Current Sensors and Measuring Devices

Abstract

To provide a current sensor and a measuring apparatus that can withstand repetitive opening and closing in measurement in a Rogowski manner with a measurement object such as an electronic component surrounded to reduce an influence of a common mode voltage.SOLUTION: There is provided a current sensor which is flexible and comprises a detection body detecting a physical quantity of a measurement object with the measurement object surrounded, and the detection body has: a conductive wire (11) which is wound spirally around a hollow core (12) and folded back at a tip part of the core (12) to be returned to a base end part of the core (12); an inner insulation layer (13); a conductive electrostatic shield layer (15) which is provided to form a gap (15a) without making a round in a circumferential direction outside the internal insulation layer (13); and an outer coating (16) which is provided to make one round in the circumferential direction outside the electrostatic shield layer (15).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a current sensor and a measuring device for detecting a current in a measurement object. [Background technology]

[0002] Various current sensors have been proposed so far, including the CT type, Hall element type, Rogowski type, and zero-flux type. Among them, the Rogowski type has no magnetic core, so it can measure large currents without magnetic saturation, and has characteristics such as no heat generation due to magnetic loss, saturation, or hysteresis. These characteristics make it possible to measure a variety of objects.

[0003] For example, Patent Document 1 describes a Rogowski-type current detector used to detect relatively large currents such as the current flowing through the central conductor of a GIS (Gas Insulated Switchgear) or the current flowing through the heating coil of a high-frequency induction heating device. The Rogowski-type sensor performs measurements by passing one end of the ring, with one part of the ring open, behind the object to be measured and then closing the ring to form a ring that surrounds the object to be measured.

[0004] The GIS and high-frequency induction heating devices that are the measurement targets of the current detector in Patent Document 1 are thought to operate at relatively low frequencies, similar to commercial frequencies. In this current detector, the openable, ring-shaped detection unit is configured with a first insulating layer, an electric field shield, a second insulating layer, a magnetic field shield, and a coating layer, all of which are cylindrically arranged so as to penetrate the center of a flexible tube and cover the Rogowski coil wound around it. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-329826 Summary of the Invention [Problem to be solved by the invention]

[0006] Rogowski-type sensors have a wide range of applications, including measuring currents at frequencies of several MHz or higher that flow through electronic components mounted on a circuit board. Because electronic components are relatively small, the sensors used to measure them must be smaller than sensors that measure current in devices such as those described in Patent Document 1 in order to be able to pass through narrow spaces.

[0007] However, the Rogowski-type sensor described in Patent Document 1 is not intended to be passed through narrow spaces to measure small objects. Even if the sensor described in Patent Document 1 were to be made small enough to measure electronic components, the radius of curvature would be too small, causing problems with the cylindrical copper mesh or foil copper tape used as an electric field shield. Repeated opening and closing of the sensor end during measurement would destroy the foil copper tape, causing it to lose its electric field shielding function. Furthermore, if the radius of curvature is too small, the copper mesh used as an electric field shield would not be able to flex sufficiently.

[0008] For these reasons, conventional Rogowski-type current sensors used to measure electronic components have not been equipped with electric field shields. That is, as shown in Figure 7, a Rogowski-type current sensor for measuring electronic components has a minimal configuration: Rogowski coil 102 passes through the center of flexible tube 101 and is wound around the periphery, and is covered with exterior coating 103.

[0009] On the other hand, Rogowski current sensors, which measure electronic components, may measure, for example, switching power semiconductors. In recent years, switching power semiconductors have become increasingly high-frequency, creating a situation where the measurement itself is impossible unless the influence of common-mode voltage is reduced. However, a Rogowski sensor with a minimal configuration that does not have an electric field shield is susceptible to the influence of the surrounding environment, particularly common-mode voltage.

[0010] The present invention has been made in consideration of the above-mentioned problems of the conventional art, and an object of the present invention is to provide a current sensor and measuring device that can withstand repeated opening and closing when surrounding a measurement object such as an electronic component and measuring it using the Rogowski method, and that can reduce the influence of common-mode voltage. [Means for solving the problem]

[0011] A current sensor according to a representative embodiment of the present invention is a current sensor comprising: a flexible detection body that surrounds the measurement object and detects a physical quantity of the measurement object; and a holding part to which the base end of the detection body is attached and that holds the tip end of the detection body. The detection body comprises a conductive wire that is spirally wound around a winding core and folded back at the tip end of the winding core and returned to the base end of the winding core; an internal insulating layer that is provided around the spirally wound conductive wire in a circumferential direction; a conductive electrostatic shielding layer that is provided around the internal insulating layer in a circumferential direction so as to form a gap without making a full turn; and an exterior coating that is provided around the electrostatic shielding layer in a circumferential direction so as to make a full turn. [Effects of the Invention]

[0012] The current sensor and measuring device according to the present invention can withstand repeated opening and closing when surrounding an object to be measured, such as an electronic component, and performing measurements using the Rogowski method, and can reduce the effects of common-mode voltage. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing a schematic configuration of a measurement device using a current sensor according to an embodiment of the present invention. [Figure 2] 1 is a diagram illustrating a configuration of a current sensor according to an embodiment of the present invention. [Figure 3] 10A and 10B are diagrams illustrating the shape of a detection body when the current sensor is in a closed state. [Figure 4] FIG. 2 is a diagram showing a cross-sectional configuration of a detection main body. [Figure 5]FIG. 10 is a diagram showing the arrangement of current sensors when measuring the current of an electronic component. [Figure 6] 10A and 10B are diagrams for explaining a procedure for sending the tip of the detection main body from behind the terminal of the electronic component to the front. [Figure 7] FIG. 10 is a diagram showing a cross-sectional configuration of a detection body in a conventional current sensor. DETAILED DESCRIPTION OF THE INVENTION

[0014] 1. Overview of the embodiment First, a typical embodiment of the invention disclosed in this application will be outlined. In the following description, as an example, reference numerals in the drawings corresponding to the components of the invention in Figure 4 are written in parentheses.

[0015] [1] A current sensor according to a representative embodiment includes a flexible detection body that surrounds the object to be measured and detects a physical quantity of the object to be measured, and a holding part to which the base end of the detection body is attached and that holds the tip end of the detection body. The detection body includes a conductive wire (11) that is spirally wound around a winding core (12), folded back at the tip end of the winding core (12), and returned to the base end of the winding core (12), an internal insulating layer (13) that is provided around the spirally wound conductive wire (11) in a circumferential direction outside the internal insulating layer (13), a conductive electrostatic shielding layer (15) that is provided around the circumferential direction outside the internal insulating layer (13) so as to form a gap (15a) without completing a full turn, and an outer coating (16) that is provided around the electrostatic shielding layer (15) in a circumferential direction outside the electrostatic shielding layer (15).

[0016] According to this aspect, by winding the electrostatic shield layer at intervals so as not to make a full turn, induced currents do not flow in the circumferential direction, thereby improving measurement accuracy. By providing gaps in the electrostatic shield layer, the detection body can be configured to be easily bent. By winding the electrostatic shield layer so as not to overlap, the detection body can be easily bent and can be made thin. The detection body can withstand repeated opening and closing when surrounding a measurement object such as an electronic component and measuring it using the Rogowski method, and the effects of common-mode voltage can be reduced.

[0017] [2] In the current sensor described in [1] above, the electrostatic shield layer may have a circumferential length shorter than that of the inner insulating layer.

[0018] According to this embodiment, the electrostatic shield layer 15 can easily form the gaps 15a in the circumferential direction D of the detection body 1. Even when the electrostatic shield layer 15 is formed in close contact with the internal insulating layer 13, the gaps 15a of the electrostatic shield layer 15 can be ensured at constant intervals.

[0019] [3] In the current sensor described in [1] or [2] above, the electrostatic shield layer may be a conductive cloth.

[0020] According to this embodiment, durability and elasticity sufficient to withstand repeated deformations that occur when the current sensor 10 is opened and closed can be ensured.

[0021] [4] In the current sensor according to any one of [1] to [3] above, the electrostatic shield layer may be made of a low-magnetic material.

[0022] According to this embodiment, magnetic flux can be efficiently passed through the conductive wire 11 configured as a Rogowski coil.

[0023] [5] In the current sensor according to any one of [1] to [4] above, the internal insulating layer may be made of a low dielectric constant material.

[0024] According to this embodiment, it is possible to prevent the formation of parasitic capacitance between the conductive line 11 and the electrostatic shield layer 15 . [6] In the current sensor according to any one of [1] to [5] above, the outer covering may be a heat-shrinkable tube.

[0025] This embodiment is easy to fabricate, since it can be fabricated simply by wrapping the shielding material around it, covering it with a heat-shrinkable tube, and heating it. Furthermore, there is no effect on the external dimensions, and electrical continuity can be achieved between the electrostatic shield layer 15 and the connecting wires 14 because the contact pressure is ensured by the pressure generated when the heat-shrinkable tube shrinks during the formation of the exterior coating.

[0026] [7] In the current sensor according to any one of [1] to [6] above, the object to be measured may be an electronic component.

[0027] According to this aspect, the object to be measured can be surrounded through a narrow space, and the influence of common mode voltage can be reduced, so that measurement of electronic components can be performed reliably regardless of the frequency to be measured.

[0028] [8] A measuring device according to a representative embodiment includes any one of the current sensors described above in [1] to [7], and a measuring unit that measures a physical quantity of the object to be measured based on a detection signal detected by the current sensor.

[0029] According to this aspect, by winding the electrostatic shield layer at intervals so as not to make a full turn, induced currents do not flow in the circumferential direction, thereby improving measurement accuracy. By providing gaps in the electrostatic shield layer, the detection body can be configured to be easily bent. By winding the electrostatic shield layer so as not to overlap, the detection body can be easily bent and can be made thin. The detection body can withstand repeated opening and closing when surrounding a measurement object such as an electronic component and measuring it using the Rogowski method, and the effects of common-mode voltage can be reduced.

[0030] 2. Specific examples of embodiments Specific examples of embodiments of the present invention will be described below with reference to the drawings. In the following description, components common to each embodiment will be given the same reference numerals, and repeated description will be omitted. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from the actual situation. The drawings may also include portions with different dimensional relationships and ratios.

[0031] (Embodiment) FIG. 1 is a diagram showing a schematic configuration of a measurement device using a current sensor according to this embodiment.

[0032] <Measuring equipment> As shown in FIG. 1, a measuring device 100 using a current sensor of this embodiment includes a current sensor 10 that detects a current flowing through an object to be measured, an integration circuit 20 that integrates a detection signal output from the current sensor 10, and a measuring unit 30 that measures a physical quantity of the object to be measured based on the signal output from the integration circuit 20.

[0033] The measurement object may be the terminals of an electronic component mounted on a circuit board, etc. The physical quantities of the measurement object may be the value of the AC current flowing through the measurement object, the value of the AC power, or the value of the AC magnetic field generated around the measurement object.

[0034] (current sensor) FIG. 2 is a diagram showing the configuration of the current sensor according to this embodiment.

[0035] Current sensor 10 surrounds a measurement object and detects an AC current flowing through the object. Current sensor 10 includes detection body 1 that detects the AC current flowing through the object, and holding part 2 to which base end 1b of detection body 1 is attached and which holds tip end 1a of detection body 1.

[0036] The detection body 1 may be formed in a shape that is curved in advance and has a predetermined curvature so that it can easily surround the measurement object. The detection body 1 is flexible and can bend when surrounding the measurement object. The detection body 1 is elastic and recovers to its original shape or nearly its original shape when the external force is removed.

[0037] The detection body 1 has a Rogowski coil formed along the longitudinal direction (extension direction). In other words, the detection body 1 constitutes a flexible current sensor of the Rogowski coil type. The Rogowski coil has a configuration in which a conductive wire is wound spirally around the outer periphery of a winding core, is folded back near the tip 1a of the detection body 1, which is one end of the winding core, passes through the inside of the winding core, and returns to the base end 1b of the detection body 1. The configuration of the detection body 1 will be described later.

[0038] The holding unit 2 is an operation portion that is operated by the user's hand or finger. The holding unit 2 includes a fixing unit 21 that fixes a part of the detection main body 1, and an insertion unit 22 into which the user inserts the tip 1a of the detection main body 1 when the measurement target is surrounded.

[0039] The current sensor 10 is closed when the tip 1a of the detection body 1 is inserted into the insertion portion 22, and conversely, the current sensor 10 is opened when the tip 1a of the detection body 1 is pulled out from the insertion portion 22. In addition, the base end 1b of the detection body 1 and the cable 3 of the integrating circuit 20 are electrically connected at the fixed portion 21.

[0040] The opening and closing of the current sensor 10 in this embodiment will now be further described with reference to FIGS.

[0041] FIG. 2 is a diagram showing the shape of the detection body 1 when the current sensor 10 is in an open state. A matching circuit 23 is disposed inside the holding part 2 to match the impedance of the detection main body 1 side with the impedance of the measuring part 30 side.

[0042] When the current sensor 10 is in an open state, the tip 1c of the detection body 1 has a portion formed therein whose curvature is greater than the curvature of the base end 1e that includes the base end 1b of the detection body 1. The tip 1c is a portion of a specific length that includes the tip 1a of the detection body 1, and the curvature of the tip 1a may be the greatest, or the tip 1a may have no curvature and the curvature of other portions may be greater than the curvature of the base end 1e.

[0043] The detection body 1 may be formed so that the curvature of the detection body 1 increases stepwise or continuously from the base end 1e toward the tip end 1c. This makes it easier for the user's force to be transmitted from the holding part 2 to the detection body 1, and also makes it less likely for the detection body 1 to get caught on the measurement target or its adjacent members.

[0044] In the holding part 2, a part of the base end 1e of the detection body 1 is fixed to the fixing part 21. A part of the base end 1e is housed in the fixing part 21, and the other part is exposed from the fixing part 21. The insertion part 22 forms an insertion passage through which the tip 1a of the detection body 1 is inserted, and is formed so that the tip 1a of the detection body 1 abuts against the base end 1b of the detection body 1.

[0045] 3 is a diagram showing the shape of the detection body 1 when the current sensor 10 is in a closed state. In this figure, the matching circuit 23 and the cable 3 of the integrating circuit 20 shown in FIG. 2 are omitted.

[0046] 3, when the user inserts the tip 1a of the detection main body 1 into the insertion opening 22a of the insertion part 22, the tip 1a of the detection main body 1 is held by the holding part 2. This brings the current sensor 10 into a closed state, allowing the detection main body 1 to surround the measurement target.

[0047] When the tip 1a of the detection body 1 is pulled out from the insertion portion 22 of the holding portion 2, the flexible detection body 1 returns to its original shape with the tip portion 1c of the detection body 1 bent inward, as shown in Figure 2.

[0048] 3, the radius of curvature of detection body 1 is substantially constant when current sensor 10 is in a closed state with tip 1a of detection body 1 held by insertion portion 22 of holder 2. Therefore, the curvature of detection body 1 needs to change in order for current sensor 10 to change from an open state to a closed state.

[0049] Electronic components measured by the measuring device 100 equipped with the current sensor 10 of this embodiment include switching power semiconductors, which have become increasingly high-frequency in recent years. When measuring such high-frequency electronic components, situations arise where the measurement itself is impossible unless the influence of common-mode voltage is reduced. To reduce the influence of common-mode voltage, electrostatic shielding of the Rogowski coil of the detection body 1 is considered. However, the detection body 1 must be able to withstand repeated changes in curvature, and the electrostatic shields installed in conventional Rogowski-type current sensors have durability issues. Furthermore, when performing high-frequency measurements, if a one-turn coil is formed by the electrostatic shield, induced currents are generated in the electrostatic shield, resulting in errors in the measurement values. Because of these limitations, the detection body 1 used in the current sensor of the measuring device 100, which measures electronic components, has various limitations. Therefore, the current sensor 10 of the measuring device 100 of this embodiment employs a detection body 1 with a different configuration from conventional ones. The configuration of the detection body 1 employed in the current sensor 10 of the measuring device 100 of this embodiment is further described.

[0050] FIG. 4 is a diagram showing a cross-sectional configuration of the detection body 1. As shown in FIG.

[0051] As shown in FIG. 4, the detection body 1 is configured such that an internal insulating layer 13, a connecting wire 14, an electrostatic shielding layer 15, and an outer coating 16 are arranged on the outside of a conductive wire 11 that is spirally wound around the outer periphery of a winding core 12 and that is folded back at one end of the winding core 12 and passes through the interior of the winding core 12 to form a Rogowski coil.

[0052] The core can be formed from a hollow flexible member having insulating properties. The flexible member is made of, for example, a synthetic resin such as vinyl chloride or polyethylene, or PEEK (Poly Ether Ether Ketone). The flexibility of the flexible member is determined by the application, and PEEK is used for applications requiring high toughness. The flexible member preferably has heat resistance.

[0053] The internal insulating layer 13 is provided around the conductive wire 11 in the circumferential direction D. The internal insulating layer 13 is made of a low-dielectric-constant material to prevent the formation of parasitic capacitance between the conductive wire 11 and the electrostatic shield layer 15. Specifically, a low-dielectric-constant material may have a relative dielectric constant of less than 3.0. The internal insulating layer 13 is formed as thin as possible using a flexible insulating material. The internal insulating layer 13 preferably also has heat resistance. The insulating material used may be a fluororesin-based material. For example, FEP (Fluorinated Ethylene Propylene), PEA (Phenethylamine), etc. can be used as the insulating material, but FEP is preferably used from the viewpoints of availability and processability.

[0054] The internal insulating layer 13 serves to reduce the capacitive coupling between the electrostatic shield layer 15 and the conductive wire 11 that constitutes the Rogowski coil. The pitch of the coil and the thickness of the internal insulating layer can be adjusted so that the Rogowski coil operates as an inductor at the signal frequency that is actually intended to be measured with the Rogowski coil.

[0055] The connection wire 14 is a conductive wire that passes through the inside of the detection body 1 and is drawn out in electrical contact with the electrostatic shield layer 15 in order to ground the electrostatic shield layer 15. A metal-plated wire can be used as the connection wire 14, but any conductive wire can be used. Since the ground potential can be achieved without the need for crimping to the electrostatic shield layer 15, an increase in the thickness of the detection body 1 can be suppressed.

[0056] The electrostatic shield layer 15 is a conductive layer provided outside the internal insulating layer 13 in the circumferential direction D, without going all the way around. By forming the gap 15a without going all the way around, the electrostatic shield layer 15 prevents induced current from flowing in the circumferential direction, thereby improving measurement accuracy. By providing the gap 15a in the electrostatic shield layer 15, the detection body 1 can be configured to be easily bent, and by winding the electrostatic shield layer 15 without overlapping, the detection body 1 can be made to be easily bent and thin.

[0057] The electrostatic shield layer 15 is configured to be flexible. Because it is configured to be flexible, it can be formed to have a curvature corresponding to the location of the detection body 1, and can withstand repeated deformation that occurs when the current sensor 10 is opened and closed. In order to efficiently pass magnetic flux through the conductive wire 11 configured as a Rogowski coil, it is preferable that the material constituting the electrostatic shield layer 15 is nonmagnetic. From this perspective, conductive cloth can be used as the electrostatic shield layer 15.

[0058] The electrostatic shield layer 15 is formed so that its circumferential length, which is its length in the circumferential direction D, is shorter than the circumferential length of the internal insulating layer 13. By forming it in this manner, gaps 15a can be easily formed in the electrostatic shield layer 15 in the circumferential direction D of the detection body 1. Furthermore, even when the electrostatic shield layer 15 is formed in close contact with the internal insulating layer 13, the gaps 15a in the electrostatic shield layer 15 can be maintained at regular intervals. The size of the gaps 15a in the electrostatic shield layer 15 can be determined based on the circumferential length of the internal insulating layer 13. The circumferential length of the internal insulating layer 13 can be expressed as (circumferential length of the internal insulating layer 13) = π × R, where R is the diameter of the internal insulating layer 13. Therefore, the circumferential length of the electrostatic shield layer 15 can be formed to be shorter than this. In other words, (circumferential length of the electrostatic shield layer 15) < πR.

[0059] Furthermore, the larger the gap 15a, the greater the noise picked up. On the other hand, if the gap 15a is made smaller, the conductive fabric is formed from woven polymer fibers to enhance its resistance to bending. Therefore, a smaller gap 15a of 0.1 mm or greater is preferable because it poses a risk of short circuits due to loose fibers at the cut surface. Furthermore, when processing conductive fabric with precision, cutting machines are typically set in 0.5 mm increments, so dimensions are set in 0.5 mm increments that are less than the circumference of the internal insulating layer 13 of the Rogowski sensor. Based on these conditions, the minimum requirement for gap 15a is 0.1 mm or greater, and the circumferential length of the electrostatic shield layer 15 should be set to a maximum length in 0.5 mm increments that is less than (the circumferential length of the internal insulating layer 13) = πR.

[0060] For example, when R=1.0 mm, the circumferential length of the inner insulating layer 13 is approximately 3.14 mm. Since the maximum length in 0.5 mm increments is 3.0 mm, the gap is 3.14 mm - 3.0 = 0.14 mm. This is greater than 0.1 mm, so it satisfies the minimum condition. Similarly, when R=2.0 mm, the circumferential length of the inner insulating layer 13 is approximately 6.28 mm. Since the maximum length in 0.5 mm increments is 6.0 mm, the gap is 6.28 mm - 6.0 = 0.28 mm. This is greater than 0.1 mm, so it satisfies the minimum condition.

[0061] The exterior coating 16 is provided around the outside of the electrostatic shielding layer 15 in the circumferential direction. The exterior coating 16 is made of a low-dielectric-constant material from the viewpoint of electrical insulation. The exterior coating 16 is also preferably scratch-resistant, heat-resistant, and flame-retardant. From these viewpoints, the exterior coating 16 can be made of, for example, a fluororesin heat-shrinkable tube. When the exterior coating 16 is formed from a heat-shrinkable tube, the external dimensions are not affected, and the contact pressure between the electrostatic shielding layer 15 and the connecting wires 14 is ensured by the pressure generated when the heat-shrinkable tube shrinks during the formation of the exterior coating, ensuring electrical continuity.

[0062] (integrator circuit) 1, the integrating circuit 20 converts a detection signal indicating a voltage induced in the conductive wire 11 of the detecting body 1 by a current flowing through the object to be measured into a signal proportional to the amplitude of the current flowing through the object to be measured. The integrating circuit 20 outputs the converted signal to the measuring unit 40 as a detection signal.

[0063] (Measurement part) As shown in FIG. 1, the measurement unit 30 measures a physical quantity related to the measurement object based on a detection signal from the integration circuit 20. For example, when the measurement unit 30 receives a detection signal from the integration circuit 20, it measures the AC current flowing through the measurement object based on the detection signal. The measurement unit 30 may also measure other physical quantities, such as AC power or magnetic field strength, based on the received detection signal. The measurement unit 30 displays a waveform of the measured physical quantity on a screen. The measurement unit 30 is configured, for example, by an oscilloscope, a wattmeter, or an ammeter.

[0064] <Measuring device usage> FIG. 5 shows the arrangement of the current sensor 10 in the measuring device 100 when measuring the current of the electronic component 90.

[0065] 5 , when measuring the current of an electronic component 90, the current sensor 10 of the measuring device 100 of this embodiment performs the measurement with the terminals (legs) 91 of the electronic component 90 surrounded by the detection body 1 and the tip 1a of the detection body 1 inserted into the insertion portion 22 of the holding portion 2. In order to surround the terminals 91 of the electronic component 90 with the detection body 1, it is necessary to insert the detection body 1 of the current sensor 10 between the terminals 91 and 92 of the electronic component 90.

[0066] (Procedure for placing the detector on the measurement target) Next, we will explain the procedure for measuring a measurement target using the measuring device 100, where terminals 91 of an electronic component 90 mounted on a board are the measurement target, and the procedure for surrounding the terminals of the electronic component with the detection main body 1. Figure 6 is a diagram for explaining the procedure for sending the tip 1a of the detection main body 1 from behind the terminals 91 of the electronic component 90 to the front.

[0067] 6, an electronic component such as an integrated circuit (IC) or a DC / DC converter is used as the electronic component 90. The distance between terminals 91 and 92 of the electronic component 90 is about several mm (millimeters). The thickness (diameter) of the detection body 1 is set to, for example, 1 mm or more and 2.5 mm or less so that the detection body 1 can fit into the gap between the terminals 91 and 92.

[0068] As shown in Figure 6(a), the worker holds the holding portion 2 between his fingertips and moves the holding portion 2 toward the terminal 91, thereby inserting the tip 1a of the detection body 1 between the electronic component 90 and the terminal 91.

[0069] At this time, the tip 1c of the detection body 1 is formed with a curvature equal to or greater than the curvature (reference curvature) when the current sensor 10 is closed, so when the tip 1c of the detection body 1 is inserted behind the terminal 91, the tip 1a of the detection body 1 can be moved to cover the back of the terminal 91. This makes it possible to prevent the detection body 1 from getting caught on the edge of the terminal 91 and being damaged.

[0070] Furthermore, because the tip 1c of the detection body 1 is formed with a curvature equal to or greater than the curvature when the current sensor 10 is in the closed state, the tip 1a of the detection body 1 that has passed behind the terminal 91 is more likely to face from the back surface to the front surface of the terminal 91 in the insertion direction A of the detection body 1. This makes it easier for the worker to butt the tip 1a of the detection body 1 against the side surface of the terminal 92 in order to bring the tip 1a of the detection body 1 in front of the terminal 91. This makes it possible to pass the tip 1a of the detection body 1 through the narrow gap between the terminal 92 and the terminal 91 from the back surface to the front surface of the terminal 91.

[0071] It is preferable that the radius of curvature of the tip 1c of the detection body 1 is smaller than the distance between the terminals 91 and 92 of the electronic component 90. In particular, by forming the radius of curvature of the tip 1c to be 2 mm or more and 4 mm or less, it is possible to prevent the edge of the terminal 92 provided on the electronic component 90 from getting caught on the detection body 1 and damaging the detection body 1.

[0072] 6(b), the operator further moves the holding part 2 in the insertion direction A so as to press the middle part 1d of the detection body 1 against the electronic component 90 behind the terminal 91. As a result, the middle part 1d of the detection body 1 is pressed against the electronic component 90, and this part serves as a fulcrum to orient the detection body 1 toward the inside B, making it less likely for the detection body 1 to get caught on the edges of the terminals 91 and 92. This makes it less likely for the detection body 1 to be scratched.

[0073] 6(c), the operator pushes in the holding portion 2 in the insertion direction A, thereby sending out the remaining detection body 1 toward the rear of the terminal 91. At this time, the curvature of the middle portion 1d of the detection body 1 is smaller than the curvature when the current sensor 10 is closed toward the holding portion 2, so that the tip portion 1c of the detection body 1 can be brought close to the insertion portion 22 of the holding portion 2 while preventing the detection body 1 from bending.

[0074] Thereafter, the operator inserts tip 1c of detection body 1 into insertion portion 22, thereby surrounding the measurement target with detection body 1. In this way, in current sensor 10, terminal 91 can be easily surrounded by detection body 1 with the operator's hands.

[0075] As explained using FIGS. 6(a) to 6(c), when an electronic component 90 is to be measured, the detection body 1 must be passed through a small gap to surround the terminals 91 of the electronic component 90. To pass through a small gap, the curvature of the detection body 1 must be different from the curvature when the tip 1a of the detection body 1 is inserted into the insertion portion 22 of the holding portion 2. Therefore, the detection body 1 must be frequently bent and stretched during measurement. The current sensor 10 of the measuring device 100 of this embodiment uses a flexible electrostatic shield layer 15, ensuring durability to withstand repeated changes in curvature. In particular, when a conductive fabric is used as the electrostatic shield layer 15, durability and flexural modulus can be ensured, since the sensor portion must be frequently bent when being attached to the measurement object through a narrow space.

[0076] Furthermore, even when measuring electronic components that process large signals at high frequencies, such as current measurements on next-generation switching power devices made up of discrete ICs, the influence of common-mode voltages can be reduced because the device is equipped with an electrostatic shield layer 15 that shields the conductive wire 11 that makes up the Rogowski coil.

[0077] The electrostatic shield layer 15 is provided so as to form a gap 15a in the circumferential direction outside the inner insulating layer 13 without making a full turn, and does not form a single turn in the same direction as the winding direction of the Rogowski coil. With this configuration, the electrostatic shield layer 15 does not act as a coil, and it is possible to avoid adverse effects on the frequency characteristics.

[0078] The inner insulating layer 13 is made of a low dielectric constant material, which can reduce the parasitic capacitance that occurs between the electrostatic shield layer 15 and the conductive wire 11 that constitutes the Rogowski coil when measuring high-frequency signals.

[0079] <Modifications of the embodiment> Although the measuring device of the above embodiment has been described using a specific example, it is not limited to this and various modifications can be adopted. For example, the configuration of the measuring device 100 is not limited to the configuration shown in Fig. 1. For example, although the connection wire 14 is provided between the inner insulating layer 13 and the electrostatic shielding layer 15, the connection wire 14 may be provided between the electrostatic shielding layer 15 and the exterior coating 16.

[0080] The shape of the holding portion 2 may be L-shaped, round, or other shapes. The detection body 1 may be made of not only an elastically deformable material but also a plastically deformable material.

[0081] Regarding the curvature of the detection body 1, various combinations of curvatures other than those mentioned above can be adopted, and the curvature does not have to be given in advance.

[0082] In the above embodiment, the winding core is hollow, and the conductive wire is spirally wound around the winding core, turns back at the tip of the winding core, passes through the hollow interior of the winding core, and returns to the base end. However, the configuration of the winding core and the conductive wire are not limited to this. For example, the winding core may be solid rather than hollow. In this case, the winding core may be configured so that the conductive wire is spirally wound around the winding core, turns back at the tip of the winding core, and then runs around the outside of the winding core and returns to the base end. In this case, the base end and the tip end are concepts that include the tip 1a and the base 1b of the detection body 1, respectively.

[0083] In the above embodiment, the holder 2 includes the fixed portion 21 and the insertion portion 22 having the insertion opening 22a, but the present invention is not limited to this. The holder 2 may have any configuration as long as it is configured to receive the base end 1e of the detection main body 1 and to hold the tip end 1c of the detection main body 1. For example, a groove into which the tip end 1c is fitted may be used as the configuration for holding the tip end 1c of the detection main body 1. [Explanation of symbols]

[0084] 100 Measuring device, 10 Current sensor, 1 Detection body, 1a Tip, 1b Base end, 1c Tip portion, 1d Middle portion, 1e Base end, 11 Conductive wire, 12 Winding core, 13 Internal insulating layer, 14 Connection wire, 15 Electrostatic shield layer, 16 Outer coating, 2 Holding portion, 21 Fixing portion, 22a Insertion port, 22 Insertion portion, 23 Matching circuit, 3 Cable, 20 Integration circuit, 30 Measurement portion, 90 Electronic component, 91, 92 Terminal

Claims

1. A current sensor comprising: a flexible detection body that surrounds a measurement object and detects a physical quantity of the measurement object; and a holding part to which a base end of the detection body is attached and that holds a tip end of the detection body, The detection body includes: a conductive wire that is spirally wound around a winding core, folded back at a front end of the winding core, and returned to a base end of the winding core; an inner insulating layer provided around the spirally wound conductive wire in a circumferential direction; a conductive electrostatic shield layer provided around the inner insulating layer in a circumferential direction thereof so as to form a gap without going around the entire circumference; an exterior coating provided around the electrostatic shield layer in a circumferential direction; and the electrostatic shield layer has a circumferential length shorter than that of the inner insulating layer, the outer covering is a heat-shrinkable tube adjacent to the electrostatic shielding layer; Current sensor.

2. A conductive connection wire, the connecting wire is provided between the inner insulating layer and the electrostatic shielding layer or between the electrostatic shielding layer and the outer coating; The current sensor according to claim 1 .

3. The electrostatic shielding layer is a conductive cloth.

3. The current sensor according to claim 1.

4. The electrostatic shield layer is made of a low magnetic material.

4. The current sensor according to claim 1.

5. The inner insulating layer is made of a low dielectric constant material.

5. The current sensor according to claim 1.

6. The measurement object is an electronic component.

6. A current sensor according to any one of claims 1 to 5.

7. A current sensor according to any one of claims 1 to 6; a measurement unit that measures a physical quantity of the measurement object based on a detection signal detected by the current sensor; A measuring device comprising:

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