WO2000022447A1 - Capteur magnetique, amperemetre et element de capteur magnetique - Google Patents
Capteur magnetique, amperemetre et element de capteur magnetique Download PDFInfo
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- WO2000022447A1 WO2000022447A1 PCT/JP1999/003586 JP9903586W WO0022447A1 WO 2000022447 A1 WO2000022447 A1 WO 2000022447A1 JP 9903586 W JP9903586 W JP 9903586W WO 0022447 A1 WO0022447 A1 WO 0022447A1
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- magnetic
- magnetic field
- measured
- sensor device
- detection unit
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/04—Measuring direction or magnitude of magnetic fields or magnetic flux using the flux-gate principle
Definitions
- Magnetic sensor device Description Magnetic sensor device, current sensor device, and magnetic sensor element
- the present invention relates to a magnetic sensor device for measuring a magnetic field, a current sensor device for measuring a current by measuring a magnetic field generated by a current, and a magnetic sensor element for measuring a magnetic field.
- a method of measuring the magnetic field generated by the current with a magnetic sensor device is adopted.
- Such a current sensor device usually has a configuration in which a gap is provided in a magnetic yoke that interlinks with the current to be measured, and the magnetic sensor element of the magnetic sensor device is set in the gap.
- a Hall element is often used as a magnetic sensor element used in such a current sensor device.
- MR resistance effect
- Hall elements and GMR (giant magnetoresistance) elements are mainly used as magnetic sensor elements, which are suitable for measuring high magnetic fields.
- a constant AC magnetic field is superimposed on a magnetic field to be measured generated by a current to be measured, and the AC magnetic field is adapted.
- this technique is referred to as an AC superposition method.
- magnetic sensor elements such as a Hall element, an MR element, a GMR element, and a flux gate element. Each of these elements has a suitable magnetic field measurement range. Therefore, conventionally, it was necessary to select the magnetic sensor element according to the magnitude of the magnetic field to be measured.
- each element has different characteristics such as output magnitude, linearity, and temperature dependency, even if a magnetic sensor element suitable for the magnitude of the magnetic field to be measured is selected in terms of the magnetic field measurement range, There was a problem that the required accuracy was not always satisfied. There is also a problem that there is no magnetic sensor element having a magnetic field measurement range suitable for the magnitude of the magnetic field to be measured.
- the negative feedback method may be used to improve the linearity and the temperature dependence of the output.
- the magnetic sensor element since the magnetic sensor element always operates under the condition that the magnetic field is near zero, if a small output Hall element is used as the magnetic sensor element, the drift of the element itself and the DC amplifier circuit can be reduced. It is strongly affected and causes a problem that accuracy is deteriorated.
- the GMR element has a large output, but the magnetoresistive effect does not depend on the direction of the magnetic field, so the direction of the measured magnetic field (in the case of a current sensor device, the direction of the measured current) cannot be determined. is there. Therefore, conventionally, when a magnetic field is measured using a GMR element, a bias magnetic field is applied so that the output of the magnetic sensor device changes monotonically with a change in the magnetic field to be measured. However, in this case, if the magnetic field to be measured is in the opposite direction to the bias magnetic field and the absolute value of the magnetic field to be measured exceeds the absolute value of the bias magnetic field, the monotonicity of the output of the magnetic sensor device with respect to the change in the magnetic field to be measured is maintained. If the negative feedback method is adopted, the negative feedback system may run away.
- the AC superposition method is also a technique for improving accuracy.
- the AC superposition method is a technology on the premise that the linearity of the magnetic sensor device is secured. Therefore, the AC superposition method alone does not help to improve linearity.
- the current sensor device using a Hall element which has been most developed in the prior art, has the following problems, for example.
- the magneto-resistance effect element has a problem of poor linearity.
- the negative feedback method it is necessary to apply a negative feedback magnetic field of the same magnitude as the magnetic field to be detected in the opposite direction to the magnetic sensor element. Therefore, when detecting a current of several hundred amperes, such as in an electric vehicle or solar power generation application, the feedback current is several amperes even if the number of turns of the negative return magnetic field generating coil is 100 turns. . Therefore, if the current sensor device is actually configured by this method, it becomes extremely large and expensive.
- the magnetic sensor element has high sensitivity, it is conceivable to add only a part of the detected magnetic field (for example, 1Z100) to the element to reduce the feedback current, but the Hall element as the magnetic sensor element is This is difficult because of the low sensitivity.
- a part of the detected magnetic field for example, 1Z100
- Fluxgate devices have been developed mainly for detecting small magnetic fields, and little technology has been developed for detecting large currents.
- the flux gate element has the feature that it has a simple configuration and high sensitivity, and depending on the device, it is effective as a magnetic detection unit in a current sensor device for large currents.
- FIG. 13 is a characteristic diagram showing the relationship between the inductance of a coil wound around a magnetic core and the coil current. Since the magnetic core has magnetic saturation characteristics, when the coil current increases, the effective permeability of the magnetic core decreases, and the inductance of the coil decreases. Therefore, if a bias magnetic field B is applied to the magnetic core with a magnet or the like, when the external magnetic field H Chrisis superimposed on the bias magnetic field, the magnitude of the external magnetic field H. is determined by the inductance of the coil. This is the simplest principle of operation of the flux gate element.In Fig. 13, both the bias magnetic field B and the external magnetic field H mayare the magnitudes converted to coil current. It is represented by
- the position of the bias point B changes depending on the strength of the magnetic field generated by the magnet, the positional relationship between the magnet and the magnetic core, and so the inductance value when the external magnetic field is zero is adjusted to a constant value. It is necessary to keep. However, it is extremely difficult to compensate for the instability of this value against temperature changes and other disturbances. Therefore, The method is not suitable for practical use.
- the effect of hysteresis is usually fairly small because the rod-shaped core has an open magnetic circuit. Therefore, if the hysteresis of the magnetic core is ignored, the saturation characteristics of the magnetic core do not depend on the direction of the coil current.Therefore, the inductance of the coil when the coil current is in the positive direction and that when the coil current is in the negative direction are The change characteristics are the same. For example, points P + and P ⁇ in FIG. 13 represent a positive coil current and a negative coil current having the same absolute value. In the vicinity of these points, the change characteristics of the inductance with respect to the change of the absolute value of the coil current are the same.
- the saturation region of the magnetic core refers to a region where the absolute value of the magnetic field is larger than the absolute value of the magnetic field when the magnetic permeability of the magnetic core becomes the maximum magnetic permeability.
- the inductance value decreases at the positive peak of the current (for example, point Q + in Fig. 13), and the negative peak (for example, the point in Fig. 13). In), the inductance value increases, so the difference has a value other than zero. Since the difference in inductance value depends on the external magnetic field, the external magnetic field can be measured by measuring the difference in inductance value.
- a method of applying an alternating current to the coil so that the magnetic core enters the saturation region at the peak time and measuring the difference in the decrease in the inductance at each of the positive and negative peak values of the current is described in the present application. It is called the large amplitude excitation method.
- Magnetic sensor devices using such a large-amplitude excitation method are disclosed in, for example, Japanese Patent Publication No. Sho 62-55111, Japanese Patent Publication No. Sho 63-3-52711 It is shown in Japanese Patent Application Publication No.
- Japanese Utility Model Publication No. 7-237375 discloses a technique that enables the same measurement as the large-amplitude excitation method by using two bias magnets.
- the large-amplitude excitation method is excellent because it can remove the effects of temperature changes and disturbances.
- it is not so easy to apply enough AC current to the coil to saturate the core. Therefore, in the past, the application was limited to a magnetic sensor device for detecting a small magnetic field using an amorphous magnetic core having a small saturation magnetic field.
- a method of detecting a magnetic field generated by the current with a magnetic sensor element is generally adopted.
- a magnetic yoke having an air gap is provided around a current path, a magnetic sensor element is installed in the air gap, and a magnetic field in the air gap is measured by the magnetic sensor element.
- the current value is I and the length of the gap is g
- a current sensor device uses a fluxgate element composed of one coil wound around one magnetic core as a magnetic sensor element and employs a negative feedback method.
- Japanese Patent Application Laid-Open Nos. 60-185,179 and 9-257,359 have a negative feedback method in a magnetic sensor device using a fluxgate element. The example adopted is described.
- the current sensor device when a flux gate element is used and the negative feedback method is adopted, a magnetic field due to the current to be measured is applied to the coil, but a magnetic field generated by the coil due to the negative feedback current is applied. Cancel the magnetic field. Therefore, in order to increase the measurement current range, it is necessary to increase the negative feedback current or increase the length g of the gap of the magnetic yoke to reduce the applied magnetic field.
- a first object of the present invention is to provide a magnetic sensor device and a current sensor device capable of accurately measuring a magnetic field or current of an arbitrary magnitude.
- a second object of the present invention is to provide a magnetic sensor device, a current sensor device, and a magnetic sensor element capable of easily expanding a measurement range of a magnetic field or a current.
- a third object of the present invention is to provide a magnetic sensor device, a current sensor device, and a magnetic sensor element that can easily measure a large magnetic field or current.
- the first magnetic sensor device or current sensor device of the present invention comprises:
- a magnetic detection unit that outputs a signal corresponding to a magnetic field applied corresponding to the magnetic field to be measured; and a negative feedback unit that generates a negative feedback magnetic field for negatively feeding back the output of the magnetic detection unit to the magnetic detection unit.
- a magnetic body provided around the magnetic detection unit or forming a part of the magnetic detection unit, wherein a demagnetizing coefficient for the measured magnetic field and a demagnetizing coefficient for the negative feedback magnetic field are different;
- the demagnetizing field coefficient and the negative feedback magnetic field with respect to the magnetic field to be measured are determined by the magnetic material provided around the magnetic detection unit or forming a part of the magnetic detection unit. Is different from the demagnetizing coefficient. This makes it possible to make the magnitude of the negative feedback magnetic field different from the magnitude of the magnetic field to be measured.
- the magnetic body has a cavity for accommodating the magnetic detection unit, is provided around the magnetic detection unit, and the magnetic detection unit is provided inside the cavity of the magnetic body. It may be stored in.
- the magnetic detection unit has a magnetic core and a coil wound around the magnetic core for detecting a magnetic field to be measured.
- the magnetic body may be a magnetic core that forms a part of the magnetic detection unit.
- the magnetic core refers to a core made of a magnetic material having magnetic saturation characteristics and around which a coil is wound.
- the second magnetic sensor device or current sensor device of the present invention includes:
- a magnetic detector that outputs a signal corresponding to a magnetic field applied corresponding to the magnetic field to be measured, and a magnetic body having a cavity that houses the magnetic detector.
- the magnetic detection unit is housed in the cavity of the magnetic body,
- the magnetic field to be measured and the magnetic field applied to the magnetic detection unit based on at least one of a first demagnetizing factor depending on the shape of the magnetic body and a second demagnetizing factor depending on the shape of the cavity. Is set to a predetermined value.
- the second magnetic sensor device or the current sensor device based on at least one of the first demagnetizing coefficient depending on the shape of the magnetic body and the second demagnetizing coefficient depending on the shape of the cavity.
- the ratio between the magnetic field to be measured and the magnetic field applied to the magnetic detector is set to a predetermined value.
- the magnetic field applied to the magnetic detection unit can be set to a value suitable for the magnetic field measurement range of the magnetic detection unit.
- the cavity may have an opening that opens in a direction that intersects the direction in which the magnetic flux by the measured magnetic field passes.
- the magnetic detection section has a high sensitivity direction with respect to the detection sensitivity, and the high sensitivity direction and the direction of passage of the magnetic flux by the measured magnetic field are matched. May be placed in the cavity so that
- the second magnetic sensor device or the current sensor device of the present invention further comprises a negative feedback magnetic field applying means for applying a negative feedback magnetic field for negatively feeding back the output of the magnetic detection unit to the magnetic detection unit.
- a negative feedback magnetic field applying means for applying a negative feedback magnetic field for negatively feeding back the output of the magnetic detection unit to the magnetic detection unit.
- the negative feedback magnetic field applying means may be provided in the cavity such that the demagnetizing coefficient of the magnetic substance with respect to the magnetic field to be measured is different from the demagnetizing coefficient of the magnetic substance with respect to the negative feedback magnetic field.
- the second magnetic sensor device or the current sensor device of the present invention further comprises a magnetic detection unit, wherein Reference magnetic field applying means for applying an AC magnetic field may be provided.
- the reference magnetic field applying means may be provided outside the magnetic body.
- the third magnetic sensor device or the current sensor device of the present invention includes:
- a flux gate magnetic sensor element having a magnetic core and a coil wound around the magnetic core for detecting an applied magnetic field to be measured
- Detecting means for detecting a magnetic field to be measured by detecting a change in inductance of the coil
- the magnetic core has a shape such that the demagnetizing coefficient for the magnetic field to be measured and the demagnetizing coefficient for the magnetic field generated by the coil are different.
- the demagnetizing coefficient of the magnetic core with respect to the magnetic field to be measured is different from the demagnetizing coefficient of the magnetic core with respect to the magnetic field generated by the coil.
- the negative feedback current can be changed compared to when the two demagnetizing coefficients are equal.
- the magnetic core has a shape such that a demagnetizing coefficient for a measured magnetic field is larger than a demagnetizing coefficient for a magnetic field generated by the coil. Is also good.
- the magnetic core may have a shape that forms an open magnetic path with respect to both the magnetic field to be measured and the magnetic field generated by the coil.
- the magnetic core has a shape that forms an open magnetic path with respect to the magnetic field to be measured and forms a closed magnetic path with respect to the magnetic field generated by the coil. You may.
- the third magnetic sensor device or the current sensor device according to the present invention further comprises supplying a negative feedback current for negatively feeding back the output of the detection means to the coil, whereby the output of the detection means is output from the coil.
- the flux gate magnetic sensor element of the present invention comprises:
- the magnetic core has a shape such that the demagnetizing coefficient for the magnetic field to be measured and the demagnetizing coefficient for the magnetic field generated by the coil are different.
- the demagnetizing coefficient of the magnetic core with respect to the magnetic field to be measured and the demagnetizing coefficient of the magnetic core with respect to the magnetic field generated by the coil are different, when a negative feedback current is supplied to the coil, two Compared to the case where the demagnetizing factor is equal, it is possible to change the negative feedback current.
- the magnetic core may have a shape such that a demagnetizing coefficient with respect to a magnetic field to be measured is larger than a demagnetizing coefficient with respect to a magnetic field generated by the coil.
- the magnetic core may have a shape that forms an open magnetic path with respect to both the magnetic field to be measured and the magnetic field generated by the coil.
- the magnetic core may have a shape that forms an open magnetic circuit with respect to the magnetic field to be measured and forms a closed magnetic circuit with respect to the magnetic field generated by the coil.
- FIG. 1 is an explanatory diagram showing a configuration of a magnetic sensor device according to a first embodiment of the present invention.
- FIG. 2 is a perspective view showing an example of a method for forming a cavity in the magnetic body in FIG.
- FIG. 3 is a perspective view showing another example of a method of forming a cavity in the magnetic body in FIG.
- FIG. 4 is a sectional view showing a configuration of a magnetic sensor device according to a second embodiment of the present invention.
- FIG. 5 is a cross-sectional view showing an example of a configuration of a magnetic sensor device according to a third embodiment of the present invention.
- FIG. 6 is a sectional view showing another example of the configuration of the magnetic sensor device according to the third embodiment of the present invention.
- FIG. 7 is a sectional view showing a configuration of a magnetic sensor device according to a fourth embodiment of the present invention.
- FIG. 8 is a sectional view showing a configuration of a magnetic sensor device according to a fifth embodiment of the present invention.
- FIG. 9 is a sectional view showing a configuration of a magnetic sensor element according to a sixth embodiment of the present invention.
- FIG. 10 is a sectional view showing a configuration of a magnetic sensor element according to a seventh embodiment of the present invention.
- FIG. 11 is a circuit diagram showing a configuration of a current sensor device according to an eighth embodiment of the present invention.
- FIG. 12 is a characteristic diagram showing an example of characteristics of the current sensor device according to the eighth embodiment of the present invention.
- FIG. 13 is an explanatory diagram for explaining the operation principle of the flux gate element. BEST MODE FOR CARRYING OUT THE INVENTION
- FIG. 1 is an explanatory diagram showing a configuration of a magnetic sensor device according to a first embodiment of the present invention.
- the magnetic sensor device includes: a magnetic detection unit 101 that outputs a signal corresponding to a magnetic field; and a magnetic body 110 that has a cavity 111 in which the magnetic detection unit 101 is housed.
- the magnetic detection unit 101 is housed in the cavity 111 of the magnetic body 110, and depends on the shape of the first demagnetizing field and the shape of the cavity 111, which depends on the shape of the magnetic body 110
- the ratio between the magnetic field to be measured H and the magnetic field applied to the magnetic detector 101 is set to a predetermined value based on at least one of the second demagnetizing coefficients.
- the cavity 111 may have an opening that opens in a direction that intersects with the direction in which the magnetic flux to be measured by the magnetic field H passes, for example, in a direction that intersects perpendicularly. In this case, if necessary The opening may be closed by a magnetic material different from the magnetic material 110.
- the magnetic detection unit 101 a unit having a high sensitivity direction that has an angle dependency on an applied magnetic field with respect to detection sensitivity may be used. In this case, it is preferable to dispose the magnetic detection unit 101 in the cavity 111 so that the direction of high sensitivity and the direction of passage of the magnetic flux by the magnetic field H to be measured match.
- the magnetic sensor device further includes a negative feedback magnetic field applying unit (negative feedback unit) for applying a negative feedback magnetic field for negatively feeding back the output of the magnetic detection unit 101 to the magnetic detection unit 101.
- a negative feedback magnetic field applying unit negative feedback unit
- the feedback coil 112 is provided, for example, in the cavity 111 and wound around the magnetic detection unit 101.
- the feedback coil 1 1 2 is provided in the cavity 1 1 1 1, the demagnetizing coefficient of the magnetic substance 1 10 for the magnetic field to be measured is different from the demagnetizing coefficient of the magnetic substance 1 10 for the negative feedback magnetic field.
- the feedback coil 112 need not be directly wound around the magnetic detection unit 101 as long as a negative feedback magnetic field can be applied to the magnetic detection unit 101.
- the negative feedback magnetic field applying means may not have a coil shape like the feedback coil 112 as long as the negative feedback magnetic field can be applied to the magnetic detection unit 101.
- the magnetic sensor device further includes a reference for applying a reference AC magnetic field used for controlling characteristics of the magnetic detection unit 101 to the magnetic field to be measured H to the magnetic detection unit 101.
- a reference magnetic field coil 113 as magnetic field applying means is provided.
- the reference magnetic field coil 113 is provided, for example, outside the magnetic body 110 and is wound around the magnetic body 110. Note that the reference magnetic field coil 113 may be provided in the magnetic path of the magnetic field applied to the magnetic body 110, instead of being provided directly on the magnetic body 110.
- Various magnetic sensor elements such as a Hall element, an MR element, a GMR element such as a spin valve type, and a flux gate element can be used for the magnetic detection unit 101. Since the output of the Hall element is small, if a Hall element is used, it is necessary to take measures such as DC amplification.
- Both ends of the magnetic detection unit 101 are connected to the magnetic detection unit connection line 121, and both ends of the feedback coil 112 are connected to the feedback coil connection line 122.
- a reference magnetic field coil connection wire 123 is connected to both ends.
- the magnetic detector connection line 1 2 1 3 processes the output signal of the magnetic detector 101 and outputs the output signal corresponding to the magnetic field to be measured.
- a processing circuit 124 for outputting a signal to an output terminal 127 is connected.
- a feedback current source 125 supplying a feedback current to the feedback coil 112 is connected to the feedback coil connection line 122.
- the feedback current supplied by the feedback current source 125 is controlled by the processing circuit 124.
- An AC power supply 126 for supplying a predetermined AC current to the reference magnetic field coil 113 is connected to the reference magnetic field coil connection wire 123.
- the magnetic detection section connecting line 1 2 1 and the return coil connecting line 1 2 2 may be drawn out from the opening. Even when the opening is closed, it can be drawn out using a known technique such as forming a conductive pattern on the magnetic body 110.
- a magnetic field having a predetermined ratio with respect to the magnetic field to be measured H is applied to the magnetic detection unit 101 housed in the cavity 111 of the magnetic body 110 as described later.
- the processing circuit 124 processes the output signal of the magnetic detection unit 101, and outputs an output signal corresponding to the magnetic field to be measured to the output terminal 127.
- the processing circuit 124 controls the feedback current source 125 to supply a feedback current corresponding to the output signal of the magnetic detection unit 101 to the feedback coil 112 from the feedback current source 125. Let it.
- a magnetic field having the same absolute value in the opposite direction to the magnetic field applied to the magnetic detection unit 101 corresponding to the magnetic field to be measured is generated from the feedback coil 112 in response to the magnetic field to be measured.
- the magnetic field applied to 1 is controlled to be almost zero at all times. As a result, variations in sensitivity of the magnetic detection unit 101 and output fluctuations due to temperature dependence are suppressed.
- a predetermined AC current is supplied from the AC power supply 126 to the reference magnetic field coil 113, and an AC magnetic field is generated from the reference magnetic field coil 113.
- a reference AC magnetic field corresponding to the AC magnetic field is applied to the magnetic detection unit 101 so as to be superimposed on the magnetic field corresponding to the magnetic field to be measured.
- the processing circuit 124 outputs a signal obtained by removing the reference AC magnetic field component from the output signal of the magnetic detection unit 101. Further, the processing circuit 124 extracts the reference AC magnetic field component from the output signal of the magnetic detection unit 101, and outputs the output signal of the processing circuit 124 so that the magnitude of the reference AC magnetic field component becomes constant. Adjust. Thereby, the measurement accuracy of the magnetic sensor device is improved.
- the feedback coil 112 and the reference magnetic field coil 113 are provided to improve the measurement accuracy of the magnetic sensor device, such as improving the linearity and the temperature dependency of the output. One or both may be omitted.
- FIG. 2 shows an example of a method for forming the cavity 111 in the magnetic body 110.
- a shallow concave dent that is a cavity 111 is provided, and after the magnetic detection unit 101 is housed in this dent, This cavity is closed with, for example, a plate-shaped second magnetic body 110B, thereby forming a closed cavity 111.
- the first magnetic body 110A and the second magnetic body 110B constitute the magnetic body 110.
- FIG. 3 shows another example of a method for forming the cavity 111 in the magnetic body 110.
- a hole having a predetermined cross-sectional shape is formed in a rectangular parallelepiped magnetic body 110 so as to open in a direction orthogonal to the direction in which the magnetic flux passes by the magnetic field to be measured.
- Form 1 1 1 After storing the magnetic detection unit 101 in the cavity 111, the opening of the cavity 111 may be closed by another magnetic material if necessary.
- the ferrite powder or granules formed into a desired shape may be fired to form the magnetic material 110 having the cavities 111. it can. In this case, there is no increase in processing costs.
- At least the first demagnetizing field coefficient depending on the shape of the magnetic body 110 and the second demagnetizing field coefficient depending on the shape of the cavity 111 are at least.
- Magnetic poles in opposite directions to the magnetic field are induced at both ends of the magnetic body placed in the magnetic field. Therefore, the magnetic field inside the magnetic body becomes a value obtained by subtracting the magnetic field generated by the induced magnetic pole from the external magnetic field, and is smaller than the external magnetic field.
- the rate at which the magnetic field inside a magnetic body decreases from the external magnetic field is expressed by a coefficient known as the demagnetizing coefficient or self-demagnetization rate.
- the demagnetizing factor of a magnetic material is determined only by the shape of the magnetic material. For example, the demagnetizing field coefficient is almost zero for an elongated rod-shaped magnetic material parallel to the external magnetic field, and is almost 1 for a thin plate-shaped magnetic material perpendicular to the external magnetic field.
- the internal magnetic field is almost equal to the external magnetic field, and a thin plate-shaped perpendicular to the external magnetic field.
- the internal magnetic field is one part of the relative magnetic permeability of the magnetic material with respect to the external magnetic field.
- the demagnetizing field coefficient of the magnetic body depending on the shape of the magnetic body is referred to as a first demagnetizing coefficient.
- the magnetic field induced by the poles induced in the walls of the cavity is in the same direction as the magnetic field inside the magnetic material. Therefore, the magnetic field caused by the magnetic poles induced on the wall of the cavity acts to make the magnetic field inside the cavity larger than the magnetic field inside the magnetic body.
- the rate at which the magnetic field inside the cavity increases over the magnetic field inside the magnetic body is also referred to as the demagnetizing coefficient.
- the demagnetizing factor of this cavity depends on the shape of the cavity.
- the demagnetizing factor of a cavity is almost zero for an elongated tubular cavity parallel to the magnetic field inside the magnetic body, and is almost 1 for a thin gap-like cavity perpendicular to the magnetic field inside the magnetic body. Therefore, in an elongated tubular cavity parallel to the magnetic field inside the magnetic material, the magnetic field inside the cavity is almost equal to the magnetic field inside the magnetic material, and in a thin gap-shaped cavity perpendicular to the magnetic field inside the magnetic material, The magnetic field is twice the relative permeability of the magnetic material to the magnetic field inside the magnetic material.
- the demagnetizing coefficient of the cavity that depends on the shape of the cavity is referred to as a second demagnetizing coefficient.
- the shape of the magnetic body 110 and the shape of the cavity 111 are appropriately designed, and the first demagnetizing coefficient and the second demagnetizing coefficient are set to desired values.
- only one of the first demagnetizing coefficient and the second demagnetizing coefficient is set to a desired value, and the ratio of the measured magnetic field H to the magnetic field applied to the magnetic detection unit 1 is determined. It can also be set to a value.
- the ratio between the measured magnetic field H and the magnetic field applied to the magnetic detector 1 can be set to a predetermined value based on at least one of the first demagnetizing coefficient and the second demagnetizing coefficient. Will be described more specifically.
- the magnetic field H M inside the magnetic body 110 is expressed by the following equation (1).
- H M H / ⁇ 1 + N MS -1) ⁇ ... (1)
- the magnetic field H K inside the cavity 111 is expressed by the following equation (2).
- H K H M ⁇ 1 + N KS -1) ⁇ -(2)
- the magnetic field H K inside the cavity 111 is expressed by the following equation (3).
- the shape and cavity of the magnetic material 110 are and the design of the shape suitably, the first and the demagnetisation factor N M and a second demagnetizing factor N K Ri by the setting to the desired value, and the measured magnetic field H, the cavity 1 1 1
- this magnetic sensor device as a current sensor device, a large current can be measured.
- the presence of the cavity 111 changes the magnetic flux distribution inside the magnetic body 110, so that the second demagnetizing coefficient becomes complicated, but the description of the essence of the invention changes. Therefore, the following description will be made assuming that the above equations (1) to (3) hold.
- the magnetic field applied to the magnetic detection unit 101 is merely reduced below the magnetic field to be measured, the magnetic flux is shunted so that only a part of the magnetic flux passes through the magnetic detection unit 101. It is also conceivable to use However, this method has problems that the magnetic field leaks easily and the magnetic detection unit 101 is easily affected by the noise magnetic field.
- the conversion ratio of the magnetic field can be set arbitrarily, and the magnetic detection unit 101 is magnetically shielded by the magnetic body 110. It has many advantages over the method of shunting magnetic flux, such as being stable against noise magnetic fields.
- the second demagnetizing factor is the cross-sectional area of the plane of the cavity 1 1 1 orthogonal to the direction of the magnetic field to be measured and the length of the cavity 1 1 1 in the direction of the magnetic field to be measured. It can be set by the ratio of height.
- At least one opening for inserting the magnetic detection unit 101 into the cavity 111 can be provided in a direction intersecting the magnetic field to be measured, for example, in a direction orthogonal to the magnetic field to be measured.
- the magnetic sensor device operates as a negative feedback magnetic field applying unit that applies a negative feedback magnetic field for negatively returning the output of the magnetic detection unit 101 to the magnetic detection unit 101.
- the effect of having the feedback coil 1 1 2 will be described.
- the magnetic field applied to the magnetic detection unit 101 can be made smaller than the magnetic field to be measured, the negative feedback magnetic field is also smaller than the magnetic field to be measured. Can be made smaller.
- the current to be measured is 100 A (ampere) and a gap of 10 mm is provided in a magnetic yoke linked to the current, the magnetic field in the gap is 100 OA nom.
- the relative permeability of the yoke is 100
- the magnetic field in the yoke is determined by the continuity of the magnetic flux density. This is 10 AZm, which is 1 000.
- the magnetic field in the cavity 1 1 1 can be expressed as 10 X (l + N k X 999) according to equation (2).
- N k 0.02 (corresponding to the case where the ratio of the diameter and the length of the cross section of the cavity 1 1 1 is about 10)
- the magnetic field in the cavity 1 1 1 is about 2 10 A / m
- the negative feedback method can be adopted.
- Generating a magnetic field of 210 A / m can be achieved by applying a current of 21 mA to a solenoid coil (10000 turns Zm) in which an insulated copper wire with a diameter of 0.1 mm is wound tightly. . Therefore, according to the present embodiment, it is possible to employ a negative feedback method having a remarkable effect of improving characteristics without requiring a large feedback current, thereby improving measurement accuracy. .
- the cavity 111 is directly provided in the magnetic yoke.
- a magnetic body 110 having the cavity 111 is provided separately from the magnetic yoke, and the magnetic detection unit is provided in the cavity 111.
- the magnetic path may be formed by combining the magnetic body 110 containing the 101 with the magnetic yoke.
- the magnetic sensor device applies a reference alternating magnetic field used to control the characteristics of the magnetic detection unit 101 with respect to the measured magnetic field H to the magnetic detection unit 101.
- the effect of having the reference magnetic field coil 113 as a reference magnetic field applying means for performing the operation will be described.
- the characteristics of the magnetic detection unit 101 are greatly improved, but the variation of the demagnetizing field coefficient due to the variation of the dimensions of the cavity 111 and the size of the gap of the magnetic yoke Various variations that affect the measurement accuracy, such as variations in the applied magnetic field to the magnetic detection unit 101 due to variations in the measurement, are not corrected.
- the linearity of the magnetic detection unit 101 is guaranteed, so that the AC superposition method can be used.
- the AC superposition method for example, as shown in FIG. 1, a reference magnetic field coil 113 is provided on the outer periphery of the magnetic body 110, or a reference magnetic field coil 13 is provided, a predetermined alternating current is supplied to the reference magnetic field coil 113, and the reference magnetic field coil 113 provides Generate an AC magnetic field.
- a reference AC magnetic field corresponding to the AC magnetic field is applied to the magnetic detection unit 101.
- the processing circuit 124 extracts a reference AC magnetic field component from the output signal of the magnetic detection unit 101, and outputs the output signal of the processing circuit 124 so that the magnitude of the reference AC magnetic field component becomes constant.
- Adjustment of the magnetic field affects measurement accuracy, such as variations in the demagnetizing factor due to the above-mentioned variations in the dimensions of the cavity 111 and variations in the applied magnetic field to the magnetic detector 101 due to the variations in the dimensions of the gap of the magnetic yoke. This makes it possible to completely correct the various variations that cause the magnetic field, thereby improving the measurement accuracy of the magnetic sensor device.
- the magnetic field to be measured and the magnetic field detecting section 101 are applied. Since the ratio with the magnetic field can be set to a predetermined value, it is possible to measure a magnetic field in a range beyond the magnetic field measurement range of the magnetic detector 101 used, and in particular, a high magnetic field and a large magnetic field can be measured. Current measurement becomes possible.
- the magnetic sensor device it is possible to easily adopt the negative feedback method or the AC superposition method, so that the linearity and the temperature dependence of the output can be improved as needed.
- the measurement can be performed arbitrarily, and the measurement accuracy can be improved.
- the feedback coil 112 as a negative feedback magnetic field applying means in the cavity 111, a large feedback current is not required.
- the magnetic sensor device since magnetic detection section 101 is surrounded by magnetic substance 110, the operation is stabilized by being shielded from an external noise magnetic field. Further, according to the magnetic sensor device according to the present embodiment, as the magnetic detection unit 101, a magnetic sensor element that could not be conventionally used because the magnetic field measurement range does not match the magnitude of the magnetic field to be measured Can also be used. For this reason, in the past, monotonicity of the output against changes in the magnetic field to be measured was secured, but magnetic sensor elements that could not be used in the magnetic field measurement range could be used, and such magnetic sensor elements should be used. As a result, even if the negative feedback method is used, the negative feedback system does not run away.
- the magnetic sensor device it is possible to use a magnetic sensor element which conventionally has a large output but could not be adopted in terms of a magnetic field measurement range.
- a sensor element it is possible to realize a magnetic sensor device that has a large output and is less affected by drift.
- the magnetic sensor device basically, since the magnetic detection unit 101 is housed in the cavity 111 of the magnetic body 110, the structure is simple and precise. A good magnetic sensor device can be provided at low cost. In particular, when the cavity 111 having an opening is formed in the magnetic body 110, the installation of the magnetic detection unit 101 is simple, and the magnetic sensor device can be provided at a lower cost. . In addition, by employing the AC superposition method, variations in the demagnetizing coefficient due to variations in the dimensions of the cavities 111 and variations in the applied magnetic field to the magnetic detection unit 101 due to variations in the dimensions of the gap of the magnetic yoke, etc. Various variations that affect measurement accuracy can be corrected without performing mechanical adjustment, and a highly accurate magnetic sensor device can be provided at low cost.
- the magnetic sensor device according to the present embodiment is designed to be suitable for measuring a high magnetic field.
- This magnetic sensor device includes: a magnetic detection unit 101 that outputs a signal corresponding to a magnetic field; and a magnetic body 110 having a cavity 111 in which the magnetic detection unit 101 is housed.
- the magnetic detecting unit 101 is housed in the cavity 111 of the magnetic body 110, and the first demagnetizing coefficient depending on the shape of the magnetic body 110 and the first demagnetizing coefficient depending on the shape of the cavity 111
- the ratio between the magnetic field to be measured H and the magnetic field applied to the magnetic detection unit 101 is set to a predetermined value based on at least one of the demagnetizing coefficients of 2.
- the magnetic sensor device further includes a feedback coil 1 as a negative feedback magnetic field applying means for applying a negative feedback magnetic field for negatively feeding back the output of the magnetic detection unit 101 to the magnetic detection unit 101. It has 1 2.
- This feedback coil 112 is provided in the cavity 111 and is wound around the magnetic detector 101.
- the magnetic sensor device further applies a reference AC magnetic field used to control the characteristics of the magnetic detection unit 101 with respect to the magnetic field to be measured H to the magnetic detection unit 101.
- a reference magnetic field coil 113 serving as a reference magnetic field applying means.
- the reference magnetic field coil 113 is provided outside the magnetic body 110 and is wound around the magnetic body 110.
- the relative permeability / z s of the magnetic body 110 is 100
- the first demagnetizing coefficient Nm is 0.5
- the magnetic field H k inside the cavity 1 11 is 0.042 H from the equation (3). That is, the magnetic field applied to the magnetic detection unit 101 is 4.2% of the measured magnetic field H.
- the magnetomotive force of feedback coil 112 is sufficient to be 4.2% of the magnetic field to be measured.
- the magnetomotive force of the reference magnetic field coil 113 is generally sufficient to be about 1% of the measured magnetic field. Therefore, according to the magnetic sensor device according to the present embodiment, the current consumption of the feedback coil 112 and the current consumption of the reference magnetic field coil 113 are both very small, and a practical magnetic sensor device is obtained.
- a magnetic sensor device according to a third embodiment of the present invention will be described with reference to FIG. 5 and FIG.
- the first demagnetizing coefficient depending on the shape of the magnetic body is set to a desired value, and the ratio between the magnetic field to be measured and the magnetic field applied to the magnetic detecting unit is set. This is an example in which a predetermined value is set.
- FIG. 5 is an explanatory diagram showing an example of the configuration of the magnetic sensor device according to the present embodiment.
- a magnetic detection unit 101 is housed in a cavity 111 in the magnetic sensor device according to the second embodiment
- a magnetic material 115 such as a magnetic paint is placed in a cavity 1. It is the one that fills the gap in 1 1.
- the magnetic field inside magnetic body 110 is applied to magnetism detection unit 101.
- This magnetic field, the external magnetic field H determined by first demagnetizing factor N m which depends on the shape of the magnetic substance 1 1 0.
- FIG. 6 is an explanatory diagram showing another example of the configuration of the magnetic sensor device according to the present embodiment. is there.
- This magnetic sensor device has an integral magnetic body 130 provided in place of the magnetic bodies 110 and 115 in FIG.
- the magnetic detector 101 is embedded inside the magnetic body 130.
- a magnetic sensor device having such a structure for example, uses a compound material of a resin and a magnetic material as the magnetic material 130, and has a magnetic material of a predetermined shape in which the magnetic detection unit 101 is embedded inside. It can be obtained by molding 130.
- This current sensor device includes the magnetic sensor device according to the present embodiment.
- the description will focus on the current sensor device, but the following description also serves as the description of the magnetic sensor device according to the present embodiment.
- the current sensor device is provided so as to surround a conductive portion 141 through which a current to be measured passes, and has a partially cut-out annular magnetic yoke 142, And a magnetic body 110 disposed in the cutout portion of the second.
- the magnetic body 110 is provided with a cavity 111, and the magnetism detecting unit 101 is accommodated in the cavity 111.
- the ratio between the measured magnetic field generated by the measured current and the magnetic field applied to the magnetic detector 101 is set to a predetermined value.
- the current sensor device further includes a feedback coil 1 as a negative feedback magnetic field applying means for applying a negative feedback magnetic field for negatively feeding back the output of the magnetic detection unit 101 to the magnetic detection unit 101. It has 1 2.
- the feedback coil 112 is provided in the cavity 111, and is wound around the magnetic detection unit 101.
- the current sensor device further includes, as reference magnetic field applying means for applying a reference AC magnetic field used to control characteristics of the magnetic detection unit 101 with respect to the magnetic field to be measured, to the magnetic detection unit 101.
- Reference magnetic field coils 113 are provided. This reference magnet The field coil 113 is wound around a part of the magnetic yoke 142.
- a magnetic field is generated by the measured current flowing through the conductive portion 141 in a direction perpendicular to the plane of the paper.
- This magnetic field is referred to as a measured magnetic field in the present embodiment.
- This measured magnetic field is applied to the magnetic body 110.
- a magnetic field having a predetermined ratio to the magnetic field to be measured is applied to the magnetic detection unit 101.
- the magnitude of the measured magnetic field changes according to the magnitude of the measured current.
- the direction of the measured magnetic field changes according to the direction of the measured current.
- the current sensor device indirectly measures the measured current by measuring the measured magnetic field generated by the measured current. When the device shown in FIG. 7 is used as a magnetic sensor device, this magnetic sensor device directly measures a magnetic field to be measured.
- the shapes of the magnetic yoke 142 and the magnetic body 110 cannot be excessively increased from a practical viewpoint.
- the magnetic detection unit 101 needs to have a certain size, there is a limit in reducing the size of the cavity 111. Therefore, by setting the magnetic body 1 1 0 shape optionally, it can not always be arbitrarily set first demagnetizing factor N m.
- the HiToru permeability of the magnetic substance 1 1 0 i sm the HiToru permeability of the magnetic yoke 1 4 2 and sy, and w sm »l, ⁇ . Sy » l.
- the magnetic field inside the magnetic body 110 is H m and the magnetic field in the gap of length G is H g , Hg l ZG Hm Hg / sm
- the magnetic field H k in the cavity 111 is It is expressed by an equation.
- H k (1 / G UsJ ⁇ 1 + N k ( sm -1) ⁇
- the current to be measured is 100 A
- the total air gap length G ⁇ G! + Gz is 10 mm
- the magnetic field coefficient N k is 0.02 (corresponding to the case where the ratio of the diameter to the length of the cross section of the cavity 1 1 1 is about 10) and i sm is 1 000
- the magnetic field H in the cavity 1 1 1 k is obtained as follows.
- a high-sensitivity magnetic sensor element such as a spin valve type GMR element or a flux gate element can be used for the magnetic detection unit 101.
- a high-sensitivity magnetic sensor element has a signal-to-noise ratio of the output of the magnetic sensor element when the magnetic sensor element operates near zero magnetic field, such as when the negative feedback method is employed. (S / N) is high and operation is stable.
- spin-valve GMR elements and flux gate elements guarantee the monotonicity of the element output. Therefore, if the element whose monotonicity is guaranteed is used, there is no danger of the feedback system going out of control.
- the magnetic field H k in the cavity 1 11 is 2 10 A Zm
- a negative feedback magnetic field of 2 10 A / m is required, but a magnetic field of 2 10 A / m is generated.
- This can be achieved by applying a current of only 21 mA to a solenoid coil (100 turns cm) in which an insulated copper wire with a diameter of 0.1 mm is tightly wound.
- the current required for the reference magnetic field coil 113 is 10 mA when the number of turns of the coil is 100 turns and 1% of the magnetomotive force 100 AZm due to the measured current.
- a small feedback current and the AC current for AC superposition are smaller than those of the current sensor device according to the related art, which required a large feedback current. Accordingly, it is possible to realize a current sensor device equivalent in terms of accuracy, stability, effect of reducing variation, and the like.
- a current sensor device according to a fifth embodiment of the present invention will be described with reference to FIG.
- this current sensor device only the second demagnetizing coefficient depending on the shape of the cavity in the magnetic body is set to a desired value, and the ratio of the magnetic field to be measured to the magnetic field applied to the magnetic detector is set to a predetermined value. This is an example of setting to.
- the current sensor device according to the present embodiment is different from the current sensor device shown in FIG. In place of the magnetic body 110 that is provided, a magnetic body 150 that does not include a cavity and a magnetic detection unit is provided. Further, in the current sensor device according to the present embodiment, a cavity 111 is provided inside magnetic yoke 142 in the current sensor device shown in FIG. 7, and a magnetic detection unit is provided in this cavity 111. 1 0 1 is stored.
- the magnetic yoke 144 in the present embodiment corresponds to the magnetic material having a cavity in the present invention.
- the magnetic field inside cavity 11 1 is applied to magnetism detection unit 101. This magnetic field is determined by the magnetic field to be measured corresponding to the current to be measured and the second demagnetizing factor N k depending on the shape of the cavity 111.
- the first demagnetizing field coefficient depending on the shape of the magnetic material and the second demagnetizing factor depending on the shape of the cavity are provided. Since the ratio between the magnetic field to be measured and the magnetic field applied to the magnetic detection unit is set to a predetermined value based on at least one of the magnetic field coefficients, the magnetic field applied to the magnetic detection unit is set to This makes it possible to adopt a magnetic detection unit with good characteristics and technology to improve the measurement accuracy. The current can be measured with high accuracy. Furthermore, since the magnetic detection unit is magnetically shielded by the magnetic material, it is stable against noise magnetic fields.
- the attachment of the magnetic detection unit to the cavity is further facilitated.
- the magnetic detection unit has a high sensitivity direction with respect to detection sensitivity
- the magnetic detection unit is arranged in the cavity so that the high sensitivity direction and the direction of passage of the magnetic flux by the magnetic field to be measured are matched, furthermore, The resistance to noise magnetic fields is improved.
- the magnetic sensor device or the current sensor device includes a negative feedback magnetic field applying means for applying a negative feedback magnetic field for negatively feeding back the output of the magnetic detection unit to the magnetic detection unit.
- the linearity and output temperature dependency can be improved, and the measurement accuracy can be improved.
- the negative feedback magnetic field applying means is provided in the cavity, the feedback current can be reduced even when measuring a high magnetic field and a large current.
- the magnetic sensor device or the current sensor device includes a reference magnetic field applying unit that applies a reference AC magnetic field used for controlling characteristics of the magnetic detection unit with respect to the magnetic field to be measured, in the magnetic detection unit. Furthermore, it is possible to correct various variations that affect the measurement accuracy.
- a flux gate magnetic sensor element including a magnetic core and a coil wound around the magnetic core for detecting an applied magnetic field to be measured.
- the magnetic core has such a shape that the demagnetizing field coefficient for the magnetic field to be measured and the demagnetizing field coefficient for the magnetic field generated by the coil are different.
- the magnetic core has a shape such that the demagnetizing factor for the applied magnetic field to be measured is larger than the demagnetizing factor for the magnetic field generated by the coil. ing.
- the demagnetizing coefficient of the magnetic core with respect to the applied magnetic field to be measured and the demagnetizing coefficient of the magnetic core with respect to the magnetic field generated by the coil are considered.
- H s H g / ⁇ 1 + N S (pi s - 1) ⁇ - (4)
- N s is the demagnetizing factor
- Ui s is the relative permeability of the magnetic material.
- the demagnetizing coefficient will be briefly described. Magnetic poles in opposite directions to the magnetic field are induced at both ends of the magnetic body placed in the magnetic field. Therefore, the magnetic field inside the magnetic body becomes a value obtained by subtracting the magnetic field caused by the induced magnetic pole from the external magnetic field, and is smaller than the external magnetic field. The rate at which the magnetic field inside a magnetic material decreases compared to the external magnetic field is expressed by a factor known as the demagnetizing factor or self-demagnetizing factor.
- the demagnetizing factor of a magnetic material is determined only by the shape of the magnetic material.
- the demagnetizing factor N s of the magnetic core with respect to H and the magnetic field generated by the coil wound around the magnetic core is approximately the same as a parallel magnetic field because it is simple. Therefore, in the case of using the negative feedback method, the magnetic field coil generates must an H g by the negative feedback current.
- a rod-shaped magnetic core has n coils wound over a width b (m)
- a simple approximation is that when the coil current is i, the generated magnetic field is ni Z b.
- the magnetic field H c at is expressed by the following equation (5).
- N S N C is increased without changing the gap length g of the magnetic yoke, i.e. without changing the H g, either reduce the negative feedback current i, or, conversely, a negative feedback current i
- the coil winding width (length in the axial direction of the coil) b must be reduced or the number of turns n must be increased.
- all of these methods have limitations such as the wires becoming too thin.
- the demagnetizing factor N s of the magnetic core with respect to the magnetic field to be measured H g and the demagnetizing factor N of the magnetic core with respect to the magnetic field (approximately a parallel magnetic field for simplicity) generated by the coil wound on the magnetic core If c is different and N S > N C , then from equations (4) and (5), H c > H g and the magnetic field or current to be measured is increased without changing other conditions. You can see that you can do it.
- Demagnetizing factor is dependent on the sectional area and length of the magnetic material in the pass direction of the magnetic flux, in order to N S> N C is the length of the apparent magnetic core for the magnetic flux of the applied magnetic field, Koi What is necessary is just to make the apparent length of the magnetic core differ from the magnetic flux of the magnetic field generated by the magnetic core.
- a coil formed on a vertical bar portion of a U-shaped magnetic core having a central bar portion and portions extending from both ends of the bar portion in a direction perpendicular to the axial direction of the bar portion. It can be realized by winding and applying a magnetic field to be measured in the axial direction of the vertical bar.
- a well-known flux gate element using a toroidal magnetic core has a demagnetizing field coefficient of zero with respect to an excitation magnetic field, but differs from the magnetic sensor element of the present invention in configuration, purpose, and effect.
- the principle of the former operation is as follows. In the former, Troy Since the exciting magnetic flux in the dull magnetic core has an annular path, the magnetic flux due to the external magnetic field applied in parallel to the exciting magnetic flux in the toroidal magnetic core is added in a part of the annular path. In the part, it is subtracted. Therefore, the magnetic flux in the toroidal core has a large portion and a small portion.
- the exciting magnetic flux leaks out of the magnetic core. If the exciting magnetic flux is constant, the magnitude of the leakage magnetic flux is affected by the magnitude of the external magnetic field. Therefore, an external magnetic field is detected by inserting the entire toroidal core including the excitation winding into another coil and detecting the leakage magnetic flux with the coil.
- the coil wound around the magnetic core is a coil for detecting an external magnetic field. By detecting a change in the inductance of the coil, the external magnetic field is detected. No coil is required to detect magnetic flux leakage. Furthermore, in a fluxgate device using a toroidal core, processing of a shape considering the demagnetizing factor with respect to an external magnetic field is not considered at all.
- FIG. 9 is a cross-sectional view showing a configuration of the magnetic sensor element according to the present embodiment.
- This magnetic sensor element is a flux gate magnetic sensor element including a magnetic core 1 and a coil 2 wound around the magnetic core 1 for detecting an applied magnetic field to be measured.
- the magnetic core 1 corresponds to the magnetic body in the present invention.
- the magnetic core 1 is a drum-type magnetic core having a columnar core la and disk-shaped flanges 1b formed at both ends of the core 1a.
- the magnetic core 1 forms an open magnetic path for both the magnetic field to be measured and the magnetic field generated by the coil 2.
- the core la has a diameter of 0.8 mm and a length of 1.5 mm
- the flange 1b has a diameter of 2 mm and a thickness of 0.5 mm.
- the magnetic core 1 is formed of a ⁇ -Cu-Zn-based ferrite material, and has a relative magnetic permeability s of 500.
- the coil 2 is wound around the core 1 a of the magnetic core 1.
- the coil 2 is formed, for example, by winding a urethane-coated conductor having a diameter of 0.03 mm for 180 turns.
- the inductance of the magnetic sensor element shown in FIG. 9 was 350 H, and the coil current at which the inductance was reduced by half was 60 mA.
- This magnetic sensor element is used for a magnetic sensor device or a current sensor device. Specifically, this magnetic sensor element is arranged such that the axial direction of the core 1a is parallel to the magnetic field to be measured (including the magnetic field to be measured generated by the current to be measured) indicated by the symbol H in FIG. It is arranged so that it becomes.
- an alternating current is applied to the coil 2 such that the magnetic core 1 enters a saturation region at the time of a peak, and a change in the inductance of the coil 2 is detected to detect the magnetic field to be measured. Is detected.
- a negative feedback current for generating a reverse magnetic field having the same magnitude as the detected magnetic field is supplied to the coil 2.
- the coil current i at which the magnetic field inside the coil 2 becomes zero can be approximately obtained as follows using Equation (6) as follows: it can.
- the actual measured value of the coil current at which the magnetic field inside the coil 2 becomes zero is about 1 1.6 of the coil current value when the demagnetizing factors N s and N c are equal. Therefore, it can be seen that the equivalent demagnetizing factor obtained from the ratio of the current values is N S 1.6 N C. That is, according to the magnetic sensor element according to the present embodiment, as compared with the case where the demagnetizing field coefficients N s and N c are the same, the negative force for canceling the same external magnetic field (the magnetic field to be measured) is reduced. The feedback current decreases to 11.6.
- the equivalent demagnetizing factor N s is too it larger than the demagnetizing factor N c
- the demagnetizing factor N s of the magnetic core 1 with respect to the magnetic field to be measured is 0.8 mm in diameter and 2.5 mm in length.
- the demagnetizing field coefficient N c of the magnetic core 1 with respect to the magnetic field generated by the coil 2 is equivalent to the demagnetizing field coefficient of a magnetic core having a diameter of 0.8 mm and a length of 4 mm. It is considered that the ratio of the lengths of the magnetic paths is not so large.
- the demagnetizing factor N s of the core 1 with respect to the measured magnetic field applied is, since larger Ri by demagnetizing factor N c of the magnetic core 1 relative to the magnetic field coil 2 is generated
- the negative feedback current can be reduced as compared with the case where the two demagnetizing factors N s and N c are equal. It becomes possible to measure.
- FIG. 10 is a sectional view showing the configuration of the magnetic sensor element according to the present embodiment.
- the magnetic sensor element according to the present embodiment includes the same magnetic core 1 and coil 2 as the magnetic sensor element according to the sixth embodiment, and further includes a ferrite outside the coil 2.
- the coating layer 3 is provided by coating with a so-called magnetic paint in which powder is mixed with a resin paint. The coating layer 3 connects between the two flange portions 1 b of the magnetic core 1.
- the thickness of the coating layer 3 is 0.5 mm on average, and the relative magnetic permeability of the coating layer 3 is 12.
- the inductance of coil 2 was lmH, and the coil current at which the inductance was reduced by half was 30 mA.
- this magnetic core forms an open magnetic circuit with respect to the magnetic field to be measured, but forms a closed magnetic circuit with respect to the magnetic field generated by the coil 2. Form. Therefore, the demagnetizing factor N c of the magnetic core with respect to the magnetic field generated by coil 2 Is greatly reduced.
- FIG. 11 is a circuit diagram showing a configuration of the current sensor device according to the present embodiment.
- the current sensor device according to the present embodiment is configured using the magnetic sensor element according to the sixth embodiment.
- This current sensor device includes the magnetic sensor device according to the present embodiment.
- the current sensor device includes a magnetic yoke 62 provided so as to surround the conductive portion 61 through which the current to be measured passes, and having a gap in part.
- the magnetic sensor element according to the sixth embodiment is arranged in the gap of the magnetic yoke 62.
- the portion excluding the magnetic yoke 62 is the magnetic sensor device.
- One end of the detection coil 20 is connected to one end of the coil 2.
- the other end of the detection coil 20 is grounded.
- the other end of the coil 2 is connected to one end of a feedback current path coil 6.
- the other end of the feedback current path coil 6 is grounded via a capacitor 7.
- the current sensor device further includes a series resonance circuit partially including the coil 2, and supplies a resonance current flowing through the series resonance circuit to the coil 2 as an alternating current such that the magnetic core 1 reaches a saturation region. Detects the magnetic field to be measured by detecting the change in the resonance current flowing through coil 2 corresponding to the change in the inductance of coil 2 and the drive circuit, and also provides negative feedback to coil 2 for the negative feedback method. By supplying current, It has a detection and feedback circuit for generating a negative feedback magnetic field for the negative feedback method from File 2.
- the detection / feedback circuit corresponds to the negative feedback means in the present invention.
- the drive circuit has an oscillation circuit including a series resonance circuit.
- This oscillation circuit is configured as follows. That is, the oscillation circuit has the transistor 11. The base of the transistor 11 is connected to the other end of the coil 2 via the resonance capacitor 12. One end of a feedback capacitor 13 is connected to the base of the transistor 11. The other end of the feedback capacitor 13 is connected to one end of the feedback capacitor 14 and the emitter of the transistor 11. The other end of the feedback capacitor 14 is grounded. The emitter of the transistor 11 is grounded via the load coil 15. The collector of the transistor 11 is connected to the power input terminal 16 and to the base via the bias resistor 17.
- This oscillation circuit has the configuration of a clap oscillation circuit. However, if the capacitances of the capacitors 12, 13, and 14 are respectively C s, C b, and C e, then C s ⁇ C b, C e.
- the detection and feedback circuit is configured as follows. One end of a capacitor 21 is connected to a connection point between the coil 2 and the detection coil 20, and the other end of the capacitor 21 is grounded via a resistor 22.
- the capacitor 21 and the resistor 22 constitute a differentiating circuit that differentiates a voltage generated between both ends of the detection coil 20 and outputs a signal corresponding to the magnetic field to be measured.
- connection point between the capacitor 21 and the resistor 22 is connected to the anode of the diode 23 and the power source of the diode 25.
- the power source of diode 23 is grounded through capacitor 24.
- the anode of the diode 25 is grounded via the capacitor 26.
- the diode 23 and the capacitor 24 constitute a positive peak hold circuit, and the diode 25 and the capacitor 26 constitute a negative peak hold circuit.
- resistor 27 is connected to a connection point between the diode 23 and the capacitor 24.
- resistor 28 is connected to a connection point between the diode 25 and the capacitor 26.
- the other ends of the resistors 27 and 28 are connected to one end of the resistor 31.
- Resistors 27 and 28 are connected to the positive output value held by the positive peak hold circuit.
- a resistance addition circuit is configured to add the negative direction output value held by the negative direction peak hold circuit.
- a detection signal corresponding to the external magnetic field appears at one end of the resistor 31.
- the other end of the resistor 31 is connected to the inverting input terminal of the operational amplifier 32.
- the non-inverting input terminal of the operational amplifier 32 is grounded via the resistor 33.
- the output terminal of the operational amplifier 32 is connected to the inverting input terminal via the resistor 34.
- the output terminal of the operational amplifier 32 is connected to one end of the output detection resistor 35.
- the other end of the output detection resistor 35 is connected to a connection point between the feedback current path coil 6 and the capacitor 7.
- One end of the resistor 35 is connected to the non-inverting input terminal of the operational amplifier 38 via the resistor 36, and the other end of the resistor 35 is connected to the inverting input terminal of the operational amplifier 38 via the resistor 37. It is connected.
- the non-inverting input terminal of the operational amplifier 38 is grounded via the resistor 39.
- the output terminal of the operational amplifier 38 is connected to the inverting input terminal via the resistor 40 and to the detection output terminal 41.
- the operational amplifier 38 and the resistors 36, 37, 39, 40 constitute a differential amplifier.
- the detection coil 20, the feedback current path coil 6, and the capacitor 7 are part of an oscillation circuit as a drive circuit and also part of a detection / feedback circuit.
- An alternating current is supplied to the coil 2 by the oscillation circuit so that the magnetic core 1 reaches the saturation region.
- This alternating current is a resonance current that is twice the Q value of the resonance circuit with respect to the current value limited by the power supply voltage.
- a method for detecting a change in the waveform of the resonance current is used as a method for extracting a change in the inductance of the coil 2 as an output signal of the current sensor device.
- the voltage across the detection coil 20 having a large saturation current value and connected in series with the coil 2 is differentiated by a differentiation circuit including a capacitor 21 and a resistor 22.
- the positive output value of the output of the differentiating circuit is held by a positive peak hold circuit composed of a diode 23 and a capacitor 25, and the differential output is differentiated by a negative peak hold circuit composed of a diode 24 and a capacitor 26.
- the negative output value of the output of the circuit is held, and the positive output value and the negative output value are added by a resistance addition circuit composed of resistors 27 and 28, and the external magnetic field Is obtained.
- the positive and negative parts of the differential waveform of the voltage waveform at both ends of the detection coil 20 are symmetric, and the sum of the positive and negative peak values of the differential waveform (difference in absolute value) Is zero.
- the positive part and the negative part in the differentiated waveform become asymmetric.
- the sum of the positive and negative peak values (difference in absolute value) of the differential waveform becomes a value other than zero, which depends on the external magnetic field.
- the external magnetic field can be measured from the sum of the positive and negative peak values (difference in absolute value) of the differential waveform.
- the detection / feedback circuit detects the magnetic field to be measured based on the portion of the resonance current flowing through the coil 2 where the magnetic core 1 reaches the saturation region.
- the detection / return circuit 4 detects the magnetic field to be measured based on the positive / negative asymmetric component of the resonance current flowing through the coil 2.
- the detection signal obtained by the resistance adding circuit composed of the resistors 27 and 28 is inverted and amplified by the inverting amplifier composed of the operational amplifier 32 and the resistors 31, 33 and 34, and passes through the output detecting resistor 35. Is applied to the connection point between the feedback current path coil 6 and the capacitor 7. As a result, a negative feedback current is supplied to the coil 2 through the feedback current path coil 6, and a magnetomotive force is applied to the coil 2 in a direction opposite to the external magnetic field.
- the inverting amplifier since the inverting amplifier has both positive and negative outputs, negative and positive feedback currents corresponding to the positive and negative external magnetic fields (one direction is positive) are output from the inverting amplifier output terminal. The grounding end on the coil 2 side is grounded in order to flow into coil 2.
- the measurement of the external magnetic field is performed as follows.
- the output detection resistor 35 converts the negative feedback current, that is, the current proportional to the external magnetic field, into a voltage.
- This voltage is converted into a differential amplifier consisting of an operational amplifier 38 and resistors 35, 36, 39, and 40. And is supplied to the detection output terminal 41. Then, the detection output terminal 41 outputs a detection output signal corresponding to the external magnetic field.
- the current sensor device has a small sensitivity variation, very good linearity, and is very stable against changes in temperature, power supply voltage, and the like.
- the offset is in principle due to the large amplitude excitation method. Zero, no drift due to disturbance.
- the magnetic yoke 62 a toroidal core made of Mn-Zn ferrite was used.
- the shape of the magnetic yoke 62 was an outer diameter of 20 mm, an inner diameter of 10 mm, a thickness of 5 mm, and a gap of 8 mm in width.
- the overall shape of the current sensor device was extremely small, 20 mm x 35 mm x 6 mm.
- This current sensor device was operated with a power supply of ⁇ 5 V. At zero measurement current, the current consumption was +27 mA and 1 mA. In this current sensor device, the increase in current consumption due to the negative feedback current was 5 mA per 1 OA of measured current.
- the weight of this current sensor device was 10 g.
- FIG. 12 shows an example of the relationship between the current to be measured passing through the conductive portion 61 disposed inside the magnetic yoke 62 and the output voltage of the current sensor device. As shown in this figure, according to the current sensor device according to the present embodiment, it is possible to obtain a good linear output voltage characteristic in an extremely wide range of current values.
- FIG. 12 shows output characteristics when an offset bias not shown in FIG. 11 is applied.
- the current sensor device As described above, according to the current sensor device according to the present embodiment, it is possible to minimize an increase in current consumption due to the negative feedback current while using the negative feedback method, which causes a problem such as heat generation. It can contribute to the control of DC current in industry, especially for electric vehicles and solar power generation.
- the resonance current of the resonance circuit is supplied to coil 2, it is possible to easily supply the coil 2 with an alternating current such that magnetic core 1 reaches the saturation region. Also, since there is no need to wind an exciting coil in addition to the coil 2 around the magnetic core 1, the configuration is simple.
- a negative feedback current for the negative feedback method is supplied to coil 2 via return current path coil 6 connected in parallel with coil 2 in an AC manner. Therefore, a feedback current can be easily supplied to the coil 2 without loss of the resonance current.
- the detection coil 20 is inserted into the resonance circuit. This makes it possible to easily obtain a port-order detection output without lowering the Q value of the resonance circuit, that is, without causing a shortage of the resonance current supplied to the coil 2. Also, a simple and inexpensive circuit using a diode and a capacitor can be used for the peak hold circuit. Note that the detection coil 20 can obtain a sufficiently large output even if the inductance value is several% of the inductance value of the coil 2. Accordingly, the detection coil 20 has a small number of turns and usually has a sufficiently large saturation current value, so that the detection current is not saturated by the drive current (resonance current) of the coil 2.
- the sensor coil can be driven at low power supply voltage and high frequency.
- the magnetic sensor element according to the seventh and seventh embodiments may be used as the magnetic sensor element in the current sensor device shown in FIG.
- the shape of the magnetic core is not limited to the shape described in the sixth or seventh embodiment, and may vary with respect to the applied magnetic field to be measured. Any shape may be used so that the demagnetizing factor and the demagnetizing factor for the magnetic field generated by the coil are different.
- a clap oscillation circuit has been described as an example of the oscillation circuit.
- the present invention is not limited to this, and a case where another oscillation circuit such as a Colpitts oscillation circuit or a Hartree oscillation circuit is used. Can also be applied.
- the demagnetizing factor of the magnetic core with respect to the applied magnetic field to be measured and the magnetic field generated by the coil Because the demagnetizing field coefficient of the magnetic core is different, it is possible to change the negative feedback current when supplying a negative feedback current to the coil compared to when the two demagnetizing field coefficients are equal. Or, the current measurement range can be extended.
- the demagnetizing coefficient of the magnetic core with respect to the applied magnetic field to be measured is made larger than the demagnetizing coefficient of the magnetic core with respect to the magnetic field generated by the coil, when the negative feedback current is supplied to the coil, two Compared to the case where the demagnetizing factor is equal, the negative feedback current can be reduced, and a large magnetic field or current can be easily measured.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Measuring Magnetic Variables (AREA)
- Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP99926906A EP1039307A1 (en) | 1998-10-14 | 1999-07-02 | Magnetic sensor, current sensor, and magnetic sensor element |
JP2000576292A JP3212984B2 (ja) | 1998-10-14 | 1999-07-02 | 磁気センサ装置、電流センサ装置および磁気センサ素子 |
US09/484,793 US6323634B1 (en) | 1998-10-14 | 2000-01-18 | Magnetic sensor apparatus, current sensor apparatus and magnetic sensor element |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP29249498 | 1998-10-14 | ||
JP10/292494 | 1998-10-14 | ||
JP1151299 | 1999-01-20 | ||
JP11/11512 | 1999-01-20 |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/484,793 Continuation US6323634B1 (en) | 1998-10-14 | 2000-01-18 | Magnetic sensor apparatus, current sensor apparatus and magnetic sensor element |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2000022447A1 true WO2000022447A1 (fr) | 2000-04-20 |
Family
ID=26346944
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP1999/003586 WO2000022447A1 (fr) | 1998-10-14 | 1999-07-02 | Capteur magnetique, amperemetre et element de capteur magnetique |
Country Status (6)
Country | Link |
---|---|
US (1) | US6323634B1 (ja) |
EP (1) | EP1039307A1 (ja) |
JP (1) | JP3212984B2 (ja) |
CN (1) | CN1145806C (ja) |
TW (1) | TW434411B (ja) |
WO (1) | WO2000022447A1 (ja) |
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- 1999-07-02 EP EP99926906A patent/EP1039307A1/en not_active Withdrawn
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WO2006129389A1 (ja) * | 2005-05-31 | 2006-12-07 | Clt Ltd. | 広帯域型電流検出器 |
CN103743946A (zh) * | 2014-01-24 | 2014-04-23 | 镇江天力变压器有限公司 | 一种高频除尘电源谐振电流的积分电路 |
Also Published As
Publication number | Publication date |
---|---|
EP1039307A1 (en) | 2000-09-27 |
CN1145806C (zh) | 2004-04-14 |
CN1272920A (zh) | 2000-11-08 |
TW434411B (en) | 2001-05-16 |
JP3212984B2 (ja) | 2001-09-25 |
US6323634B1 (en) | 2001-11-27 |
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