includes a first microwave oscillator that oscillates a first microwave modulated with a first phase of a predetermined modulation frequency; a second microwave oscillator that oscillates a second microwave modulated with a second phase of the predetermined modulation frequency and having a frequency different from that of the first microwave; a switch that switches between a first connection state that connects the first microwave oscillator and the antenna and a second connection state that connects the second microwave oscillator and the antenna; a lock-in amplifier that receives an output from the optical sensor, outputs a first output corresponding to the first phase of the predetermined modulation frequency, and outputs a second output corresponding to the second phase; a first integration circuit that integrates the first output output from the lock-in amplifier and outputs the first integrated output to the first microwave oscillator; a second integration circuit that integrates the second output output from the lock-in amplifier and outputs the second integrated output to the second microwave oscillator; and a magnetic field / temperature calculation unit that calculates at least one of a magnetic field and a temperature around the current line based on a difference between the first integrated output and the second integrated output, wherein the first microwave oscillator feedback-controls the frequency of the first microwave based on the first integrated output, and the second microwave oscillator feedback-controls the frequency of the second microwave based on the second integrated output. do. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a sensor that can detect a magnetic field with high accuracy by reducing the influence of an external magnetic field while reducing the restrictions on elements having a color center. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an outline of a sensor according to one embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a schematic structure of a diamond element having an NV center. [Figure 3] FIG. 3 is a diagram for explaining the principle of a diamond quantum sensor that includes a diamond element having an NV center and measures a magnetic field based on the principle of ODMR. [Figure 4] FIG. 4 is a graph showing the relationship between the frequency of the ODMR peak and the magnetic field. [Figure 5] FIG. 5 is a graph showing the relationship between the frequency of two ODMR peaks, the magnetic field, and the temperature. [Figure 6] FIG. 6 is a circuit diagram showing the first sensor unit and the second sensor unit. [Figure 7] FIG. 7 is a waveform diagram for explaining a method for detecting two ODMR peaks. [Figure 8] FIG. 8 is a sequence chart showing the relationship between the ODMR, the output pulses of the first and second microwave oscillators, and the output pulse of the square wave generator. [Figure 9] FIG. 9 is a timing chart showing the fluctuations in the analog outputs of the first and second integrating circuits and the reference frequency when the resonant frequency fluctuates. [Figure 10] FIG. 10 is a diagram showing an outline of a sensor according to another embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing an outline of a sensor according to another embodiment of the present invention. [Figure 12] FIG. 12 is a diagram showing an outline of a sensor according to another embodiment of the present invention. [Figure 13]FIG. 13 is a diagram showing changes in the magnetic field measured by the first to fourth sensor units shown in FIG. [Figure 14] FIG. 14 is a diagram showing an outline of a sensor according to another embodiment of the present invention. [Figure 15] FIG. 15 is a diagram showing ODMR spectra output by the first to fourth sensor units shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below in accordance with preferred embodiments. Note that the present invention is not limited to the embodiments shown below and can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiments shown below, some components are omitted from illustration and description, but for the details of the omitted technologies, publicly known or well-known technologies are applied as appropriate within the scope of not causing any contradictions with the content described below.

[0013] 1 is a diagram illustrating an outline of a sensor 1 according to one embodiment of the present invention. The sensor 1 shown in this diagram measures the current flowing through a bus bar 9 of a battery of an electric vehicle and the temperature around the bus bar 9. The sensor 1 includes a first sensor unit 1A, a second sensor unit 1B, a first magnet 6, a second magnet 7, an optical system 8, and a processing device 200.

[0014] The first sensor unit 1A includes a diamond element 2A, an optical sensor 4A, an antenna 5A, and a control device 100A. The diamond element 2A has an NV center and is arranged close to one surface (the bottom surface in the figure) of the bus bar 9. The optical system 8 irradiates the diamond element 2A with green light GL as excitation light. The optical sensor 4A detects an optical signal generated due to electron spin resonance of the NV center. The antenna 5A emits a frequency-variable microwave magnetic field to the diamond element 2A. The control device 100A includes a microwave generator 10A, a lock-in detector 20A, and a frequency controller 30A. The microwave generator 10A supplies microwaves to the antenna 5A. The functions of the lock-in detector 20A and the frequency controller 30A will be described later.

[0015] The second sensor unit 1B includes a diamond element 2B, an optical sensor 4B, an antenna 5B, and a control device 100B. The diamond element 2B has an NV center and is arranged close to the other surface (the upper surface in the figure) of the bus bar 9. The optical system 8 irradiates the diamond element 2B with green light GL as excitation light. The optical sensor 4B detects an optical signal generated due to electron spin resonance of the NV center. The antenna 5B emits a frequency-variable microwave magnetic field to the diamond element 2B. The control device 100B includes a microwave generator 10B, a lock-in detection device 20B, and a frequency control device 30B. The microwave generator 10B supplies microwaves to the antenna 5B. The function of the lock-in detection device 20B is the same as that of the lock-in detection device 20A described below, and the function of the frequency control device 30B is the same as that of the frequency control device 30B described below.

[0016] The diamond element 2A of the first sensor unit 1A and the diamond element 2B of the second sensor unit 1B are formed in the shape of a square plate and are arranged to face each other with the bus bar 9 sandwiched between them in the thickness direction. The distance between the diamond element 2A and the lower surface of the bus bar 9 is equal to the distance between the diamond element 2B and the upper surface of the bus bar 9. The distance between the diamond elements 2A and 2B <111> The NV axis of the diamond elements 2A and 2B is arranged parallel to the surface of the bus bar 9 and perpendicular to the direction of the current in the bus bar 9. <111> The NV axes in the direction are parallel to each other and are parallel to the magnetic field B generated by the current in the bus bar 9. I In this embodiment, the thickness direction of the diamond elements 2A and 2B is <111> The orientation of the diamond crystals of the diamond elements 2A and 2B is defined as <111> It is assumed that the directions are aligned.

[0017] The antenna 5A of the first sensor unit 1A is a coil or the like arranged facing the diamond element 2A. <111> The antenna 5B of the second sensor unit 1B is a coil or the like arranged facing the diamond element 2B, and the antenna 5B of the second sensor unit 1B is arranged facing the diamond element 2B. <111> The microwave magnetic field is emitted in a direction perpendicular to the NV axis.

[0018] The first magnet 6 and the second magnet 7 are arranged to rotate the bus bar 9 in the width direction ( <111> The first magnet 6 and the second magnet 7 are arranged to face each other across the diamond elements 2A and 2B in a direction parallel to the direction of the magnet. <111> The diamond elements 2A and 2B are arranged facing each other in the direction of the arrow. <111> A static magnetic field is applied parallel to the NV axis.

[0019] The optical system 8 comprises a light source 81, an optical fiber 82, a splitter 83, and a pair of optical fibers 84A and 84B. The light source 81 is a laser having a wavelength of 500 nm to 560 nm and emits a laser beam. The optical fiber 82 guides light from the light source 81 to the splitter 83. The splitter 83 branches the laser beam guided by the optical fiber 82. A diamond element 2A of the first sensor unit 1A is attached to the tip of one optical fiber 84A of the pair of optical fibers 84A and 84B, and the optical fiber 84A guides light from the splitter 83 to the diamond element 2A. Furthermore, a diamond element 2B of the second sensor unit 1B is attached to the tip of the other optical fiber 84B, and the optical fiber 84B guides light from the splitter 83 to the diamond element 2B.

[0020] The optical sensor 4A of the first sensor unit 1A and the optical sensor 4B of the second sensor unit 1B are photodiodes. The optical sensor 4A of the first sensor unit 1A is attached to the tip of an optical fiber 84C branched from the optical fiber 84A via a dichroic mirror (not shown in the figure). This branched optical fiber 84C guides the red fluorescence RL (described below) emitted by the diamond element 2A to the optical sensor 4A. The optical sensor 4B of the second sensor unit 1B is attached to the tip of an optical fiber 84D branched from the optical fiber 84B via a dichroic mirror (not shown in the figure). This branched optical fiber 84D guides the red fluorescence RL (described below) emitted by the diamond element 2B to the optical sensor 4B. Instead of guiding the red fluorescence RL emitted by the diamond element 2A to the optical sensor 4A via the optical fiber 84A → dichroic mirror → optical fiber 84C, the optical sensor 4A can be located in a nearby location to receive the red fluorescence RL emitted by the diamond element 2A. Similarly, instead of guiding the red fluorescence RL emitted by the diamond element 2B to the optical sensor 4B via optical fiber 84B → dichroic mirror → optical fiber 84D, it is also possible to place the optical sensor 4B in a nearby location where it receives the red fluorescence RL emitted by the diamond element 2B.

[0021] The first sensor unit 1A of the sensor 1 configured as described above irradiates the green light GL onto the NV center of the diamond element 2A, and radiates a microwave magnetic field to the NV center of the diamond element 2A while performing frequency modulation on the microwave, and generates a magnetic field B around the bus bar 9 according to the principle of ODMR. A , temperature T A Similarly, the second sensor unit 1B irradiates the NV center of the diamond element 2B with green light GL and emits a microwave magnetic field to the NV center of the diamond element 2B while frequency-modulating the microwave, and measures the magnetic field B around the bus bar 9 according to the principle of ODMR. B , temperature T B Measure the following:

[0022] Here, the magnetic field B detected by the first sensor unit 1A A is expressed by the following equation (1), and the magnetic field B detected by the second sensor unit 1B is B is expressed by the following equation (2): The magnetic field B A , magnetic field B B A magnetic field parallel to the surface of the bus bar 9 and perpendicular to the direction of the current in the bus bar 9 is reflected in the magnetic field. B A =+B I +B O …(1) B B =-B I +B O …(2) However, B I is the magnetic field generated by the current in the bus bar 9, and B O is the external magnetic field.

[0023] Here, the magnetic field B expressed by the above equations (1) and (2) A , magnetic field B B By calculating the difference between O Therefore, in the sensor 1, the arithmetic processing device 200 can eliminate the magnetic field B detected by the first sensor unit 1A. A and the magnetic field B detected by the second sensor unit 1B. B By calculating the difference betweenO Eliminate and obtain the magnetic field B expressed by the following equation (3) I Calculate. B I =(magnetic field B A -Magnetic field B B ) / twenty three)

[0024] Figure 2 is a diagram showing the structure of a diamond element having an NV center. As shown in this figure, the NV center is a complex impurity defect consisting of a pair of nitrogen N (Nitrogen) that has entered a substitutional position of carbon in the diamond lattice and a vacancy V (Vacancy) where the carbon atom adjacent to this nitrogen has been removed. This NV center captures one electron from the neutral charge state NV0 to form an NV - Then, the magnetic quantum number m S = -1, 0, +1 electron spin triplet state. Diamond quantum sensors use this electron spin triplet state to measure magnetic fields, temperature, etc.

[0025] Figure 3 is a diagram for explaining the principle of a diamond quantum sensor that is equipped with a diamond element having an NV center and measures a magnetic field based on the principle of ODMR. As shown in Figures 2 and 3, the NV center emits red fluorescence RL when irradiated with green light GL as excitation light. The intensity (brightness) of this red fluorescence RL depends on the magnetic quantum number m of the NV center in the ground state (electron spin S = 0), whereas the level at which the NV center generates electron spin resonance (magnetic quantum number m S =±1 state).

[0026] Here, when the magnitude of the magnetic field is 0, if a microwave magnetic field MW of the resonant frequency (approximately 2.87 GHz) is irradiated to the NV center, the NV center reaches a level (m S=±1). Some of the electrons excited from this level undergo non-radiative transition to the ground state and do not contribute to light emission. Therefore, as described above, when the NV center is excited from a level that causes electron spin resonance, the intensity of the red fluorescence RL decreases. In this embodiment, a static magnetic field is applied around the diamond elements 2A and 2B by the first magnet 6 and the second magnet 7, so that a magnetic field is always present around the diamond elements 2A and 2B (see Figure 1).

[0027] Figure 4 is a graph showing the relationship between the frequency of the ODMR peak and the magnetic field B. As shown in this graph, when the magnetic field B is 0, there is only one ODMR peak, whereas when the magnetic field B is greater than 0 (B1, B2, B3, B3 > B2 > B1 > 0), there are two ODMR peaks. Here, the microwave frequency split Δf (f1 - f2) corresponding to the two ODMR peaks increases in proportion to the magnitude of the magnetic field B.

[0028] Figure 5 is a graph showing the relationship between the frequency of the ODMR peaks at two points, the magnetic field, and the temperature. As shown in this graph, the ODMR peaks at both points shift in the same way as the temperature of the object being measured changes. That is, if one ODMR peak shifts to a lower frequency as the temperature of the object being measured changes, the other ODMR peak also shifts to a lower frequency by the same frequency. Conversely, if one ODMR peak shifts to a higher frequency as the temperature of the object being measured changes, the other ODMR peak also shifts to a higher frequency by the same frequency. Therefore, a change in the temperature of the object being measured changes the median frequency of the two ODMR peaks.

[0029] The sensor 1 of this embodiment is used as a battery sensor for measuring the remaining battery charge of an electric vehicle. The remaining battery charge of an electric vehicle is calculated based on the integrated value of the current flowing through the battery bus bar 9 (see FIG. 1 ). Therefore, it is required to improve the measurement accuracy of the remaining battery charge based on the accumulated current value by increasing the response speed to changes in the current value of the battery bus bar 9 and improving the measurement accuracy of the current value at each time. Furthermore, it is required to measure with high accuracy the current value of a minute leakage current when the electric vehicle is stopped, as well as to measure with high accuracy the current value at this time in response to fluctuations of several hundred amperes in the current value that occur during sudden acceleration or deceleration of the electric vehicle. To meet these requirements, in the sensor 1 of this embodiment, the control device 100A of the first sensor unit 1A includes a microwave generator 10A, a lock-in detection device 20A, and a frequency control device 30A, which will be described below. Similarly, the control device 100B of the second sensor unit 1B includes a microwave generator 10B, a lock-in detection device 20B, and a frequency control device 30B, which will be described below.

[0030] 6 is a circuit diagram showing the first sensor unit 1A and the second sensor unit 1B. The first sensor unit 1A and the second sensor unit 1B have the same configuration. Therefore, the first sensor unit 1A will be described, and the description of the first sensor unit 1A will be used for the second sensor unit 1B.

[0031] As shown in Fig. 6, the microwave generator 10A includes a first microwave oscillator 11, a second microwave oscillator 12, a switch 13, and a power amplifier 14. The output terminal Fout of the first microwave oscillator 11 is connected to a first input terminal MW1 of the switch 13, and the output terminal Fout of the second microwave oscillator 12 is connected to a second input terminal MW2 of the switch 13. The output terminal of the switch 13 is connected to the input terminal of the power amplifier 14. The switch 13 is a diode switch, and switches between a first connection state in which the first microwave oscillator 11 and the power amplifier 14 are connected and a second connection state in which the second microwave oscillator 12 and the power amplifier 14 are connected, using a switching signal S MODThe output terminal of the power amplifier 14 is connected to the input terminal of the antenna 5A.

[0032] When the switch 13 is in the first connection state, the microwaves oscillated by the first microwave oscillator 11 are amplified by the power amplifier 14 and input to the antenna 5A. On the other hand, when the switch 13 is in the second connection state, the microwaves oscillated by the second microwave oscillator 12 are amplified by the power amplifier 14 and input to the antenna 5A.

[0033] The first microwave oscillator 11 and the second microwave oscillator 12 each have an FM (Frequency Modulation) modulation input terminal FMa, an FM modulation input terminal FMb, and a reference frequency input terminal FD.

[0034] The lock-in detection device 20A includes a preamplifier 21, a lock-in amplifier 22, a first integrating circuit 23, and a second integrating circuit 24. The input terminal of the preamplifier 21 is connected to the output terminal of the optical sensor 4A.

[0035] The output terminal of the preamplifier 21 is connected to the input terminal of the lock-in amplifier 22. A detection signal indicating the intensity of the red fluorescence RL output from the optical sensor 4A is amplified by the preamplifier 21 and input to the lock-in amplifier 22. The XA output terminal of the lock-in amplifier 22 is connected to the input terminal of a first integrating circuit 23, and the YA output terminal of the lock-in amplifier 22 is connected to the input terminal of a second integrating circuit 24.

[0036] The frequency control device 30A includes an MC (microcontroller) 31, a square wave generator 32, a timing controller 33, a first AD converter 34, and a second AD converter 35. The output terminal of the square wave generator 32 is connected to the FM modulation input terminal FMa of the first microwave oscillator 11 and the FM modulation input terminal FMa of the second microwave oscillator 12, and a square wave of frequency FM1 generated by the square wave generator 32 is input to the first microwave oscillator 11 and the second microwave oscillator 12 as a modulated signal.

[0037] An FM modulated signal with a frequency FM1 output from a square wave generator 32 is input to the lock-in amplifier 22. The lock-in amplifier 22 synchronizes with this output signal from the square wave generator 32 and outputs an analog signal of a differential ODMR, which will be described later.

[0038] The output terminal of the first integrating circuit 23 is connected to the input terminal of the first AD converter 34 and the FM modulation input terminal FMb of the first microwave oscillator 11. On the other hand, the output terminal of the second integrating circuit 24 is connected to the input terminal of the second AD converter 35 and the FM modulation input terminal FMb of the second microwave oscillator 12. The output XA, which is an analog signal output from the XA output terminal of the lock-in amplifier 22, is integrated by the first integrating circuit 23. The integrated output IXA of the first integrating circuit 23 is input to the first AD converter 34 and the first microwave oscillator 11. On the other hand, the output YA, which is an analog signal output from the YA output terminal of the lock-in amplifier 22, is integrated by the second integrating circuit 24. The integrated output IYA of the second integrating circuit 24 is input to the second AD converter 35 and the second microwave oscillator 12.

[0039] The first AD converter 34 converts the integration output IXA, which is an analog signal output from the first integration circuit 23, into a digital signal. The second AD converter 35 converts the integration output IYA, which is an analog signal output from the second integration circuit 24, into a digital signal.

[0040] The lock-in amplifier 22 detects the input signal from the preamplifier 21 in synchronization with the FM modulated signal of frequency FM1 output from the square wave generator 32. The MC 31 includes a monitoring unit 311, a first feedback control unit 312, a second feedback control unit 313, and a magnetic field / temperature calculation unit 314. Note that the magnetic field / temperature calculation unit 314 is only required to calculate at least one of the magnetic field and the temperature, and it is not essential to calculate both the magnetic field and the temperature.

[0041] The output terminal of the first feedback control unit 312 is connected to the reference frequency input terminal FD of the first microwave oscillator 11. The first feedback control unit 312 calculates the reference frequency FD1 of the first microwave oscillator 11 based on the first digital signal output from the first AD converter 34, and outputs the reference frequency FD1 to the first microwave oscillator 11. The reference frequency FD1 is set to a value corresponding to the peak of the ODMR (resonance frequency R L ) is set to an approximate value.

[0042] The output terminal of the second feedback control unit 313 is connected to the reference frequency input terminal FD of the second microwave oscillator 12. The second feedback control unit 313 calculates the reference frequency FD2 of the second microwave oscillator 12 based on the second digital signal output from the second AD converter 35, and outputs the reference frequency FD2 to the second microwave oscillator 12. The reference frequency FD2 is set to a value corresponding to the peak of the ODMR (resonance frequency R H ) is set to an approximate value.

[0043] The reference frequency FD1 output from the first feedback control unit 312 and the reference frequency FD2 output from the second feedback control unit 313 are input to the monitoring unit 311. The monitoring unit 311 integrates the sum of the reference frequency FD1 output from the first feedback control unit 312 and the frequency output from the first AD converter 34 and input to the first feedback control unit 312 (which is an AD-converted version of the analog output of the first integration circuit 23 and input to the first feedback control unit 312), and monitors the integrated value. On the other hand, the monitoring unit 311 integrates the sum of the reference frequency FD2 output from the second feedback control unit 313 and the frequency output from the second AD converter 35 and input to the second feedback control unit 313 (which is an AD-converted version of the analog output of the second integration circuit 24 and input to the second feedback control unit 313), and monitors the integrated value.

[0044] The first microwave oscillator 11 receives as input a signal of a reference frequency FD1 which is a digital output of the first feedback control section 312, an FM-modulated signal of a frequency FM1 which is a square wave output of the square wave generator 32, and an integrated output IXA which is an analog output of the first integration circuit 23. The first microwave oscillator 11 generates a signal of a frequency FAL (See equation (4) below) F AL =FD1+IXA*α±F DEV …(4) where α is the frequency deviation width due to an input of 1 V to the FMb terminal of the first microwave oscillator 11.

[0045] The second microwave oscillator 12 receives as input a signal of a reference frequency FD2 which is a digital output of the second feedback control section 313, an FM modulated signal of a frequency FM1 which is a square wave output of the square wave generator 32, and an integrated output IYA which is an analog output of the second integration circuit 24. The second microwave oscillator 12 generates a signal of a frequency F AH (See equation (5) below) F AH =FD2+IYA*α±F DEV …(5) where α is the frequency deviation width due to an input of 1 V to the FMb terminal of the second microwave oscillator 12.

[0046] The magnetic field / temperature calculation unit 314 calculates the magnetic field B A Calculate the temperature T A Calculate. B A =1 / γ*{(FD1+IXA*α)-(FD2+IYA*α)} …(6) T A =1 / T*{((FD1+IXA*α)+(FD2+IYA*α)) / 2} …(7) γ is the gyromagnetic ratio (28.07 MHz / mT), and T is the temperature coefficient of the NV center (-74.2 kHz / K).

[0047] Figure 7 is a waveform diagram for explaining the method of detecting two ODMR peaks. The upper waveform in Figure 7 shows the spectrum of the fluorescence intensity of ODMR, and the lower waveform in Figure 7 shows the spectrum of the rate of change of the fluorescence intensity of ODMR (hereinafter referred to as differential ODMR) obtained when a signal with a reference frequency FD1 is frequency-modulated with an FM-modulated signal with a frequency FM1. The frequency of the ODMR peak on the left side of this figure (resonance frequency R L ) is an approximation of the reference frequency FD1, and corresponds to the frequency of the ODMR peak on the right side of this figure (the resonant frequency R H ) is an approximation of the reference frequency FD2.

[0048] The frequency at which the differential ODMR shown in the lower left of Figure 7 becomes 0 is the resonant frequency R L The differential ODMR shown in the lower left of Figure 7 is the output from the XA output terminal of the lock-in amplifier 22. On the other hand, the frequency at which the differential ODMR shown in the lower right of Figure 7 becomes 0 is the resonance frequency R H The differential ODMR shown on the lower right side of FIG.

[0049] In the first sensor unit 1A, the microwave frequencies F of the first and second microwave oscillators 11 and 12 are calculated using the outputs XA and YA from the output terminals XA and YA of the lock-in amplifier 22. AL ,F AH is a set of resonant frequencies R L ,R H The magnetic field B A Measure.

[0050] 8 is a sequence chart showing the relationship between the ODMR, the output pulses of the first and second microwave oscillators 11 and 12, and the output pulse of the square wave generator 32 (see FIG. 6). As shown in this sequence chart, the frequency FM1 of the FM modulated signal of the first microwave oscillator 11 and the frequency FM1 of the FM modulated signal of the second microwave oscillator 12 are the same. On the other hand, the phases of the FM modulated signal of the first microwave oscillator 11 and the FM modulated signal of the second microwave oscillator 12 are different by 90°. In addition, a switching signal S MOD The frequency of this switching signal is twice that of frequency FM1. Furthermore, the change points (rising and falling phases) of this switching signal differ by 45° from the change points (rising and falling phases) of the FM modulated signals of the first microwave oscillator 11 and the second microwave oscillator 12.

[0051] Here, the output XA of the lock-in amplifier 22 is L The output YA of the lock-in amplifier 22 is a value that represents the deviation from the resonant frequency R H It is a value that represents the deviation from the XA=K((P LA +P LB ) / 2-R L )…(8) YA=K((P HA +P HB ) / 2―R H )…(9) However, P LA is the resonant frequency R L is the operating point on the low frequency side of the LB is the resonant frequency R L is the operating point on the high frequency side of the frequency, and is expressed by the following equation (11): where K is a proportionality constant. P LA =FD1+IXA*α-F DEV …(10) P LB =FD1+IXA*α+F DEV …(11) Also, P HA is the resonant frequency R H is the operating point on the low frequency side of the HB is the resonant frequency R H is the operating point on the high frequency side of the P HA =FD2+IYA*α-F DEV …(12) P HB =FD2+IYA*α+F DEV …(13)

[0052] 4 operating points P LA ,P LB ,P HA ,P HB are points of the same fluorescence intensity on both slopes of the “valley” in the spectrum near the resonance frequency of ODMR, and appear with a phase shift of 90° within one period of the FM modulation signals of the first and second microwave oscillators 11 and 12.

[0053] The outputs XA and YA of the lock-in amplifier 22 are in a quadrature phase relationship with each other. The output XA is integrated to obtain an integrated output IXA, which is input to the FM modulation input terminal FMb of the first microwave oscillator 11, thereby modulating the microwave frequency F AL Furthermore, the integrated output IYA obtained by integrating YA is input to the FM modulation input terminal FMb of the second microwave oscillator 12, thereby controlling the microwave frequency F AH As a result, the microwave frequencies F of the first and second microwave oscillators 11 and 12 are controlled. AL ,F AH The feedback controls can be performed independently of each other.

[0054] Here, the microwave frequency F of the first microwave oscillator 11 AL is the resonant frequency R L In order to follow the resonant frequency R L Operating point P LA ,P LB Median (P LA +P LB) / 2 must be within about H / 2, the full width at half maximum of the "valley" peak of the ODMR spectrum. H is the full width at half maximum, and varies depending on the characteristics of the NV center of the diamond element 2A, but is generally in the range of several hundred kHz to several MHz.

[0055] Similarly, the microwave frequency F of the second microwave oscillator 12 AH is the resonant frequency R H In order to follow the resonant frequency R H Operating point P HA ,P HB Median (P HA +P HB ) / 2 must be within about H / 2, the half-width at half maximum of the "valley" peak of the ODMR spectrum.

[0056] In particular, in order to accommodate the expansion of the measurement range accompanying the expansion of the output current range of the electric vehicle, the microwave frequency F of the first and second microwave oscillators 11 and 12 is AL ,F AH At the operating point P LA ,P LB ,P HA ,P HB Therefore, in this embodiment, as will be described below, the analog output of the first integrating circuit 23 is adjusted to follow the fluctuation of the resonant frequency R L The analog output of the second integrating circuit 24 is converted into an analog signal at a fixed time interval that is sufficiently shorter than the fluctuation time of the resonant frequency R. H The second AD converter 35 performs AD conversion at regular intervals that are sufficiently shorter than the fluctuation time of the second microwave oscillator 12, and feedback control is performed to the reference frequency FD2 of the second microwave oscillator 12.

[0057] Figure 9 shows the resonant frequency R L 10 is a timing chart showing the fluctuation of the analog output of the first integrating circuit 23 and the reference frequency FD1 when the resonant frequency R LThe following describes the fluctuations in the analog output of the first integrating circuit 23 and the reference frequency FD1 when the resonant frequency R H The same applies to the fluctuations in the analog output of the second integration circuit 24 and the reference frequency FD2 when the frequency fluctuates.

[0058] As shown in the timing chart of Figure 9, the resonant frequency R L If the amount of change in is within the half-width at half maximum H / 2 of the ODMR peak, the analog output of the first integrating circuit 23 is L However, the resonant frequency R L When the amount of change in the half-width at half maximum exceeds H / 2, the analog output of the first integrating circuit 23 is L Therefore, the resonance frequency R L If the amount of change in the resonant frequency R is equal to or greater than a certain percentage of the half width at half maximum H / 2, the reference frequency FD1 is changed by a certain percentage of the half width at half maximum H / 2. Here, the certain percentage is a constant less than 1. As a result, the analog output of the first integration circuit 23 returns to 0. L If the amount of change in the resonant frequency R increases further and reaches a certain rate of the half width at half maximum H / 2, the reference frequency FD1 is further changed by a certain rate of the half width at half maximum H / 2. As a result, the analog output of the first integration circuit 23 returns to 0. In this way, L By repeatedly changing the reference frequency FD1 in accordance with the amount of change in the reference frequency FD1, the output of the first integration circuit 23 can be suppressed within a value corresponding to a certain proportion of the half-width at half maximum H / 2 of the ODMR peak, as the frequency modulation width of the first microwave oscillator 11.

[0059] Here, since the control path from the first integrating circuit 23 to the FM modulation input terminal FMb of the first microwave oscillator 11 is an analog signal, the resonant frequency R L However, the feedback control, the update of the reference frequency FD1, and the change in the microwave frequency F of the first microwave oscillator 11 based on the update of the reference frequency FD1 can be quickly followed. ALThe change in the reference frequency FD1 is accompanied by a certain delay since it is a digital signal path that involves AD conversion in the first AD converter 34 and digital signal processing of the result. LA ,P LB This does not mean that the company is monitoring the system.

[0060] In addition, since the control path from the second integrating circuit 24 to the FM modulation input terminal FMb of the second microwave oscillator 12 is an analog signal, the resonant frequency R H However, the feedback control, the update of the reference frequency FD2, and the microwave frequency F of the second microwave oscillator 12 based on the update of the reference frequency FD2 can be quickly followed. AH The change in the reference frequency FD2 is accompanied by a certain delay since it is a digital signal path that involves AD conversion in the second AD converter 35 and digital signal processing of the result. HA ,P HB This does not mean that the company is monitoring the system.

[0061] Therefore, in this embodiment, in order to accurately measure the remaining battery capacity, the monitoring unit 311 integrates the sum of the reference frequency FD1 output from the first feedback control unit 312 and the frequency output from the first AD converter 34 and input to the first feedback control unit 312 (which is an AD-converted version of the analog output of the first integration circuit 23 and input to the first feedback control unit 312), and monitors the integrated value. In addition, the monitoring unit 311 integrates the sum of the reference frequency FD2 output from the second feedback control unit 313 and the frequency output from the second AD converter 35 and input to the second feedback control unit 313 (which is an AD-converted version of the analog output of the second integration circuit 24 and input to the second feedback control unit 313), and monitors the integrated value.

[0062] As described above, in the sensor 1 according to this embodiment, the first and second sensor units 1A and 1B separate the influence of the temperature drift from the magnetic field B A ,B B Therefore, the measured magnetic field B A ,B BThe difference between the two is calculated, and the magnetic field B due to the current of the bus bar 9 is calculated based on the difference. I By calculating the temperature difference between the positions of the diamond elements 2A and 2B, the external magnetic field B O High-precision magnetic field B that suppresses the influence of I Measurement of

[0063] In particular, in the sensor 1 according to this embodiment, the diamond element 2A of the first sensor unit 1A and the diamond element 2B of the second sensor unit 1B are arranged to face each other with the bus bar 9 in between. In addition, the distance between the diamond element 2A and the lower surface of the bus bar 9 and the distance between the diamond element 2B and the upper surface of the bus bar 9 are set equal. This allows the first and second sensor units 1A and 1B to measure the magnetic field and temperature around the bus bar 9. In addition, the temperature gradient on both the upper and lower sides of the bus bar 9 can be measured.

[0064] In the first and second sensor units 1A and 1B, the red fluorescence RL emitted from the diamond elements 2A and 2B is detected by the optical sensors 4A and 4B, and then the microwave frequency F is controlled by feedback control from the lock-in detection device 20A to the microwave generator 10A via the frequency control device 30A and from the lock-in detection device 20B to the microwave generator 10B via the frequency control device 30B. AL ,F AH ,F BL ,F BH In this control, the center position of the "valley" of the ODMR spectrum of the diamond elements 2A and 2B is tracked, and there is no effect even if the detailed characteristics such as the depth and width of the "valley" are slightly different between the diamond elements 2A and 2B. Therefore, regardless of the variation in the characteristics of the diamond elements 2A and 2B, the external magnetic field B O High-precision magnetic field B that suppresses the influence of IFurthermore, the outputs XA and YA of the lock-in amplifier 22 are integrated by the first and second integration circuits 23 and 24 and then fed back directly to the first and second microwave oscillators 11 and 12, thereby enabling control of direct feedback from the lock-in detection device 20A to the microwave generator 10A and control of direct feedback from the lock-in detection device 20B to the microwave generator 10B. AL ,F AH ,F BL ,F BH at high speeds to the resonant frequency R L ,R H can be made to follow.

[0065] In the sensor 1 according to this embodiment, the outputs of the lock-in detectors 20A and 20B are input to the frequency controllers 30A and 30B. When the outputs of the lock-in detectors 20A and 20B are equal to or greater than a certain percentage less than 1 of the half-width at half maximum H / 2 of the ODMR, the reference frequencies of the microwave generators 10A and 10B are changed. This allows the frequency F of the microwave generators 10A and 10B to be adjusted in accordance with the fluctuation of the ODMR peak, even when the fluctuation range of the ODMR peak is large enough to exceed the half-width at half maximum H / 2 of the ODMR peak. AL ,F AH ,F BL ,F BHThis allows for adjustment of the time constant. This allows for tracking of disturbances with a wide dynamic range, enabling highly accurate detection of leakage currents in busbars 9 of electric vehicles. Furthermore, the output of lock-in detectors 20A and 20B is the integration of the output changes of optical sensors 4A and 4B, which in turn integrates the magnetic field and temperature changes detected by diamond elements 2A and 2B. Therefore, even if a sudden, transient change in the magnetic field or temperature occurs, the output of lock-in detectors 20A and 20B only exhibits a change smoothed by the integration time constant. Therefore, frequency control devices 30A and 30B integrate the output of lock-in detectors 20A and 20B and the reference frequency change instructions they issue to microwave generators 10A and 10B based on the measurement results at time intervals sufficiently shorter than the integration time constant, enabling accurate integration of the magnetic field and temperature. Therefore, even if there is a transient delay in the feedback control of the negative feedback circuit, once the feedback control of the negative feedback circuit has caught up after a certain time has passed, the integrated value of the current can be measured accurately, making it possible to accurately grasp the amount of charge being charged and discharged from the battery, which is particularly important in electric vehicles.

[0066] In the sensor 1 according to this embodiment, the FM modulated signal of the first microwave oscillator 11 and the FM modulated signal of the second microwave oscillator 12 are out of phase with each other by 90°. In addition, the switch 13 switches between the outputs of the first microwave oscillator 11 and the second microwave oscillator 12 through a switching signal S MOD The frequency of this switching signal is twice the frequency FM1 of the FM modulated signals of the first and second microwave oscillators 11 and 12. Furthermore, the change points (rising phase and falling phase) of this switching signal are 45° different from the change points (rising phase and falling phase) of the FM modulated signals of the first microwave oscillator 11 and the second microwave oscillator 12. This means that it is only necessary to provide one lock-in amplifier 22 in each of the first and second sensor units 1A and 1B, simplifying the device configuration of the first and second sensor units 1A and 1B.

[0067] In addition, in the sensor 1 according to this embodiment, a pair of first and second magnets 6 and 7 are arranged to face each other across the bus bar 9, and a static magnetic field is applied around the bus bar 9, so that the resonant frequency R L ,R H Split (R L -R H ) is maintained at a predetermined value (>0) or more. L ,R H Even if the split of the magnetic field B is significantly decreased, the split can be maintained and the magnetic field B defined by the split can be maintained. A ,B B can be measured.

[0068] Furthermore, in the sensor 1 according to this embodiment, the diamond elements 2A and 2B are arranged to face each other across the bus bar 9, so that the bus bar 9 functions as an electromagnetic shield between the diamond elements 2A and 2B. This makes it possible to prevent microwave interference between the first and second sensor units 1A and 1B.

[0069] Furthermore, in the sensor 1 according to this embodiment, the first sensor unit 1A and the second sensor unit 1B share the light source 81 of the optical system 8, so that the sensor 1 can be insensitive to common-mode noise of the light source 81.

[0070] 10 is a diagram showing an outline of a sensor 1' according to another embodiment of the present invention. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description of the above-described embodiment is incorporated herein.

[0071] As shown in Fig. 10, in the sensor 1' of this embodiment, the diamond element 2A of the first sensor unit 1A and the diamond element 2B of the second sensor unit 1B are arranged to face each other with the bus bar 9 sandwiched between them in the thickness direction. <111> The direction of the wires is perpendicular to the upper and lower surfaces of the bus bar 9. <111> In the past, the NV axes of diamond elements 2A and 2B were arranged so that their directions were parallel to the top and bottom surfaces of bus bar 9. However, even when arranged perpendicularly like this, the multiple NV axes of diamond elements 2A and 2B include NV axes having components parallel to the top and bottom surfaces of bus bar 9. This is because NV axes always have four directions, as shown in FIG. 2. As in FIG. 1, first magnet 6 and second magnet 7 sandwich diamond elements 2A and 2B and apply a static magnetic field to diamond elements 2A and 2B in a direction parallel to the top and bottom surfaces of bus bar 9. In contrast, antennas 5A and 5B radiate a microwave magnetic field in a direction perpendicular to the NV axis, which is oriented perpendicular to the direction of the current in bus bar 9.

[0072] FIG. 11 is a diagram showing an outline of a sensor 1″ according to another embodiment of the present invention. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description of the above-described embodiment is incorporated herein.

[0073] As shown in FIG. 11, the sensor 1″ of this embodiment includes third and fourth sensor units 1C and 1D in addition to first and second sensor units 1A and 1B. The configuration of the first and second sensor units 1A and 1B is similar to that of the sensor 1′ of the above-described embodiment.

[0074] The third sensor unit 1C includes a diamond element 2C, an optical sensor 4C, an antenna 5C, and a control device 100C. The diamond element 2C has an NV center and is arranged close to one side of the bus bar 9 (the left side in the figure). The optical system 8 irradiates the diamond element 2C with green light GL as excitation light. The optical sensor 4C detects an optical signal generated due to electron spin resonance of the NV center. The antenna 5C emits a frequency-variable microwave magnetic field to the diamond element 2C. The control device 100C includes a microwave generator 10C, a lock-in detection device 20C, and a frequency control device 30C. The microwave generator 10C supplies microwaves to the antenna 5C. The function of the lock-in detection device 20C is the same as that of the lock-in detection devices 20A and 20B described above, and the function of the frequency control device 30C is the same as that of the frequency control devices 30A and 30B described above.

[0075] The fourth sensor unit 1D includes a diamond element 2D, an optical sensor 4D, an antenna 5D, and a control device 100D. The diamond element 2D has an NV center and is arranged close to the other side (the right side in the figure) of the bus bar 9. The optical system 8 irradiates the diamond element 2D with green light GL as excitation light. The optical sensor 4D detects an optical signal generated due to electron spin resonance of the NV center. The antenna 5D emits a frequency-variable microwave magnetic field to the diamond element 2D. The control device 100D includes a microwave generator 10D, a lock-in detection device 20D, and a frequency control device 30D. The microwave generator 10D supplies microwaves to the antenna 5D. The function of the lock-in detection device 20D is the same as that of the lock-in detection devices 20A, 20B, and 20C described above, and the function of the frequency control device 30D is the same as that of the frequency control devices 30A, 30B, and 30C described above.

[0076] The diamond element 2C and the diamond element 2D are arranged to face each other with the bus bar 9 sandwiched between them in a direction perpendicular to the direction of the current. <111> The direction is arranged parallel to the side surface of the bus bar 9. The multiple NV axes of the diamond elements 2C and 2D include an NV axis in a direction perpendicular to the direction of the current in the bus bar 9. In contrast, the antennas 5C and 5D radiate a microwave magnetic field in a direction perpendicular to the NV axes of the diamond elements 2C and 2D in a direction perpendicular to the direction of the current in the bus bar 9.

[0077] The first magnet 6 and the second magnet 7 are arranged in the thickness direction of the bus bar 9 so as to sandwich the diamond elements 2A, 2B and the bus bar 9, and apply a static magnetic field in a direction parallel to the NV axis, which is perpendicular to the direction of the current in the bus bar 9 of the diamond elements 2A to 2D.

[0078] The arithmetic processing device 200 detects the magnetic field B I is calculated using the following equation (14). B I =((B D -B C )+(B B -B A ) / β) / 4…(14) However, B A is the magnetic field measured by the first sensor unit 1A and is calculated by the following equation (15). B is the magnetic field measured by the second sensor unit 1B, and is calculated by the following equation (16). Also, β is the magnetic field B generated by the current flowing through the bus bar 9. I of diamond elements 2A and 2B <111> This constant β is set in consideration of the decrease in sensitivity of the first and second sensor units 1A and 1B due to the application of a voltage perpendicular to the direction B. This constant β is estimated by prior calibration or simulation. C is the magnetic field measured by the third sensor unit 1C, and is calculated by the following equation (17). D is the magnetic field measured by the fourth sensor unit 1D, and is calculated by the following equation (18). BA =-β×B I +B O …(15) B B =β×B I +B O …(16) B C =-B I +B O …(17) B D =B I +B O …(18)

[0079] According to the sensor 1″ of this embodiment, the external magnetic field B O By more precisely eliminating the influence of the magnetic field B I can be measured.

[0080] 12 is a diagram showing an outline of a sensor 1Y according to another embodiment of the present invention. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description of the above-described embodiment is incorporated herein.

[0081] 12, sensor 1Y of this embodiment includes first to fourth sensor units 1A to 1D. Diamond element 2A of first sensor unit 1A and diamond element 2B of second sensor unit 1B face each other with bus bar 9 sandwiched between them in the thickness direction of the bus bar 9. Diamond element 2A is located close to the lower surface of bus bar 9, and diamond element 2B is located close to the upper surface of bus bar 9.

[0082] Diamond element 2C of third sensor unit 1C and diamond element 2D of fourth sensor unit 1D are arranged to sandwich bus bar 9 and diamond elements 2A and 2B in the thickness direction of bus bar 9. Here, the distance between diamond element 2C and bus bar 9 is longer than the distance between diamond element 2A and bus bar 9. Also, the distance between diamond element 2D and bus bar 9 is longer than the distance between diamond element 2B and bus bar 9.

[0083] Fig. 13 is a diagram showing changes in the magnetic field measured by the first to fourth sensor units 1A to 1D shown in Fig. 12. This diagram shows changes in the magnetic field measured by the first to fourth sensor units 1A to 1D when the current in the bus bar 9 is the same. The horizontal axis of this diagram represents the microwave frequency, and the vertical axis of this diagram represents the ODMR (fluorescence intensity).

[0084] As shown in FIG. 13, a magnetic field B generated around the bus bar 9 due to the current in the bus bar 9 I The magnitude of the microwave frequency F of the first and second sensor units 1A and 1B decreases as the distance from the bus bar 9 increases. On the other hand, a sudden change in the current of the bus bar 9 appears as a large change in the magnetic field in the first and second sensor units 1A and 1B near the bus bar 9. Therefore, the sudden change in the current of the bus bar 9 is reflected in the microwave frequency F of the first and second sensor units 1A and 1B. AL ,F AH ,F BL ,F BH On the other hand, the change in the magnetic field appearing in the third and fourth sensor units 1C and 1D that are separated from the bus bar 9 is small.

[0085] Therefore, in this embodiment, when there is a sudden change in the current of the bus bar 9, the third and fourth sensor units 1C and 1D are used to make the magnetic measurement of the sensor 1Y follow the sudden change in the current of the bus bar 9. Specifically, the arithmetic processing device 200 (see FIG. 1, etc.) calculates the absolute value of (IYA-IXA)-(IYB-IXB), and when the calculated value shows a change exceeding a predetermined value within a certain short period of time, it determines that there has been a sudden change in the current of the bus bar 9, and calculates the magnetic field B I Calculate.

[0086] As described above, IXA is a set of operating points P LA ,P LB The resonant frequency R L is the integral value of the output XA, which represents the deviation from the set of operating points P HA ,P HB The resonant frequency R HSimilarly, IXB is the integral value of the output YA representing the deviation from a set of operating points P LA ,P LB The resonant frequency R L is the integral value of the output XB, which represents the deviation from the set of operating points P HA ,P HB The resonant frequency R H The increase in the absolute value of (IYA-IXA)-(IYB-IXB) is the integral value of the output YB that represents the deviation from the operating point P LA ,P LB ,P HA ,P HB That is, the sudden increase in the absolute value of (IYA-IXA)-(IYB-IXB) indicates that a sudden change has occurred in the current of the bus bar 9.

[0087] Here, when observing the absolute value of (IYA-IXA) or (IYB-IXB), the external magnetic field B O On the other hand, by observing the absolute value of (IYA-IXA)-(IYB-IXB), we can determine the influence of the external magnetic field B O The influence of the noise is eliminated, and the magnetic field B generated by the current of the bus bar 9 is I The size can be measured with high accuracy.

[0088] 14 is a diagram showing an outline of a sensor 1Z according to another embodiment of the present invention. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description of the above-described embodiment is incorporated herein.

[0089] As shown in Fig. 14, sensor 1Z of this embodiment includes first to fourth sensor units 1A to 1D. Diamond element 2A of first sensor unit 1A and diamond element 2C of third sensor unit 1C are arranged side by side in the width direction of busbar 9 on the upper surface side of busbar 9. On the other hand, diamond element 2B of second sensor unit 1B and diamond element 2D of fourth sensor unit 1D are arranged side by side in the width direction of busbar 9 on the lower surface side of busbar 9. Diamond element 2A and diamond element 2D are arranged to face each other with busbar 9 sandwiched between them in the thickness direction, and diamond element 2C and diamond element 2B are arranged to face each other with busbar 9 sandwiched between them in the thickness direction.

[0090] FIG. 15 is a diagram showing ODMR spectra output by the first to fourth sensor units 1A to 1D shown in FIG. 14. As shown in this figure, the width of the "valley" in the ODMR spectra of the first and second sensor units 1A and 1B is narrower than the width of the "valley" in the ODMR spectra of the third and fourth sensor units 1C and 1D. Here, the narrower the width of this "valley," the larger the proportionality constant K in the above equations (8) and (9). The larger this proportionality constant K, the more likely it is that the sensor output will reach its maximum value (saturation state). Therefore, in this embodiment, similar to the sensor 1Y of the above embodiment, when there is a sudden change in the current of the bus bar 9, the third and fourth sensor units 1C and 1D are used to allow the magnetic measurement of the sensor 1Y to follow the sudden change in the current of the bus bar 9. Specifically, the arithmetic processing device 200 (see FIG. 1, etc.) calculates the absolute value of (IYA-IXA)-(IYB-IXB), and if the calculated value shows a change exceeding a predetermined value within a certain short period of time, it determines that there has been a sudden change in the current of the bus bar 9, and calculates the magnetic field B I Calculate.

[0091] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and modifications may be made within the scope of the spirit of the present invention, and publicly known or well-known technologies may be combined as appropriate.

[0092] For example, in this embodiment, the element having the color center to be excited is a diamond element having an NV center, but the element may also be something else, such as a diamond element having an SnV color center made of tin (Sn) and vacancies, a diamond element having an SiV color center made of silicon (Si) and vacancies, or a diamond element having a GeV color center made of germanium (Ge) and vacancies. [Explanation of symbols]

[0093] 1,1', 1”, 1Y,1Z: Sensor 1A: First sensor unit (first magnetic sensor) 1B: Second sensor unit (second magnetic sensor) 1C: Third sensor unit (third magnetic sensor) 1D: 4th sensor unit (4th magnetic sensor) 2A, 2B, 2C, 2D: Diamond element (element) 4A, 4B, 4C, 4D: Optical sensors 5A, 5B, 5C, 5D: Antenna 6,7: Magnet (magnet pair) 8:Optical system 9: Bus bar (current line) 11: First microwave oscillator 12: Second microwave oscillator 13: Switch 22: Lock-in amplifier 23:First integration circuit 24:Second integration circuit 81 :Light source 100A, 100B: Control device (control section) 100C, 100D: Control device (control section) 200: Processing unit (processing unit) 314:Magnetic field / temperature calculation section B A ,B B ,B C ,B D ,B I: Magnetic field (output) F AL : Frequency (frequency of the first microwave) F AH : Frequency (frequency of the second microwave) S MOD : Switching signal T A ,T B : Temperature (output) FM1: Frequency (predetermined modulation frequency) XA: Output (first output) YA: Output (2nd output) IXA: Integral output (first integral output) IYA: Integral output (second integral output) GL: Green light (excitation light) RL: Red fluorescence (fluorescence)

Claims

1. a first magnetic sensor and a second magnetic sensor that detect and output a magnetic field around the current line; a computing device that computes a difference between an output of the first magnetic sensor and an output of the second magnetic sensor; Equipped with The first magnetic sensor and the second magnetic sensor each include: an element disposed around the current line and having a color center; an antenna for radiating a microwave magnetic field to the element; an optical system that irradiates the element with excitation light; an optical sensor that detects and outputs the intensity of the fluorescence emitted from the element; a control unit that oscillates the microwave, calculates at least one of a magnetic field and a temperature around the current line based on an output of the optical sensor, and outputs the calculated value to the arithmetic unit; Equipped with The control unit a first microwave oscillator that oscillates a first microwave modulated at a first phase with a predetermined modulation frequency; a second microwave oscillator that oscillates a second microwave that is modulated with a second phase of the predetermined modulation frequency and has a different frequency from the first microwave; a switch for switching between a first connection state in which the first microwave oscillator and the antenna are connected and a second connection state in which the second microwave oscillator and the antenna are connected; a lock-in amplifier that receives the output of the optical sensor, outputs a first output corresponding to the first phase of the predetermined modulation frequency, and outputs a second output corresponding to the second phase; a first integration circuit that integrates the first output output from the lock-in amplifier and outputs the resulting first integrated output to the first microwave oscillator; a second integration circuit that integrates the second output output from the lock-in amplifier to output a second integrated output to the second microwave oscillator; a magnetic field / temperature calculation unit that calculates at least one of a magnetic field and a temperature around the current line based on a difference between the first integral output and the second integral output; Equipped with the first microwave oscillator feedback-controls the frequency of the first microwave based on the first integrated output; The second microwave oscillator is a sensor that feedback controls the frequency of the second microwave based on the second integrated output.

2. The sensor according to claim 1 , wherein the element of the first magnetic sensor and the element of the second magnetic sensor are arranged opposite to each other with the current line interposed therebetween.

3. a magnet pair that generates a static magnetic field around the current line; The sensor according to claim 2 , wherein the magnet pair generates the static magnetic field in a direction perpendicular to a direction in which the element of the first magnetic sensor and the element of the second magnetic sensor face each other.

4. The modulation frequency input to the first microwave and the modulation frequency input to the second microwave are out of phase with each other by 90°; the switch switches between the first connection state and the second connection state using a signal having a frequency twice the predetermined modulation frequency; 4. The sensor of claim 1 or claim 3, wherein the rising and falling phases of the signal differ by 45° from the rising and falling phases of the modulation frequency input to the first microwave and the modulation frequency input to the second microwave.

5. 5. The sensor according to claim 1, wherein the optical system of the first magnetic sensor and the optical system of the second magnetic sensor share a light source.

6. the color center is an NV center, 6. The sensor according to claim 1, wherein the antenna radiates the microwave magnetic field in a direction perpendicular to the <111> direction of the NV center.

7. a third magnetic sensor and a fourth magnetic sensor that detect and output a magnetic field around the current line; the calculation device calculates a difference between an output of the third magnetic sensor and an output of the fourth magnetic sensor, The third magnetic sensor and the fourth magnetic sensor each include: the element; The antenna; the optical system; the optical sensor; the control unit; Equipped with A sensor described in any one of claims 2, 3, or claims 4 to 6 that cite claim 1, wherein the elements of the third magnetic sensor and the elements of the fourth magnetic sensor are arranged opposite each other across the current line in a direction perpendicular to the opposing direction of the elements of the first magnetic sensor and the elements of the second magnetic sensor.

8. a third magnetic sensor and a fourth magnetic sensor that detect and output a magnetic field around the current line; the calculation device calculates a difference between an output of the third magnetic sensor and an output of the fourth magnetic sensor, The third magnetic sensor and the fourth magnetic sensor each include: the element; The antenna; the optical system; the optical sensor; the control unit; Equipped with the element of the third magnetic sensor and the element of the fourth magnetic sensor are arranged opposite to each other with the element of the first magnetic sensor and the element of the second magnetic sensor sandwiched therebetween in an opposing direction of the element of the first magnetic sensor and the element of the second magnetic sensor, A sensor described in any one of claims 2, 3, or claims 4 to 6 that cite claim 1, wherein the change in output of the third magnetic sensor and the fourth magnetic sensor due to a change in the magnetic field around the current line is smaller than the change in output of the first magnetic sensor and the second magnetic sensor due to a change in the magnetic field around the current line.

9. a third magnetic sensor and a fourth magnetic sensor that detect and output a magnetic field around the current line; the calculation device calculates a difference between an output of the third magnetic sensor and an output of the fourth magnetic sensor, The third magnetic sensor and the fourth magnetic sensor each include: the element; The antenna; the optical system; the optical sensor; the control unit; Equipped with the elements of the third magnetic sensor and the elements of the fourth magnetic sensor are arranged opposite to each other across the current line in a direction in which the elements of the first magnetic sensor and the elements of the second magnetic sensor face each other, the width of the optically detected magnetic resonance spectrum of the elements of the first magnetic sensor and the second magnetic sensor is narrower than the width of the optically detected magnetic resonance spectrum of the elements of the third magnetic sensor and the fourth magnetic sensor; A sensor described in any one of claims 2, 3, or claims 4 to 6 that cite claim 1, wherein the change in output of the third magnetic sensor and the fourth magnetic sensor due to a change in the magnetic field around the current line is smaller than the change in output of the first magnetic sensor and the second magnetic sensor due to a change in the magnetic field around the current line.

Images