JP2022074306A - Current sensor and electricity meter - Google Patents

Abstract

To provide a current sensor and an electricity meter that are capable of measuring a current with high accuracy by reducing the influence of an external magnetic field, capable of being downsized, and capable of reducing cost.SOLUTION: A current sensor comprises: a conductor 21 through which a current to be measured flows; a pair of magnetism collection cores 11a, 11b that are arranged to face each other across an air gap g, and that collect magnetic fluxes generated by the current to be measured; coil patterns 13a, 13b that are arranged in the air gap g, and that act as magnetism detection means in which an induction voltage is generated due to interlinkage of magnetic fluxes; and calculation means for calculating the current to be measured on the basis of the induction voltage. The coil patterns 13a, 13b are arranged at a substantially equal distance from opposed surfaces of the pair of magnetism collection cores 11a, 11b forming the air gap g. Electric energy is measured using a current and a voltage respectively detected by the current sensor and a voltage sensor.SELECTED DRAWING: Figure 1

Description

The present invention relates to a current sensor that magnetically measures the current flowing through a conductor, and a watt-hour meter provided with the current sensor.

Conventionally, as this type of current sensor, a current transformer (CT), a magnetic / electric conversion element such as a Hall element or a coil arranged in a gap portion (gap portion) of the magnetic collection core, and a gap portion of the magnetic collection core are also used. It is known that a coil pattern on a printed circuit board is arranged on the printed circuit board.
Since these current sensors are electrically separated from the primary side circuit through which the measured current flows, the current can be measured with high accuracy without adversely affecting the primary side circuit.

Among the above-mentioned current sensors, in particular, a current sensor in which a coil pattern on a printed circuit board is arranged as a magnetic detection means in a gap of a magnetic collecting core is excellent in linearity and temperature characteristics, has a small number of parts, and is easy to manufacture. For example, it is described in Patent Document 1.
FIG. 10 is a schematic configuration diagram of the current sensor described in Patent Document 1. This current sensor forms an entire ring by abutting the end faces of a pair of substantially U-shaped magnetic collecting cores 51a and 51b through a gap portion, and a bar through which a current to be measured flows flows through the central opening thereof. The coil patterns 53a and 53b connected in series to each other on the printed circuit board 52 are arranged in the gap portion while penetrating the conductor 61 in the shape of the shape.

In the above configuration, when the measured current flows through the conductor 61, a magnetic flux F1 proportional to the magnitude of the measured current is generated around the conductor 61, and this magnetic flux F1 is magnetized by the magnetic collecting cores 51a and 51b. .. When the measured current changes periodically, the magnetic flux F1 also changes periodically, and an induced voltage having the same polarity according to the magnitude and frequency of the measured current is generated in the coil patterns 53a and 53b. By integrating this induced voltage with the integrator circuit 71, a voltage signal corresponding to the measured current can be obtained.

In FIG. 10, F2 is a magnetic flux generated by an external magnetic field and orthogonal to the printed circuit board 52, and the induced voltages generated in the coil patterns 53a and 53b by this magnetic flux F2 are canceled out because they have opposite polarities. Therefore, the integrating circuit 71 can measure the current flowing through the conductor 61 with high accuracy based only on the induced voltage generated by the magnetic flux F1.

Japanese Unexamined Patent Publication No. 2009-210406 ([0018]-[0021], FIG. 3, etc.)

In the current sensor of FIG. 10, when the coil patterns 53a and 53b are displaced from the vertical center position of the gap portion and are arranged near the end surface of any of the magnetic collecting cores 51a and 51b, the direction parallel to the printed substrate 52 is obtained. When the external magnetic field is present, the induced voltages of the coil patterns 53a and 53b are affected by the external magnetic field, so that the current flowing through the conductor 61 cannot be accurately measured.
In order to reduce the influence of the external magnetic field, the conductor 61 is arranged at the center of the central opening of the magnetic collecting cores 51a and 51b, and the coil patterns 53a and 53b are located at the center position in the vertical direction of the gap portion. It is desirable to arrange the printed circuit board 52, but such an arrangement is physically impossible because the conductor 61 and the printed circuit board 52 interfere with each other.

Further, in the structure of FIG. 10, since the conductor 61 is arranged above the printed circuit board 52, the size of the central opening of the magnetic collecting cores 51a and 51b is at least the thickness of the printed circuit board 52 and the diameter of the conductor 61. This made it difficult to reduce the size of the magnetic collecting cores 51a and 51b, and eventually to the size and cost of the current sensor.

Therefore, the solution to the present invention is to provide a current sensor capable of reducing the influence of an external magnetic field to measure a current with high accuracy, reducing the cost, and reducing the size. It is an object of the present invention to provide an electric energy meter using this current sensor.

In order to solve the above problem, the current sensor according to claim 1 is
The conductor through which the measured current flows and
A magnetic collecting core having a pair of facing surfaces forming a gap and collecting magnetic flux generated by the measured current,
A magnetic detection means that is arranged in the gap and that the magnetic flux interlinks to generate an induced voltage.
An arithmetic means for calculating the measured current based on the induced voltage, and
In a current sensor equipped with
The magnetic detection means is arranged at positions substantially equidistant from the pair of facing surfaces.

The current sensor according to claim 2 is
The conductor through which the measured current flows and
A magnetic collecting core having a pair of facing surfaces forming a gap and collecting magnetic flux generated by the measured current,
A magnetic detection means that is arranged in the gap and that the magnetic flux interlinks to generate an induced voltage.
An arithmetic means for calculating the measured current based on the induced voltage, and
In a current sensor equipped with
It is characterized in that the printed circuit board is arranged so that the center line of the plate thickness of the printed circuit board provided with the magnetic detection means is located at positions substantially equidistant from the pair of facing surfaces.

The current sensor according to claim 3 is the current sensor according to claim 1 or 2.
The magnetic detection means is formed by a coil pattern on a printed circuit board.

The current sensor according to claim 4 is the current sensor according to claim 3.
It is characterized in that a plurality of the coil patterns are arranged in the gap portion formed by facing the first magnetic collecting core and the second magnetic collecting core, and the coil patterns are connected in series.

The current sensor according to claim 5 is the current sensor according to any one of claims 2 to 4.
It is characterized in that the conductor is arranged substantially on the center line of the plate thickness of the printed circuit board.

The current sensor according to claim 6 is the current sensor according to any one of claims 3 to 5.
A plurality of the coil patterns are formed on a single printed circuit board.

The current sensor according to claim 7 is the current sensor according to any one of claims 3 to 5.
It is characterized in that a plurality of the coil patterns are each formed on the individual printed circuit boards.

The current sensor according to claim 8 is the current sensor according to any one of claims 2 to 7.
The conductor is arranged in a notch formed in the printed circuit board.

The current sensor according to claim 9 is the current sensor according to any one of claims 2 to 7.
It is characterized in that the printed circuit board is passed through the through hole formed in the conductor.

The current sensor according to claim 10 is the current sensor according to any one of claims 3 to 9.
The printed circuit board is configured by laminating a plurality of unit substrates, and the coil pattern is formed on the front surface or the back surface of the unit substrate.

The electric energy meter according to claim 11 includes the current sensor according to any one of claims 1 to 10, a voltage sensor that measures a voltage between a plurality of conductors including the conductor, and current detection by the current sensor. It is characterized by including a power amount calculation unit for calculating a power amount using a value and a voltage detection value by the voltage sensor.

According to the current sensor according to the present invention, a magnetic detecting means such as a coil pattern is arranged at a position substantially equal to the facing surface of the magnetic collecting core forming the gap portion, or a print provided with the magnetic detecting means. By arranging the printed circuit board so that the center line of the plate thickness of the substrate is located, the influence of the external magnetic field can be reduced and the current can be measured with high accuracy. Further, by improving the relative position between the printed circuit board and the conductor, it is possible to reduce the size and cost of the current sensor and the watt-hour meter using the current sensor.

1 is a front view (FIG. 1 (a)) and a perspective view (FIG. 1 (b)) showing a first embodiment of the current sensor according to the present invention, and an enlarged front view (FIG. 1 (c)) of a main part. It is a top view of the printed circuit board and the coil pattern in FIG. 2 is a front view (FIG. 3 (a)) and a perspective view (FIG. 3 (b)) showing a second embodiment of the current sensor according to the present invention. It is a front view (FIG. 4 (a)) and a characteristic diagram (FIG. 4 (b)) for demonstrating the operation of the current sensor shown in FIG. It is a front view (FIG. 5 (a)) and a perspective view (FIG. 5 (b)) which show the 3rd Embodiment of the current sensor which concerns on this invention. It is a front view (FIG. 6 (a)) and a perspective view (FIG. 6 (b)) which show 4th Embodiment of the current sensor which concerns on this invention. It is a front view (FIG. 7A) and the perspective view (FIG. 7B) which show 5th Embodiment of the current sensor which concerns on this invention. It is a front view (FIG. 8 (a)) which shows the 6th Embodiment of the current sensor which concerns on this invention, and is the front view (FIG. 8 (b)) which shows the 7th Embodiment. It is a block diagram of the electric energy meter which concerns on this invention. It is a schematic block diagram of the current sensor described in Patent Document 1.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A and 1B are a first embodiment of a current sensor according to this embodiment, FIG. 1A is a front view, FIG. 1B is a perspective view, and FIG. 1C is an enlarged front view of a main part. be.
In FIGS. 1A and 1B, substantially U-shaped magnetic collecting cores 11a and 11b are butted with each other through the gap g, and a bar-shaped current to be measured flows in the center of the central opening 30. The conductor 21 penetrates in the direction orthogonal to the paper surface.

Plate-shaped printed circuit boards 12a and 12b are arranged in the gaps g, respectively, and on their surfaces, the magnetic flux generated by the current to be measured and passing through the magnetic collecting cores 11a and 11b is interlinked. Coil patterns 13a and 13b as magnetic detection means are formed, respectively. The coil patterns 13a and 13b are connected in series, and the output voltage of the series circuit is input to an integrating circuit as an arithmetic means for calculating the measured current as shown in FIG. 10 described above, and the coil patterns 13a and 13b are input to the coil patterns 13a and 13b. The voltage proportional to the induced voltage generated in (in other words, the magnitude of the measured current) is calculated.
Note that FIG. 2 is a plan view showing an example of the coil patterns 13a and 13b on the printed circuit boards 12a and 12b. Needless to say, the shapes of the printed circuit boards 12a and 12b and the coil patterns 13a and 13b are not limited to the example shown in FIG.

Returning to FIG. 1, (c) is an enlarged front view of the vicinity of the gap portion g.
The coil pattern 13a on the printed circuit board 12a is arranged at a distance Lg substantially equal to the end faces (opposing surfaces facing the printed circuit board 12a) _11a'and 11b' of the magnetic collecting cores 11a and 11b. Although only the coil pattern 13a on one printed circuit board 12a is shown in FIG. 1 (c), the end faces (printed) of the magnetic collecting cores 11a and 11b are also shown for the coil pattern 13b on the other printed circuit board 12b. It is arranged at an approximately equal distance _Lg from the surface facing the substrate 12b).
Here, as shown in FIG. 1 (c), if the conductor 21 is arranged on the center line c of the plate thickness of the printed circuit boards 12a and 12b, the area of the central opening 30 is smaller than that of the conventional structure of FIG. This makes it possible to reduce the size of the magnetic collecting cores 11a and 11b, and thus the overall size of the current sensor.

Next, FIG. 3 is a second embodiment of the current sensor, FIG. 3A is a front view, and FIG. 3B is a perspective view.
In this second embodiment, linear magnetic collecting cores 11c and 11d are used instead of the substantially U-shaped magnetic collecting cores 11a and 11b in the first embodiment. Also in this embodiment, the coil patterns 13a and 13b on the printed circuit boards 12a and 12b are arranged at substantially the same distance _Lg from the inner surface of the magnetic collecting cores 11c and 11d (the surface facing the printed circuit boards 12a and 12b). ..

FIG. 4 shows the vertical positions of the coil patterns 13a and 13b (distance L in FIG. 3A) when an external magnetic field in a direction parallel to the printed substrates 12a and 12b acts on the second embodiment described above. The relationship between the position in the _g direction) and the error of the induced voltage of the coil patterns 13a and 13b due to the external magnetic field is shown. In FIG. 4B, the vertical position when the coil patterns 13a and 13b are at a distance _Lg substantially equal to the facing surfaces of the magnetic collecting cores 11c and 11d is set to 0 [mm], and the error in that case is 0. It is set to [%].

As is clear from FIG. 4B, the vertical position and the error of the induced voltage are almost proportional to each other. Therefore, if the coil patterns 13a and 13b are arranged at approximately the same distance _Lg from the facing surfaces of the magnetic collecting cores 11c and 11d, the induced voltage due to the coil patterns 13a and 13b is not affected by the external magnetic field and the error is the smallest. Therefore, it becomes possible to accurately measure the measured current flowing through the conductor 21.
This also applies to the first embodiment shown in FIG. 1. By arranging the coil patterns 13a and 13b at substantially the same distance _Lg from the facing surfaces of the magnetic collecting cores 11a and 11b, the coil patterns 13a, The error of the induced voltage of 13b is the smallest.

Next, FIG. 5 is a front view (FIG. 5 (a)) and a perspective view (FIG. 5 (b)) showing a third embodiment of the current sensor.
In this third embodiment, coil patterns 13a and 13b are formed on the upper surfaces of both ends of a single substantially U-shaped printed circuit board 12c having a notch portion 12e, and these coil patterns 13a and 13b are formed in the gap portion g. The magnetic collecting cores 11a and 11b are arranged at approximately the same distance _Lg from the facing surfaces thereof. In this case, the conductor 22 through which the measured current flows is formed in a substantially L-shape so as to bend in the perpendicular direction at the notch portion 12e.

Also in this embodiment, by arranging the coil patterns 13a and 13b at approximately the same distance _Lg from the facing surfaces of the magnetic collecting cores 11a and 11b, the induced voltage of the coil patterns 13a and 13b is not affected by the external magnetic field. The error becomes smaller.
The structure of the printed circuit board 12c and the conductor 22 described above can also be used in combination with the linear magnetic collecting cores 11c and 11d shown in FIG.

Next, FIG. 6 is a front view (FIG. 6 (a)) and a perspective view (FIG. 6 (b)) showing a fourth embodiment of the current sensor.
In the fourth embodiment, the through holes 23a are formed in a part of the conductor 23, and the coil patterns 13a and 13b formed on the upper surfaces of both ends of the single printed circuit board 12d penetrated through the through holes 23a are linear. The magnetic collecting cores 11c and 11d are arranged at approximately the same distance _Lg from the facing surfaces.

Also in this embodiment, the error of the induced voltage of the coil patterns 13a and 13b can be reduced by arranging the coil patterns 13a and 13b at a distance _Lg substantially equal to the facing surfaces of the magnetic collecting cores 11c and 11d.
The structures of the printed circuit board 12d and the conductor 23 described above can also be used in combination with the substantially U-shaped magnetic collecting cores 11a and 11b shown in FIGS. 1 and 5.

As in the first to fourth embodiments described above, the arrangement structure in which the plate thickness of the printed circuit board is absorbed by the thickness of the conductor (as shown in FIG. 1C, the center of the plate thickness of the printed circuit boards 12a and 12b). If the conductor 21 is arranged on the wire c), the area of the central opening of the magnetic collecting core and the distance between the magnetic collecting cores can be reduced, and the current sensor can be made smaller and thinner. Become.

Further, FIG. 7 is a front view (FIG. 7 (a)) and a perspective view (FIG. 7 (b)) showing a fifth embodiment of the current sensor.
In the fifth embodiment, the printed circuit board 12d is arranged between the linear magnetic collecting cores 11c and 11d, and the conductor 21 is arranged between the printed circuit board 12d and one of the magnetic collecting cores 11d, and the printed circuit board 12d is arranged. The coil patterns 13a and 13b formed on the upper surfaces of both ends thereof are arranged at a distance _Lg substantially equal to the facing surfaces of the magnetic collecting cores 11c and 11d.

In this embodiment, the positional relationship between the printed circuit board 12d and the conductor 21 is almost the same as in FIG. 10, but the current sensor as a whole can be made thinner by forming the magnetic collecting cores 11c and 11d in a straight line. can. Further, as in the first to fourth embodiments, by making the distance Lg between the coil patterns 13a and 13b and the facing surfaces of the magnetic collecting cores 11c and _11d substantially equal, the induced voltage due to the coil patterns 13a and 13b is external. The error is small without being affected by the magnetic field.

In the first to fifth embodiments, the coil patterns 13a and 13b are formed only on the front surfaces of the printed circuit boards 12a, 12b, 12c and 12d, but the coil patterns are also formed on the back surface of each printed circuit board and the front surface and the back surface are formed. The coil patterns may be connected in series by a through hole or the like. That is, coil patterns may be formed on both the front and back surfaces of the printed circuit boards 12a, 12b, 12c, and 12d.

Next, FIG. 8A is a front view showing a sixth embodiment of the current sensor, and FIG. 8B is a front view showing the seventh embodiment as well.
In the first to fifth embodiments described above, a coil pattern is formed on the surface of a printed circuit board composed of a single substrate, but as described below, a plurality of substrates (hereinafter referred to as unit substrates) are laminated. A single printed circuit board is formed, a coil pattern is formed on the front or back surface of each unit board, and the center line of the thickness of the printed circuit board is located at approximately the same distance from the facing surface of the magnetic collecting core. A printed circuit board may be arranged.

That is, in the sixth embodiment of FIG. 8A, for example, four unit substrates 12e'and 12f' are laminated to form printed circuit boards 12e and 12f, respectively, and the surfaces of the unit substrates 12e'and 12f' are formed. Alternatively, it is an example in which the coil patterns 13a and 13b are formed on the back surface, and in the seventh embodiment of FIG. 8B, two unit substrates 12g'and 12h' are laminated to form a printed circuit board 12g and 12h, respectively. This is an example in which coil patterns 13a and 13b are formed on the front surface or the back surface of each unit substrate 12g'and 12h'. Here, the number of laminated unit substrates constituting each printed circuit board is not limited to the above example, and is arbitrary.
In this way, the idea of stacking a plurality of unit substrates to form one printed circuit board and forming a coil pattern on the front surface or the back surface of each unit substrate is based on the magnetic collecting cores shown in the second to fifth embodiments. It can also be applied to the shape, structure, and positional relationship between the magnetic collecting core and the printed circuit board.

The plurality of coil patterns 13a in the printed circuit board 12e in FIG. 8A are connected in series by a through hole or the like to form a first series coil, and the plurality of coil patterns 13b in the other printed circuit board 12f are also formed. A second series coil is formed by being connected in series, and these first and second series coils are connected in series. The above configuration is the same for the plurality of coil patterns 13a and 13b in the printed circuit boards 12g and 12h in FIG. 8B.

Further, in FIG. 8 (a), the distance L g'between the center line of the plate thickness of the printed circuit boards 12e and 12f and the facing surfaces of the magnetic collecting cores 11a and 11b is kept equal, and in FIG. 8 (b), the distance L _g'is kept equal. The distance _Lg'between the center line of the thickness of the printed circuit boards 12g and 12h and the facing surfaces of the magnetic collecting cores 11a and 11b is kept equal. In such a configuration, it can be considered that a plurality of coil patterns 13a and 13b are integrated into one coil pattern, and the coil patterns are arranged equidistantly from the facing surfaces of the magnetic collecting cores 11a and 11b. This is equivalent to the arrangement of the coil patterns 13a and 13b in the first to fifth embodiments.
Therefore, the error of the induced voltage of the coil patterns 13a and 13b due to the external magnetic field in the direction parallel to the printed circuit boards 12e, 12f, 12g and 12h can be reduced, and the current flowing through the conductor 21 can be accurately measured.

In the first to seventh embodiments described above, the frontal substantially U-shaped magnetic collecting core as shown in FIGS. 1, 5, and 8, or the linear collecting core as shown in FIGS. 3, 6, and 7. Two magnetic cores are used each, and each pair of magnetic collecting cores face each other to have a gap portion, but the configuration of the current sensor is not limited to these.
That is, as a modification of the current sensor, a gap portion is formed by the facing surfaces of the end portions of a single magnetic collecting core (not shown) having a substantially C-shape or a U-shape, and the gap portion is formed in the gap portion. The distance between the coil pattern on the arranged printed circuit board and the facing surface may be substantially equal, or a printed circuit board board composed of one or more unit boards on which the coil pattern is formed. The printed circuit board may be arranged so that the distance between the thick center line and the facing surface is substantially equal.

Next, FIG. 9 is a configuration diagram of a watt-hour meter according to an embodiment of the present invention, and a current sensor according to any one of the first to seventh embodiments can be used, for example, Japanese Patent Application Laid-Open No. 2020-60504 by the present applicant. This is the case when applied to the watt-hour meter described in the publication.

In FIG. 9, the power lines 101R, 101S, 101T of each phase connected to the three-phase AC power supply SP (R, S, T are the output terminals of each phase, N is the neutral point) and the three-phase load LD. The electric energy meter 200 according to the present invention is connected between the two.
The power meter 200 is connected to the power supply lines 101R and 101T (both corresponding to the conductors 21 to 23 described above), respectively, and measures the _R -phase current IR and the _T -phase current IT, respectively, according to the present invention. , 100b, a voltage sensor 201a connected between the power supply lines 101R and 101S to measure the voltage between the R phase and the S phase, and connected between the power supply lines 101S and 101T to measure the voltage between the S phase and the T phase. The voltage sensor 201b, the current / voltage detection values of the current sensors 100a and 100b and the voltage sensors 201a and 201b are calculated and processed to calculate the power amount, and the calculated power amount is displayed or output to the outside. It is composed of an output unit 203 for transmission and output.

According to this watt-hour meter 200, it is possible to accurately measure the amount of power based on the current measured with high accuracy by the current sensors 100a and 100b according to the present invention and the voltage measured by the voltage sensors 201a and 201b. Is.
Further, the miniaturization of the current sensors 100a and 100b has an advantage that the watt-hour meter 200 itself can be miniaturized.

11a, 11b, 11c, 11d: Magnetic collecting core 11a', 11b': End face (opposing surface)
12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h: Printed circuit board 12e', 12f', 12g', 12h': Unit substrate 12e: Notch 13a, 13b: Coil pattern 21, 22, 23: Conductor 23a: Through hole 30: Central opening 100a, 100b: Current sensor 101R, 101S, 101T: Power supply line 200: Electric energy meter 201a, 201b: Voltage sensor 202: Electric energy calculation unit 203: Output unit g: Air gap SP: AC power supply R, S, T: Output terminal N: Neutral point LD: Load

Claims (11)

The conductor through which the measured current flows and
A magnetic collecting core having a pair of facing surfaces forming a gap and collecting magnetic flux generated by the measured current,
A magnetic detection means that is arranged in the gap and that the magnetic flux interlinks to generate an induced voltage.
An arithmetic means for calculating the measured current based on the induced voltage, and
In a current sensor equipped with
A current sensor characterized in that the magnetic detection means is arranged at positions substantially equidistant from the pair of facing surfaces. The conductor through which the measured current flows and
A magnetic collecting core having a pair of facing surfaces forming a gap and collecting magnetic flux generated by the measured current,
A magnetic detection means that is arranged in the gap and that the magnetic flux interlinks to generate an induced voltage.
An arithmetic means for calculating the measured current based on the induced voltage, and
In a current sensor equipped with
A current sensor characterized in that the printed circuit board is arranged so that the center line of the plate thickness of the printed circuit board provided with the magnetic detection means is located at positions substantially equidistant from the pair of facing surfaces. In the current sensor according to claim 1 or 2.
A current sensor characterized in that the magnetic detection means is formed by a coil pattern on a printed circuit board. In the current sensor according to claim 3,
A current sensor characterized in that a plurality of the coil patterns are arranged in the gap portion formed by facing the first magnetic collecting core and the second magnetic collecting core, and the coil patterns are connected in series. In the current sensor according to any one of claims 2 to 4.
A current sensor characterized in that the conductor is arranged substantially on a center line of the plate thickness of the printed circuit board. In the current sensor according to any one of claims 3 to 5.
A current sensor, characterized in that a plurality of the coil patterns are formed on a single printed circuit board. In the current sensor according to any one of claims 3 to 5.
A current sensor, characterized in that a plurality of the coil patterns are each formed on the individual printed circuit boards. In the current sensor according to any one of claims 2 to 7.
A current sensor characterized in that the conductor is arranged in a notch formed in the printed circuit board. In the current sensor according to any one of claims 2 to 7.
A current sensor characterized in that the printed circuit board is passed through a through hole formed in the conductor. In the current sensor according to any one of claims 3 to 9.
A current sensor characterized in that the printed circuit board is configured by laminating a plurality of unit boards, and the coil pattern is formed on the front surface or the back surface of the unit board. The current sensor according to any one of claims 1 to 10, a voltage sensor that measures a voltage between a plurality of conductors including the conductor, a current detection value by the current sensor, and a voltage detection value by the voltage sensor. A power meter characterized by being equipped with a power amount calculation unit that calculates the amount of power using the power amount.

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