JP2015206596A - Current sensor and measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily provide a current sensor with detection frequency characteristics having a higher frequency band through a small amount of modification.SOLUTION: A current sensor includes: a coil 5 wound around a magnetic core 2, through which an electrical line 21 under measurement is inserted; a first serial circuit 6 comprising a resistor 6a and a capacitor 6b connected between one end 5a of the coil 5 and the ground G; a second serial circuit 7 comprising an inductor element 7a and a capacitor 7b connected between the one end 5a and the ground G; and a termination resistor 9 which is provided between the other end 5b of the coil 5 and the ground G to convert current I2 (I3), that flows through the coil 5 in response to a flow of measurement target current I1 through the electrical line 21 under measurement, into detection voltage V2, where the resistor 6a is designed to have a resistance value that matches the coil 5 to the termination resistor 9.

Description

  The present invention relates to a current sensor that has a coil wound around a magnetic core and detects a current to be measured that flows through a measurement target inserted into the magnetic core, and a measuring apparatus including the current sensor. is there.

  As this type of current sensor, a current sensor disclosed in Patent Document 1 below is known. This current sensor is a current sensor that employs a zero flux method, and includes a magnetic core through which a measurement target (measured line) is inserted, a magnetoelectric conversion output unit such as a Hall element disposed in the magnetic core, and a magnetic core. A wound coil (feedback coil), a voltage-current conversion amplifier, and a voltage detection resistor are provided.

  In this current sensor, in a low-frequency region including direct current, the magnetoelectric conversion output unit takes out the magnetic flux induced in the magnetic core by the current flowing through the measurement object as a voltage, and the voltage-current conversion amplifier predefines this voltage. Amplified with the gain and converted into a current and supplied to one end of the coil. In this case, the coil generates a magnetic flux of reverse polarity in the magnetic core by the current supplied from the voltage-current conversion amplifier, and cancels the magnetic flux caused by the current flowing through the measurement object to zero. The voltage detection resistor is connected to the other end of the coil, converts a current (feedback current) flowing through the coil into a voltage, and outputs the voltage signal indicating the current flowing through the measurement target.

  Further, in this current sensor, although not described in Patent Document 1 below, a high frequency region (a magnetoelectric conversion output unit and a voltage −) where the lower frequency region overlaps the upper frequency region in the low frequency region described above. In the frequency range including the upper limit frequency range in the operating frequency range of the current conversion amplifier), the coil functions as a single CT (current transformer), detects the current flowing through the measurement target, A current signal whose amplitude changes according to the amplitude is output. As a result, the voltage detection resistor converts this current signal into a voltage signal and outputs it as a voltage signal indicating the current flowing through the measurement target.

  In this current sensor, in order to improve the detection frequency characteristic in the high frequency region, a capacitive load is connected to the connection line connecting the output terminal of the voltage-current conversion amplifier and the coil. Yes.

Japanese Patent Laying-Open No. 2005-55300 (page 3-4, FIG. 1)

  However, the above current sensor has the following problems to be improved. That is, in this current sensor, although the characteristic in the high frequency region of the detection frequency characteristic is improved by connecting the capacitive load as described above, it is desired to further increase the frequency (broadband) of the current sensor. ing. It is known that this further increase in frequency can be realized by adopting a configuration that reduces the number of turns of a coil that functions as a CT in a high frequency region. However, in this configuration, even if the current value of the current flowing through the measurement target is the same, the current flowing through the coil increases, so the wire used for the coil can be changed to a wire with a larger wire diameter, Various changes are required, such as changing the resistance used for the detection resistor to a higher wattage resistance.

  The present invention has been made to improve such a problem, and a main object of the present invention is to provide a current sensor and a measuring apparatus that can easily realize high frequency detection frequency characteristics with a small change.

  In order to achieve the above object, the current sensor according to claim 1 is connected between a magnetic core into which a measurement target is inserted, a coil wound around the magnetic core, and one end of the coil and a reference potential. A resistance to be measured, an inductor element connected between the one end of the coil and the reference potential, and a device to be measured that is disposed between the other end of the coil and the reference potential and flows to the measurement object A current-voltage conversion unit that converts a detection current flowing through the coil into a detection voltage at a current value corresponding to the current value of the current, and the resistor matches the output impedance of the coil to the input impedance of the current-voltage conversion unit The resistance value to be set is set.

  The current sensor according to claim 2 is the current sensor according to claim 1, wherein the inductor element has a parasitic capacitance of the coil and a resonance frequency of a resonance circuit mainly composed of the inductor element. It is set to the inductance value prescribed | regulated to the frequency more than the cut-off frequency in the frequency characteristic of the said detection voltage in the state which is not connected.

  The current sensor according to claim 3 is the current sensor according to claim 1 or 2, wherein the first capacitor is connected in series to the resistor and connected between the one end of the coil and the reference potential. A second capacitor connected in series to the inductor element and connected between the one end of the coil and the reference potential, wherein the first capacitor and the second capacitor are approximately equal to a capacitance value of the parasitic capacitance. The capacitance value is set to 100 times or more.

  A measuring device according to claim 4 measures the current value of the current under measurement based on the current sensor according to any one of claims 1 to 3 and the detected voltage converted by the current sensor. And a measurement unit.

  The current sensor according to claim 1 and the measuring device according to claim 4 include a resistor and an inductor element connected between one end of the coil and a reference potential.

  Therefore, according to the current sensor and the measuring device including the current sensor, in the high frequency region where the coil functions as CT, the output impedance of the coil is matched with the input impedance of the current-voltage conversion unit by the resistor, Due to the resonance of the parasitic capacitance and the inductor element, the upper limit frequency in the high frequency region of the amplitude-frequency characteristic of the detected voltage can be extended to a higher frequency side than the current sensor in a state where the inductor element is not connected. Therefore, the detection frequency characteristic can be easily increased in frequency with a small change.

  According to the current sensor of claim 2 and the measuring device of claim 4, the inductor element is connected to the parasitic capacitance of the coil and the resonance frequency of the resonance circuit mainly composed of the inductor element. Since the inductance value is set to a frequency equal to or higher than the cut-off frequency in the frequency characteristic of the detected voltage in the absence state, the amplitude of the detected voltage is less than the current sensor in the state where the inductance value is not set. The upper limit frequency in the high frequency region of the frequency characteristics can be reliably extended to the higher frequency side.

  In the current sensor according to claim 3 and the measuring device according to claim 4, the first capacitor having a capacitance value sufficiently large with respect to the parasitic capacitance is connected in series with the resistor, and the capacitance is sufficiently large with respect to the parasitic capacitance. A second capacitor of value is connected in series with the inductor element.

  Therefore, according to the current sensor and the measuring apparatus including the current sensor, the current sensor is a current sensor that employs a zero flux method (a magnetoelectric conversion output unit such as a Hall element disposed in the coil, and a magnetoelectric conversion output). Even if it is configured as a current sensor provided with a voltage-current conversion amplifier that converts the voltage output from the current into a current and supplies it to the coil, the current sensor does not function as a sensor of the zero flux method, and the coil In the high frequency region that functions as the above, it is possible to increase the detection frequency characteristic by the inductor element while matching by the resistance as described above. Further, in a low frequency region including direct current where the current sensor functions as a sensor of the zero flux method, the resistor and the inductor element can be equivalently separated from the reference potential by the first capacitor and the second capacitor. Since most of the current output from the conversion amplifier can be supplied to the coil, efficient measurement can be realized.

It is each block diagram of measuring apparatus MD which has the current sensor 1 and the current sensor 1. FIG. It is an equivalent circuit of the current sensor 1 (in a high frequency region) when the coil 5 functions as a CT. FIG. 3 is an explanatory diagram showing a cut-off frequency fc in the frequency characteristic of the amplitude of the detection voltage V2 output from the current sensor 1 when the inductance value L of the inductor element 7a is changed in the equivalent circuit of FIG. FIG. 3 is a frequency characteristic diagram showing a change in amplitude of a detection voltage V2 output from the current sensor 1 when the inductance value L of the inductor element 7a is changed in the equivalent circuit of FIG. It is each block diagram of measuring apparatus MD which has 1 A of current sensors and 1 A of current sensors.

  Hereinafter, embodiments of the current sensor 1 and the measuring device MD will be described with reference to the accompanying drawings.

  First, the configuration of the current sensor 1 will be described with reference to FIG.

  As shown in FIG. 1, the current sensor 1 includes, as an example, a magnetic core 2, a magnetoelectric conversion output unit 3, a voltage / current conversion amplification unit 4, a coil 5, a first series circuit 6, a second series circuit 7, and a current / voltage conversion. Part IVC, which is configured to be operable as a zero-flux current sensor, operates as a zero-flux current sensor in a low-frequency region including direct current, and operates as a CT in a high-frequency region. Thus, the current I1 to be measured flowing in the measurement circuit 21 as the measurement object inserted through the magnetic core 2 is detected over a wide band.

  As an example, the magnetic core 2 has an annular shape as a whole, and is formed in a split type that can be opened and closed with a base end (lower end in FIG. 1) as a center, and can clamp the measurement circuit 21 in a live state. (The measurement electric circuit 21 can be inserted inside). In addition, about the magnetic core 2, it is not limited to a split type, It can also be a penetration type (non-split type).

  In this example, the magnetoelectric conversion output unit 3 is configured by a Hall element (hereinafter also referred to as “Hall element 3”) as an example, and is disposed in a gap formed in the magnetic core 2. In the operating state, the Hall element 3 detects a magnetic flux generated inside the magnetic core 2 and outputs an output voltage V1 having a voltage value corresponding to the magnetic flux density (specifically, proportional or substantially proportional). . In this case, the magnetic flux generated in the magnetic core 2 includes a magnetic flux φ1 generated when the measured current I1 flows through the measurement circuit 21 inserted in the magnetic core 2, and a negative feedback current I2 described later in the coil 5. This is a magnetic flux of a difference (φ1−φ2) from the magnetic flux φ2 generated by flowing. In addition to the Hall element, a fluxgate magnetic detection element or the like can be used for the magnetoelectric conversion output unit 3.

  The voltage-current conversion amplifier 4 receives the output voltage V1 from the Hall element 3, generates a negative feedback current I2 as a detection current based on the output voltage V1, and supplies the negative feedback current I2 to the one end 5a of the coil 5. In this case, the voltage-current conversion amplification unit 4 has a magnetic flux density of the magnetic flux (φ1-φ2) generated in the magnetic core 2 detected in the Hall element 3 so that the output voltage V1 becomes zero volts. The current value of the negative feedback current I2 is controlled to be zero (in other words, so as to cancel the magnetic flux φ1 with the magnetic flux φ2).

  The coil 5 is formed by winding a wire around the magnetic core 2. One end 5a of the coil 5 is connected to the reference potential (ground G) side. In this example, as an example, one end 5a of the coil 5 is connected to a reference potential (ground G) via a first series circuit 6 as a capacitive load.

  The first series circuit 6 includes a resistor 6a (as an example, 50Ω matched to a characteristic impedance of a transmission path 8 (which will be described later) (an input impedance of the current-voltage converter IVC) constituting the current-voltage converter IVC) and a first capacitor 6b ( Hereinafter, it is also referred to as a capacitor 6b, which is a series circuit of a capacitor having a capacitance value sufficiently larger than a parasitic capacitance 5d described later of the coil 5, and is connected between one end 5a of the coil 5 and the ground G. . In this case, the capacitance value of the first capacitor 6b is preferably set to a capacitance value that is about 100 times or more of the parasitic capacitance 5d. Specifically, since the parasitic capacitance 5d of the coil 5 is normally about several pF to several tens pF, the capacitance value of the first capacitor 6b is preferably set to several nF or more. In this example, since the parasitic capacitance 5d of the coil 5 is 10 pF as will be described later, the capacitance value of the first capacitor 6b is preferably set to 1 nF or more.

  Further, the first series circuit 6 has a crossover frequency (a frequency at which the frequency characteristic of the negative feedback current I2 and the frequency characteristic of the current I3 intersect) when the frequency of the current (negative feedback current I2 or current I3 described later) flowing through the coil 5 crosses. ) The potential of the one end 5a of the coil 5 at this time is regulated to the potential of the ground G, and the output impedance of the coil 5 is matched with the input impedance of the current-voltage converter IVC by the resistor 6a. As for the resistor 6a and the capacitor 6b constituting the first series circuit 6, the resistor 6a can be disposed on the ground G side instead of the configuration in which the capacitor 6b is disposed on the ground G side as shown in FIG. .

  The second series circuit 7 includes an inductor element 7a (for example, an inductor element having an inductance value of several nH to several hundred nH) and a second capacitor 7b (hereinafter, also referred to as a capacitor 7b, which is sufficiently larger than a parasitic capacitance 5d described later). A capacitance value, specifically, a capacitor having a capacitance value equivalent to that of the capacitor 6b), is connected between the one end 5a of the coil 5 and the ground G.

  Further, the inductor element 7a has a function of extending the frequency band of the high frequency region in which the coil 5 operates as CT to the higher frequency side by resonating with the parasitic capacitance 5d (parallel resonance). In this case, the preferable inductance value of the inductor element 7a varies depending on the configuration of the current sensor. However, in the current sensor 1 of this example which is an example of the “current sensor”, the inductance value of the inductor element 7a is 1000 nH or more. When the value becomes large, the impedance value in the high frequency region (in the vicinity of the cutoff frequency (for example, 100 MHz) for the current sensor configured not to connect the inductor element 7a) becomes sufficiently larger than the resistance value of the resistor 6a. It becomes a state very close to the state where 7a is not connected. On the other hand, when the inductance value is less than 1 nH, it is difficult to distinguish the inductance value from the wiring itself connected to the one end 5a side of the coil 5. For this reason, the inductance value of the inductor element 7a is preferably defined within the range of several nH to several hundred nH as described above, and more preferably within the range of 1 nH to 100 nH.

  Specifically, when the inductance value of the inductor element 7a is L and the capacitance value of the parasitic capacitance 5d is C, the resonance frequency f is expressed by 1 / 2π√ (L × C). The inductance value L and the capacitance value C are set so that the frequency f is equal to or higher than the cut-off frequency. As described above, when the cutoff frequency of the current sensor configured not to connect the inductor element 7a is 100 MHz and the parasitic capacitance 5d is 10 pF, the inductance value L of the inductor element 7a is set to 254 nH. As for the inductor element 7a and the capacitor 7b constituting the second series circuit 7, the inductor element 7a is disposed on the ground G side instead of the structure in which the capacitor 7b is disposed on the ground G side as shown in FIG. You can also.

  In this example, the current-voltage conversion unit IVC includes a transmission line 8 and a termination resistor 9 as an example. In this case, the transmission line 8 has a characteristic impedance defined to a predetermined value, and one end 8 a is connected to the other end 5 b of the coil 5. In this example, as an example, the transmission line 8 is configured by a coaxial cable, and thus the characteristic impedance is regulated to 50Ω or 75Ω (50Ω in this example). The transmission line 8 is not limited to a coaxial cable, and may be configured by various transmission lines such as a twisted pair cable, for example, as long as the characteristic impedance is defined by a predetermined characteristic impedance. Of course, it can also be done.

  In this example, the termination resistor 9 is configured by a resistance element connected between the other end 8b of the transmission line 8 and the ground G, for example. The termination resistor 9 may be configured with an input resistance of a measuring instrument such as an oscilloscope. With this configuration, the termination resistor 9 converts a current (negative feedback current I2 or current I3 described later) flowing through the coil 5 into a detection voltage V2 and outputs it.

  Next, the configuration of the measuring apparatus MD including the current sensor 1 will be described with reference to FIG. The measuring device MD includes a current sensor 1, a measuring unit 10, and an output unit 11. Based on the detection voltage V 2 converted by the current sensor 1, the measuring device MD flows through a measuring circuit 21 as a measuring object inserted through the magnetic core 2. The measurement current I1 can be measured.

  As an example, the measurement unit 10 includes an A / D conversion unit and a CPU, and the A / D conversion unit converts the detection voltage V2 converted by the current sensor 1 into a digital value, and the CPU receives the detected voltage V2 based on the digital value. The current value I1a of the measurement current I1 is measured (calculated). Further, the measurement unit 10 outputs the measured current value I1a to the output unit 11.

  The output unit 11 is configured by a display device such as an LCD as an example, and displays the current value I1a output from the measurement unit 10 on the screen. Note that the output unit 11 is not limited to the display device, and may be configured by, for example, an external interface circuit. In this case, the measuring device MD outputs a current value I1a to another external device connected to the external interface circuit via a transmission path (wired transmission path or wireless transmission path), or is connected to the external interface circuit. The current value I1a can be stored in the external storage device.

  Next, the operation of the measuring device MD together with the operation of the current sensor 1 will be described with reference to the drawings.

  First, when the measured current I1 flowing through the measurement circuit 21 is a signal having a frequency within a low frequency region including direct current, since the Hall element 3 and the voltage-current conversion amplification unit 4 are in a frequency region, the Hall element 3 is The magnetic flux generated in the magnetic core 2 (the magnetic flux of the difference (φ1−φ2)) is detected, and the output voltage V1 is output. Next, the voltage-current conversion amplifier 4 receives the output voltage V1 from the Hall element 3, generates a negative feedback current I2 based on the output voltage V1, and supplies the negative feedback current I2 to the one end 5a of the coil 5 from the output terminal. In this case, the first series circuit 6 and the second series circuit 7 are connected between the output terminal of the voltage-current conversion amplification unit 4 (one end 5a of the coil 5) and the ground G. At the frequency of 1, the impedance of the capacitor 6b of the first series circuit 6 and the impedance of the capacitor 7b of the second series circuit 7 are both sufficiently large. As a result, when the negative feedback current I2 output from the output terminal of the voltage-current conversion amplifier 4 is a direct current (that is, when the measured current I1 is a direct current), the negative feedback current I2 is an alternating current in the low frequency region. When the current I1 to be measured is an alternating current in the low frequency region, the negative feedback current I2 does not flow to the ground G via the first series circuit 6 and the second series circuit 7, Most is supplied to one end 5 a of the coil 5.

  Further, the voltage-current conversion amplification unit 4 has a magnetic flux density of the magnetic flux (φ1-φ2) generated in the magnetic core 2 detected by the Hall element 3 so that the output voltage V1 becomes zero volts. (In other words, the magnetic flux φ1 is canceled by the magnetic flux φ2), and the current value of the negative feedback current I2 is controlled. Thereby, the current value of the negative feedback current I2 is approximately equal to the current value of the current I1 to be measured divided by the number n of turns when the number of turns of the coil 5 is n.

  In this way, the negative feedback current I2 supplied to the coil 5 from the one end 5a side flows to the termination resistor 9 via the coil 5 and the transmission path 8. Therefore, the termination resistor 9 converts the negative feedback current I2 into the detection voltage V2. In this low frequency region, the current sensor 1 detects the measured current I1 flowing through the measurement circuit 21 with the frequency characteristics of the Hall element 3 and the voltage / current conversion amplifier 4, and outputs a detection voltage V2.

  Next, the current to be measured I1 flowing in the measurement circuit 21 includes the upper limit side frequency region in the operating frequency region of the Hall element 3 and the voltage / current conversion amplifier 4 (the upper limit side frequency region in the low frequency region) on the lower limit side. When the signal has a frequency in the high frequency region, the coil 5 functions as a single CT, detects the measured current I1 flowing through the measurement circuit 21, and according to the amplitude (current value) of the measured current I1. A current I3 is output as a detection current whose amplitude (current value) changes.

  In this case, at all frequencies in the high frequency region, each impedance of the capacitor 6b of the first series circuit 6 and the capacitor 7b of the second series circuit 7 having a capacitance value sufficiently larger than the parasitic capacitance 5d is set to a sufficiently small value. Become. Thereby, the resistor 6a of the first series circuit 6 and the inductor element 7a of the second series circuit 7 are equivalently connected directly to the ground G. For this reason, when the measured current I1 flowing through the measurement circuit 21 is a signal in this high frequency region, the current I3 output from the coil 5 functioning as CT is the ground G, the first series circuit 6, and one end of the coil 5. 5a, the coil 5, the other end 5b of the coil 5, the current flowing through the transmission path 8 and the terminating resistor 9 to the current path to the ground G, the ground G, the second series circuit 7, the one end 5a of the coil 5, the coil 5 and the other current 5 b of the coil 5, the transmission path 8, and the terminating resistor 9, and the current flowing through the current path reaching the ground G is added. The termination resistor 9 converts this current I3 into a detection voltage V2 and outputs it.

  Further, in this way, in the high frequency region where the coil 5 functions as CT, the coil 5 is equivalent to the current source 5c that outputs the current I3 as described above and the coil 5 as shown in FIG. Can be regarded as a parallel circuit with a parasitic capacitance 5d (in this example, about 10 pF as an example) existing between the wires forming the. In this case, the resistance value of the wire forming the coil 5 varies depending on the thickness and length of the wire used, but is usually less than several Ω, so the output impedance of the coil 5 is equivalent to the resistance value of the resistor 6a. Is set. Therefore, in this example, since the resistance value of the resistor 6a is defined to be the same resistance value (50Ω in this example) as the characteristic impedance of the transmission line 8, the output impedance and current-voltage conversion of the coil 5 are performed by the resistor 6a. Matching with the input impedance of the part IVC is achieved.

  In this high frequency region, the inductor element 7a of the second series circuit 7 forms a parallel resonance circuit with the parasitic capacitance 5d of the coil 5. The actual current sensor 1 includes an inductance component other than the inductor element 7a, such as an inductance component included in a wire material or a wiring pattern, and a capacitance component other than the parasitic capacitance 5d of the coil 5 such as a stray capacitance. However, in order to facilitate understanding of the invention, these inductance components and capacitance components are sufficiently small and can be ignored. Therefore, the parallel resonance circuit can be regarded as a resonance circuit including the inductor element 7a and the parasitic capacitance 5d.

  In the current sensor 1, the inductor element 7a is connected to the above-described value (a value in the range of several nH to several hundred nH), specifically, the resonant frequency of the resonant circuit with the parasitic capacitance 5d of the coil 5. The inductance value of the inductor element 7a is defined so as to be a frequency equal to or higher than the cut-off frequency fc (100 MHz) in the high frequency region of the amplitude-frequency characteristic with respect to the detection voltage V2 when the configuration is not performed. Therefore, in the simulation performed with the equivalent circuit shown in FIG. 2, as shown in FIGS. 3 and 4, the cut-off frequency fc (amplitude is −3 [dB]) in the high frequency region of the amplitude-frequency characteristic for the detection voltage V2. It has been confirmed that the frequency at the same time extends higher than the cutoff frequency fc when the inductor element 7a is not connected.

  In this simulation, as an example, the current source 5c is a constant current source that supplies a current I3 of 20 mA, the parasitic capacitance 5d is 10 pF, and the resistor 6a and the terminating resistor 9 are 50Ω.

  In the measurement apparatus MD, the measurement unit 10 measures the current value I1a of the current I1 to be measured based on the detection voltage V2 output from the current sensor 1 as described above, and outputs the current value I1a to the output unit 11. However, this current value I1a is displayed on the screen.

  Thus, in the current sensor 1 and the measuring device MD, between the one end 5a of the coil 5 and the ground G, the first series circuit 6 (series circuit of the resistor 6a and the capacitor 6b) and the second series circuit 7 (inductor). A series circuit of an element 7a and a capacitor 7b) is connected.

  Therefore, according to the current sensor 1 and the measuring device MD, the first series circuit 6 and the second series circuit 7 are connected between the one end 5a of the coil 5 and the ground G, and the resistor 6a of the first series circuit 6 is connected. The inductor element 7a of the second series circuit 7 is parasitic while the output impedance of the coil 5 is matched with the input impedance of the current-voltage converter IVC by a simple configuration in which the resistance value of the coil 5 is matched with the input impedance of the current-voltage converter IVC. By resonating with the capacitor 5d (parallel resonance), the frequency band of the high frequency region in which the coil 5 operates as CT can be easily extended to the higher frequency side. Thereby, according to the current sensor 1 and the measuring device MD, the detection frequency characteristic can be easily increased in frequency with a small change.

  Further, according to the current sensor 1 and the measuring device MD, the inductance value L of the inductor element 7a is regulated to a value within the range of several nH to several hundreds nH, so that the inductance value is not set. As compared with the current sensor 1, the upper limit frequency in the high frequency region of the amplitude-frequency characteristic (detection frequency characteristic) for the detection voltage V2 can be reliably extended to the higher frequency side.

  Further, according to the current sensor 1 and the measuring apparatus MD, the capacitor 6b having a sufficiently large capacitance value with respect to the parasitic capacitance 5d is connected in series to the resistor 6a, and the capacitance value sufficiently large with respect to the parasitic capacitance 5d. Since the capacitor 7b is connected in series to the inductor element 7a, the resistor 6a and the inductor element 7a are grounded by the capacitors 6b and 7b in the low frequency region where the current sensor 1 functions as a current sensor employing the zero flux method. Since it can be equivalently separated from G, and most of the current output from the voltage-current conversion amplifier 4 can be supplied to the coil 5, an efficient measurement can be realized.

  The current sensor 1 employing the zero flux method has been described as an example, but includes the magnetic core 2, the coil 5, the resistor 6a, the inductor element 7a, and the terminating resistor 9 in FIG. 1, and the resistor 6a and the inductor element 7a A current sensor configured by directly connecting an end opposite to the end connected to one end 5a of the coil 5 to the ground G (a current configured by CT like the current sensor 1A shown in FIG. 5). In the sensor), the inductor element 7a has a simple configuration in which the resistance value of the resistor 6a is matched with the input impedance of the current-voltage conversion unit IVC, while matching the output impedance of the coil 5 with the input impedance of the current-voltage conversion unit IVC. By resonating with the parasitic capacitance 5d (parallel resonance), the frequency band of the high frequency region in which the coil 5 operates as CT is reduced. It can be easily extended to the high-frequency side Ri. Thereby, according to this current sensor 1A and measuring device MD provided with this current sensor 1A, a high frequency detection frequency characteristic can be easily realized with a small change.

  Further, according to the current sensor 1A and the measuring apparatus MD, the current in a state where the inductance value is not set by defining the inductance value of the inductor element 7a within a range of several nH to several hundred nH. The upper limit frequency in the high frequency region of the amplitude-frequency characteristic (detection frequency characteristic) for the detection voltage V2 can be reliably extended to a higher frequency side than the sensor. In addition, about the structure same as the current sensor 1, the same code | symbol was attached | subjected and the overlapping description was abbreviate | omitted.

  In the current sensors 1 and 1A, the current / voltage converter IVC is configured to include the transmission path 8 that connects the other end 5b of the coil 5 and the termination resistor 9, but the current / voltage converter IVC transmits the current / voltage converter IVC. A configuration that does not include the path 8, that is, the other end 5 b of the coil 5 and the termination resistor 9 are directly connected without using an electric circuit defined by a specific impedance, or connected through a normal electric wire or wiring pattern. It is also possible to adopt a configuration such as 1 and 5, the connection point A between the one end 5 a side of the coil 5 and the second series circuit 7, the output terminal of the voltage-current conversion amplification unit 4, and the connection point B of the first series circuit 6. It is also possible to adopt a configuration in which a gap is connected by a transmission line (not shown) similar to the transmission line 8.

1,1A current sensor
2 Magnetic core
3 Hall element
4 Voltage-current conversion amplifier
5 coils
6 1st series circuit 6a Resistance 6b Capacitor
7 Second series circuit 7a Inductor element 7b Capacitor
8 Transmission path
9 Terminal resistance 10 Measuring section 11 Output section 21 Wire to be measured
G ground I1 current to be measured I2 negative feedback current I3 current IVC current voltage converter MD measuring device

Claims (4)

A magnetic core into which the measurement object is inserted;
A coil wound around the magnetic core;
A resistor connected between one end of the coil and a reference potential;
An inductor element connected between the one end of the coil and the reference potential;
Current-voltage conversion that is arranged between the other end of the coil and the reference potential and converts the detected current flowing in the coil to a detected voltage with a current value corresponding to the current value of the current to be measured flowing in the measurement target With
The resistor is a current sensor that is set to a resistance value that matches the output impedance of the coil with the input impedance of the current-voltage converter.   The inductor element has a parasitic frequency of the coil and a resonance frequency of a resonance circuit mainly composed of the inductor element, a frequency equal to or higher than a cutoff frequency in the frequency characteristic of the detection voltage in a state where the inductor element is not connected. The current sensor according to claim 1, wherein the current value is set to an inductance value defined in 1. A first capacitor connected in series with the resistor and connected between the one end of the coil and the reference potential;
A second capacitor connected in series to the inductor element and connected between the one end of the coil and the reference potential;
3. The current sensor according to claim 1, wherein the first capacitor and the second capacitor are set to have a capacitance value of about 100 times or more of a capacitance value of the parasitic capacitance.   A measuring apparatus comprising: the current sensor according to claim 1; and a measuring unit that measures the current value of the current to be measured based on the detected voltage converted by the current sensor.

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