CN112424618A - Current sensor - Google Patents

Abstract

The invention can switch the detection rate and reduce the influence of noise generated by the amplifier. The current sensor includes: a magnetic core (2); a magnetoelectric conversion unit (3); a feedback winding (4); a voltage-current conversion circuit (5) that generates a negative feedback current (I2) on the basis of a voltage (V1) from the magnetoelectric conversion unit (3) and supplies the negative feedback current to one end (4a) of the feedback winding (4); an output terminal (9); a voltage conversion unit (6a) that converts the negative feedback current (I2) output from the other end (4b) of the feedback winding (4) into a 1 st detection voltage (Vd1) at a 1 st detection rate using a 1 st detection resistor (13) and outputs the voltage as an output voltage (Vo) to an output terminal (9); a voltage conversion unit (6b) that converts the negative feedback current (I2) into a 2 nd detection voltage (Vd2) at a 2 nd detection rate using a 2 nd detection resistor (23) and outputs the voltage as an output voltage (Vo) to an output terminal (9); and a switching unit (7) that switches to a connection state in which either one of the voltage conversion units (6a, 6b) is connected between the other end (4b) of the feedback winding (4) and the output terminal (9).

Description

Current sensor

Technical Field

The present invention relates to a current sensor for detecting a detection current flowing through a detection conductor by a zero-flux method.

Background

As such a current sensor, patent document 1 below discloses a current sensor capable of switching a detection rate (conversion rate when converting a measured current into an output voltage) by detecting a detected current (measured current) flowing through a conductor (a wire to be measured) by a zero-magnetic-flux method (a method including a core, a magneto-electric conversion unit (a hall element, a fluxgate element, or the like), a feedback winding (a negative feedback coil), a voltage-current conversion circuit, a detection resistance circuit that converts a negative feedback current into a voltage and outputs the voltage, and an amplification circuit that amplifies the voltage output from the detection resistance circuit and outputs the voltage as an output voltage), and switching a combination of a detection resistance constituting the detection resistance circuit and an input resistance of an operational amplifier constituting the amplification circuit.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-215065 (pages 5-8, FIG. 1)

Disclosure of Invention

Technical problem to be solved by the invention

However, the above-described conventional current sensor has the following problems to be improved. That is, in the conventional current sensor, the detection voltage detected by the detection resistor is amplified by the operational amplifier constituting the amplification circuit and is output as the output voltage regardless of the detection rate, and therefore, the current sensor has the following problems: the output voltage outputted at all the detection rates will be affected by noise generated by the operational amplifier itself constituting the amplifying circuit.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a current sensor capable of switching a detection rate and reducing the influence of noise generated by an amplifier.

Technical scheme for solving technical problem

In order to achieve the above object, the current sensor according to claim 1 comprises: a magnetic core into which a detection conductor is inserted; a magnetoelectric conversion portion disposed on the magnetic core; a feedback winding wound around the magnetic core; a voltage-current conversion circuit that generates a negative feedback current that cancels magnetic flux generated in the magnetic core by a detection current flowing through the detection conductor, based on a voltage output from the magnetoelectric conversion unit, and supplies the generated negative feedback current to one end of the feedback winding; and an output terminal, the current sensor having: 1 or 2 or more 1 st voltage conversion units that convert the negative feedback current output from the other end of the feedback winding into a voltage using a 1 st detection resistor, convert the detection current into a 1 st detection voltage at a 1 st detection rate, and output the voltage; 1 or 2 or more 2 nd voltage converting units which convert the negative feedback current into a voltage using a 2 nd detection resistor and amplify the voltage using an amplifier, thereby converting the detection current into a 2 nd detection voltage at a 2 nd detection rate larger than the 1 st detection rate and outputting the 2 nd detection voltage; and a switching unit that switches to the following connection state: any one element of the 1 st or 2 or more voltage converting parts and the 1 or 2 or more voltage converting parts is connected between the other end and the output terminal.

In the current sensor according to claim 2, in the current sensor according to claim 1, a resistance value of the detection resistor included in the one of the 1 st detection resistor and the 2 nd detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the one of the elements.

Further, the current sensor according to claim 3 is the current sensor according to claim 1 or 2, including: a sensor unit that houses the magnetic core, the magnetoelectric conversion portion, and the feedback winding; a relay unit that houses the voltage-current conversion circuit and a transmission path; a terminal unit that houses the switching unit, the 1 st voltage conversion unit, the 2 nd voltage conversion unit, and the output terminal; 1 st connecting cable; and a 2 nd connection cable, the sensor unit and the relay unit being connected via the 1 st connection cable, and the voltage-current conversion circuit being connected between the magneto-electric conversion section and the one end of the feedback winding via a wiring constituting the 1 st connection cable, and one end of the transmission path being connected to the other end of the feedback winding via another wiring constituting the 1 st connection cable, the relay unit and the terminal unit being connected via the 2 nd connection cable, and the switching section being switched to a connection state of: the arbitrary one element is connected between the output terminal and the other end of the transmission path connected via the wiring constituting the 2 nd connection cable.

Further, the current sensor of claim 4 comprises: a magnetic core into which a detection conductor is inserted; a magnetoelectric conversion portion disposed on the magnetic core; a feedback winding wound around the magnetic core; a voltage-current conversion circuit that generates a negative feedback current that cancels magnetic flux generated in the magnetic core by a detection current flowing through the detection conductor, based on a voltage output from the magnetoelectric conversion unit, and supplies the generated negative feedback current to one end of the feedback winding; and an output terminal, wherein the current sensor includes a 1 st detection resistor for converting a supplied current into a voltage, a 2 nd detection resistor for converting the supplied current into a voltage, an amplifier for amplifying the voltage converted from the 2 nd detection resistor and outputting the amplified voltage, a transmission path, and a switching unit for switching the negative feedback current output from the other end of the feedback winding to be supplied to one of an element of a current-voltage conversion circuit including the 2 nd detection resistor and the amplifier and the transmission path and supplying a signal output from the one element to the 1 st detection resistor, and the 1 st detection resistor converts the negative feedback current into a voltage in a switching state in which the switching unit is switched to the transmission path as the one element, thereby converting the detection current into a 1 st detection voltage at a 1 st detection rate and outputting the 1 st detection voltage to the output terminal, in a switching state in which the switching unit is switched to the current-voltage conversion circuit as the one element, the current-voltage conversion circuit and the 1 st detection resistor convert and amplify the negative feedback current into a voltage, and convert and output the detection current into a 2 nd detection voltage at a 2 nd detection rate larger than the 1 st detection rate to the output terminal.

In the current sensor according to claim 5, in the current sensor according to claim 4, a resistance value of the 1 st detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the 1 st detection resistor in a switching state in which the switching unit switches the transmission path to the one element.

In the current sensor according to claim 6, in the current sensor according to claim 4, a resistance value of the 2 nd detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the current-voltage conversion circuit in a switching state in which the switching unit switches to the current-voltage conversion circuit as the one element.

In the current sensor according to claim 7, in the current sensor according to claim 6, a resistance value of the 1 st detection resistor is defined as a characteristic impedance of a line from the current-voltage conversion circuit to the 1 st detection resistor.

Further, the current sensor according to claim 8 is the current sensor according to any one of claims 4 to 7, including: a sensor unit that houses the magnetic core, the magnetoelectric conversion portion, and the feedback winding; a relay unit that houses the voltage-current conversion circuit, the transmission path, the current-voltage conversion circuit, and the switching unit; a terminal unit that houses the 1 st detection resistor and the output terminal; 1 st connecting cable; and a 2 nd connection cable, the sensor unit and the relay unit being connected via the 1 st connection cable, and the voltage-current conversion circuit being connected between the magneto-electric conversion section and the one end of the feedback winding via a wiring constituting the 1 st connection cable, and the switching section being connected to the other end of the feedback winding via another wiring constituting the 1 st connection cable, the relay unit and the terminal unit being connected via the 2 nd connection cable, and the switching section being switched to a connection state of: and a 1 st detection resistor connected between the other end of the feedback winding connected via the other wiring constituting the 1 st connection cable and the wiring constituting the 2 nd connection cable.

Further, the current sensor of claim 9 comprises: a magnetic core into which a detection conductor is inserted; a magnetoelectric conversion portion disposed on the magnetic core; a feedback winding wound around the magnetic core; a voltage-current conversion circuit that generates a negative feedback current that cancels magnetic flux generated in the magnetic core by a detection current flowing through the detection conductor, based on a voltage output from the magnetoelectric conversion unit, and supplies the generated negative feedback current to one end of the feedback winding; and an output terminal, the current sensor having a 1 st detection resistor for converting a supplied current into a voltage, a 2 nd detection resistor for converting the supplied current into a voltage, an amplifier for amplifying and outputting a voltage converted from the 2 nd detection resistor, a 3 rd detection resistor for converting the supplied current into a voltage, a transmission path, a 1 st switching unit for switching and supplying the negative feedback current outputted from the other end of the feedback winding to a 1 st element of either one of a current-voltage conversion circuit composed of the 2 nd detection resistor and the amplifier and the transmission path and supplying a signal outputted from the 1 st element to the 2 nd switching unit, and a 2 nd switching unit for switching and supplying the signal supplied from the 1 st switching unit to a 2 nd element of either one of the 1 st detection resistor and the 3 rd detection resistor, and outputs a signal output from the one 2 nd element to the output terminal, in a switching state in which the 1 st switching unit is switched to the transmission path as the one 1 st element and the 2 nd switching unit is switched to the 1 st detection resistor as the one 2 nd element, the 1 st detection resistor converts the negative feedback current into a voltage to convert the detection current into a 1 st detection voltage at a 1 st detection rate and outputs the detection current to the output terminal, and in a switching state in which the 1 st switching unit is switched to the current-voltage conversion circuit as the one 1 st element and the 2 nd switching unit is switched to the 1 st detection resistor as the one 2 nd element, the current-voltage conversion circuit and the 1 st detection resistor convert the negative feedback current into a voltage and amplify the negative feedback current, and a 3 rd detection resistor converting the negative feedback current into a voltage in a 2 nd detection state in which the 1 st switching unit is switched to the transmission path as the one 1 st element and the 2 nd switching unit is switched to the 3 rd detection resistor as the one 2 nd element, and converting the detection current into a 3 rd detection voltage at a 3 rd detection rate smaller than the 1 st detection rate and outputting the detection current to the output terminal.

In the current sensor according to claim 10, in the current sensor according to claim 9, a resistance value of the 1 st detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the 1 st detection resistor in a switching state in which the 1 st switching unit switches the transmission path to be the one 1 st element and the 2 nd switching unit switches the 1 st detection resistor to be the one 2 nd element.

In the current sensor according to claim 11, in the current sensor according to claim 9, a resistance value of the 2 nd detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the current-voltage conversion circuit in a switching state in which the 1 st switching unit is switched to the current-voltage conversion circuit as the one 1 st element and the 2 nd switching unit is switched to the 1 st detection resistor as the one 2 nd element.

In the current sensor according to claim 12, in the current sensor according to claim 11, a resistance value of the 1 st detection resistor is defined as a characteristic impedance of a line from the current-voltage conversion circuit to the 1 st detection resistor.

In the current sensor according to claim 13, in the current sensor according to claim 9, a resistance value of the 3 rd detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the 3 rd detection resistor in a switching state in which the 1 st switching unit switches the transmission path to be the one 1 st element and the 2 nd switching unit switches the 3 nd detection resistor to be the one 2 nd element.

Further, the current sensor according to claim 14 is the current sensor according to any one of claims 9 to 13, including: a sensor unit that houses the magnetic core, the magnetoelectric conversion portion, and the feedback winding; a relay unit that houses the voltage-to-current conversion circuit, the transmission path, the current-to-voltage conversion circuit, and the 1 st switching unit; a terminal unit that houses the 1 st detection resistor, the 3 rd detection resistor, the 2 nd switching unit, and the output terminal; 1 st connecting cable; and a 2 nd connection cable, the sensor unit and the relay unit being connected via the 1 st connection cable, and the voltage-current conversion circuit being connected between the magneto-electric conversion section and the one end of the feedback winding via a wiring constituting the 1 st connection cable, and the 1 st switching section being connected to the other end of the feedback winding via another wiring constituting the 1 st connection cable, the relay unit and the terminal unit being connected via the 2 nd connection cable, the 1 st switching section being switched to the following connection state: connecting the 1 st element between the other end of the feedback winding connected via the other wiring constituting the 1 st connection cable and the 2 nd switching unit connected via a wiring constituting the 2 nd connection cable, the 2 nd switching unit switching to the following connection state: the 2 nd element is connected between the wiring constituting the 2 nd connection cable and the output terminal.

Effects of the invention

In the current sensor according to claims 1 and 4, the negative feedback current is also small because the current value of the detection current is small, and when the 1 st detection voltage that cannot be converted to a sufficient voltage value by the 1 st detection resistor alone is output, the circuit including the 2 nd detection resistor and the amplifier converts the detection current to the 2 nd detection voltage of a sufficient voltage value at the 2 nd detection rate, but when the current value of the detection current is large, the negative feedback current is also large because the current value of the detection current is large, and when the 1 st detection voltage that can be converted to a sufficient voltage value by the 1 st detection resistor alone is output, the circuit for voltage conversion including the 1 st detection resistor without the amplifier converts the detection current to the 1 st detection voltage of a sufficient voltage value at the 1 st detection rate.

Therefore, according to this current sensor, the detection rate can be switched, and the detection current can be converted into the 1 st detection voltage and output by a configuration not including an amplifier at the 1 st detection rate (the 1 st detection rate), that is, without being affected by noise generated by the amplifier.

The current sensor according to claim 9, wherein the negative feedback current is small because the current value of the detection current is small, and when the 1 st detection voltage which cannot be converted into the sufficient voltage value by the 1 st detection resistor alone is present, the circuit including the 2 nd detection resistor and the amplifier converts the detection current into the 2 nd detection voltage of the sufficient voltage value at the 2 nd detection rate and outputs the same, but when the current value of the detection current is large, the negative feedback current is large because the current value of the detection current is present, and when the 1 st detection voltage which can be converted into the sufficient voltage value by the 1 st detection resistor alone is present, the circuit including the 1 st detection resistor without the amplifier converts the detection current into the 1 st detection voltage of the sufficient voltage value at the 1 st detection rate and outputs the same. Further, since the current value of the detection current is further increased, the negative feedback current is also further increased, and when the voltage value is excessively large in the voltage conversion by the 1 st detection resistor, the circuit including the 3 rd detection resistor having a smaller resistance value than the 1 st detection resistor without including an amplifier converts the detection current into the 3 rd detection voltage at the 3 rd detection rate smaller than the 1 st detection rate and outputs the 3 rd detection voltage.

Therefore, according to this current sensor, the detection current having a large current value can be converted into the 1 st detection voltage and the 3 rd detection voltage without including an amplifier and output. That is, according to this current sensor, the detection current can be converted into the 1 st detection voltage and the 3 rd detection voltage and output by a configuration not including an amplifier at 2 detection rates (the 1 st detection rate and the 3 rd detection rate), that is, without being affected by noise generated by the amplifier.

In the current sensor according to claim 3, when a negative feedback current having a large current value flows (at the 1 st detection rate), the voltage-current conversion circuit and the 1 st detection resistor, which have large heat generation amounts, are housed in separate units (the voltage-current conversion circuit is housed in the relay unit, and the 1 st detection resistor is housed in the terminal unit), and therefore, the heat generation amounts of the voltage-current conversion circuit and the 1 st detection resistor can be dispersed to the separate units. Thus, according to the current sensor, the temperature rise in the relay unit and the temperature rise in the terminal unit can be suppressed to be low together. Further, the influence of the heat generation of the 1 st detection resistor on the voltage-current conversion circuit can be avoided. Further, the influence of the heat generation of the 1 st detection resistor on the magnetic core, the magnetoelectric conversion portion, and the feedback winding disposed in the sensor unit can also be avoided.

In the current sensor according to claim 8, when a negative feedback current having a large current value flows (at the 1 st detection rate), the voltage-current conversion circuit and the 1 st detection resistor, which have a large heat generation amount together, are housed in separate units (the voltage-current conversion circuit is housed in the relay unit, and the 1 st detection resistor is housed in the terminal unit), and therefore, the heat generation of each of the voltage-current conversion circuit and the 1 st detection resistor can be dispersed to the separate units. Thus, according to the current sensor, the temperature rise in the relay unit and the temperature rise in the terminal unit can be suppressed to be low together. Further, according to the current sensor, since the voltage-current conversion circuit and the current-voltage conversion circuit (the circuit including the 2 nd detection resistor and the amplifier) are housed in the relay unit different from the 1 st detection resistor, it is possible to avoid an influence of heat generation of the 1 st detection resistor on the amplifiers of the voltage-current conversion circuit and the current-voltage conversion circuit, unlike a configuration housed in the terminal unit having a tendency to further increase the average temperature due to heat generation of the 1 st detection resistor.

The current sensor according to claim 14, wherein when a negative feedback current of a large current value flows (at the 1 st detection rate and the 3 rd detection rate), the voltage-current conversion circuit of the 1 st detection resistor and the 3 rd detection resistor, and the 1 st detection resistor and the 3 rd detection resistor, which have a larger heat generation amount together, are housed in different units (the voltage-current conversion circuit is housed in the relay unit, and the 1 st detection resistor and the 3 rd detection resistor are housed in the terminal unit), and therefore, heat generation in the voltage-current conversion circuit and heat generation in the 1 st detection resistor and the 3 rd detection resistor can be dispersed to different units. Thus, according to the current sensor, the temperature rise in the relay unit and the temperature rise in the terminal unit can be suppressed to be low together while switching the detection rates by 3. Further, according to the current sensor, since the voltage-current conversion circuit and the current-voltage conversion circuit (the circuit including the 2 nd detection resistor and the amplifier) are housed in the relay unit different from the 1 st detection resistor and the 3 rd detection resistor, the influence of the heat generation of the 1 st detection resistor and the 3 rd detection resistor on the amplifiers of the voltage-current conversion circuit and the current-voltage conversion circuit can be avoided, unlike the configuration housed in the terminal unit in which the average temperature tends to become higher due to the heat generation of the 1 st detection resistor and the 3 rd detection resistor.

The current sensor according to claim 2, wherein a resistance value of the detection resistor that converts the negative feedback current into the corresponding one of the 1 st detection voltage and the 2 nd detection voltage is defined as a characteristic impedance of a line that supplies the negative feedback current to the detection resistor, and therefore, waveform distortion with respect to the detection voltage can be suppressed to be low.

According to the current sensor of claims 5 and 10, the resistance value of the 1 st detection resistor that converts the negative feedback current into the 1 st detection voltage is specified as the characteristic impedance of the line that supplies the negative feedback current to the 1 st detection resistor, and therefore, the waveform distortion with respect to the 1 st detection voltage can be suppressed low.

According to the current sensor of claims 6 and 11, since the resistance value of the 2 nd detection resistor that converts the negative feedback current into a voltage is defined as the characteristic impedance of the line that supplies the negative feedback current to the current-voltage conversion circuit including the 2 nd detection resistor, the waveform distortion with respect to the voltage converted by the 2 nd detection resistor can be suppressed to be low.

According to the current sensor as claimed in claims 7 and 12, the resistance value of the 1 st detection resistor is defined as the characteristic impedance of the line for transmitting the voltage converted by the current-voltage conversion circuit including the 2 nd detection resistor to the 1 st detection resistor, and therefore, the waveform distortion with respect to the 2 nd detection voltage outputted from the 1 st detection resistor can be further suppressed to be low.

The current sensor according to claim 13, wherein a resistance value of a 3 rd detection resistor that converts the negative feedback current into a 3 rd detection voltage is specified as a characteristic impedance of a line that supplies the negative feedback current to the 3 rd detection resistor, and therefore, waveform distortion with respect to the 3 rd detection voltage can be suppressed low.

Drawings

Fig. 1 is a structural diagram of a current sensor 1A.

Fig. 2 is a configuration diagram showing an example in which the configuration elements of the current sensor 1A are divided into two and arranged as a sensor unit 51 and a terminal unit 52.

Fig. 3 is a structural diagram of the current sensor 1B.

Fig. 4 is a structural diagram of the current sensor 1C.

Fig. 5 is a structural diagram of the current sensor 1D.

Fig. 6 is a structural diagram of the current sensor 1E.

Fig. 7 is a structural diagram of the current sensor 1F.

Detailed Description

Hereinafter, embodiments of the current sensor will be described with reference to the drawings.

First, the structure of a current sensor 1A as a current sensor will be described with reference to fig. 1.

As shown in fig. 1, the current sensor 1A includes a magnetic core 2, a magneto-electric conversion unit 3, a feedback winding 4, a voltage-current conversion circuit 5, a plurality of voltage conversion units (in this example, 2 voltage conversion units 6a and 6b), a 1 st switching unit 7 (hereinafter, simply referred to as a switching unit 7), and an output terminal 9, and is configured as a zero-magnetic-flux current sensor. Further, the current sensor 1A outputs an output voltage Vo, a voltage value of which varies in accordance with a current value of the detection current I1 flowing in the detected electric wire 61 as one example of the detection conductor inserted into the inside of the magnetic core 2, from the output terminal 9.

As an example, the core 2 is formed in a split type that can be opened and closed around a base end portion (lower end portion in fig. 1), and is configured to be able to clamp the wire 61 to be detected in an electrically charged state (to be able to insert the wire 61 into the inside). The core 2 is not limited to the split type, and may be a through type (non-split type).

As an example, the magneto-electric conversion portion 3 is configured by a magneto-electric conversion element such as a hall element or a fluxgate. Further, as an example, the magneto-electric conversion portion 3 is provided at the base end portion of the magnetic core 2. The magneto-electric conversion portion 3 detects magnetic flux generated inside the magnetic core 2 in an operating state, and outputs a voltage V1 having a voltage value corresponding to (specifically, proportional to or substantially proportional to) the magnetic flux density. In this case, the magnetic flux generated inside the magnetic core 2 is a composite magnetic flux (Φ 1- Φ 2) of a magnetic flux Φ 1 generated by the current I1 flowing through the current-to-be-detected wire 61 inserted into the magnetic core 2 and a magnetic flux Φ 2 (a magnetic flux in the opposite direction to the magnetic flux Φ 1) generated by the current I2 flowing through the feedback winding 4, which will be described later.

The feedback winding 4 is configured by winding a wire around the core 2 with a predetermined number of turns n (n is 50 in this example). The voltage-current conversion circuit 5 is configured by an operational amplifier or the like, receives a voltage V1 from the magneto-electric conversion unit 3, and generates a negative feedback current I2 based on the voltage V1 to supply the negative feedback current to the one end 4a of the feedback winding 4. In this case, the voltage-current conversion circuit 5 controls the current value of the negative feedback current I2 so that the voltage V1 approaches zero volts, that is, so that the magnetic flux density of the resultant magnetic flux (Φ 1- Φ 2) generated inside the magnetic core 2 detected in the magnetoelectric conversion section 3 approaches zero (in other words, the magnetic flux Φ 1 is cancelled out by the magnetic flux Φ 2). That is, the negative feedback current I2 is a value obtained by dividing the detection current I1 by the number of turns n (I2 — I1/n).

The switching unit 7 is configured to have 2 switches 7a and 7b having a 1-circuit 2 contact structure, for example, and switches to a connection state in which 1 st element (voltage conversion unit) of any 1 of the 2 voltage conversion units 6a and 6b is connected between the other end 4b of the feedback winding 4 and the output terminal 9. Specifically, the changeover switch 7a is connected between the other end 4b of the feedback winding 4 and the input units 11 and 21 of the voltage converting units 6a and 6b, which will be described later, and selectively switches to either one of the voltage converting units 6a and 6b to output the negative feedback current I2 output from the other end 4b of the feedback winding 4. The changeover switch 7b is connected between the output units 12 and 22 of the voltage conversion units 6a and 6b, which will be described later, and the output terminal 9, and is switched in conjunction with the changeover switch 7 a. Specifically, when the changeover switch 7a is switched so as to connect the other end 4b of the feedback winding 4 to the input portion 11 of the voltage converting unit 6a, the changeover switch 7b is switched so as to connect the output portion 12 of the voltage converting unit 6a to the output terminal 9. When the changeover switch 7a is switched so as to connect the other end 4b of the feedback winding 4 to the input portion 21 of the voltage converting unit 6b, the changeover switch 7b is switched so as to connect the output portion 22 of the voltage converting unit 6b to the output terminal 9. According to this configuration, the switching unit 7 outputs the detection voltage outputted from one of the voltage conversion units 6a and 6b to which the negative feedback current I2 is supplied (the 1 st detection voltage Vd1 outputted from the voltage conversion unit 6a when the negative feedback current I2 is supplied to the voltage conversion unit 6a, and the 2 nd detection voltage Vd2 outputted from the voltage conversion unit 6b when the negative feedback current I2 is supplied to the voltage conversion unit 6b) as the output voltage Vo to the output terminal 9. The switching unit 7 (in this example, the switching switches 7a and 7b) is configured by a mechanical switch such as a relay or a switch configured by a semiconductor element such as an analog switch.

The voltage converter 6a is a 1 st voltage converter, the input unit 11 is connected to the changeover switch 7a of the changeover unit 7, and when the negative feedback current I2 is output from the changeover switch 7a to the input unit 11, the negative feedback current I2 is converted into a 1 st detection voltage Vd1, and the 1 st detection voltage Vd1 is directly output from the output unit 12. In this example, the voltage converting unit 6a is configured to include the 1 st detection resistor 13 having a predetermined resistance value R1 (e.g., 50 Ω). The 1 st detection resistor 13 has one end connected to the input unit 11 and the output unit 12 and the other end connected to a portion (ground G) of the current sensor 1A at the reference potential, and constitutes a current-voltage conversion circuit. With this configuration, the voltage converter 6a converts the negative feedback current I2 input to the input unit 11 into the 1 st detection voltage Vd1 (I2 × R1) by the 1 st detection resistor 13 (resistance value R1) and directly outputs the voltage from the output unit 12. The 1 st detection voltage Vd1 is represented as (I1 × R1/n) using a 1 st detection rate (R1/n) defined by the resistance value R1 and the number of turns n. In this example, R1 is 50 Ω, and n is 50, so the voltage conversion section 6a converts the detection current I1 into the 1 st detection voltage Vd1 at the 1 st detection rate (numerical value "1").

The voltage converter 6b is a 2 nd voltage converter, the input unit 21 is connected to the changeover switch 7b of the changeover unit 7, and when the negative feedback current I2 is output from the changeover switch 7b to the input unit 21, the negative feedback current I2 is converted into a 2 nd detection voltage Vd2 and is output from the output unit 22. In this example, as one example, the voltage converting section 6b includes: a 2 nd detection resistor 23 having a predetermined resistance value R2 (e.g., 50 Ω); an amplifier (for example, a wide band amplifier composed of an operational amplifier) 24 that amplifies an input voltage by k times (k is a real number exceeding 1, which is specified in advance; in the present example, the numerical value "10") and outputs the amplified voltage; and an output resistor 25 (a resistance value Ro., 50 Ω in this example) connected between the output terminal of the amplifier 24 and the output unit 22, and configured as a current-voltage conversion circuit. The 2 nd detection resistor 23 has one end connected to the input section 21 and the input terminal of the amplifier 24, and the other end connected to the ground G. According to this configuration, the voltage converter 6b converts the negative feedback current I2 input to the input unit 21 into the 2 nd detection voltage Vd2 (I2 × R2 × k), and outputs the voltage from the output unit 12. The 2 nd detection voltage Vd2 is represented as (I1 × R2/n × k) using a 2 nd detection rate (R2/n × k) defined by the resistance value R2, the number of turns n, and the value k (amplification rate k of the amplifier 24). In this example, since R2 is 50 Ω, n is 50, and k is 10, the voltage conversion section 6b converts the detection current I1 into the 2 nd detection voltage Vd2 at the 2 nd detection rate (value "10") which is greater than the 1 st detection rate.

Next, a method of using the current sensor 1A and an operation thereof will be described with reference to the drawings. In the current sensor 1A, the output terminal 9 is connected to a measuring instrument (for example, a waveform observing device such as an oscilloscope) having a high input impedance (for example, 1M Ω or more) for use. Thus, the measuring device can perform waveform observation or the like on the detection current I1 detected by the current sensor 1A.

In a state where the detection electric wire 61 through which the detection current I1 flows is inserted into the magnetic core 2, the magneto-electric conversion section 3 detects magnetic flux generated inside the magnetic core 2 and outputs a voltage V1 having a voltage value corresponding to the magnetic flux density. In this case, a magnetic flux having a difference (Φ 1- Φ 2) between a magnetic flux Φ 1 generated when the detection current I1 flows through the detection target wire 61 and a magnetic flux Φ 2 generated when the negative feedback current I2 (current output from the voltage-current converter circuit 5) flows through the feedback winding 4 is generated inside the magnetic core 2.

The voltage-current conversion circuit 5 controls the current value of the negative feedback current I2 based on the voltage V1 input from the magnetoelectric conversion section 3, generates the negative feedback current I2, and outputs the generated negative feedback current to the feedback winding 4 such that the voltage V1 becomes zero volts, that is, such that the magnetic flux density of the magnetic flux (Φ 1- Φ 2) generated inside the magnetic core 2 detected in the magnetoelectric conversion section 3 becomes zero. Thus, the current value of the negative feedback current I2 is obtained by dividing the current value of the detection current I1 by the number of turns n of the feedback winding 4.

In the current sensor 1A, the switching unit 7 switches according to the magnitude of the current value of the detection current I1 to be detected. Specifically, when the current value of the detection current I1 is large, the switching unit 7 switches the connection state in which the voltage converting unit 6a is connected to the other end 4b of the feedback winding 4 and the output terminal 9 via the switching unit 7. On the other hand, when the current value of the detection current I1 is small, the switching unit 7 switches the connection state in which the voltage converting unit 6b is connected between the other end 4b of the feedback winding 4 and the output terminal 9 via the switching unit 7.

The 1 st switching unit 7 and the 2 nd switching unit 8 may be configured such that the user of the current sensor 1A determines the magnitude of the current value of the detected current I1 and operates, for example, an unillustrated operation unit (i.e., manually) provided in the current sensor 1A based on the determination result to switch the 1 st switching unit 7 and the 2 nd switching unit 8, or may be configured such that an unillustrated processing unit including a CPU, an a/D converter, and the like is provided in the current sensor 1A, and the voltage value of the output voltage Vo is detected by the processing unit via the a/D converter, and the 1 st switching unit 7 and the 2 nd switching unit 8 are switched based on the magnitude of the detected voltage value of the output voltage Vo (a configuration for automatically switching the detection rate).

First, since the current value of the detection current I1 is large, when the switching unit 7 switches to a connection state in which the voltage conversion unit 6a is connected between the other end 4b of the feedback winding 4 and the output terminal 9, the voltage conversion unit 6a converts the negative feedback current I2 input via the changeover switch 7a of the switching unit 7 into the 1 st detection voltage Vd1 only by the 1 st detection resistor 13, and outputs the same from the output unit 12 to the output terminal 9 via the changeover switch 7b of the switching unit 7. Accordingly, in the current sensor 1A, since the current value of the detection current I1 is large, the negative feedback current I2 also increases, and when the voltage can be converted to a sufficient voltage value only by the detection resistor, the voltage conversion unit 6a configured without including an amplifier converts the negative feedback current I2 to the 1 st detection voltage Vd1, that is, converts the detection current I1 to the 1 st detection voltage Vd1 (i.e., I1 × R1/n) at the 1 st detection rate (R1/n, in the present example, the numerical value "1") by using only the 1 st detection resistor 13 (i.e., without being affected by noise generated by the amplifier), and outputs the converted voltage.

On the other hand, since the current value of the detection current I1 is small, when the switching unit 7 switches to a connection state in which the voltage conversion unit 6b is connected between the other end 4b of the feedback winding 4 and the output terminal 9, the voltage conversion unit 6b converts the negative feedback current I2 input via the switch 7a of the switching unit 7 into the 2 nd detection voltage Vd2, that is, converts the detection current I1 into the 1 st detection voltage Vd1 (i.e., I1 × R2/n × k) at the 2 nd detection rate (R2/n × k in the present example, the numerical value "10") that is greater than the 1 st detection rate, by using the 2 nd detection resistor 23 and the amplifier 24, and outputs the detection current I1 to the output terminal 9 via the switch 7b of the switching unit 7 from the output unit 22. As described above, in the current sensor 1A, since the current value of the detection current I1 is small, the negative feedback current I2 is also small, and when the voltage cannot be converted to a sufficient voltage value by only the detection resistor, the voltage conversion unit 6b including the configuration of the amplifier 24 is affected by noise generated by the amplifier 24, but converts the negative feedback current I2 to the 2 nd detection voltage Vd2 of a sufficient voltage value and outputs the voltage.

Accordingly, in the current sensor 1A, the negative feedback current I2 is small because the current value of the detection current I1 is small, and when the voltage cannot be converted to a sufficient voltage value only by the detection resistor, the voltage conversion unit 6b including the amplifier 24 converts the detection current I1 to the 2 nd detection voltage Vd2 of a sufficient voltage value at the 2 nd detection rate and outputs the voltage, but the negative feedback current I2 is large because the current value of the detection current I1 is large, and when the voltage can be converted to a sufficient voltage value only by the detection resistor, the voltage conversion unit 6a not including the amplifier converts the detection current I1 to the 1 st detection voltage Vd1 of a sufficient voltage value at the 1 st detection rate smaller than the 2 nd detection rate and outputs the voltage.

Therefore, according to the current sensor 1A, unlike the conventional current sensor having a configuration in which the detection voltage detected by the detection resistor can be amplified by an amplifier (operational amplifier) at any detection rate and output as the output voltage, the detection current I1 having a large current value can be converted into the 1 st detection voltage Vd1 having a sufficient voltage value by the voltage conversion unit 6a not including an amplifier and output. That is, according to the current sensor 1A, the detection rate can be switched, and the 1 st detection voltage Vd1 can be output by a configuration not including an amplifier at the 1 st detection rate (the 1 st detection rate), that is, without being affected by noise generated by the amplifier.

In addition, a current sensor having a configuration in which an output terminal is connected to a measuring instrument and used is divided into a sensor unit housing a magnetic core, a magnetoelectric conversion portion, and a feedback winding, and a terminal unit housing a voltage conversion portion and having an output terminal connected to a connector of the measuring instrument disposed on a surface thereof, and the units are connected to each other by a connection cable (a coaxial cable, a shield cable, or the like), and it is known that the current sensor 1A is applied to this configuration, as shown in fig. 2. In this case, since the magneto-electric conversion section 3 is susceptible to temperature changes, the voltage-current conversion current 5, which is formed of an operational amplifier or the like and whose heat generation amount is increased when outputting the negative feedback current I2 having a large current value, is stored in the terminal unit 52 instead of the sensor unit 51, which is the same as the magneto-electric conversion section 3.

However, unlike the 2 nd detection resistor 23 through which the negative feedback current I2 having a small current value flows, the 1 st detection resistor 13 housed in the terminal unit 52 generates a large amount of heat because the negative feedback current I2 having a large current value flows. Therefore, when the negative feedback current I2 having a large current value flows (at the 1 st detection rate), the voltage-current conversion circuit 5 and the 1 st detection resistor 13, which have large heat generation amounts, are housed in the same terminal unit 52 in the configuration of fig. 2, and thus there is a possibility that the temperature rise in the terminal unit 52 becomes large, which is not preferable.

Therefore, the current sensor 1B shown in fig. 3 has a configuration in which the sensor unit 51 and the terminal unit 52 are provided with the relay unit 53. The current sensor 1B will be explained below. Note that the same components as those of the current sensor 1A and the current sensor shown in fig. 2 are denoted by the same reference numerals, and redundant description thereof is omitted.

As shown in fig. 3, the current sensor 1B includes a magnetic core 2, a magnetoelectric conversion portion 3, a feedback winding 4, a voltage- current conversion circuit 5, 2 voltage conversion portions 6a and 6B, a switching portion 7, and an output terminal 9. The sensor unit 51 houses the magnetic core 2, the magneto-electric conversion portion 3, and the feedback winding 4, the terminal unit 52 houses the voltage conversion portions 6a and 6b and the switching portion 7, and has the output terminal 9 disposed on the surface, and the relay unit 53 houses the voltage-current conversion circuit 5. Further, the relay unit 53 is connected to the sensor unit 51 via a 1 st connection cable CB1 (coaxial cable, shielded cable, etc.), and the terminal unit 52 is connected to the relay unit 53 via a 2 nd connection cable CB2 (coaxial cable, shielded cable, etc.). Further, the relay unit 53 houses a transmission path TL1 for connecting the other end 4b of the feedback winding 4 in the sensor unit 51 and the switching unit 7 in the terminal unit 52 via the connection cables CB1 and CB 2. The voltage-current conversion circuit 5 in the relay unit 53 is connected between the magneto-electric conversion unit 3 in the sensor unit 51 and the one end 4a of the feedback winding 4 via 2 wires constituting the 1 st connection cable CB1, and one end of the transmission path TL1 is connected to the other end 4b of the feedback winding 4 via another wire constituting the 1 st connection cable CB 1. Further, the other end of the transmission path TL1 is connected to the switching section 7 in the terminal unit 52 via a wiring constituting the 2 nd connection cable CB 2.

As described above, the current sensor 1B differs from the current sensor 1A in the configuration in which the respective components are divided into the sensor unit 51, the relay unit 53, and the terminal unit 52 and housed, but the basic configuration (the configuration having the magnetic core 2, the magnetoelectric conversion portion 3, the feedback winding 4, the voltage-current conversion circuit 5, the 2 voltage conversion portions 6a and 6B, the switching portion 7, and the output terminal 9) is the same as the current sensor 1A, and therefore operates in the same manner as the current sensor 1A.

In this case, the relay unit 53 inputs the voltage V1 from the magneto-electric conversion section 3 of the sensor unit 51 via the 1 st connection cable CB1, and outputs the negative feedback current I2 output from the voltage-current conversion circuit 5 to the one end 4a of the feedback winding 4 in the sensor unit 51 via the 1 st connection cable CB 1. Further, the relay unit 53 inputs the negative feedback current I2 output from the other end 4b of the feedback winding 4 in the sensor unit 51 via the 1 st connection cable CB1, and outputs to the 2 nd connection cable CB2 via the transmission path TL 1. On the other hand, in the terminal unit 52, similarly to the current sensor 1A, the switching unit 7 switches to one of the voltage converting units 6a and 6b to output the negative feedback current I2 input via the 2 nd connection cable CB2, and outputs the detection voltage (the 1 st detection voltage Vd1 or the 2 nd detection voltage Vd2) output from the one voltage converting unit to the output terminal 9.

Thus, the current sensor 1B converts the detection current I1 flowing through the detected electric wire 61 into one detection voltage corresponding to one detection rate of the 1 st detection voltage Vd1 and the 2 nd detection voltage Vd2 at the selected one detection rate of the 1 st detection rate and the 2 nd detection rate, and outputs the converted detection voltage as the output voltage Vo from the output terminal 9.

Therefore, according to the current sensor 1B, as in the current sensor 1A, the detection rate can be switched, and the detection current I1 can be converted into the 1 st detection voltage Vd1 having a sufficient voltage value and output, by a configuration not including an amplifier at the 1 st detection rate (the 1 st detection rate), that is, without being affected by noise generated by the amplifier. Further, according to the current sensor 1B, when the negative feedback current I2 having a large current value flows (at the 1 st detection rate), the voltage-current conversion circuit 5 and the 1 st detection resistor 13, which have increased heat generation amounts together, are housed in separate units (the voltage-current conversion circuit 5 is housed in the relay unit 53, and the 1 st detection resistor 13 is housed in the terminal unit 52), and therefore, the heat generation amounts of the voltage-current conversion circuit 5 and the 1 st detection resistor 13 can be dispersed to the separate units. Thus, according to the current sensor 1B, the temperature rise in the relay unit 53 and the temperature rise in the terminal unit 52 can be suppressed to be low together. Further, the influence of the heat generation of the 1 st detection resistor 13 on the voltage-current conversion circuit 5 can be avoided. Further, the influence of the heat generation of the 1 st detection resistor 13 on the magnetic core 2, the magneto-electric conversion portion 3, and the feedback winding 4 disposed in the sensor unit 51 can also be avoided.

In addition, the current sensors 1A and 1B have the following configurations: the configuration is not limited to this, but the configuration is such that the 1 st voltage conversion unit (the voltage conversion unit of the current-voltage conversion circuit is configured only with the detection resistor) has 1 voltage conversion unit 6a, and the 2 nd voltage conversion unit (the voltage conversion unit of the current-voltage conversion circuit is configured with the detection resistor and the amplifier) has 1 voltage conversion unit 6 b. Although not shown, the following structure may be adopted: a switching unit (7) having 1 st voltage converting unit in which a current-voltage converting circuit is constituted by 2 or more detection resistors only and 2 or more 2 nd voltage converting units in which a current-voltage converting circuit is constituted by 2 or more detection resistors and an amplifier is constituted, and having 1 circuit n-contact structure (n is 3 or more) switching switches (7 a, 7b) switches to a connection state in which any 1 st element (voltage converting unit) in the voltage converting units is connected between the other end (4b) of the feedback winding (4) and the output terminal (9).

In the current sensor 1B, when the negative feedback current I2 having a large current value flows (at the 1 st detection rate), the voltage-current conversion circuit 5 and the 1 st detection resistor 13, which have large heat generation amounts, are configured such that only the voltage-current conversion circuit 5 is housed in the relay unit 53, but the configuration is not limited to the configuration in which the voltage-current conversion circuit 5 and the 1 st detection resistor 13 are housed in separate units. For example, as in the current sensor 1C shown in fig. 4, the following configuration may be adopted: of the other components (the voltage-current conversion circuit 5, the 2 voltage- current conversion portions 6a, 6b, the switching portion 7, and the output terminal 9) except the magnetic core 2, the magneto-electric conversion portion 3, and the feedback winding 4 housed in the sensor unit 51, only the voltage conversion portion 6a and the output terminal 9 are housed in the terminal unit 52, and the remaining components (the voltage-current conversion circuit 5, the voltage conversion portion 6b, and the switching portion 7) are housed in the relay unit 53. The current sensor 1C will be explained below. Note that the same components as those of the current sensor 1B are denoted by the same reference numerals, and redundant description thereof is omitted.

The relay unit 53 of the current sensor 1C inputs the voltage V1 from the magneto-electric conversion section 3 of the sensor unit 51 via the 1 st connection cable CB1, and outputs the negative feedback current I2 output from the voltage-current conversion circuit 5 to the one end 4a of the feedback winding 4 in the sensor unit 51 via the 1 st connection cable CB 1. Further, the relay unit 53 inputs the negative feedback current I2 output from the other end 4b of the feedback winding 4 in the sensor unit 51 via the 1 st connection cable CB 1.

In this case, since the switches 7a and 7b of the switching unit 7 are configured to be switched in conjunction with each other, when the switch 7a is switched to one end of the transmission line TL1 to output the negative feedback current I2, the switch 7b is in a switching state in which the other end of the transmission line TL1 is connected to the terminal unit 52 via the 2 nd connection cable CB 2. Further, when the changeover switch 7a is in a changeover state of switching to the input section 21 of the voltage converting section 6b to output the negative feedback current I2, the changeover switch 7b is in a changeover state of connecting the output section 22 of the voltage converting section 6b to the terminal unit 52 via the 2 nd connection cable CB 2. According to this configuration, in the relay unit 53, the switching section 7 switches to the 1 st element of any one of the 2 nd voltage converting section 6b and the transmission path TL1 to output (supply) the negative feedback current I2, and outputs (supplies) the 2 nd detection voltage Vd2, which is a signal output from the 2 nd voltage converting section 6b, to the 1 st voltage converting section 6a of the terminal unit 52 via the 2 nd connection cable CB2 when the 1 st element of the one is the 2 nd voltage converting section 6b, and outputs (supplies) the negative feedback current I2, which is a signal output from the transmission path TL1, to the 1 st voltage converting section 6a of the terminal unit 52 via the 2 nd connection cable CB2 when the 1 st element of the one is the transmission path TL 1.

On the other hand, in the termination unit 52, when the negative feedback current I2 is input from the relay unit 53 through the 2 nd connection cable CB2 to the 1 st voltage conversion section 6a, the voltage is converted into the 1 st detection voltage Vd1(═ I2 × R1) by the 1 st detection resistor 13 (resistance value R1), and is output to the output terminal 9 as the output voltage Vo. The 1 st detection voltage Vd1 is represented as (I1 × R1/n) using the 1 st detection rate (R1/n).

Further, when the 1 st voltage conversion section 6a inputs the 2 nd detection voltage Vd2 from the relay unit 53 via the 2 nd connection cable CB2, the 2 nd detection voltage Vd2 is output to the output terminal 9 as the output voltage Vo.

In this case, when the resistance value Ro of the output resistor 25 of the voltage converting unit 6b is a value that is negligible with respect to the resistance value R1 of the 1 st detection resistor 13 constituting the 1 st voltage converting unit 6a, the 1 st voltage converting unit 6a outputs the 2 nd detection voltage Vd2 as it is to the output terminal 9 as the output voltage Vo. That is, the detection current I1 is converted into the 2 nd detection voltage Vd2 (I1 × R2/n × k) at the 2 nd detection rate (R2/n × k) and is output as the output voltage Vo. On the other hand, as in the present example, when the resistance value Ro (50 Ω in the present example) of the output resistor 25 of the voltage converting unit 6b is not a value that can be ignored with respect to the resistance value R1 (50 Ω in the present example) of the 1 st detection resistor 13 constituting the 1 st voltage converting unit 6a, the 1 st voltage converting unit 6a outputs the 2 nd detection voltage Vd2 obtained by dividing the voltage between the 1 st detection resistor 13 and the output resistor 25 as the output voltage Vo to the output terminal 9. That is, the detection current I1 is converted into the 2 nd detection voltage Vd2 at the 2 nd detection rate (R2/n × k × R1/(R1+ Ro)) different from the 2 nd detection rate described above, and further converted into the 1 st detection voltage Vd1(═ I1 × R2/n × k × R1/(R1+ Ro)), and is output as the output voltage Vo. Therefore, in the current sensor 1C, the 2 nd detection rate can be matched to the 2 nd detection rate (the numerical value "10") in the current sensors 1A and 1B by setting k to 20.

Therefore, according to the current sensor 1C, as in the current sensor 1A, the detection rate can be switched, and the detection current I1 can be converted into the 1 st detection voltage Vd1 having a sufficient voltage value and output, by a configuration not including an amplifier at the 1 st detection rate (the 1 st detection rate), that is, without being affected by noise generated by the amplifier. Further, according to the current sensor 1C, when the negative feedback current I2 having a large current value flows (at the 1 st detection rate), the voltage-current conversion circuit 5 and the 1 st detection resistor 13, which have increased heat generation amounts together, are housed in separate units (the voltage-current conversion circuit 5 is housed in the relay unit 53, and the 1 st detection resistor 13 is housed in the terminal unit 52), and therefore, the heat generation amounts of the voltage-current conversion circuit 5 and the 1 st detection resistor 13 can be dispersed to the separate units. Thus, according to the current sensor 1C, the temperature rise in the relay unit 53 and the temperature rise in the terminal unit 52 can be suppressed to be low together. Further, according to the current sensor 1C, since the voltage-to-current conversion circuit 5 and the current-to-voltage conversion circuit (the circuit composed of the 2 nd detection resistor 23 and the amplifier 24: the voltage conversion section 6b) are housed in the relay unit 53 different from the 1 st detection resistor 13, the influence of the heat generation of the 1 st detection resistor 13 on the voltage-to-current conversion circuit 5 and the amplifier 24 of the current-to-voltage conversion circuit can be avoided, unlike the configuration housed in the terminal unit 52 in which the average temperature tends to become higher due to the heat generation of the 1 st detection resistor 13.

In addition, in each of the current sensors 1A, 1B, and 1C, as an example of a configuration capable of switching a plurality of detection rates, a configuration capable of switching 2 detection rates, that is, the 1 st detection rate and the 2 nd detection rate, is adopted, but a configuration capable of switching 3 detection rates may be adopted. Hereinafter, the current sensors 1D and 1E configured to be capable of switching 3 detection rates will be described based on the current sensors 1B and 1C including the sensor unit 51, the relay unit 53, and the terminal unit 52. Note that the same components as those of the current sensors 1B and 1C are denoted by the same reference numerals, and redundant description thereof is omitted.

First, a current sensor 1D configured to be capable of switching 3 detection rates will be described with reference to fig. 5 based on the current sensor 1B. In addition, the configuration of the terminal unit 52 different from the current sensor 1B will be described below.

The terminal unit 52 houses a voltage converter 6c (other 1 st voltage converter) in addition to the voltage converters 6a and 6b, the switching unit 7, and the output terminal 9. Further, switches 7a and 7b constituting switching unit 7 are constituted as switches having a 1-circuit 3-contact structure, for example, and switching unit 7 switches to a connection state in which the 1 st element of any one of 3 voltage converting units 6a, 6b, and 6c is connected between 2 nd connecting cable CB2 and output terminal 9.

The input section 31 of the voltage converting section 6c is connected to the 1 st switching section 7, converts the negative feedback current I2 into the 3 rd detection voltage Vd3 when the negative feedback current I2 is input from the 1 st switching section 7 to the input section 31, and outputs it from the output section 32 as the output voltage Vo. In this example, the voltage converting unit 6c as the 1 st voltage converting unit is constituted by the 3 rd detection resistor 33 having a predetermined resistance value R3 (for example, 5 Ω). One end of the 3 rd detection resistor 33 is connected to the input unit 31 and the output unit 32, and the other end is connected to a portion of the reference potential (ground G) in the current sensor 1D. With this configuration, the voltage converter 6c converts the negative feedback current I2 input to the input unit 31 into the 3 rd detection voltage Vd3 (I2 × R3) by the 3 rd detection resistor 33 (resistance value R3), and outputs the converted voltage as the output voltage Vo directly from the output unit 12. The 3 rd detection voltage Vd3 is represented by (I1 × R3/n) using a 3 rd detection rate (R3/n) defined by the resistance value R3 and the number of turns n. In this example, R3 is 5 Ω, and n is 50, so the voltage conversion section 6c converts the detection current I1 into the 3 rd detection voltage Vd3 at the 3 rd detection rate (value "0.1").

According to this configuration, the current sensor 1D can be switched to any one of 21 st detection rates (numerical value "1") and 2 nd detection rates (numerical value "10") in the current sensors 1A and 1B and 3 detection rates including the 3 rd detection rate (numerical value "0.1") added thereto, and can convert the negative feedback current I2 into the output voltage Vo. Therefore, according to the current sensor 1D, the detection current I1 can be converted into and output from the 1 st detection voltage Vd1 and the 3 rd detection voltage Vd3 by a configuration in which 3 detection rates are switchable, and 2 detection rates (the 1 st detection rate and the 3 rd detection rate) are not included, that is, without being affected by noise generated by an amplifier. In addition, in the current sensor 1D, similarly to the current sensor 1B, since the heat generation in the voltage-current conversion circuit 5 and the heat generation in the 1 st detection resistor 13 and the 3 rd detection resistor 33 are dispersed to different units, the temperature rise in the relay unit 53 and the temperature rise in the termination unit 52 can be suppressed to be low together. Further, the influence of the heat generation of the 1 st detection resistor 13 and the 3 rd detection resistor 33 on the voltage-current conversion circuit 5 can be avoided.

Next, a current sensor 1E configured to be capable of switching 3 detection rates will be described with reference to fig. 6 based on the current sensor 1C. In addition, the configuration of the terminal unit 52 different from the current sensor 1C will be described below.

The terminal unit 52 houses a voltage converter 6c (other 1 st voltage converter) and a 2 nd switching unit 8 (hereinafter, also simply referred to as switching unit 8) in addition to the voltage converter 6a and the output terminal 9. Similarly to the switching unit 7, the switching unit 8 is constituted by switching switches 8a and 8b having a 1-circuit 2-contact structure, the switching switch 8a is disposed between the 2 nd connecting cable CB2 and the input units 11 and 31 of the voltage converting units 6a and 6c, and the switching switch 8b is disposed between the output units 12 and 32 of the voltage converting units 6a and 6c and the output terminal 9. According to this configuration, by switching the changeover switches 8a and 8b of the switching unit 8 in an interlocking manner, the 2 nd element of any one of the 2 voltage converting units 6a and 6c is switched to the connection state in which the 2 nd connecting cable CB2 and the output terminal 9 are connected. The voltage conversion unit 6c is configured similarly to the current sensor 1D.

In the current sensor 1E having this configuration, the switching unit 7 switches to the 1 st element of either the voltage converting unit 6b having the current-voltage converting circuit including the 2 nd detection resistor 23 and the amplifier 24 or the transmission path TL1 to output (supply) the negative feedback current I2 output from the other end 4b of the feedback winding 4, and outputs (supplies) the signal output from the 1 st element to the switching unit 8 via the 2 nd connection cable CB 2. The switching unit 8 switches the signal supplied from the switching unit 7 to the 2 nd element of either the 1 st detection resistor 13 (voltage conversion unit 6a) or the 3 rd detection resistor 33 (voltage conversion unit 6c), and outputs the signal output from the 2 nd element to the output terminal 9.

Specifically, in the current sensor 1E, in the switching state in which the switching unit 7 switches to the transmission line TL1 as the 1 st element and in the switching state in which the switching unit 8 switches to the 1 st detection resistor 13 as the 2 nd element, the 1 st detection resistor 13 converts the negative feedback current I2 supplied from the transmission line TL1 into the 1 st detection voltage Vd1 and outputs the same to the output terminal 9 as the output voltage Vo. In the current sensor 1E, in the switching state in which the switching unit 7 switches to the voltage conversion unit 6b (the current-voltage conversion circuit including the 2 nd detection resistor 23 and the amplifier 24) as the 1 st element and in the switching state in which the switching unit 8 switches to the 1 st detection resistor 13 as the 2 nd element, the voltage conversion unit 6b and the 1 st detection resistor 13 convert the negative feedback current I2 into a voltage by the 2 nd detection resistor 23 having a resistance value R2 larger than that of the 1 st detection resistor 13 and amplify the voltage, thereby converting the voltage into the 2 nd detection voltage Vd2 and outputting the voltage as the output voltage Vo to the output terminal 9. In the current sensor 1E, in the switching state in which the switching unit 7 is switched to the transmission line TL1 as the 1 st element and in the switching state in which the switching unit 8 is switched to the 3 rd detection resistor 33 as the 2 nd element, the 3 rd detection resistor 33 converts the negative feedback current I2 into the 3 rd detection voltage Vd3 by the 3 rd detection resistor 33 having a resistance value R3 smaller than the 1 st detection resistor 13 and outputs the 3 rd detection voltage Vd3 to the output terminal 9 as the output voltage Vo.

With this configuration, the current sensor 1E can be switched to any one of 21 st detection rate (numerical value "1") and 22 nd detection rate (numerical value "10") in the current sensor 1C and 3 detection rates including the 3 rd detection rate (numerical value "0.1") added thereto, and can convert the detection current I1 into the output voltage Vo.

In addition, the current sensor 1E is also configured to be capable of switching the detection rate, as in the current sensor 1C, and to convert the detection current I1 into the 1 st detection voltage Vd1 and the 3 rd detection voltage Vd3 and output the same, by a configuration not including an amplifier at the 2 detection rates (the 1 st detection rate and the 3 rd detection rate), that is, without being affected by noise generated by the amplifier. In addition, in the current sensor 1E, similarly to the current sensor 1C, since the heat generation in the voltage-current conversion circuit 5 and the heat generation in the 1 st detection resistor 13 and the 3 rd detection resistor 33 are dispersed to different units, the temperature rise in the relay unit 53 and the temperature rise in the termination unit 52 can be suppressed to be low together. Further, according to the current sensor 1E, since the voltage-current conversion circuit 5 and the current-voltage conversion circuit (the circuit composed of the 2 nd detection resistor 23 and the amplifier 24: the voltage conversion section 6b) are housed in the relay unit 53 different from the 1 st detection resistor 13 and the 3 rd detection resistor 33, the influence of the heat generation of the 1 st detection resistor 13 on the voltage-current conversion circuit 5 and the amplifier 24 of the current-voltage conversion circuit can be avoided, unlike the configuration housed in the terminal unit 52 in which the average temperature tends to become higher due to the heat generation of the 1 st detection resistor 13 and the 3 rd detection resistor 33.

As described in the current sensor 1A, the following process (automatic switching process for automatically switching the detection rate of the detection rate) may be executed for the other current sensors 1B to 1E: a processing unit (not shown) including a CPU, an a/D converter, and the like is provided, and the processing unit detects the voltage value of the output voltage Vo via the a/D converter, and switches the switching unit 7 (the current sensor 1E further includes the switching unit 8) based on the magnitude of the detected voltage value of the output voltage Vo.

The current sensors 1A to 1E may be provided with a processing unit including a D/a converter in addition to the CPU and the a/D converter, and the processing unit may perform the automatic switching processing of the detection rate and may also perform offset adjustment processing for adjusting the offset of the operational amplifier constituting the voltage/current conversion circuit 5 and the offset of the operational amplifier constituting the amplifier 24. Hereinafter, a current sensor 1F including the configuration of the processing unit will be described with reference to fig. 7 based on the current sensor 1E. Note that the same components as those of the current sensor 1E are denoted by the same reference numerals, and redundant description thereof is omitted.

The current sensor 1F includes a buffer 16 and a processing unit 17 in addition to the configuration of the current sensor 1E. The buffer 16 detects the voltage of the 2 nd connection cable CB2 with high input impedance and outputs the voltage to the processing unit 17.

The processing unit 17 includes a CPU17a, an a/D converter (simply referred to as "a/D" in fig. 7) 17b, and 2D/a converters (simply referred to as "D/a" in fig. 7) 17c and 17D. The a/D converter 17b converts the voltage output from the buffer 16 (as an example, a voltage of the same voltage value as the voltage of the 2 nd connection cable CB2) into voltage data D1 representing the voltage value and outputs to the CPU17 a.

In the automatic switching process of the detection rate, the CPU17a outputs a control signal S1 for switching the switching unit 7 and outputs a control signal S2 for switching the switching unit 8. The control signal S2 is output to the terminal unit 52 via the 2 nd connection cable CB 2. Further, the CPU17a outputs, in the offset adjustment processing, adjustment data D2 for adjusting the offset of the operational amplifier constituting the voltage-current conversion circuit 5 to the D/a converter 17c, and outputs adjustment data D3 for adjusting the offset of the operational amplifier constituting the amplifier 24 to the D/a converter 17D. The D/a converter 17c converts the adjustment data D2 input from the CPU17a into an adjustment voltage S3, and outputs to an offset adjustment terminal of an operational amplifier constituting the voltage-current conversion circuit 5. Further, the D/a converter 17D converts the adjustment data D3 input from the CPU17a into an adjustment voltage S4, and outputs to an offset adjustment terminal of an operational amplifier constituting the amplifier 24.

Next, the offset adjustment process will be specifically described.

First, offset adjustment of an operational amplifier constituting the voltage-current conversion circuit 5 will be described. In this case, in a state where the detected electric wire 61 is not inserted into the core 2, the CPU17a first outputs the control signal S1 for switching to the transmission path TL1 side to the switching section 7, and outputs the control signal S2 for switching to the voltage converting section 6a side to the switching section 8. As a result, the negative feedback current I2 due to the offset of the operational amplifier constituting the voltage-current conversion circuit 5 is output from the relay unit 53 to the sensor unit 51, then output to the terminal unit 52 via the relay unit 53, and converted into the 1 st detection voltage Vd1 in the voltage conversion unit 6 a.

The CPU17a detects the voltage value of the 1 st detection voltage Vd1 based on the voltage data D1 input via the buffer 16 and the a/D converter 17b, and changes the adjustment data D2 for the adjustment voltage S3 to output to the D/a converter 17c such that the voltage value of the 1 st detection voltage Vd1 approaches zero. The D/a converter 17c converts the adjustment data D2 into an adjustment voltage S3, and outputs the adjustment voltage to an offset adjustment terminal of an operational amplifier constituting the voltage-current conversion circuit 5. The CPU17a repeats the change of the adjustment data D2 to the D/a converter 17c until the voltage value of the detected 1 st detection voltage Vd1 becomes zero. The CPU17a stores the adjustment data D2 at the time when the voltage value of the 1 st detection voltage Vd1 becomes zero, and continues the output of the adjustment data D2 to the D/a converter 17 c. Thus, the voltage value of the adjustment voltage S3 to the offset adjustment terminal of the operational amplifier constituting the voltage-current conversion circuit 5 is maintained at the voltage value at the time when the voltage value of the 1 st detection voltage Vd1 becomes zero. That is, the offset of the operational amplifier constituting the voltage-current conversion circuit 5 is maintained at zero. Thereby, the offset adjustment of the operational amplifier constituting the voltage-current conversion circuit 5 is completed.

Further, the CPU17a includes not only the offset of the operational amplifier constituting the voltage-current conversion circuit 5 but also the voltage generated by the offset generated in the magneto-electric conversion section 3 in (the voltage data D1 of) the 1 st detection voltage Vd1 detected via the buffer 16 and the a/D converter 17b, and therefore, in the offset adjustment of the operational amplifier constituting the voltage-current conversion circuit 5, as a result, the offset adjustment of the operational amplifier constituting the voltage-current conversion circuit 5 and the magneto-electric conversion section 3 as a whole is completed.

Next, offset adjustment of the operational amplifier constituting the amplifier 24 will be described. In this case, as described above, in a state where the offset adjustment of the entire operational amplifier and the magneto-electric conversion section 3 constituting the voltage-current conversion circuit 5 is completed and the detected electric wire 61 is not inserted into the magnetic core 2, the CPU17a first outputs the control signal S1 for switching to the voltage conversion section 6b side to the switching section 7 and outputs the control signal S2 for switching to the voltage conversion section 6a side to the switching section 8. Thus, the voltage converter 6b converts the negative feedback current I2 output from the voltage/current conversion circuit 5 in the state in which the offset adjustment is completed into the 2 nd detection voltage Vd2 and outputs the converted voltage. At this time, the negative feedback current I2 is zero ampere, and therefore the 2 nd detection voltage Vd2 is a voltage due to an offset of the operational amplifier constituting the amplifier 24.

The CPU17a detects the voltage value of the 2 nd detection voltage Vd2 based on the voltage data D1 input via the buffer 16 and the a/D converter 17b, and changes the adjustment data D3 for the adjustment voltage S4 to output to the D/a converter 17D such that the voltage value of the 2 nd detection voltage Vd2 approaches zero. The D/a converter 17D converts the adjustment data D3 into an adjustment voltage S4, and outputs the adjustment voltage to an offset adjustment terminal of an operational amplifier constituting the amplifier 24. The CPU17a repeats the change of the adjustment data D3 to the D/a converter 17D until the voltage value of the detected 2 nd detection voltage Vd2 becomes zero. The CPU17a stores the adjustment data D3 at the time when the voltage value of the 2 nd detection voltage Vd2 becomes zero, and continues the output of the adjustment data D3 to the D/a converter 17D. Thus, the voltage value of the adjustment voltage S4 for the offset adjustment terminal of the operational amplifier constituting the amplifier 24 is maintained at the voltage value at the time when the voltage value of the 2 nd detection voltage Vd2 becomes zero. That is, the offset of the operational amplifier constituting the amplifier 24 is maintained at zero. This completes the offset adjustment of the operational amplifier constituting the amplifier 24.

Next, the automatic switching process of the detection rate will be specifically described. In addition, in the current sensor 1F based on the current sensor 1E, there are 3 detection rates, that is: the 3 rd detection rate (value "0.1") when the negative feedback current I2 is supplied to the voltage conversion section 6c within the terminal unit 52 via the transmission path TL1 of the relay unit 53; the 1 st detection rate (numerical value "1") when the negative feedback current I2 is supplied to the voltage conversion section 6a within the terminal unit 52 via the transmission path TL1 of the relay unit 53; and the 2 nd detection rate (numerical value "10") when the negative feedback current I2 is supplied to the voltage converting section 6b of the relay unit 53 and the voltage output from the voltage converting section 6b is supplied to the voltage converting section 6a in the terminal unit 52. Therefore, the current sensor 1F has 3 detection ranges, that is: a detection range of the lowest 3 rd detection rate (maximum detection range in which the maximum detection current I1 can be detected); a detection range of the second lowest 1 st detection rate (a middle detection range capable of detecting the second largest detection current I1); and a detection range of the highest 2 nd detection rate (a minimum detection range capable of detecting the minimum detection current I1).

In the automatic switching process of the detection rate, the CPU17a detects the detection voltage (any one of the detection voltages Vd1, Vd2, and Vd 3) in the current detection range based on the voltage data D1 input via the buffer 16 and the a/D converter 17b, and determines whether the detection voltage is included in a predetermined range-up voltage range (for example, a voltage range that is 90% or more of the maximum voltage value of the output voltage Vo) or a predetermined range-down voltage range (for example, a voltage range that is 10% or less of the maximum voltage value of the output voltage Vo) with respect to the output voltage Vo.

As a result of the determination, when the detection voltage is included in the range-up voltage range and the detection range on the current detection range exists, the CPU17a outputs the control signal S1 to the switching unit 7, outputs the control signal S2 to the switching unit 8, and switches the switching unit 7 and the switching unit 8 so as to be in the detection range (the detection rate is lowered by 1 step). When the detection voltage is included in the range-down voltage range and the detection range in the current detection range is present as a result of the determination, the CPU17a outputs the control signal S1 to the switching unit 7 and outputs the control signal S2 to the switching unit 8, and switches the switching unit 7 and the switching unit 8 to the detection range below them in an interlocking manner (the detection rate is increased by 1 level). As a result of the determination, when the detected voltage is not included in either the range-up voltage range or the range-down voltage range, the CPU17a maintains the current state of the control signal S1 output to the switching unit 7 and the control signal S2 output to the switching unit 8 (i.e., does not switch between the switching unit 7 and the switching unit 8) so as to maintain the current detection range (i.e., maintains the current detection rate).

In the current sensor 1F, by arranging the buffer 16 and the processing unit 17 in the relay unit 53 in which the voltage-current conversion circuit 5 and the amplifier 24 are housed as described above, the signal line of the 2 nd connection cable CB2 connecting the relay unit 53 and the terminal unit 52 can be realized only by the signal line for the control signal S2, in addition to the signal line for transmitting the negative feedback current I2 and the detection voltage (any one of the detection voltages Vd1, Vd2, and Vd 3).

In the current sensors 1A, 1B, 1C, 1E, and 1F, the resistance value R1 of the 1 st detection resistor 13 and the resistance value R2 of the 2 nd detection resistor 23 are set to 50 Ω as an example, because the 1 st detection resistor 13 functions as a termination resistor of a line (hereinafter, also referred to as the 1 st line for distinction) from the other end 4B of the feedback winding 4 to the voltage conversion unit 6a including the 1 st detection resistor 13, and the 2 nd detection resistor 23 functions as a termination resistor of a line (hereinafter, also referred to as the 2 nd line for distinction) from the other end 4B of the feedback winding 4 to the voltage conversion unit 6B including the 2 nd detection resistor 23, and therefore, the characteristic impedances (50) of the 1 st line and the 2 nd line are determined to be the same for impedance matching.

In this case, in the current sensor 1A shown in fig. 1 and 2, the 1 st line is a line from the other end 4b of the feedback winding 4 to the input portion 11 of the voltage converting unit 6a (substantially to the 1 st detection resistor 13 of the voltage converting unit 6a) via the changeover switch 7a (the current sensor 1A is divided into two, namely, the sensor unit 51 and the terminal unit 52, and when connected to each other by the connection cable CB). The 2 nd line is a line from the other end 4b of the feedback winding 4 to the input unit 21 of the voltage converting unit 6b (substantially to the 2 nd detection resistor 23 of the voltage converting unit 6b) via the changeover switch 7a (or the connection cable CB and the changeover switch 7 a).

In the current sensor 1B shown in fig. 3 and the current sensor 1D shown in fig. 5, the 1 st line is a line from the other end 4B of the feedback winding 4 to the input unit 11 of the voltage converting unit 6a via the 1 st connecting cable CB1, the transmission path TL1, the 2 nd connecting cable CB2, and the changeover switch 7 a. The 2 nd line is a line from the other end 4b of the feedback winding 4 to the input unit 21 of the voltage converting unit 6b via the 1 st connection cable CB1, the transmission path TL1, the 2 nd connection cable CB2, and the changeover switch 7 a.

In the current sensor 1C shown in fig. 4, the 1 st line is a line from the other end 4b of the feedback winding 4 to the input unit 11 of the voltage converting unit 6a via the 1 st connecting cable CB1, the changeover switch 7a, the transmission path TL1, the changeover switch 7b, and the 2 nd connecting cable CB 2. The 2 nd line is a line from the other end 4b of the feedback winding 4 to the input unit 21 of the voltage converting unit 6b via the 1 st connecting cable CB1 and the changeover switch 7 a.

In the current sensor 1E shown in fig. 6 and the current sensor 1F shown in fig. 7, the 1 st line is a line from the other end 4b of the feedback winding 4 to the input unit 11 of the voltage converting unit 6a via the 1 st connection cable CB1, the changeover switch 7a, the transmission path TL1, the changeover switch 7b, the 2 nd connection cable CB2, and the changeover switch 8 a. The 2 nd line is a line from the other end 4b of the feedback winding 4 to the input unit 21 of the voltage converting unit 6b via the 1 st connecting cable CB1 and the changeover switch 7 a.

With this configuration, the resistance value R1 of the 1 st detection resistor 13 for converting the negative feedback current I2 into the 1 st detection voltage Vd1 is defined as the characteristic impedance (50 Ω) of the 1 st line for supplying the negative feedback current I2 to the 1 st detection resistor 13 by the current sensors 1A, 1B, 1C, 1D, 1E, and 1F, and therefore, the waveform distortion with respect to the 1 st detection voltage Vd1 can be suppressed to be low. When the detection current I1 is an ac signal, the negative feedback current I2 has the same frequency as the detection current I1, and when a parasitic capacitance exists between the 1 st line and the ground G, the detection current I1 is converted into the 1 st detection voltage Vd1 by the combined impedance of the parallel circuit of the 1 st detection resistor 13 and the parasitic capacitance. In this case, the conversion to the 1 st detection voltage Vd1 in the parallel circuit is affected by a parameter represented by a multiplication value (C · R1) of the capacitance value C of the parasitic capacitance and the resistance value R1 of the 1 st detection resistor 13, and the voltage value of the 1 st detection voltage Vd1 decreases as the frequency of the negative feedback current I2 increases (that is, the detection band of the negative feedback current I2 is limited). However, according to the current sensors 1A, 1B, 1C, 1D, 1E, and 1F, since the resistance value R1 of the 1 st detection resistor 13 constituting the parallel circuit is 50 Ω and is a low value, the influence of the multiplier (C · R1) on the limitation of the detection band can be reduced, and the detection band of the negative feedback current I2 can be expanded to a higher frequency.

Further, according to the above-described current sensors 1A, 1B, 1C, 1D, 1E, and 1F, since the resistance value R2 of the 2 nd detection resistor 23 (terminal resistor of the 2 nd line) included in the voltage conversion unit 6B that converts the negative feedback current I2 into the 2 nd detection voltage Vd2 is defined as the characteristic impedance (50 Ω) of the 2 nd line that supplies the negative feedback current I2 to the 2 nd detection resistor 23, it is possible to suppress the waveform distortion with respect to the voltage between both ends of the 2 nd detection resistor 23 and the 2 nd detection voltage Vd2 output from the voltage conversion unit 6B.

In the current sensors 1A, 1B, 1C, 1D, 1E, and 1F, the 1 st detection voltage Vd1 is directly output as the output voltage Vo from the output terminal 9 to the outside at the 1 st detection rate, and therefore, the waveform distortion of the output voltage Vo at the 1 st detection rate can be suppressed to a low level. In each of the current sensors 1A, 1B, and 1D, the 2 nd detection voltage Vd2 is directly output to the outside as the output voltage Vo from the output terminal 9 at the 2 nd detection rate, and therefore, the waveform distortion with respect to the output voltage Vo at the 2 nd detection rate can be suppressed to a low level.

In addition, each of the current sensors 1C, 1E, 1F is configured such that, at the 2 nd detection rate, the 2 nd detection voltage Vd2 is outputted as the output voltage Vo from the output terminal 9 to the outside through a line terminated by the 1 st detection resistor 13 as another resistor, but the line (in the current sensor 1C, as shown in fig. 4, the line from the output part 22 of the voltage converting part 6b to the 1 st detection resistor 13 through the switch 7b and the 2 nd connecting cable CB2, and in the current sensors 1E, 1F, as shown in fig. 6, 7, the line from the output part 22 of the voltage converting part 6b to the 1 st detection resistor 13 through the switch 7b, the 2 nd connecting cable CB2, and the switch 8 a. hereinafter, in order to distinguish the 1 st line and the 2 nd line transmitting the negative feedback current I2, also referred to as a voltage transmission line) is as shown in fig. 4, 6, 7, substantially overlapping with a portion of the 1 st line described above. Therefore, the characteristic impedance of the voltage transmission line is defined to be the same as that of the 1 st line. Therefore, the 2 nd detection voltage Vd2 output from the voltage conversion section 6b to the line is transmitted to the 1 st detection resistor 13 with waveform distortion suppressed low, and is output as the output voltage Vo. Therefore, the waveform distortion of the output voltage Vo at the 2 nd detection rate can be suppressed to be low in the current sensors 1C, 1E, and 1F.

In each of the current sensors 1C, 1E, and 1F, when the resistance value Ro of the output impedance 25 of the voltage converting unit 6b is defined to be equal to the characteristic impedance of the voltage transmission line (50 Ω in the present example), the output impedance of the voltage converting unit 6b is matched to the characteristic impedance of the voltage transmission line. Therefore, according to the current sensors 1C, 1E, and 1F having this configuration, the 2 nd detection voltage Vd2 output from the voltage converting unit 6b is transmitted to the 1 st detection resistor 13 via the voltage transmission line in the state where the waveform distortion is further suppressed to be low at the 2 nd detection rate (R2/n × k × R1/(R1+ Ro)).

In addition, the voltage transmission line described above is configured as follows: the characteristic impedance at a portion not overlapping with a part of the 1 st line (a portion from the output unit 22 of the voltage converting unit 6b to the changeover switch 7b) cannot be made equal to the characteristic impedance of the 1 st line, and the main portion (the 2 nd connecting cable CB2) is common to them, so that the waveform distortion with respect to the output voltage Vo can be suppressed low.

In the current sensors 1D, 1E, and 1F of the present example, as described above, the line (the line from the other end 4b of the feedback winding 4 to the voltage converting unit 6c including the 3 rd detection resistor 33, hereinafter also referred to as the 3 rd line for distinction) that transmits the negative feedback current I2 at the 3 rd detection rate overlaps substantially the entire 1 st line that transmits the negative feedback current I2 at the 1 st detection rate, and therefore, the characteristic impedance thereof is configured to be equal to the characteristic impedance (50 Ω) of the 1 st line. On the other hand, the resistance value R3 of the 3 rd detection resistor 33 functioning as the termination resistor of the 3 rd line is 5 Ω in the present example. Therefore, at the 3 rd detection rate, the resistance value R3 of the 3 rd detection resistor 33 does not match the characteristic impedance of the 3 rd line.

However, when emphasis is placed on the waveform distortion of the output voltage Vo at the time of reducing the 3 rd detection rate rather than the waveform distortion of the output voltage Vo at the time of reducing the 1 st detection rate and the 2 nd detection rate, it is needless to say that the resistance value R3 of the 3 rd detection resistor 33 may be defined as the characteristic impedance (50 Ω) of the 3 rd line.

Industrial applicability of the invention

According to the present invention, since the 1 st detection voltage converted into a sufficient voltage value at the 1 st detection rate is output in the 1 st voltage conversion unit configured not to include an amplifier for a detection current having a large current value, the detection rate can be switched to a plurality of detection rates (the 1 st detection rate and the 2 nd detection rate larger than the 2 nd voltage conversion unit configured to include an amplifier) including the 1 st detection rate, and the 1 st detection voltage can be output by a configuration not including an amplifier at the 1 st detection rate, that is, without being affected by noise generated by the amplifier. Therefore, the current sensor can be widely applied to the current sensor.

Description of the reference symbols

1A, 1B, 1C, 1D, 1E, 1F current sensor

2 magnetic core

3 magnetoelectric conversion part

4 feedback winding

5 voltage current conversion circuit

6a, 6b voltage conversion part

7 st switching part

8 nd 2 nd switching part

9 output terminal

13 st detection resistor

23 nd 2 detection resistance

33 No. 3 detection resistor

61 detection conductor

I1 detection Current

I2 negative feedback current

Vd 11 st detection voltage

Vd 22 nd detection voltage

Vd3 No. 3 detection voltage

Vo outputs a voltage.

Claims (14)

1. A current sensor, comprising:

a magnetic core into which a detection conductor is inserted; a magnetoelectric conversion portion disposed on the magnetic core; a feedback winding wound around the magnetic core; a voltage-current conversion circuit that generates a negative feedback current that cancels magnetic flux generated in the magnetic core by a detection current flowing through the detection conductor, based on a voltage output from the magnetoelectric conversion unit, and supplies the generated negative feedback current to one end of the feedback winding; and an output terminal, wherein the current sensor includes:

1 or 2 or more 1 st voltage conversion units that convert the negative feedback current output from the other end of the feedback winding into a voltage using a 1 st detection resistance, thereby converting the detection current into a 1 st detection voltage at a 1 st detection rate and outputting the 1 st detection voltage; 1 or 2 or more 2 nd voltage converting units which convert the negative feedback current into a voltage using a 2 nd detection resistor and amplify the voltage using an amplifier, thereby converting the detection current into a 2 nd detection voltage at a 2 nd detection rate larger than the 1 st detection rate and outputting the 2 nd detection voltage; and

a switching unit that switches to the following connection state: any one element of the 1 st or 2 or more voltage converting parts and the 1 or 2 or more voltage converting parts is connected between the other end and the output terminal.

2. The current sensor of claim 1,

a resistance value of the detection resistor included in the any one of the 1 st detection resistor and the 2 nd detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the any one of the elements.

3. The current sensor according to claim 1 or 2, comprising:

a sensor unit that houses the magnetic core, the magnetoelectric conversion portion, and the feedback winding;

a relay unit that houses the voltage-current conversion circuit and a transmission path;

a terminal unit that houses the switching unit, the 1 st voltage conversion unit, the 2 nd voltage conversion unit, and the output terminal;

1 st connecting cable; and

the 2 nd-connection cable is connected to the cable,

the sensor unit and the relay unit are connected via the 1 st connection cable, and the voltage-current conversion circuit is connected between the magneto-electric conversion section and the one end of the feedback winding via a wiring constituting the 1 st connection cable, and one end of the transmission path is connected to the other end of the feedback winding via another wiring constituting the 1 st connection cable,

the relay unit and the terminal unit are connected via the 2 nd connection cable, and the switching unit switches to the following connection state: the arbitrary one element is connected between the output terminal and the other end of the transmission path connected via the wiring constituting the 2 nd connection cable.

4. A current sensor, comprising:

a magnetic core into which a detection conductor is inserted; a magnetoelectric conversion portion disposed on the magnetic core; a feedback winding wound around the magnetic core; a voltage-current conversion circuit that generates a negative feedback current that cancels magnetic flux generated in the magnetic core by a detection current flowing through the detection conductor, based on a voltage output from the magnetoelectric conversion unit, and supplies the generated negative feedback current to one end of the feedback winding; and an output terminal, the current sensor being characterized in that,

comprises a 1 st detection resistor for converting a supplied current into a voltage, a 2 nd detection resistor for converting a supplied current into a voltage, an amplifier for amplifying the voltage converted from the 2 nd detection resistor and outputting the amplified voltage, a transmission path, and a switching unit,

the switching unit switches the negative feedback current output from the other end of the feedback winding to be supplied to one element of the current-voltage conversion circuit including the 2 nd detection resistor and the amplifier and the transmission path, and supplies a signal output from the one element to the 1 st detection resistor,

in a switching state in which the switching unit is switched to the transmission path as the one element, the 1 st detection resistor converts the negative feedback current into a voltage, thereby converting the detection current into a 1 st detection voltage at a 1 st detection rate and outputting the 1 st detection voltage to the output terminal,

in a switching state in which the switching unit is switched to the current-voltage conversion circuit as the one element, the current-voltage conversion circuit and the 1 st detection resistor convert and amplify the negative feedback current into a voltage, and convert and output the detection current into a 2 nd detection voltage at a 2 nd detection rate larger than the 1 st detection rate to the output terminal.

5. The current sensor of claim 4,

the resistance value of the 1 st detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the 1 st detection resistor in a switched state in which the switching unit is switched to the transmission path as the one element.

6. The current sensor of claim 4,

the resistance value of the 2 nd detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the current-voltage conversion circuit in a switching state in which the switching unit switches to the current-voltage conversion circuit as the one element.

7. The current sensor of claim 6,

the resistance value of the 1 st detection resistor is defined as a characteristic impedance of a line from the current-voltage conversion circuit to the 1 st detection resistor.

8. The current sensor according to any one of claims 4 to 7, comprising:

a sensor unit that houses the magnetic core, the magnetoelectric conversion portion, and the feedback winding;

a relay unit that houses the voltage-current conversion circuit, the transmission path, the current-voltage conversion circuit, and the switching unit;

a terminal unit that houses the 1 st detection resistor and the output terminal;

1 st connecting cable; and

the 2 nd-connection cable is connected to the cable,

the sensor unit and the relay unit are connected via the 1 st connection cable, and the voltage-current conversion circuit is connected between the magneto-electric conversion section and the one end of the feedback winding via a wiring constituting the 1 st connection cable, and the switching section is connected to the other end of the feedback winding via another wiring constituting the 1 st connection cable,

the relay unit and the terminal unit are connected via the 2 nd connection cable, and the switching unit switches to the following connection state: and a 1 st detection resistor connected between the other end of the feedback winding connected via the other wiring constituting the 1 st connection cable and the wiring constituting the 2 nd connection cable.

9. A current sensor, comprising:

a magnetic core into which a detection conductor is inserted; a magnetoelectric conversion portion disposed on the magnetic core; a feedback winding wound around the magnetic core; a voltage-current conversion circuit that generates a negative feedback current that cancels magnetic flux generated in the magnetic core by a detection current flowing through the detection conductor, based on a voltage output from the magnetoelectric conversion unit, and supplies the generated negative feedback current to one end of the feedback winding; and an output terminal, the current sensor being characterized in that,

has a 1 st detection resistor for converting a supplied current into a voltage, a 2 nd detection resistor for converting a supplied current into a voltage, an amplifier for amplifying and outputting a voltage converted from the 2 nd detection resistor, a 3 rd detection resistor for converting a supplied current into a voltage, a transmission path, a 1 st switching unit, and a 2 nd switching unit,

the 1 st switching unit switches the negative feedback current output from the other end of the feedback winding to supply to the 1 st element of either one of the current-voltage conversion circuit including the 2 nd detection resistor and the amplifier and the transmission path, and supplies a signal output from the 1 st element to the 2 nd switching unit,

the 2 nd switching unit switches and supplies the signal supplied from the 1 st switching unit to the 2 nd element of either one of the 1 st detection resistor and the 3 rd detection resistor, and outputs a signal output from the 2 nd element to the output terminal,

in a switching state in which the 1 st switching unit is switched to the transmission path as the one 1 st element and the 2 nd switching unit is switched to the 1 st detection resistor as the one 2 nd element, the 1 st detection resistor converts the negative feedback current into a voltage, converts the detection current into a 1 st detection voltage at a 1 st detection rate, and outputs the 1 st detection voltage to the output terminal,

in a switching state in which the 1 st switching unit is switched to the current-voltage conversion circuit as the one 1 st element and the 2 nd switching unit is switched to the 1 st detection resistor as the one 2 nd element, the current-voltage conversion circuit and the 1 st detection resistor convert and amplify the negative feedback current into a voltage, convert the detection current into a 2 nd detection voltage at a 2 nd detection rate larger than the 1 st detection rate, and output the 2 nd detection voltage to the output terminal,

in a switching state in which the 1 st switching unit is switched to the transmission path as the one 1 st element and the 2 nd switching unit is switched to the 3 rd detection resistor as the one 2 nd element, the 3 rd detection resistor converts the negative feedback current into a voltage, converts the detection current into a 3 rd detection voltage at a 3 rd detection rate smaller than the 1 st detection rate, and outputs the 3 rd detection voltage to the output terminal.

10. The current sensor of claim 9,

the resistance value of the 1 st detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the 1 st detection resistor in a switching state in which the 1 st switching unit is switched to the transmission path as the one 1 st element and the 2 nd switching unit is switched to the 1 st detection resistor as the one 2 nd element.

11. The current sensor of claim 9,

the resistance value of the 2 nd detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the current-voltage conversion circuit in a switching state in which the 1 st switching unit is switched to the current-voltage conversion circuit as the one 1 st element and the 2 nd switching unit is switched to the 1 st detection resistor as the one 2 nd element.

12. The current sensor of claim 11,

the resistance value of the 1 st detection resistor is defined as a characteristic impedance of a line from the current-voltage conversion circuit to the 1 st detection resistor.

13. The current sensor of claim 9,

the resistance value of the 3 rd detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the 3 rd detection resistor in a switching state in which the 1 st switching unit is switched to the transmission path as the one 1 st element and the 2 nd switching unit is switched to the 3 rd detection resistor as the one 2 nd element.

14. The current sensor according to any one of claims 9 to 13, comprising:

a sensor unit that houses the magnetic core, the magnetoelectric conversion portion, and the feedback winding;

a relay unit that houses the voltage-to-current conversion circuit, the transmission path, the current-to-voltage conversion circuit, and the 1 st switching unit;

a terminal unit that houses the 1 st detection resistor, the 3 rd detection resistor, the 2 nd switching unit, and the output terminal;

1 st connecting cable; and

the 2 nd-connection cable is connected to the cable,

the sensor unit and the relay unit are connected via the 1 st connection cable, and the voltage-current conversion circuit is connected between the magneto-electric conversion section and the one end of the feedback winding via a wiring constituting the 1 st connection cable, and the 1 st switching section is connected to the other end of the feedback winding via another wiring constituting the 1 st connection cable,

the relay unit and the terminal unit are connected via the 2 nd connection cable,

the 1 st switching unit switches to the following connection state: connecting the one 1 st element between the other end of the feedback winding connected via the other wiring constituting the 1 st connection cable and the 2 nd switching part connected via a wiring constituting the 2 nd connection cable,

the 2 nd switching unit switches to the following connection state: the 2 nd element is connected between the wiring constituting the 2 nd connection cable and the output terminal.

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