JP2009092538A - Clamp tester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a clamp tester capable of accurately measuring a minute amount of DC current even in a noisy electromagnetic environment. <P>SOLUTION: The clamp tester 30 includes: a ring-shaped clamp part 32 configured to open in a C shape by separating a prescribed portion, so as to enable an electric cable to be clamped in its live-wire state; a head core 53 which is built in the clamp part 32 and has a magnetic core 61 composed of a magnetic material; a magnetic sensor 55 for detecting the strength of a magnetic field passing in the magnetic core 61; and a current measuring means 54 for computing the DC current flowing in the electric cable, based on the strength of the magnetic field detected by the magnetic sensor 55. Nonmagnetic material members 62, 63 and 64 are attached to the outer wall surface of at least a portion of the magnetic core 61, and tabular magnetic members 66, 67 are attached to the outer wall surface of at least a portion of the nonmagnetic material members 62, 63 and 64. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a clamp tester capable of measuring a value of a direct current flowing through an electric wire by clamping an electric wire through which a direct current flows.

2. Description of the Related Art Conventionally, a clamp tester that can measure the value of a current flowing through an electric wire while keeping the state of a live wire without connecting or disconnecting the electric wire is known (see, for example, Patent Document 1).
In addition, a tester for measuring a direct current flowing through an electric wire passes through the magnetic core with a magnetic core for forming a magnetic path of a magnetic field generated around the electric wire and a part of the magnetic core notched. A hall element for detecting the magnetic field strength and a calculation unit for calculating a direct current flowing in the electric wire based on the voltage value output by the hall element, and the current value calculated by the calculation unit is digitally displayed on the display unit Has been conventionally known (for example, see Patent Document 2).

JP-A-6-235735 JP 2007-78374 A

In recent years, it has become necessary to measure a weak DC current, and the clamp tester is also configured to be able to measure a weak DC current on the order of mA.
However, for example, when measuring a weak DC current in wiring in an engine room of a vehicle, there is a problem that there is a possibility that accurate DC current cannot be measured because there is too much electromagnetic noise.

  Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a clamp tester capable of accurately measuring a weak direct current in the order of mA even in an environment with a lot of electromagnetic noise. There is.

According to the clamp tester of the present invention, a ring-shaped clamp portion provided so as to be split into a predetermined portion and opened in a C shape so that the electric wire can be clamped in a live state, and the clamp A magnetic core formed of a magnetic material and a head core having a magnetic sensor for detecting the strength of a magnetic field passing through the magnetic core, and an electric wire based on the strength of the magnetic field detected by the head core. A clamp tester comprising a current measuring means for calculating a flowing direct current, wherein a flat non-magnetic member is attached to at least a part of the outer wall surface of the magnetic core, and at least one of the non-magnetic members. A flat magnetic member is attached to the outer wall surface of the unit.
By adopting this configuration, it is possible to accurately measure a weak direct current even if there is electromagnetic noise in the surroundings. The reason is that by attaching a flat non-magnetic member to a part of the outer wall surface of the magnetic core, the non-magnetic member is magnetized so that the magnetic field constituting the surrounding noise does not enter the magnetic core. Can be a shield. Further, by disposing the magnetic member outside the non-magnetic member, the magnetic field constituting the surrounding noise generates magnetic lines of force using the magnetic member as a magnetic path. The lines of magnetic force that flow using this magnetic member as a magnetic path flow in parallel in the flat plate-like magnetic member, so there is no risk of entering the non-magnetic member. Therefore, it is considered that by providing a flat magnetic member on the outer wall surface of the nonmagnetic member, a higher magnetic shielding effect can be achieved than when a magnetic shield is formed only by the nonmagnetic member.

The nonmagnetic member and the magnetic member may be attached to an outer wall surface other than the inner wall surface facing the inside of the clamp portion of the magnetic core.
According to this configuration, the magnetic field generated based on the weak current flowing through the electric wire can be surely passed through the magnetic core while shielding the surrounding magnetic field, which is noise, and an accurate DC current value can be obtained. It can be measured. That is, on the side facing the electric wire arranged to be measured inside the clamp part, the non-magnetic member and the magnetic member are not attached, and the magnetic core is exposed. A magnetic field generated based on a weak current flowing through the electric wire can be reliably detected without shielding.

The non-magnetic material may be brass, and the magnetic material may be permalloy.
Further, the magnetic member may be attached to an upper surface and a lower surface of the head core.

  According to the clamp tester of the present invention, it is possible to reliably measure even a weak DC current without being affected by ambient noise.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.
First, the external appearance structure of the clamp tester of this embodiment is shown in FIGS.
The clamp tester 30 is configured by providing a ring-shaped clamp portion 32 at the tip of a substantially rectangular parallelepiped body portion 31. The clamp part 32 is divided in a semicircular shape in the middle part, and one of the divided parts rotates on the main body part 31 side, so that the clamp part 32 opens in a C shape.
The main body 31 is of a size that can be grasped by the operator's hand, and the display unit 34 is arranged on the surface. The display unit 34 uses an LCD. However, the configuration of the display unit 34 is not particularly limited to the LCD.
The main body 31 is provided with a power switch 36.

Further, a lever 42 for opening and closing the clamp portion 32 is provided on the side surface on the distal end side of the main body portion 31. The lever 42 is provided so as to have a position and size that can be operated by a hand held by an operator.
When the lever 42 is operated in the direction of the broken line arrow in FIG. 1, the movable-side clamp part 32a of the divided clamp part 32 rotates about the main body part 31 side as an axis, and the divided part opens (broken line in FIG. 1). In this way, the electric wire can be accommodated inside the circle of the clamp portion 32 while being a live wire.

Next, the schematic internal configuration of the present embodiment will be described with reference to FIG.
Inside the clamp tester 30 are provided a measuring means 46 for measuring a direct current and a display unit 34 for displaying a direct current value measured by the measuring means 46.

  Specifically, the measuring means 46 is applied to the head core 53 based on the head core 53 disposed inside the clamp portion 32, the Hall element 55 provided in the head core 53, and the output voltage value detected by the Hall element 55. It comprises a current measuring circuit 54 that calculates the magnetic field strength and measures the current value based on the magnetic field strength. Here, the Hall element is taken as an example of the magnetic sensor for measuring the magnetic field strength, but another sensor such as a magnetoresistive element may be used as the magnetic sensor for measuring the magnetic field intensity.

  The head core 53 is composed of two magnetic cores that are formed in a substantially semicircular shape. That is, the head core 53 is disposed on both of the divided clamp portions 32 and is magnetically coupled to form a ring-shaped core when the clamp portion 32 is in a circular shape. The head core 53 disposed in the movable clamp portion 32a is the movable core 53a, and the head core 53 disposed in the fixed clamp portion 32b is the fixed core 53b.

When a direct current is measured, by arranging the electric wire that is a live wire inside the circle of the clamp portion 32, a magnetic field is generated along with the current flowing through the electric wire along the circumference of the clamp portion 32. This magnetic field uses a magnetic path in the head core 53, and magnetic lines of force based on the magnetic field pass through the head core 53.
The Hall element 55 provided in the head core 53 generates an electromotive force having a strength based on this magnetic field. The current measurement circuit 54 calculates the current value of the direct current flowing through the measurement target electric wire based on the electromotive force generated in the Hall element 55, and the calculated current value is transmitted to the control means 50 described later.

The control unit 50 includes a CPU 56 and a storage unit 48 including a ROM and a RAM. Further, the control means 50 has an A / D converter 58, and the A / D converter 58 converts the current value input as an analog value from the current measurement circuit 54 into a digital value.
Further, the power switch 36 and the display unit 34 are connected to the control means 50.
The control unit 50 can perform a predetermined operation by reading and executing a control program stored in the storage unit 48 in advance.

Next, the head core will be described with reference to FIGS.
The head core 53 has a substantially semicircular movable side core 53a and a substantially semicircular fixed side core 53b. The movable side core 53a is disposed in the movable side clamp part 32a, and the fixed side core 53b is disposed in the fixed side clamp part 32b. Attachment holes 59, 59,... For attachment to the respective covers of the movable side clamp part 32a and the fixed side clamp part 32b are formed in each of the movable side core 53a and the fixed side core 53b.
When the clamp portion 32 is closed, a gap 60 is formed between the end face of the movable core 53a and the end face of the fixed core 53b. The hall element 55 is disposed in the gap 60.

As shown in FIG. 6, the magnetic core disposed at the center of the head core has a laminated structure.
FIG. 6 is a side view of the fixed core 53b as viewed from the AA direction in FIG. 5, and the end face to which the Hall element 55 is attached is shown.
The head core 53 has a magnetic core (laminated core) 61 formed by laminating flat magnetic materials. A permalloy etc. can be mention | raise | lifted as a magnetic material. Permalloy has a high magnetic permeability and is preferable as a core material. However, the material of the magnetic core 61 is not limited to permalloy, and may be other magnetic bodies such as iron.

A magnetic shield member 62 (non-magnetic member referred to in the claims) made of a non-magnetic material is attached to the outer peripheral side wall surface of the magnetic core 61. Thereby, the influence of the magnetic noise from the outer peripheral side of the head core 53 can be reduced. Attachment of the magnetic shield member 62 to the outer peripheral side wall surface of the magnetic core 61 is performed using an adhesive or the like.
Magnetic shield members 63 and 64 made of a non-magnetic material are attached to the upper and lower surfaces of the magnetic core 61, respectively. The magnetic shield members 63 and 64 are attached to the upper and lower surfaces of the magnetic core 61 using an adhesive or the like. Here, the upper surface and the lower surface of the magnetic core are the upper surface when the direction along the axial direction of the electric wire to be clamped is the vertical direction, and the lower surface is the side where the display portion 34 is not provided. It is said.
It is preferable to use brass as the magnetic shield members 62, 63, 64 described above. This is because brass is easily available among non-magnetic materials and is advantageous in terms of cost, and it has been proved experimentally that the magnetic shielding effect is high. Aluminum, copper, or the like can be used as a material other than brass.

  Further, flat magnetic members 66 and 67 are attached to the outer sides of the magnetic shield members 63 and 64 attached to the upper and lower surfaces of the magnetic core 61. Here, as the flat magnetic members 66 and 67, the same material as that of the magnetic core 61 can be used. Specifically, it is preferable to use permalloy. The flat magnetic members 66 and 67 are attached to the magnetic shield members 63 and 64 using an adhesive or the like.

  As described above, by providing the flat magnetic members 66 and 67 on the outer side of the magnetic shield members 63 and 64, magnetic noise from the outside is magnetized in the flat magnetic members 66 and 67. Magnetic field lines can flow in parallel to the body members 66 and 67, and the entry of the magnetic field lines to the magnetic shield members 63 and 64 can be reduced, so that a weak DC current can be detected more reliably.

  Further, the magnetic shield member is not attached to the inside of the ring shape of the head core 53. This is because the electric wire to be measured is arranged inside the head core 53, so that a magnetic field based on a weak DC current flowing through the electric wire can be reliably detected.

  In FIG. 5, the magnetic shield members 62, 63, 64 and the magnetic members 66, 67 are not provided at the fixed side end of the magnetic core 61 of the movable core 53 a, and the magnetic core 61 is about 1 mm. Although there is a part that is exposed, this is done due to manufacturing problems such as attachment of the movable side core 53a to the movable side clamp part 32a.

In the embodiment described above, the magnetic member is provided on the outer side of the magnetic shield members on the upper and lower surfaces of the head core. However, the present invention is not limited to this configuration, and a magnetic member may be provided outside the magnetic shield member on the outer peripheral surface of the head core in addition to the upper and lower surfaces of the head core.
Further, the magnetic member may not be provided on the magnetic shield members on the upper and lower surfaces of the head core, but may be provided only on the outer side of the magnetic shield member on the outer peripheral surface.

  While the present invention has been described in detail with reference to a preferred embodiment, the present invention is not limited to this embodiment, and it goes without saying that many modifications can be made without departing from the spirit of the invention. .

It is a top view of the clamp tester of the present invention. It is a side view of the clamp tester of FIG. It is a bottom view of the clamp tester of FIG. It is a block diagram explaining the internal structure of the clamp tester of this invention. It is a top view of a head core. It is a side view of a fixed side core among the head cores shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 Clamp tester 31 Main body part 32 Clamp part 32a Movable side clamp part 32b Fixed side clamp part 34 Display part 36 Power switch 42 Lever 46 Measuring means 48 Storage means 50 Control means 53 Head core 53a Movable side core 53b Fixed side core 54 Current measurement circuit 55 Hall element 56 CPU
58 A / D converter 59 Mounting hole 60 Air gap 61 Magnetic core 62, 63, 64 Magnetic shield member 66, 67 Magnetic member

Claims (4)

A ring-shaped clamp part that is provided so as to be split in a predetermined portion and opened in a C-shape so that the electric wire can be clamped in a live state,
A head core having a magnetic core built in the clamp portion and made of a magnetic material;
A magnetic sensor for detecting the intensity of a magnetic field passing through the magnetic core;
A clamp tester comprising current measuring means for calculating a direct current flowing in the electric wire based on the intensity of the magnetic field detected by the magnetic sensor,
A flat non-magnetic member is attached to at least a part of the outer wall surface of the magnetic core, and a flat magnetic member is attached to at least a part of the outer wall surface of the non-magnetic member. Clamp tester featuring.   2. The clamp tester according to claim 1, wherein the non-magnetic member and the magnetic member are attached to an outer wall surface other than the inner peripheral surface facing the inside of the clamp portion of the magnetic core.   The clamp tester according to claim 1, wherein the non-magnetic material is brass, and the magnetic material is permalloy.   The said magnetic body member is attached to the outer side of the nonmagnetic body member attached to the upper surface and lower surface of a magnetic body core, The any one of Claims 1-3 characterized by the above-mentioned. Clamp tester.

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