JP6153416B2 - Current sensor and measuring device - Google Patents

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, Significant design changes are required, such as changing the resistance used for the sensing resistor to a higher wattage resistor.

  The present invention has been made in order to improve such a problem, and has as its main object to provide a current sensor and a measuring apparatus that can easily realize high frequency detection frequency characteristics without making a significant design change. To do.

In order to achieve the above object, the current sensor according to claim 1 includes a magnetic core into which a measurement target is inserted, a coil wound around the magnetic core and having one end connected to a reference potential side, A current-voltage conversion unit that is arranged between the other end and the reference potential and converts a detection current flowing in the coil to a detection voltage with a current value corresponding to a current value of a current to be measured flowing in the measurement target; An inductor element connected between at least one of the one end of the coil and the reference potential, and between the other end of the coil and the current-voltage conversion unit, and a parasitic capacitance of the coil; A resonance frequency of a parallel resonance circuit mainly composed of the inductor element is 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. , And the be less than the cutoff frequency, amplitude in the pass band of the detected voltage - any frequency where the frequency characteristic is the Q value the peak value falls within 3 [dB] to the amplitude in the frequency band of flat One frequency is specified.

  The current sensor according to claim 2 is the current sensor according to claim 1, wherein the other end of the coil and the current-voltage converter are connected via a transmission line having a predetermined characteristic impedance, and the inductor The element is connected between the other end of the coil and an end of the transmission path on the coil side.

  According to a third aspect of the present invention, there is provided a measuring apparatus comprising: the current sensor according to the first or second aspect; 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. I have.

The current sensor according to claim 1 and the measuring apparatus according to claim 3, wherein the inductor is connected to at least one of one end of the coil and the reference potential and between the other end of the coil and the current-voltage converter. A resonance frequency of a parallel resonance circuit mainly composed of a parasitic capacitance of a coil and an inductor element is equal to or higher than a cutoff frequency in a frequency characteristic of a detection voltage in a state where the inductor element is not connected. Specified as one of the frequencies that are less than the off-frequency and have a Q value within which the peak value with respect to the amplitude in the frequency band in which the amplitude-frequency characteristic in the pass band of the detection voltage is flat is within 3 [dB]. Has been.

  Therefore, according to the current sensor and the measuring apparatus, it is a simple configuration in which an inductor element having an appropriate inductance having a resonance frequency as described above is connected, but the inductor element is not connected. 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 and the measuring device.

  According to the current sensor of claim 2 and the measuring device of claim 3, when the configuration in which the other end of the coil and the current-voltage converter are connected via the transmission line is adopted, the one end of the transmission line and the coil By connecting an inductor element between the other end of the inductor, the effect of reflection of the detected current is better than when the inductor element is connected between one end of the transmission line and the current-voltage converter. Can be reduced.

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. When the inductance of the inductor element 7 is changed in the equivalent circuit of FIG. 2, the parallel resonance frequency fr of the inductor element 7 and the parasitic capacitance 5d, the cutoff frequency fc in the frequency characteristic of the amplitude of the detection voltage V2, and the parallel resonance. It is explanatory drawing which shows Q value showing the sharpness of the peak of a circuit. 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 of the inductor element 7 is changed in the equivalent circuit of FIG.

  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 capacitive load 6, an inductor element 7, a transmission line 8, and a current voltage. A conversion unit 9 is provided, which is configured as a zero-flux current sensor, and detects a current I1 to be measured flowing in a measurement circuit 21 as a measurement object inserted through the magnetic core 2.

  As an example, the magnetic core 2 is formed in a split type that can be opened and closed with a base end portion (lower end portion in FIG. 1) as a center, and can clamp the measurement electric circuit 21 in a live state (the measurement electric circuit 21 is inserted inside). Possible). 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 capacitive load 6 composed of a series circuit of a resistor 6a (50Ω as an example) and a capacitor 6b (0.1 μF as an example). , The frequency of the current flowing through the coil 5 (negative feedback current I2 or current I3 described later) is equal to or higher than the crossover frequency (frequency at which the frequency characteristic of the negative feedback current I2 and the frequency characteristic of the current I3 intersect). The potential at this time is substantially defined as the potential of the ground G. As for the resistor 6a and the capacitor 6b constituting the capacitive load 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 inductor element 7 is connected between the other end 5 b of the coil 5 and the current-voltage conversion unit 9. In this example, as an example, the other end 5 b of the coil 5 is connected to the current-voltage conversion unit 9 via the transmission line 8, so that the inductor element 7 includes the other end 5 b of the coil 5 and one end of the transmission line 8. 8a. The inductor element 7 is not an inductance component such as a conductor pattern or wiring that electrically connects each component of the current sensor 1, but is composed of an independent electronic component such as an inductor (coil).

  Further, the inductor element 7 has a resonance frequency fr of a parallel resonance circuit with a parasitic capacitance 5d (see FIG. 2) of the coil 5 described later in a state where the inductor element 7 is not connected (the other end 5b of the coil 5 is the transmission line). 8 is a frequency that is higher than or equal to the cutoff frequency fc0 in the high frequency region of the amplitude-frequency characteristics of the detection voltage V2 of the current sensor 1 in the configuration directly connected to one end of the current sensor 8, and less than the cutoff frequency fc0. The inductance is defined so as to be one of the frequencies near the cutoff frequency fc0.

  In the transmission line 8, the characteristic impedance is specified to a predetermined value. 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.

  As an example in this example, the current-voltage conversion unit 9 includes a termination resistor connected between the other end 8b of the transmission line 8 and the ground G or an input resistance of a measuring instrument such as an oscilloscope (hereinafter referred to as “ Also referred to as a terminating resistor 9 ”). 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 V <b> 1 from the Hall element 3, generates a negative feedback current I <b> 2 based on the output voltage V <b> 1, and supplies it to one end 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). 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 case, the negative feedback current I2 flows to the termination resistor 9 via the coil 5, the inductor element 7 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, since the frequency of the negative feedback current I2 is low, the inductor element 7 hardly functions as an impedance. For this reason, in this low frequency region, the current sensor 1 detects the measured current I1 flowing in the measurement circuit 21 with the frequency characteristics of the Hall element 3 and the voltage / current conversion amplification unit 4, and outputs the detected 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. This current I3 flows through the other end 5b of the coil 5, the inductor element 7, the transmission path 8, the termination resistor 9, the ground G, and the capacitive load 6 to the current path reaching the one end 5a of the coil 5. Therefore, the termination resistor 9 converts this current I3 into a detection voltage V2 and outputs it.

In this high frequency region, since the frequency of the current I3 is high, the inductor element 7 functions as an inductor. In this high frequency region, the coil 5 functions as a CT. Therefore, as shown in FIG. 2, the current source ( high-impedance signal source) 5c that outputs the current I3 equivalently as described above, and the coil 5 can be regarded as a parallel circuit with the parasitic capacitance 5d existing between the wires forming the wire 5. Thereby, the inductor element 7 forms a parallel resonance circuit with the parasitic capacitance 5d. Note that the actual current sensor 1 includes an inductance component other than the inductor element 7 such as an inductance component included in a wire or a wiring pattern, and a capacitance component other than the parasitic capacitance 5d of the coil 5 such as a stray capacitance. However, these are sufficiently smaller than the inductor element 7 and the parasitic capacitance 5d. For this reason, the parallel resonant circuit described above can be regarded as a resonant circuit mainly composed of the inductor element 7 and the parasitic capacitance 5d.

  In the current sensor 1, as described above, the resonance frequency fr of the parallel resonance circuit of the inductor element 7 and the parasitic capacitance 5d of the coil 5 is the detection voltage V2 of the current sensor 1 when the inductor element 7 is not connected. The inductor element 7 has a frequency that is higher than or equal to the cutoff frequency fc0 in the high frequency region of the amplitude-frequency characteristic of the first and second frequencies that is lower than the cutoff frequency fc0 and in the vicinity of the cutoff frequency fc0. Inductance is specified.

  Specifically, the equivalent circuit shown in FIG. 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 termination resistor 9 is 50Ω. In this case, the cut-off frequency fc0 in the high frequency region of the amplitude-frequency characteristic for the detection voltage V2 of the current sensor 1 in a state where the inductor element 7 is not connected is C, and the termination resistance 9 Is represented by the equation (1 / (2 × π × C × R). Thus, in this example, the cutoff frequency fc0 is defined as 318 MHz.

  Therefore, when the inductance of the inductor element 7 is L, the resonance frequency fr (= 1 / (2 × π × √ (L × C))) of the parallel resonance circuit of the inductor element 7 and the parasitic capacitance 5d of the coil 5 Is determined so that the frequency is equal to or higher than the cut-off frequency fc0 (= 318 MHz) or less than the cut-off frequency fc0 (= 318 MHz) and in the vicinity of the cut-off frequency fc0. Has been.

  In this example, as shown in FIG. 3, when the inductance L is changed in 8 steps from 5 nH to 10 nH, 20 nH, 30 nH, 40 nH, 50 nH, 60 nH, 100 nH (zero nH is the inductor element 7 Is not connected (the other end 5b of the coil 5 is connected to one end 8a of the transmission line 8), the resonance frequency fr is changed from 712 MHz to 503 MHz, 356 MHz as shown in FIG. 291 MHz, 252 MHz, 225 MHz, 205 MHz, 159 MHz and so on. For this reason, in this example, the inductor element 7 has 5 nH, 10 nH and 20 nH in which the resonance frequency fr is equal to or higher than the cut-off frequency fc0 among the eight inductances L shown in FIG. It is less than fc0 and in the vicinity of the cutoff frequency fc0 (when the resonance frequency fr is less than the cutoff frequency fc0, the sharpness of the peak of the parallel resonance circuit is increased as shown by the amplitude-frequency characteristics of the detection voltage V2 shown in FIG. Since the indicated Q value (= 1 / R × √ (L / C)) becomes larger and the amplitude of the detection voltage V2 changes too much depending on the frequency, the amplitude-frequency characteristic in the pass band is flat. The resonance frequency fr (252M) at which the peak value with respect to the amplitude in the frequency region becomes a Q value (1.26) that falls within 3 [dB]. Up to z) are defined in any of the inductance L of 30nH and 40nH made to) the vicinity of the cut-off frequency fc0 here.

  Thereby, in this current sensor 1, since the inductance L of the inductor element 7 is defined as one of 5nH, 10nH, 20nH, 30nH and 40nH, as shown in FIG. Even when the cut-off frequency fc in the high frequency region of the amplitude-frequency characteristics for the current sensor 1 when the inductor element 7 is connected is the cut-off frequency fc0 (= 318 MHz) when the inductor element 7 is not connected. Than can be higher. Accordingly, in this current sensor 1, as shown in FIG. 4, the upper limit frequency in the high frequency region of the amplitude-frequency characteristic for the detection voltage V2 of the current sensor 1 is when the inductor element 7 is not connected (FIG. The amplitude-frequency characteristic indicated by a broken line in Fig. 4 (amplitude-frequency characteristic of 0 nH) is extended to the high frequency side.

  As shown in FIGS. 3 and 4, in the range where the resonance frequency fr is equal to or higher than the cutoff frequency fc0, the cutoff frequency fc (the upper limit frequency in the high frequency region of the amplitude-frequency characteristic) is always the cutoff frequency fc0. However, the resonance frequency fr gradually decreases from when it exceeds a certain frequency (in this example, near 503 MHz). In addition, the amplitude-frequency characteristic of the detection voltage V2 gradually approaches the amplitude-frequency characteristic in a state where the inductor element 7 is not connected, and the decrease in the amplitude in the high frequency region becomes large. For this reason, the resonance frequency fr is preferably set to a frequency equal to or lower than a frequency at which the decrease in amplitude in the high frequency region is within an allowable range.

  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, the current sensor 1 and the measuring device MD include the inductor element 7 connected between the other end 5b of the coil 5 and the termination resistor 9, and are mainly configured by the parasitic capacitance 5d and the inductor element 7 of the coil 5. The resonant frequency fr of the parallel resonant circuit to be performed is a frequency that is equal to or higher than the cutoff frequency fc0 in the amplitude-frequency characteristic of the detection voltage V2 in a state where the inductor element 7 is not connected, and is lower than the cutoff frequency fc0. One of the frequencies in the vicinity of the frequency fc0 is defined.

  Therefore, according to the current sensor 1 and the measuring apparatus MD, the inductor element 7 is connected to the current sensor 1 and the measuring device MD while the inductor element 7 has a simple configuration in which the inductor L 7 having an appropriate inductance L having the resonance frequency fr as described above is connected. The upper limit frequency in the high frequency region of the amplitude-frequency characteristic for the detection voltage V2 can be extended to a higher frequency side than the current sensor 1 in a state where the detection is not performed.

  In the current sensor 1 and the measuring device MD described above, one end of the transmission line 8 that is an end portion on the other end 5b side of the coil 5 of the transmission line 8 that connects the other end 5b of the coil 5 and the current-voltage conversion unit 9. The configuration in which the inductor element 7 is connected between the other end 5b of the coil 5 is adopted, but the inductor element 7 is connected between the other end 8b of the transmission line 8 and the current-voltage conversion unit 9. Configuration is also conceivable. However, as a result of the experiment, when the configuration in which the inductor element 7 is connected between the other end 8b of the transmission line 8 and the current-voltage conversion unit 9, the one end 8a of the transmission line 8 and the other end 5b of the coil 5 are connected. It was confirmed that the influence of the reflection of the current I3 appears significantly as compared with the configuration in which the inductor element 7 is connected therebetween. For this reason, when the configuration in which the other end 5b of the coil 5 is connected to the current-voltage conversion unit 9 via the transmission line 8, the influence of the reflection of the current I3 can be satisfactorily reduced. And the other end 5 b of the coil 5 are preferably connected to the inductor element 7.

  Moreover, the other end 5b of the coil 5 and the current-voltage conversion unit 9 can be directly connected without passing through the transmission line 8, or can be connected via a normal electric wire or wiring pattern. In these configurations, the inductor element 7 can be connected to an arbitrary position between the other end 5 b of the coil 5 and the current-voltage converter 9.

  Further, in the current sensor 1 and the measurement device MD described above, a configuration in which the inductor element 7 is connected between the other end 5b of the coil 5 and the current-voltage conversion unit 9 is adopted, but the present invention is not limited to this configuration. A configuration in which the inductor element 7 is connected between the one end 5a of the coil 5 and the reference potential (ground G) side can also be adopted. In this configuration as well, the other end 5b of the coil 5 and the current-voltage conversion unit 9 described above can be used. In the same manner as the configuration in which the inductor element 7 is connected to the upper limit frequency, the upper limit frequency in the high frequency region of the amplitude-frequency characteristic of the detection voltage V2 of the current sensor can be extended to a higher frequency side.

  In the configuration in which the inductor element 7 is connected between the one end 5a of the coil 5 and the reference potential (ground G) side, as shown in FIG. 1, a connection line connecting the one end 5a of the coil 5 and the capacitive load 6 When the connection point with the output side line of the voltage-current conversion amplifier 4 is a point A (hereinafter also referred to as “connection point A”), the connection is made between one end 5a of the coil 5 and the connection point A. It is possible to adopt at least one of the configuration and the configuration of connecting between the connection point A and the capacitive load 6.

  Further, the configuration in which the inductor element 7 is connected between the other end 5b of the coil 5 and the current-voltage conversion unit 9, and the inductor element between the one end 5a of the coil 5 and the reference potential (ground G) side. 7 can be used together, and in this configuration as well, the same configuration as the configuration in which the inductor element 7 is connected between the other end 5b of the coil 5 and the current-voltage conversion unit 9 described above. There is an effect.

1 Current sensor
2 Magnetic core
3 Hall element
4 Voltage-current conversion amplifier
5 coils
7 Inductor element
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 MD Measuring device

Claims (3)

A magnetic core into which the measurement object is inserted;
A coil wound around the magnetic core and having one end connected to a reference potential side;
Current-voltage conversion that is arranged between the other end of the coil and the reference potential and converts the detected current flowing through the coil to a detected voltage with a current value corresponding to the current value of the current to be measured flowing through the measurement target. And
An inductor element connected between at least one of the one end of the coil and the reference potential and between the other end of the coil and the current-voltage conversion unit;
The resonance frequency of the parallel resonance circuit mainly composed of the parasitic capacitance of the coil and the inductor element is equal to or higher than the cutoff frequency in the frequency characteristic of the detection voltage in a state where the inductor element is not connected, and the cut It is less than the off-frequency, and the peak value with respect to the amplitude in the frequency band in which the amplitude-frequency characteristic in the pass band of the detection voltage is flat is set to any one of the frequencies having a Q value that falls within 3 [dB]. Specified current sensor. The other end of the coil and the current-voltage converter are connected via a transmission line having a predetermined characteristic impedance,
The current sensor according to claim 1, wherein the inductor element is connected between the other end of the coil and an end of the transmission line on the coil side.   3. 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.

Images