JP2002168884A - Electrostatic capacitance type current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic capacitance type current sensor with a simple structure that can stably measure a current without influence by a surrounding environment. SOLUTION: The electrostatic capacitance type current sensor 1, which is a current sensor detecting a current value of a measured current, includes a current passage 2 that the measured current flows, a sensor means 3 that electrostatic capacitance changes by a magnetic field generated by the measured current in this current passage 2, an electric capacitance-voltage converting means 4 that converts a change of the capacitance of the sensor means 3 to a voltage, a displaying device 5 that displays the current value of the measured current based on the output voltage of the electrostatic capacitance-voltage converting means 4, and then the sensor means 3 is constituted of two electrodes 11, 12 that a distance between both opposed electrodes 11, 12 changes by the magnetic field generated by the measured current, and a glass tube 3 that inert gas is enclosed together with these electrodes 11, 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current sensor for detecting a current value, and more particularly to a current sensor for detecting a current value as a change in capacitance, which has a simple structure and is not affected by surrounding environment. The present invention relates to a capacitance-type current sensor capable of measuring a current stably.

[0002]

2. Description of the Related Art As a conventional current detection sensor, there is, for example, a current detection sensor device disclosed in Japanese Patent Application Laid-Open No. 10-26638. As shown in FIG. 8, a conventional current detection sensor device 101 is a series of electrically good conductors made of a single material or a mixture of copper, aluminum, tin, zinc, and the like, and
The conductor 61 is made of a nonmagnetic metal, and the conductor 61 is provided with a perforation 69 for inserting the magnetoresistive elements 62a and 62b and the magnetic bias magnet 60.

In the perforated portion 69, the magnetoresistive elements 62a, 62b, the magnetic bias magnet 60, and the conductor 6
In order to obtain electrical insulation from the magnet 6, an insulating layer 64 called a series of insulators made of nylon, polyester, polycarbonate and polyethylene is held around the magnet.

Further, a soft magnetic layer 67 appropriately selected from permalloy, iron plate, silicon steel plate, ferrite or the like is formed on the entire back surface of the conductor portion 66 or a part thereof as shown in FIG. The magnetic circuit is formed so as to constitute a magnetic circuit and to function so that a magnetic field generated in the conductor layer enters the magnetoresistive element at right angles.

[0005]

However, in the current detection sensor device 101 described above, the MR (Magneto Resi
Since a stance) element or a GMR (Giant Magneto Resistance) element is used, a metal through which a current flows or a magnet for supplementing a magnetic circuit is required, resulting in a problem that the structure becomes complicated.

Further, since the MR element and the GMR element have a temperature characteristic, there is a problem that they are affected by the surrounding environment.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrostatic capacitance type having a simple structure and capable of measuring a stable current without being affected by the surrounding environment. It is to provide a current sensor.

[0008]

According to a first aspect of the present invention, there is provided a capacitance type current sensor for detecting a current value of a current to be measured. A current path through which a measurement current flows, a sensor means whose capacitance changes due to a magnetic field generated by the measured current flowing through this current path, and an electrostatic element which converts the change in the capacitance of the sensor means into a voltage. And a capacitance-voltage conversion unit.

According to the first aspect of the present invention, the structure is simple, and stable current measurement can be performed without being affected by the surrounding environment.

The sensor means of the capacitance type current sensor according to the second aspect of the present invention comprises two opposing electrodes whose distance between the electrodes changes due to a magnetic field generated by the current to be measured, and the two electrodes together with the two electrodes. And a glass tube for filling an inert gas.

According to the second aspect of the present invention, the current is not affected by the surrounding environment, in particular, the humidity, so that the current can be measured more stably.

According to a third aspect of the present invention, the current path of the capacitance type current sensor is sealed in the glass tube.

According to the third aspect of the present invention, since the condition between the electrode and the magnetic field generated from the current path becomes constant, stable current measurement is possible.

According to a fourth aspect of the present invention, the current path of the capacitance type current sensor is formed in a coil shape.

According to the fourth aspect of the invention, the strength of the magnetic field generated in proportion to the number of turns of the coil increases, so that the detection sensitivity of the sensor means can be increased.

According to a fifth aspect of the present invention, there is provided a capacitance-type current sensor comprising a plurality of the sensor units, the capacitances of the sensor units are converted into voltages, and these voltages are added. The current to be measured is detected.

According to the invention of claim 5, since a large output voltage can be obtained, the detection sensitivity can be improved.

According to a sixth aspect of the present invention, in the capacitance type current sensor, a second current path is provided in the sensor means.
A current is caused to flow through the second current path by the voltage converted by the capacitance-voltage conversion means, and the direction of the magnetic field generated by the current to be measured is opposite to that of the magnetic field generated by the measured current, and the magnitude of the magnetic field is the same. It is characterized by generating a certain magnetic field.

According to the sixth aspect of the present invention, since the position of the electrode is fixed, stable current measurement can be performed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration of a capacitance type current sensor according to a first embodiment will be described with reference to FIG.

As shown in FIG. 1, the capacitance of the capacitance type current sensor 1 is changed by a current path 2 through which a current to be measured flows and a magnetic field generated by the current to be measured flowing through the current path 2. A sensor unit 3, a capacitance-voltage conversion unit 4 for converting a change in capacitance of the sensor unit 3 into a voltage, and a current to be measured based on the voltage output by the capacitance-voltage conversion unit 4. And a display device 5 for displaying the value of.

Here, the current path 2 may be an electric plate or the like through which a current flows in addition to the electric wire, and may be any as long as it is used as a current path.

As shown in FIG. 1, the sensor means 3 comprises two electrodes 11 and 12 arranged opposite to each other so as to constitute a variable capacitor, and a glass tube 13 for enclosing these electrodes 11 and 12. It is composed of The electrodes 11 and 12 may be made of a magnetic material such as a nickel-iron alloy, or may be formed by depositing a magnetic material. Although FIG. 1 shows that the electrodes 11 and 12 are sealed in the glass tube 13, the glass tube 13 may be omitted.
However, by filling an inert gas such as argon in the glass tube 13, the influence of humidity can be eliminated, so that the current can be measured accurately.

Further, the electrodes 11 and 12 are configured such that the spring coefficient increases significantly as the force applied to the electrodes increases. For example, as shown in FIG. 2, an electrode is formed by bringing materials 1 and 2 having different spring coefficients into close contact with each other, and the spring coefficient is significantly increased as the force applied to the electrode is increased.

By doing so, the magnetic field is applied to the electrode 1.
An S pole and an N pole are formed on the first and second electrodes, and a attracting force is generated. The attracting force increases as the distance between the electrodes becomes shorter, and the electrodes 11 and 12 come into contact with each other, so that the capacitance cannot be measured. Can be prevented.

Next, the capacitance-to-voltage conversion means 4 may be of any type as long as it can convert a change in capacitance into a voltage. Here, an example is shown in FIG.

The circuit shown in FIG. 3 is a circuit for converting a change in the capacitance of the sensor means 3 into a frequency, smoothing this frequency and outputting a voltage. In the circuit shown in FIG. 3, the change C of the capacitance outputted from the sensor means 3 is converted into a frequency f based on f = 1 / (2.2 × R × C), and this frequency f is converted into a smoothing capacitor 21. Is converted to DC voltage. Further, the differential amplifier 22 is provided for subtracting the offset voltage from the smoothed voltage.

In the capacitance type current sensor 1 of the first embodiment having the above-described configuration, when the measured current having the current value Ι flows through the current path 2,

(Equation 1) , A magnetic field having a magnetic field strength H is generated.

When this magnetic field is generated, the distance between the electrodes 11 and 12 of the sensor means 3 is changed by the magnetic substance, and the capacitance of the variable capacitor formed by the electrodes 11 and 12 is changed.

Then, the change in the capacitance is calculated as
The voltage is converted into a voltage by the voltage conversion means 4, and the display device 5 displays the current value of the measured current based on the voltage.

As described above, since the capacitance type current sensor 1 of the first embodiment does not use the MR element or the GMR element, the structure can be simplified, and the size can be reduced.

Further, since it is not affected by the surrounding environment such as temperature, it is possible to measure a stable current.

Next, the configuration of the capacitance type current sensor of the second embodiment will be described with reference to FIG.

As shown in FIG. 4, in the capacitance type current sensor 31 of the second embodiment, the current path 2
It is installed in.

By providing the current path 2 in the glass tube 13 as described above, the condition between the magnetic field generated from the current path 2 and the electrode becomes constant, so that stable current measurement becomes possible.

Further, the current path 2 and a plurality of sensor means may be installed in the glass tube 13 so that the current is measured by the plurality of sensor means.

Next, the configuration of the capacitance type current sensor of the third embodiment will be described with reference to FIG.

As shown in FIG. 5, in the capacitance type current sensor 41 of the third embodiment, the current path 2 is formed in a coil shape.

As described above, by forming the current path 2 in a coil shape,

(Equation 2) As shown in (2), the strength of the magnetic field increases in proportion to the number of turns of the coil, so that the detection sensitivity of the sensor means 3 can be increased.

Although a plurality of sensor means 3 are provided in FIG. 5, one sensor means 3 may be provided. further,
The coil-shaped current path 2 may be sealed in the glass tube of the sensor means 3.

Next, the configuration of the capacitance type current sensor of the fourth embodiment will be described with reference to FIG.

As shown in FIG. 6, in the capacitance type current sensor 51 of the fourth embodiment, a plurality of sensor means 3A and 3B are installed in the current path 2 and a plurality of capacitance-voltage The conversion means 4A and 4B are provided, and these output voltages are added by the addition circuit 52.

As described above, a large output voltage can be obtained by installing a plurality of sensor means and a plurality of capacitance-voltage conversion means and adding their output voltages, thereby improving the detection sensitivity. Can be.

Next, the configuration of the capacitance type current sensor of the fifth embodiment will be described with reference to FIG.

As shown in FIG. 7, in the capacitance type current sensor 71 of the fifth embodiment, the glass tube 1
A current path 72 different from the current path 2 through which the current to be measured flows is provided in 3.

The current generated by the output voltage of the capacitance-voltage converter 4 is fed back through the current path 72, and the sensor 3
To generate a magnetic field. However, this magnetic field is
The direction of the magnetic field generated by the current to be measured is opposite to the direction of the magnetic field and the strength of the magnetic field is the same.

As described above, by generating a magnetic field having the same strength in the opposite direction to the magnetic field generated by the current to be measured, the electrodes 11 and 12 are changed by the magnetic field due to the current to be measured, and then changed by the magnetic field in the current path 72. In addition, since the electrodes 11 and 12 are returned to the original positions, the positions of the electrodes 11 and 12 become constant, and stable current measurement can be performed.

[0048]

As described above, according to the capacitance type current sensor of the present invention, the structure is simple, and a stable current can be measured without being affected by the surrounding environment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a capacitance type current sensor according to the present invention.

FIG. 2 is a diagram for explaining characteristics of electrodes 11 and 12 shown in FIG.

FIG. 3 is a circuit diagram showing an example of the configuration of the capacitance-voltage converter 4 shown in FIG.

FIG. 4 is a block diagram showing a configuration of a second embodiment of the capacitance type current sensor according to the present invention.

FIG. 5 is a block diagram showing a configuration of a third embodiment of the capacitance type current sensor according to the present invention.

FIG. 6 is a block diagram showing a configuration of a fourth embodiment of the capacitance type current sensor according to the present invention.

FIG. 7 is a block diagram showing a configuration of a fifth embodiment of the capacitance type current sensor according to the present invention.

FIG. 8 is a block diagram showing a configuration of a conventional current detection sensor device.

[Explanation of symbols]

 1, 31, 51, 71 Capacitance type current sensor 2, 72 Current path 3, 3A, 3B Sensor means 4, 4A, 4B Capacitance-voltage conversion means 5 Display device 11, 12 Electrode 13 Glass tube 21 For smoothing Capacitor 22 Differential amplifier 52 Adder circuit 60 Magnetic bias magnet 61 Conductor 62 Magnetic resistance element 66 Conductor 67 Soft magnetic layer 69 Perforation 101 Current detection sensor device

Claims (6)

[Claims] 1. A current sensor for detecting a current value of a measured current, wherein a capacitance is changed by a current path through which the measured current flows and a magnetic field generated by the measured current flowing through the current path. A capacitance-type current sensor comprising: sensor means; and capacitance-voltage conversion means for converting a change in the capacitance of the sensor means into a voltage. 2. The sensor means comprises: two opposing electrodes whose distance between the electrodes changes due to a magnetic field generated by the current to be measured; and a glass tube enclosing an inert gas together with the two electrodes. The capacitance type current sensor according to claim 1, wherein 3. The capacitance type current sensor according to claim 2, wherein the current path is sealed in the glass tube. 4. The capacitance type current sensor according to claim 1, wherein said current path is formed in a coil shape. 5. A method according to claim 1, wherein a plurality of said sensor means are provided, a capacitance of said sensor means is converted into a voltage, and said measured current is detected by adding these voltages. 5. The capacitance-type current sensor according to 2, 3, or 4. 6. A second current path is provided in the sensor means, and a current is caused to flow through the second current path by the voltage converted by the capacitance-to-voltage conversion means. 6. The capacitance type current sensor according to claim 1, wherein the generated magnetic field has a direction opposite to that of the generated magnetic field and has the same magnetic field intensity.