CN110346627A - Weak current detection device - Google Patents

Abstract

The present invention solves the problem that the conventional magnetic sensor has a problem of being unable to detect a small current, for example, a leakage current of the order of nA, due to the limit of sensitivity. In addition, in the conventional detection method, a widely distributed magnetic field is generated between the electrodes by the applied alternating current, and as a result, the magnetic field fluctuation caused by the leakage current cannot be clearly seen. The present invention provides a micro current detection device including a magnetic sensor including NVC and a vector potential device, which can detect micro leakage current and improve the sensitivity as a magnetic sensor.

Description

Micro current detection device

technical field

The invention relates to a tiny current detection device.

Background technique

In recent years, a structure containing a nitrogen vacancy center (NVC: Nitrogen Vacancy Center) has attracted attention in the field of magnetic sensor technology.

Under normal circumstances, after the electrons in the ground state are excited by green light, red light is generated when they return to the ground state. On the other hand, for example, nitrogen atoms in the diamond structure and electrons in a lattice vacancy center (NVC: Nitrogen Vacancy Center) are irradiated with a high-frequency magnetic field of about 2.87 GHz, and the lowest among the three sub-levels in the ground state level (m _s =0), the level of the transition to a higher energy orbital in the ground state (m _s =±1). If the electrons in this state are excited by green light, since they return to the lowest level (m _s = 0) of the three sub-levels in the ground state without radiation, the amount of luminescence will decrease. Whether magnetic resonance occurs in the high frequency magnetic field.

In one measurement system, a ring-slit resonator (Split Ring Resonator), a coil-type antenna, or a wire-type antenna is installed below a diamond sample, and a high-frequency magnetic field in the microwave region of about 2.87 GHz is irradiated to the sample from the resonator, Scanning a high-frequency magnetic field and excitation light, and detecting a reduction in red light from electrons by a detection device, obtains information on cells in the vicinity of the diamond structure (see, for example, Non-Patent Document 1).

In addition, in the field of battery technology, especially for batteries such as lithium batteries widely used in automobiles and consumer fields, it is expected that there may be leakage or short-circuit between electrodes due to electrode peeling or harsh use environment. In order to monitor such a situation at any time, for example, a device that detects leakage current using a magnetic sensor without destroying the battery has been developed.

Patent Document 1: Japanese Patent Laid-Open No. 2016-090581

Non-Patent Document 1: Kento Sasaki, et.al., "Broadband, large-area microwaveantenna for optically-detected magnetic resonance of nitrogen-vacancy centers in diamode" REVIEW OF SCIENTIFIC INSTRUMENTS 87, 053904 (2016)

SUMMARY OF THE INVENTION

However, since the magnetic sensor used in the above-mentioned case has a limit of sensitivity, there is a problem that it cannot detect a small current, for example, a leakage current of the order of nA.

In addition, the sensitivity of magnetic sensors such as NVC is known to have high sensitivity in the high frequency region due to the influence of 1/f noise. In order to improve the measurement sensitivity more effectively, AC modulation is performed at the measurement site. It's effective.

In addition, as shown in FIG. 4 , when an alternating current is supplied from the power source 130 to the electrodes 150, the leakage current between the electrodes 150 can be detected by the magnetic detection element 120 provided above the electrodes 150, but the leakage current between the electrodes 150 can be detected. 5. From the simulation results, it can be understood that since the alternating current generates a widely distributed magnetic field between the electrodes 150, as a result, the magnetic field fluctuation caused by the leakage current cannot be clearly seen. In other words, for nA-level leakage currents, existing detection methods have limitations in improving sensitivity.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a microcurrent detection device capable of improving detection sensitivity by utilizing a structure having a nitrogen lattice vacancy center.

The minute current detection device according to the present invention includes: a magnetic sensor including an NVC; and a vector potential device.

According to the present invention, it is possible to obtain a minute current detection device capable of detecting minute leakage currents and improving the sensitivity as a magnetic sensor.

Description of drawings

FIG. 1 is a diagram showing a minute current detection device according to Embodiment 1 of the present invention.

2 is a schematic diagram showing a magnetic sensor including NVC according to Embodiment 1 of the present invention.

Fig. 3 is a cross-section taken along A-A' in Fig. 1 showing the minute current detection device according to Embodiment 1 of the present invention.

FIG. 4 is a diagram showing a conventional leakage current detection device.

FIG. 5 is a simulation diagram of a magnetic field between electrodes based on a conventional detection method.

Symbol Description

10: Microcurrent detection device; 20: Magnetic sensor including NVC; 21: Sensing part including substrate including NVC; 22: Incident device; 23: Exit detection device; 40: Battery; 50, 150: Electrodes; 60, 160: micro current path; 70: vector potential device; 71: tubular body; 72: coil body; 120: magnetic detection element; 130: power supply.

Detailed ways

Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

Embodiment 1

FIG. 1 is a diagram showing a minute current detection device 10 according to Embodiment 1 of the present invention. The minute current detection device 10 includes: a magnetic sensor 20 including an NVC; and a vector potential device 70 . Above the electrode 50 of the battery 40 to be inspected, the NVC-containing magnetic sensor 20 of the minute current detection device 10 is provided in parallel with the electrode 50 and not in contact with the battery 40 .

2 is a schematic diagram showing a magnetic sensor including NVC according to Embodiment 1 of the present invention. As shown in FIG. 2 , the magnetic sensor 20 including NVC includes a sensor unit 21 including a substrate including NVC, an incident device 22 , an emission detection device 23 , and a magnetic field generation device 24 .

The operation principle of the NVC-containing magnetic sensor 20 will be described.

In the NVC structure in the diamond substrate of the sensing portion 21 , the trapped electrons form spin triplet states with magnetic quantum numbers m _s =−1, 0, +1. Originally, the electrons are excited from the ground state of m _s =0 to a high energy level by the green laser light emitted from the incident device 22 , but then return to the ground state of m _s =0 while emitting red fluorescence. However, even when such electrons transition to the ground state of m _s =+1 or -1 by the alternating magnetic field B generated by the magnetic field generator 24 and are excited by laser light from there, some of the electrons return without emitting light. ground state phenomenon. That is, when the outgoing light is detected, the outgoing detection device 23 can detect the drop point of the luminance of the red light. Using this phenomenon, the magnetic field strength can be measured. That is, the brightness of the outgoing light further changes due to the influence of the magnetic field from the leakage current described later, and the change in the intensity of the magnetic field can be known by detecting this change by the outgoing detection device 23 .

In addition, in order to improve the sensitivity of the magnetic sensor 20 containing NVC, when the magnetic field of the object to be measured has an AC component, the sensitivity is improved. By applying a change in AC voltage to the object to be measured, the leakage current changes according to the AC voltage, and the magnetic field generated thereby also has an AC component, which enables more accurate detection.

However, simply applying an AC current between the electrodes 50 generates an AC magnetic field as in the prior art. To solve this problem, a vector potential device 70 described later is used.

The vector potential device 70 is, for example, a large coil body 72 formed by winding a wire into a coil shape to form a long tubular body 71 , and then further winding the tubular body 71 . That is, the vector potential device 70 is a closed loop. In addition, the vector potential device 70 is formed so as to surround the battery 40 to be inspected. In addition, since the diameter of the tubular body 71 is small, in FIG. 1 , the tubular body 71 is indicated by a solid line. In other words, the electrode 50 of the battery 40 is arranged in parallel with the opening surface of the coil body of the vector potential device 70 .

Fig. 3 is a cross-section taken along A-A' in Fig. 1 showing the minute current detection device according to Embodiment 1 of the present invention. In FIG. 3, the solid line which shows the tubular body 71 is a lead wire. In addition, a plurality of circular shapes formed by conducting wires represent the cross-section of the tubular body 71 . As shown in FIG. 3 , when an alternating current is applied to such a vector potential device 70 , a state in which there is no magnetic field and only an alternating electric field can be created in the inner space of the winding structure of the large coil body 72 . Thereby, as shown in FIG. 3 , a uniform AC electric field (AC voltage) can be created between the electrodes 50 of the battery 40 .

With such a structure, even if a minute current path 60 is formed between the electrodes 50 of the battery 40 due to cracks, peeling of the electrodes, etc., a minute leakage current is generated through the minute current path 60, and a minute leakage current is generated through the minute current path 60. The formed magnetic field applies an AC component from the vector potential device 70, so the leakage current can be easily detected by the magnetic sensor 20 including NVC.

In addition, in the vector potential device 70 , the diameter D of the coil body 72 formed by the tubular body 71 is preferably larger than that of the battery 40 , and in particular, larger than that of the electrode 50 .

In addition, when the area of the battery 40 is large, the leakage current can be checked while scanning the magnetic sensor 20 including the NVC.

In addition, in FIG. 2 , the magnetic field generating device 24 , the incident device 22 , and the emission detection device 23 are shown on a different side from the sensor portion 21 including the substrate containing NVC, but they may be provided on the same side. side.

Industrial applicability

The present invention can be applied to, for example, a device that detects a minute current with respect to a battery or the like.

Claims (3)

1. a kind of Weak current detection device, which is characterized in that have: the Magnetic Sensor containing NVC；And vector potential device.

2. Weak current detection device according to claim 1, which is characterized in that the Magnetic Sensor tool containing NVC It is standby: detecting means, incidence mount comprising the substrate containing NVC, outgoing detection device and magnetic field generation device.

3. Weak current detection device according to claim 1 or 2, which is characterized in that the vector potential device is formed as Surround the shape of check object.