JP2020016643A - Current sensor - Google Patents

Abstract

To reduce noise generated by an amplifier while changing over a detection rate.SOLUTION: A current sensor comprises a magnetic core 2, a magnetoelectric conversion part 3, a feedback coil 4, a voltage current conversion circuit 5 generating negative feedback current I2 based on a voltage V1 from the magnetoelectric conversion part 3 and supplying the current to one end 4a of the feedback coil 4, and an output terminal 9. The current sensor further comprises: a voltage conversion part 6a converting, at a first detection rate, the negative feedback current I2 outputted from the other end 4b of the feedback coil 4 into first detection voltage Vd 1 with a first detection resistor 13 and outputting the first detection voltage to the output terminal 9 as output voltage Vo; and a voltage conversion part 6b converting at a second detection rate the negative feedback current I2 into second detection voltage Vd 2 with a second detection resistor 23 and outputting the second detection voltage to the output terminal 9 as output voltage Vo. The current sensor still further comprises a changeover part 7 switching to a connection state in which any one of the voltage conversion parts 6a, 6b is connected between the other end 4b of the feedback coil 4 and the output terminal 9.SELECTED DRAWING: Figure 1

Description

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

  As a current sensor of this type, in Patent Document 1 below, a detection current (measurement current) flowing through a detection conductor (measured electric wire) is measured by a zero flux method (a core, a magnetoelectric conversion unit (such as a Hall element or a flux gate element), and a return winding). Line (negative feedback coil), a voltage-current conversion circuit, a detection resistor circuit that converts the negative feedback current into a voltage and outputs the voltage, and an amplifier circuit that amplifies the voltage output from the detection resistor circuit and outputs the amplified voltage as an output voltage A current sensor that detects by using a combination of the detection resistor that forms the detection resistor circuit and the input resistance of the operational amplifier that forms the amplifier circuit. A current sensor that can switch the conversion rate of the current sensor is disclosed.

JP 2014-215065 A (page 5-8, FIG. 1)

  However, the conventional current sensor described above has the following problems to be improved. That is, in the conventional current sensor, at any detection rate, the detection voltage detected by the detection resistor is all amplified by the operational amplifier included in the amplifier circuit and output as the output voltage. However, there is a problem that the output voltage output at all detection rates is affected by noise generated in the operational amplifier itself constituting the amplifier circuit.

  The present invention has been made to solve such a problem, and has as its main object to provide a current sensor capable of switching the detection rate and reducing the influence of noise generated in an amplifier.

  In order to achieve the above object, the current sensor according to claim 1, wherein a magnetic core through which a detection conductor is inserted, a magnetoelectric converter disposed on the magnetic core, a feedback winding wound around the magnetic core, and a detection current A voltage-current conversion circuit that generates a negative feedback current that cancels a magnetic flux generated in the magnetic core by flowing through the detection conductor based on a voltage output from the magnetoelectric conversion unit and supplies the negative feedback current to one end of the feedback winding. And a current sensor having an output terminal, wherein the negative detection current output from the other end of the feedback winding is converted into a voltage using a first detection resistor, so that the detection current is first detected. One or more first voltage converters that convert and output a first detection voltage at a rate, and convert the negative feedback current into a voltage using a second detection resistor and amplify the voltage with an amplifier. , One or more second voltage conversion units for converting the detection current into a second detection voltage at a second detection rate greater than the first detection rate and outputting the second detection voltage, and wherein the one or more first voltage conversion units A switching unit is provided for switching to a connection state in which any one element of the conversion unit and the one or more second voltage conversion units is connected between the other end and the output terminal.

  The current sensor according to claim 2 is the current sensor according to claim 1, wherein a resistance value of a detection resistor included in the arbitrary one of the first detection resistor and the second detection resistor is: The characteristic impedance of the line from the other end of the feedback winding to the arbitrary one element is defined.

  According to a third aspect of the present invention, there is provided the current sensor according to the first or second aspect, wherein the magnetic core, the magnetoelectric conversion unit, and the feedback winding are accommodated in the sensor unit, the voltage-current conversion circuit, and the transmission unit. A relay unit in which a path is stored, a terminal unit in which the switching unit, the first voltage converter, the second voltage converter, and the output terminal are stored, a first connection cable, and a second connection cable. The sensor unit and the relay unit are connected via the first connection cable, and the voltage-current conversion circuit is connected to the magneto-electric conversion unit and the return winding via wiring constituting the first connection cable. And one end of the transmission line is connected to the other end of the feedback winding via another wiring constituting the first connection cable, The relay unit and the terminal unit are connected via the second connection cable, and the switching unit is connected to the other end of the transmission path connected via the wiring configuring the second connection cable and the output terminal. The state is switched to a connection state in which the arbitrary one element is connected to a terminal.

  Also, the current sensor according to claim 4, wherein the magnetic core through which the detection conductor is inserted, a magnetoelectric converter disposed on the magnetic core, a feedback winding wound around the magnetic core, and a detection current supplied to the detection conductor. A voltage-current conversion circuit that generates a negative feedback current for canceling a magnetic flux generated in the magnetic core by flowing to the one end of the feedback winding based on a voltage output from the magnetoelectric conversion unit, and an output terminal. A current sensor comprising: a first detection resistor that converts a supplied current into a voltage; a second detection resistor that converts a supplied current into a voltage; and amplifies a voltage converted by the second detection voltage. An amplifier, a transmission line, and a switching unit. The switching unit converts the negative feedback current output from the other end of the feedback winding into a current configured by the second detection resistor and the amplifier. Voltage conversion circuit and While switching to any one element of the transmission path and supplying the same, a signal output from the one element is supplied to the first detection resistor, and the switching unit supplies the transmission path as the one element to the transmission path. In the switched switching state, the first detection resistor converts the negative feedback current into a voltage, converts the detection current into a first detection voltage at a first detection rate, and outputs the first detection voltage to the output terminal. In a switching state in which the switching unit switches to the current-to-voltage conversion circuit as the one element, the current-to-voltage conversion circuit and the first detection resistor convert the negative feedback current into a voltage and amplify the voltage, thereby enabling the detection. The current is converted to a second detection voltage at a second detection rate greater than the first detection rate and output to the output terminal.

  According to a fifth aspect of the present invention, in the current sensor according to the fourth aspect, the resistance value of the first detection resistor is such that the feedback in the switching state in which the switching unit switches to the transmission line as the one element. It is defined by the characteristic impedance of the line from the other end of the winding to the first detection resistor.

  According to a sixth aspect of the present invention, in the current sensor according to the fourth aspect, the resistance value of the second detection resistor is in a switching state in which the switching unit switches to the current-voltage conversion circuit as the one element. The characteristic impedance of the line from the other end of the feedback winding to the current-voltage conversion circuit is defined.

  According to a seventh aspect of the present invention, in the current sensor of the sixth aspect, a resistance value of the first detection resistor is defined by a characteristic impedance of a line from the current-voltage conversion circuit to the first detection resistor. ing.

  The current sensor according to claim 8 is the current sensor according to claim 4, wherein the magnetic core, the magnetoelectric conversion unit, and the feedback winding are housed in the sensor unit; A relay unit accommodating the conversion circuit, the transmission line, the current-voltage conversion circuit, and the switching unit; a termination unit accommodating the first detection resistor and the output terminal; a first connection cable; A cable, wherein the sensor unit and the relay unit are connected via the first connection cable, and the voltage / current conversion circuit is connected to the magneto-electric conversion unit via a wire constituting the first connection cable. The switching unit is connected to the one end of the feedback winding, and the switching unit is connected to the other end of the feedback winding via another wiring constituting the first connection cable. The relay winding, wherein the relay unit and the terminal unit are connected via the second connection cable, and wherein the switching unit is connected via the other wiring constituting the first connection cable. Is switched to a connection state in which the one element is connected between the other end of the first detection resistor and the first detection resistor connected via the wiring configuring the second connection cable.

  The current sensor according to claim 9, wherein the magnetic core through which the detection conductor is inserted, a magnetoelectric converter disposed on the magnetic core, a feedback winding wound around the magnetic core, and a detection current supplied to the detection conductor. A voltage-current conversion circuit that generates a negative feedback current for canceling a magnetic flux generated in the magnetic core by flowing to the one end of the feedback winding based on a voltage output from the magnetoelectric conversion unit, and an output terminal. A current sensor comprising: a first detection resistor that converts a supplied current into a voltage; a second detection resistor that converts a supplied current into a voltage; and amplifies a voltage converted by the second detection voltage. Amplifier, a third detection resistor for converting a supplied current to a voltage, a transmission line, a first switching unit and a second switching unit, wherein the first switching unit is connected to the other end of the feedback winding from the other end. The output negative feedback current is The switch is supplied to an arbitrary first element of the current-voltage conversion circuit and the transmission line, which is composed of the second detection resistor and the amplifier, and a signal output from the one first element is The second switching unit supplies the signal supplied from the first switching unit to the second switching unit. The second switching unit supplies an arbitrary one of the first detection resistor and the third detection resistor to the signal. And a signal output from the one second element is output to the output terminal, and the first switching unit switches to the transmission path as the one first element, and In a switching state in which the second switching unit switches to the first detection resistor as the one second element, the first detection resistor converts the negative feedback current into a voltage, thereby detecting the detection current for the first detection. The first detection voltage at the rate The first switching unit switches to the current-voltage conversion circuit as the one first element, and the second switching unit performs the switching as the one second element. In the switching state in which the detection current is switched to the first detection resistance, the current-voltage conversion circuit and the first detection resistance convert the negative feedback current into a voltage and amplify the voltage, so that the detection current is higher than the first detection rate. A second detection voltage is converted to a second detection voltage at a second detection rate and output to the output terminal, and the first switching unit switches to the transmission line as the one first element, and the second switching unit switches to the transmission path. In a switching state in which the third detection resistor is switched as the second element, the third detection resistor converts the negative feedback current into a voltage, thereby reducing the detection current smaller than the first detection rate. 3 The voltage is converted to a third detection voltage at a detection rate and output to the output terminal.

  According to a tenth aspect of the present invention, in the current sensor according to the ninth aspect, the resistance of the first detection resistor is switched by the first switching unit to the transmission line as the one first element. And the characteristic impedance of the line from the other end of the feedback winding to the first detection resistor in a state where the second switching unit switches to the first detection resistor as the one second element. ing.

  In the current sensor according to the eleventh aspect, in the current sensor according to the ninth aspect, the resistance value of the second detection resistor is switched by the first switching unit to the current-voltage conversion circuit as the one first element. In the switching state, and the characteristic impedance of the line from the other end of the feedback winding to the current-voltage conversion circuit in the switching state in which the second switching unit switches to the first detection resistor as the one second element. Stipulated.

  According to a twelfth aspect of the present invention, in the current sensor of the eleventh aspect, the resistance value of the first detection resistor is defined by a characteristic impedance of a line from the current-voltage conversion circuit to the first detection resistor. ing.

  According to a thirteenth aspect of the present invention, in the current sensor according to the ninth aspect, the resistance of the third detection resistor is switched by the first switching unit to the transmission path as the one first element. State and the characteristic impedance of the line from the other end of the feedback winding to the third detection resistor in the switching state in which the second switching unit switches to the third detection resistor as the one second element. ing.

  According to a fourteenth aspect of the present invention, in the current sensor according to the ninth to thirteenth aspect, a sensor unit accommodating the magnetic core, the magnetoelectric converter, and the feedback winding; A relay unit in which the conversion circuit, the transmission line, the current-voltage conversion circuit, and the first switching unit are housed, and the first detection resistor, the third detection resistor, the second switching unit, and the output terminal are housed. A termination unit, a first connection cable, and a second connection cable, the sensor unit and the relay unit are connected via the first connection cable, and the voltage / current conversion circuit is connected to the first connection cable. The first connection unit is connected between the magnetoelectric conversion unit and the one end of the feedback winding via a wiring constituting a connection cable, and the first switching unit configures the first connection cable. Is connected to the other end of the feedback winding via the wiring, the relay unit and the terminal unit are connected via the second connection cable, and the first switching unit connects the first connection cable The first switching device connected between the other end of the feedback winding connected via the other wiring to be configured and the second switching unit connected via the wiring configuring the second connection cable; Switching to a connection state in which the elements are connected, and the second switching unit switches to a connection state in which the one second element is connected between the wiring configuring the second connection cable and the output terminal.

  In the current sensor according to the first and fourth aspects, the negative feedback current is also small because the current value of the detection current is small, and when the first detection resistor alone cannot convert the voltage to the first detection voltage having a sufficient voltage value, , A circuit having a configuration including the second detection resistor and the amplifier converts the detection current into a second detection voltage having a sufficient voltage value at the second detection rate and outputs the converted voltage. However, since the current value of the detection current is large, negative feedback is performed. If the current also increases and the first detection resistor alone can convert the voltage to a first detection voltage having a sufficient voltage value, a circuit for voltage conversion constituted by the first detection resistor without the amplifier is used. The current is converted to a first detection voltage having a sufficient voltage value at the first detection rate and output.

  Therefore, according to this current sensor, the detection rate can be switched, and at one detection rate (first detection rate), the amplifier does not include an amplifier, that is, without being affected by noise generated in the amplifier. The detection current can be converted into a first detection voltage and output.

  In the current sensor according to the ninth aspect, the negative feedback current is also small because the current value of the detection current is small, and when the first detection resistor alone cannot convert the voltage to the first detection voltage having a sufficient voltage value, (2) A circuit having a configuration including a detection resistor and an amplifier converts the detection current into a second detection voltage having a sufficient voltage value at a second detection rate and outputs the second detection voltage. When the first detection resistor becomes large and can be converted to a first detection voltage having a sufficient voltage value by the first detection resistor alone, the circuit including the amplifier and not including the amplifier detects the detection current at the first detection rate. The voltage is converted into a first detection voltage having a sufficient voltage value and output. Further, the negative feedback current is further increased because the current value of the detection current is further increased. If the voltage value is too large in the voltage conversion by the first detection resistor, a resistor smaller than the first detection resistor without the amplifier is included. A circuit constituted by a third detection resistor having a value converts the detection current into a third detection voltage at a third detection rate smaller than the first detection rate and outputs the third detection voltage.

  Therefore, according to this current sensor, a detection current having a large current value can be converted into the first detection voltage or the third detection voltage and output without using an amplifier. That is, according to this current sensor, three detection rates can be switched, and two of the detection rates (the first detection rate and the third detection rate) do not include an amplifier, that is, the current is generated by the amplifier. The detection current can be converted into the first detection voltage or the third detection voltage and output without being affected by the noise.

  In the current sensor according to the third aspect, when a negative feedback current having a large current value flows (at the first detection rate), the voltage-current conversion circuit and the first detection resistor, both of which generate large amounts of heat, are different from each other in the unit. (Because the voltage-current conversion circuit is housed in the relay unit and the first detection resistor is housed in the terminal unit), the heat generated by the voltage-current conversion circuit and the first detection resistor is different. Can be distributed in units. Thus, according to this current sensor, it is possible to suppress both the temperature rise in the relay unit and the temperature rise in the terminal unit. Further, it is possible to avoid the influence of the heat generated by the first detection resistor on the voltage-current conversion circuit. Further, it is possible to avoid the influence of the heat generated by the first detection resistor on the magnetic core, the magnetoelectric converter, and the feedback winding provided in the sensor unit.

  In the current sensor according to the present invention, when a negative feedback current having a large current value flows (at the first detection rate), the voltage-current conversion circuit and the first detection resistor, both of which generate a large amount of heat, are different from each other in a unit. Due to the configuration accommodated (because the voltage-current conversion circuit is accommodated in the relay unit and the first detection resistor is accommodated in the termination unit), each heat generated by the voltage-current conversion circuit and the first detection resistor is different from each other. Can be dispersed. Thus, according to this current sensor, it is possible to suppress both the temperature rise in the relay unit and the temperature rise in the terminal unit. According to this current sensor, the voltage-current conversion circuit and the current-voltage conversion circuit (a circuit configured by the second detection resistor and the amplifier) are housed in a relay unit different from the first detection resistor. Unlike the configuration in which the average temperature tends to be higher due to the heat generation of the first detection resistor, the heat generation of the first detection resistor to the voltage-current conversion circuit and the amplifier of the current-voltage conversion circuit is different. Can be avoided.

  In the current sensor according to the fourteenth aspect, when a negative feedback current having a large current value flows (at the first detection rate or the third detection rate), the voltage-current conversion circuit, the first detection resistance, and the heat generation amount are both increased. Since the voltage-current conversion circuit and the first detection resistance and the third detection resistance of the third detection resistance are housed in different units (the voltage-current conversion circuit is housed in the relay unit and the first detection resistance Since the resistor and the third detection resistor are housed in the termination unit), heat generated by the voltage-current conversion circuit and heat generated by the first detection resistor and the third detection resistor can be distributed to different units. Thus, according to this current sensor, it is possible to switch both the three detection rates and to suppress both the temperature rise in the relay unit and the temperature rise in the terminal unit. Further, according to this current sensor, the voltage-current conversion circuit and the current-voltage conversion circuit (a circuit composed of the second detection resistor and the amplifier) are housed in a relay unit different from the first detection resistor and the third detection resistor. Therefore, unlike the configuration in which the average temperature tends to be higher due to the heat generated by the first detection resistor and the third detection resistor, the voltage-current conversion circuit and the current-voltage conversion circuit Of the first detection resistor and the third detection resistor can be avoided.

  According to the current sensor of the second aspect, the resistance value of the detection resistor that converts the negative feedback current into the corresponding detection voltage of the first detection voltage and the second detection voltage supplies the negative feedback current to the detection resistor. Since it is defined by the characteristic impedance of the line, the waveform distortion of the detected voltage can be suppressed low.

  According to the present invention, the resistance value of the first detection resistor that converts the negative feedback current into the first detection voltage is defined by the characteristic impedance of the line that supplies the negative feedback current to the first detection resistor. Therefore, the waveform distortion of the first detection voltage can be suppressed low.

  According to the current sensor of the sixth or eleventh aspect, the resistance value of the second detection resistor for converting the negative feedback current into a voltage is a characteristic of a line that supplies the negative feedback current to the current-voltage conversion circuit including the second detection resistor. Since the impedance is specified, the waveform distortion of the voltage converted by the second detection resistor can be reduced.

  According to the present invention, the resistance value of the first detection resistor is equal to the characteristic impedance of the line transmitting the voltage converted by the current-voltage conversion circuit including the second detection resistor to the first detection resistor. Since it is specified, the waveform distortion of the second detection voltage output from the first detection resistor can be further reduced.

  According to the current sensor of the thirteenth aspect, the resistance value of the third detection resistor that converts the negative feedback current into the third detection voltage is defined by the characteristic impedance of the line that supplies the negative feedback current to the third detection resistor. Therefore, waveform distortion of the third detection voltage can be suppressed low.

It is a block diagram of 1 A of current sensors. FIG. 3 is a configuration diagram showing an example in which the components of a current sensor 1A are divided into two parts, a sensor unit 51 and a terminal unit 52; It is a block diagram of a current sensor 1B. It is a block diagram of the current sensor 1C. It is a block diagram of a current sensor 1D. It is a block diagram of a current sensor 1E. It is a block diagram of the current sensor 1F.

  Hereinafter, an embodiment of a current sensor will be described with reference to the accompanying drawings.

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

  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, and a plurality of voltage conversion units (in the present example, as an example, two voltage conversion units 6a , 6b), a first switching unit 7 (hereinafter also simply referred to as the switching unit 7), and an output terminal 9 to constitute a zero-flux current sensor. Further, the current sensor 1A outputs from the output terminal 9 an output voltage Vo whose voltage value changes in accordance with the current value of the detection current I1 flowing through the detected electric wire 61 as an example of the detection conductor inserted through the inside of the magnetic core 2. Output.

  As an example, the magnetic core 2 is formed in a split type that can be opened and closed around a base end (a lower end in FIG. 1), and can clamp the detected wire 61 in a live state (the detected wire 61 inside). Can be inserted). Note that the magnetic core 2 is not limited to the split type, and may be a penetration type (non-split type).

  The magnetoelectric conversion unit 3 is configured by a magnetoelectric conversion element such as a Hall element or a flux gate, for example. The magnetoelectric conversion unit 3 is provided, for example, at the base end of the magnetic core 2. In the operating state, the magnetoelectric conversion unit 3 detects a magnetic flux generated inside the magnetic core 2 and generates a voltage V1 having a voltage value (specifically, proportional or almost proportional) according to the magnetic flux density. Output. In this case, the magnetic flux generated inside the magnetic core 2 includes a magnetic flux φ1 generated when the detection current I1 flows through the detected electric wire 61 inserted into the magnetic core 2, and a negative feedback current described later in the feedback winding 4. It is a combined magnetic flux (φ1−φ2) with a magnetic flux φ2 (a magnetic flux opposite to the magnetic flux φ1) generated by flowing I2.

  The feedback winding 4 is configured by winding the wire around the magnetic core 2 with a predetermined number of turns n (the number of turns n; in this example, n = 50 as an example). The voltage-current conversion circuit 5 is configured by an operational amplifier or the like, receives the voltage V1 from the magnetoelectric conversion unit 3, generates a negative feedback current I2 based on the voltage V1, and supplies the negative feedback current I2 to one end 4a of the feedback winding 4. Supply. In this case, the voltage-current conversion circuit 5 determines that the voltage V1 approaches zero volts, that is, the magnetic flux density of the composite magnetic flux (φ1−φ2) generated inside the magnetic core 2 detected in the magnetoelectric conversion unit 3 is reduced. The current value of the negative feedback current I2 is controlled so as to approach zero (in other words, to cancel the magnetic flux φ1 with the magnetic flux φ2). 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 includes, for example, two changeover switches 7a and 7b having a one-circuit two-contact structure, and a first element (voltage conversion unit) of any one of the two voltage conversion units 6a and 6b. Switches to a connection state 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 conversion units 6a and 6b, which will be described later. Negative feedback current I2 output from 4b is selectively switched to one of voltage converters 6a and 6b and output. Further, the changeover switch 7b is connected between the output terminals 12, 22 of the voltage converters 6a, 6b, which will be described later, and the output terminal 9, and is switched in conjunction with the changeover switch 7a. Specifically, when the changeover switch 7a is switched to connect the other end 4b of the feedback winding 4 and the input unit 11 of the voltage conversion unit 6a, the changeover switch 7b operates the output unit 12 of the voltage conversion unit 6a. And the output terminal 9 is connected. When the changeover switch 7a is switched to connect the other end 4b of the feedback winding 4 to the input unit 21 of the voltage conversion unit 6b, the changeover switch 7b switches between the output unit 22 of the voltage conversion unit 6b and the output terminal. 9 to be connected. With this configuration, the switching unit 7 detects the detection voltage output from one of the voltage conversion units 6a and 6b to which the negative feedback current I2 is supplied (when the negative feedback current I2 is supplied to the voltage conversion unit 6a). When the first detection voltage Vd1 output from the voltage conversion unit 6a and the negative feedback current I2 are supplied to the voltage conversion unit 6b, the second detection voltage Vd2 output from the voltage conversion unit 6b is output to the output terminal 9. Output as the output voltage Vo. Further, the switching unit 7 (in this example, the changeover switches 7a and 7b) is configured by a mechanical switch such as a relay or a switch formed of a semiconductor element such as an analog switch.

  The voltage conversion unit 6a is a first voltage conversion unit. When the input unit 11 is connected to the changeover switch 7a of the changeover unit 7 and the changeover switch 7a outputs the negative feedback current I2 to the input unit 11, The negative feedback current I2 is converted into a first detection voltage Vd1, and the first detection voltage Vd1 is output from the output unit 12 as it is. In this example, as an example, the voltage conversion unit 6a includes the first detection resistor 13 having a predetermined resistance value R1 (for example, 50Ω). One end of the first detection resistor 13 is connected to the input unit 11 and the output unit 12, and the other end is connected to a portion (ground G) of the reference potential in the current sensor 1A, and is configured as a current-voltage conversion circuit. With this configuration, the voltage conversion unit 6a converts the negative feedback current I2 input to the input unit 11 into the first detection voltage Vd1 (= I2 × R1) using the first detection resistor 13 (resistance value R1), and as it is. Output from the output unit 12. The first detection voltage Vd1 is represented as (I1 × R1 / n) using a first detection rate (R1 / n) defined by the resistance value R1 and the number of turns n. In this example, since R1 = 50Ω and n = 50, the voltage conversion unit 6a converts the detection current I1 to the first detection voltage Vd1 at the first detection rate (numerical value “1”).

  The voltage conversion unit 6b is a second voltage conversion unit. When the input unit 21 is connected to the changeover switch 7b of the changeover unit 7 and the changeover switch 7b outputs the negative feedback current I2 to the input unit 21, The negative feedback current I2 is converted into a second detection voltage Vd2 and output from the output unit 22. In the present example, as an example, the voltage conversion unit 6b uses the second detection resistor 23 having a predetermined resistance value R2 (for example, 50Ω) and k times the input voltage (k is a real number exceeding 1 which is predetermined). In this example, as an example, an amplifier (for example, a broadband amplifier constituted by an operational amplifier) 24 that amplifies and outputs a numerical value “10”, and an output resistor 25 connected between the output terminal of the amplifier 24 and the output unit 22 (Resistance value Ro; in this example, 50Ω as an example), and is configured as a current-voltage conversion circuit. The second detection resistor 23 has one end connected to the input terminals of the input unit 21 and the amplifier 24 and the other end connected to the ground G. With this configuration, the voltage conversion unit 6b converts the negative feedback current I2 input to the input unit 21 into the second detection voltage Vd2 (= I2 × R2 × k) and outputs the same from the output unit 12. Further, the second detection voltage Vd2 is calculated by using the second detection rate (R2 / n × k) defined by the resistance value R2, the number of turns n, and the numerical value k (the amplification factor k of the amplifier 24), as (I1 × R2 / N × k). In this example, since R2 = 50Ω, n = 50, and k = 10, the voltage conversion unit 6b outputs the detected current at the second detection rate (numerical value “10”) larger than the first detection rate. I1 is converted to a second detection voltage Vd2.

  Next, how to use and operate the current sensor 1A will be described with reference to the drawings. The output terminal 9 of the current sensor 1A is connected to a measuring instrument (for example, a waveform observation device such as an oscilloscope) having a high input impedance (for example, 1 MΩ or more). Thereby, in this measuring instrument, it is possible to observe the waveform of the detection current I1 detected by the current sensor 1A.

  In a state where the detected electric wire 61 in which the detection current I1 is flowing is inserted through the inside of the magnetic core 2, the magnetoelectric conversion unit 3 detects the magnetic flux generated inside the magnetic core 2 and responds to the magnetic flux density. A voltage V1 having a voltage value is output. In this case, inside the magnetic core 2, the magnetic flux φ1 generated by the detection current I1 flowing through the detected electric wire 61 and the negative feedback current I2 (output from the voltage / current conversion circuit 5 to the feedback winding 4). (Φ1−φ2) from the magnetic flux φ2 that is generated by the flow of the current that is flowing.

  The voltage-current conversion circuit 5 generates the voltage V1 based on the voltage V1 input from the magnetoelectric conversion unit 3 so that the voltage V1 becomes zero volt, that is, the voltage V1 is generated inside the magnetic core 2 detected by the magnetoelectric conversion unit 3. The negative feedback current I2 is generated and output to the feedback winding 4 while controlling the current value of the negative feedback current I2 so that the magnetic flux density of the existing magnetic flux (φ1−φ2) becomes zero. Thus, the current value of the negative feedback current I2 is a value 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 voltage conversion unit 6a is switched to the 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 via the switching unit 7. The unit 7 is switched. On the other hand, when the current value of the detection current I1 is small, the switching unit 7 is switched to the 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 via the switching unit 7. Can be switched.

  The first switching unit 7 and the second switching unit 8 allow the user of the current sensor 1A to determine the magnitude of the current value of the detected current I1 and to provide the first switching unit 7 and the second switching unit 8 to the current sensor 1A based on the result of the determination. By operating the operation unit (not shown) provided (that is, manually), the first switching unit 7 and the second switching unit 8 can be switched, and the CPU and the A / D are provided in the current sensor 1A. A processing unit (not shown) constituted by a converter or the like is provided, and the processing unit detects the voltage value of the output voltage Vo via the A / D converter, and based on the magnitude of the detected voltage value of the output voltage Vo. Thus, a configuration in which the first switching unit 7 and the second switching unit 8 are switched (a configuration in which the detection rate is automatically switched) can be adopted.

  First, since the current value of the detection current I1 is large, when the switching unit 7 is switched 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 through the changeover switch 7a of the changeover unit 7 into the first detection voltage Vd1 only by the first detection resistor 13, and outputs the changeover signal from the output unit 12 to the changeover unit. 7 to the output terminal 9 via the changeover switch 7b. As described above, in the current sensor 1A, the negative feedback current I2 also increases because the current value of the detection current I1 is large, and if the voltage can be converted to a voltage having a sufficient voltage value only by the detection resistor, the configuration including no amplifier is included. Converts the negative feedback current I2 to the first detection voltage Vd1 only by the first detection resistor 13 (that is, in a state where it is not affected by noise generated by the amplifier), that is, the detection current I1 Is converted to a first detection voltage Vd1 (= I1 × R1 / n) at a first detection rate (R1 / n; numerical value “1” in this example) and output.

  On the other hand, when the switching unit 7 is switched to the 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 because the current value of the detection current I1 is small. The voltage conversion unit 6b converts the negative feedback current I2 input via the changeover switch 7a of the changeover unit 7 into the second detection voltage Vd2 by the second detection resistor 23 and the amplifier 24, that is, the detection current I1 Is converted to a first detection voltage Vd1 (= I1 × R2 / n × k) at a second detection rate (R2 / n × k; numerical value “10” in this example) higher than the first detection rate, and the output unit The signal is output from the output terminal 9 to the output terminal 9 via the changeover switch 7b of the changeover unit 7. As described above, in the current sensor 1A, since the current value of the detection current I1 is small, the negative feedback current I2 also becomes small. If the detection resistor alone cannot convert the voltage into a voltage having a sufficient voltage value, the amplifier 24 is turned off. The voltage converter 6b having the configuration includes the negative feedback current I2, which is affected by noise generated in the amplifier 24, and outputs the second detection voltage Vd2 having a sufficient voltage value.

  As described above, in the current sensor 1A, since the current value of the detection current I1 is small, the negative feedback current I2 also becomes small. If the detection resistor alone cannot convert the voltage to a voltage having a sufficient voltage value, the amplifier 24 is turned off. The voltage conversion unit 6b having a configuration including the detection current I1 converts the detection current I1 into a second detection voltage Vd2 having a sufficient voltage value at the second detection rate and outputs the converted voltage. However, since the current value of the detection current I1 is large, the negative feedback current I2 When the voltage can be converted to a voltage having a sufficient voltage value only by the detection resistor, the voltage converter 6a having no amplifier includes the detection current I1 at the first detection rate smaller than the second detection rate. The voltage is converted into a first detection voltage Vd1 having a sufficient voltage value and output.

  Therefore, according to this current sensor 1A, at any detection rate, unlike a conventional current sensor employing a configuration in which a detection voltage detected by a detection resistor is amplified by an amplifier (operational amplifier) and output as an output voltage. The detection current I1 having a large current value can be converted into the first detection voltage Vd1 having a sufficient voltage value and output by the voltage conversion unit 6a having no amplifier. That is, according to the current sensor 1A, the detection rate can be switched, and at one detection rate (first detection rate), the configuration does not include the amplifier, that is, without being affected by noise generated in the amplifier. , The first detection voltage Vd1.

  A current sensor having a configuration in which an output terminal is connected to a measuring instrument has a sensor unit in which a magnetic core, a magnetoelectric converter and a feedback winding are accommodated, a voltage converter in which the voltage converter is accommodated, and a connector of the measuring instrument. It is known that the output terminal connected to the terminal is divided into two parts and a terminal unit arranged on the surface, and the units are connected to each other by a connection cable (a coaxial cable, a shielded cable, or the like). FIG. 2 shows the result when the current sensor 1A is applied. In this case, since the magnetoelectric conversion unit 3 is easily affected by a change in temperature, the voltage / current conversion circuit 5 is configured by an operational amplifier or the like, and generates a large amount of heat when outputting the negative feedback current I2 having a large current value. Are stored in the terminal unit 52 without being stored in the same sensor unit 51 as the magnetoelectric conversion unit 3.

  However, the first detection resistor 13 accommodated in the termination unit 52 is different from the second detection resistor 23 in which the negative feedback current I2 having a small current value flows, and the negative feedback current I2 having a larger current value flows therethrough. The calorific value is also large. Therefore, when the negative feedback current I2 having the large current value flows (at the first detection rate), the voltage-current conversion circuit 5 and the first detection resistor 13 that generate a large amount of heat are housed in the same termination unit 52. In the configuration shown in FIG. 2, the temperature rise in the terminal unit 52 may increase, which is not preferable.

  Therefore, the current sensor 1B shown in FIG. 3 employs a configuration having a relay unit 53 in addition to the sensor unit 51 and the terminal unit 52. Hereinafter, the current sensor 1B will be described. 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 will be omitted.

  As shown in FIG. 3, the current sensor 1B includes a magnetic core 2, a magnetoelectric conversion unit 3, a feedback winding 4, a voltage / current conversion circuit 5, two voltage conversion units 6a and 6b, a switching unit 7, and an output terminal 9. ing. The sensor unit 51 houses the magnetic core 2, the magnetoelectric converter 3, and the feedback winding 4, and the termination unit 52 houses the voltage converters 6a, 6b and the switching unit 7, and has an output terminal on the surface. 9 are provided, and the relay unit 53 houses the voltage-current conversion circuit 5. The relay unit 53 is connected to the sensor unit 51 via a first connection cable CB1 (a coaxial cable or a shielded cable), and the termination unit 52 is connected to the relay unit 53 and a second connection cable CB2 (a coaxial cable or a shielded cable). And so on). The relay unit 53 has a transmission line 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 CB2. It is stored. Further, the voltage-current conversion circuit 5 in the relay unit 53 is connected between the magnetoelectric conversion unit 3 in the sensor unit 51 and one end 4a of the feedback winding 4 via two wires constituting the first connection cable CB1. , And one end of the transmission line TL1 is connected to the other end 4b of the feedback winding 4 via another wiring configuring the first connection cable CB1. Further, the other end of the transmission line TL1 is connected to the switching unit 7 in the terminal unit 52 via the wiring configuring the second connection cable CB2.

  As described above, the current sensor 1B differs from the current sensor 1A in the configuration in which each component is housed separately in the sensor unit 51, the relay unit 53, and the terminal unit 52, but the basic configuration (the magnetic core 2, The configuration including the magnetoelectric conversion unit 3, the feedback winding 4, the voltage-current conversion circuit 5, the two voltage conversion units 6a and 6b, the switching unit 7, and the output terminal 9) is the same as the current sensor 1A. It operates the same as 1A.

  In this case, the relay unit 53 receives the voltage V1 from the magnetoelectric conversion unit 3 of the sensor unit 51 via the first connection cable CB1, and outputs the negative feedback current I2 output from the voltage-current conversion circuit 5 to the first connection cable CB1. The signal is output to one end 4a of the feedback winding 4 in the sensor unit 51 via CB1. In addition, 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 first connection cable CB1, and also inputs the second connection cable via the transmission line TL1. Output to CB2. On the other hand, in the termination unit 52, the switching unit 7 switches the negative feedback current I2 input via the second connection cable CB2 to one of the voltage conversion units 6a and 6b in the same manner as the current sensor 1A. At the same time, the detection voltage (the first detection voltage Vd1 or the second detection voltage Vd2) output from the one voltage converter is output to the output terminal 9.

  Thereby, the current sensor 1B detects the first detection voltage Vd1 and the second detection current I1 flowing through the detected electric wire 61 at an arbitrary one of the first detection rate and the second detection rate. The detection voltage Vd2 is converted into one detection voltage corresponding to the one detection rate, and output from the output terminal 9 as the output voltage Vo.

  Therefore, even with the current sensor 1B, the detection rate can be switched in the same manner as the current sensor 1A, and at one detection rate (first detection rate), the current does not include the amplifier, that is, the current is generated by the amplifier. The detection current I1 can be converted to the first detection voltage Vd1 having a sufficient voltage value and output without being affected by noise. Further, according to the current sensor 1B, when the negative feedback current I2 having a large current value flows (at the first detection rate), the voltage-current conversion circuit 5 and the first detection resistor 13, which both generate a large amount of heat, are connected. Since the configuration is accommodated in different units (because the voltage-current conversion circuit 5 is accommodated in the relay unit 53 and the first detection resistor 13 is accommodated in the termination unit 52), the voltage-current conversion circuit 5 and the first Each heat generated by the detection resistor 13 can be distributed to different units. Thereby, according to the current sensor 1B, both the temperature rise in the relay unit 53 and the temperature rise in the terminal unit 52 can be suppressed to be low. Further, it is possible to avoid an influence on the voltage-current conversion circuit 5 due to the heat generated by the first detection resistor 13. In addition, it is possible to avoid the influence of the heat generated by the first detection resistor 13 on the magnetic core 2, the magnetoelectric converter 3, and the feedback winding 4 provided in the sensor unit 51.

  Further, the current sensors 1A and 1B have one voltage conversion unit 6a as a first voltage conversion unit (a voltage conversion unit in which a current-voltage conversion circuit is configured only by the detection resistor), and a second voltage conversion unit. The configuration includes one voltage conversion unit 6b as a (voltage conversion unit in which a current-voltage conversion circuit includes a detection resistor and an amplifier), but is not limited to this configuration. Although not shown, there are two or more first voltage converters in which a current-to-voltage conversion circuit is constituted only by detection resistors, or a second voltage conversion unit in which a current-to-voltage conversion circuit is constituted by detection resistors and an amplifier. As a configuration having two or more, a switching unit 7 having changeover switches 7a and 7b having a one-circuit n-contact structure (n is 3 or more) is a first element (voltage conversion unit) of any one of these voltage conversion units. May be switched to a connection state in which is connected between the other end 4b of the feedback winding 4 and the output terminal 9.

  In the above-described current sensor 1B, when the negative feedback current I2 having a large current value flows (at the first detection rate), the voltage-current conversion circuit 5 and the first detection resistor 13 that generate large amounts of heat are: Although the configuration in which only the voltage-to-current conversion circuit 5 is housed in the relay unit 53 is employed, the configuration in which the voltage-to-current conversion circuit 5 and the first detection resistor 13 are housed in different units is not limited to this. For example, like the current sensor 1C shown in FIG. 4, other components (the voltage-current conversion circuit 5, two voltage conversion circuits) except the magnetic core 2, the magneto-electric conversion unit 3, and the feedback winding 4 housed in the sensor unit 51. Only the voltage conversion unit 6a and the output terminal 9 of the units 6a and 6b, the switching unit 7 and the output terminal 9) are housed in the termination unit 52, and the remaining components (the voltage-current conversion circuit 5, the voltage conversion unit 6b and the switching unit) A configuration in which the unit 7) is stored in the relay unit 53 may be employed. Hereinafter, the current sensor 1C will be described. The same components as those of the current sensor 1B are denoted by the same reference numerals, and redundant description will be omitted.

  The relay unit 53 of the current sensor 1C receives the voltage V1 from the magnetoelectric conversion unit 3 of the sensor unit 51 via the first connection cable CB1, and outputs the negative feedback current I2 output from the voltage / current conversion circuit 5 to the first connection cable CB1. The signal is output to one end 4a of the feedback winding 4 in the sensor unit 51 via the connection cable CB1. 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 first connection cable CB1.

  In this case, since the changeover switches 7a and 7b of the changeover unit 7 are switched in an interlocked manner, when the changeover switch 7a is in a changeover state in which the negative feedback current I2 is switched to one end of the transmission line TL1, the changeover switch is set. 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 second connection cable CB2. When the changeover switch 7a is in a switching state in which the negative feedback current I2 is switched to the input unit 21 of the voltage conversion unit 6b and output, the changeover switch 7b connects the output unit 22 of the voltage conversion unit 6b via the second connection cable CB2. The state of switching to the terminal unit 52 is established. With this configuration, in the relay unit 53, the switching unit 7 switches and outputs (supplies) the negative feedback current I2 to one of the first element of the second voltage conversion unit 6b and the transmission line TL1. When the first element is the second voltage converter 6b, the second detection voltage Vd2 as a signal output from the second voltage converter 6b is used. When the first element is the transmission path TL1, this transmission path is used. The negative feedback current I2 as a signal output from the TL1 is output (supplied) to the first voltage converter 6a of the termination unit 52 via the second connection cable CB2.

  On the other hand, in the termination unit 52, when the first voltage converter 6a receives the negative feedback current I2 from the relay unit 53 via the second connection cable CB2, the first detection resistor 13 (resistance value R1) performs the first detection. The voltage is converted to a voltage Vd1 (= I2 × R1) and output to the output terminal 9 as an output voltage Vo. The first detection voltage Vd1 is expressed as (I1 × R1 / n) using the first detection rate (R1 / n).

  Further, when the second voltage Vd2 is input from the relay unit 53 via the second connection cable CB2, the first voltage converter 6a outputs the second voltage Vd2 to the output terminal 9 as the output voltage Vo.

  In this case, if the resistance value Ro of the output resistor 25 of the voltage conversion unit 6b is a small value that can be ignored with respect to the resistance value R1 of the first detection resistor 13 that configures the first voltage conversion unit 6a, the first voltage The converter 6a outputs the second 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 second detection voltage Vd2 (= I1 × R2 / n × k) at the second detection rate (R2 / n × k) and output as the output voltage Vo. On the other hand, as in the present example, the resistance value Ro (50Ω in this example) of the output resistor 25 of the voltage conversion unit 6b is equal to the resistance value R1 (50Ω in this example) of the first detection resistor 13 constituting the first voltage conversion unit 6a. ), The first voltage converter 6a outputs the second detection voltage Vd2 divided by the first detection resistor 13 and the output resistor 25 to the output terminal 9 as the output voltage Vo. That is, the detection current I1 is a second detection rate (R2 / n × k × R1 / (R1 + Ro)) different from the second detection rate, and the second detection voltage Vd2 and further the first detection voltage Vd1 (= It is converted into I1 × R2 / n × k × R1 / (R1 + Ro) and output as the output voltage Vo. Therefore, in the current sensor 1C, by setting k = 20, the second detection rate can be made equal to the second detection rate (numerical value “10”) of the current sensors 1A and 1B.

  Therefore, even with the current sensor 1C, the detection rate can be switched in the same manner as the current sensor 1A, and at one detection rate (first detection rate), the current does not include an amplifier, that is, the current is generated by the amplifier. The detection current I1 can be converted to the first detection voltage Vd1 having a sufficient voltage value and output without being affected by noise. Further, according to the current sensor 1C, when the negative feedback current I2 having a large current value flows (at the first detection rate), the voltage-current conversion circuit 5 and the first detection resistor 13, both of which generate a large amount of heat, are connected. Since the configuration is accommodated in different units (because the voltage-current conversion circuit 5 is accommodated in the relay unit 53 and the first detection resistor 13 is accommodated in the termination unit 52), the voltage-current conversion circuit 5 and the first Each heat generated by the detection resistor 13 can be distributed to different units. Thus, according to the current sensor 1C, both the temperature rise in the relay unit 53 and the temperature rise in the terminal unit 52 can be suppressed to be low. Further, according to the current sensor 1C, the voltage-current conversion circuit 5 and the current-voltage conversion circuit (a circuit including the second detection resistor 23 and the amplifier 24: the voltage conversion unit 6b) are different from the first detection resistor 13. Since it is housed in the relay unit 53, unlike the structure in which it is housed in the terminal unit 52 in which the average temperature tends to be higher due to heat generation of the first detection resistor 13, the voltage-current conversion circuit 5 and the The influence of the heat generated by the first detection resistor 13 on the amplifier 24 of the current-voltage conversion circuit can be avoided.

  In each of the current sensors 1A, 1B, and 1C, as an example of a configuration that can switch a plurality of detection rates, a configuration that can switch between two detection rates of a first detection rate and a second detection rate is employed. However, a configuration is also possible in which three detection rates can be switched. Hereinafter, current sensors 1D and 1E configured to be able to switch three detection rates based on the current sensors 1B and 1C each including the sensor unit 51, the relay unit 53, and the terminal unit 52 will be described. Note that the same components as those of the current sensors 1B and 1C are denoted by the same reference numerals, and redundant description will be omitted.

  First, a current sensor 1D configured to be able to switch between three detection rates based on the current sensor 1B will be described with reference to FIG. Hereinafter, a configuration of the terminal unit 52 different from the current sensor 1B will be described.

  The terminating unit 52 houses a voltage converter 6c (another first voltage converter) in addition to the voltage converters 6a and 6b, the switching unit 7, and the output terminal 9. Further, the changeover switches 7a and 7b constituting the changeover unit 7 are configured as, for example, changeover switches having a one-circuit three-contact structure, and the changeover unit 7 is provided with an arbitrary one of the three voltage conversion units 6a, 6b and 6c. One of the first elements is switched to a connection state in which it is connected between the second connection cable CB2 and the output terminal 9.

  When the input unit 31 is connected to the first switching unit 7 and the negative feedback current I2 is output from the first switching unit 7 to the input unit 31, the voltage conversion unit 6c converts the negative feedback current I2 to the third detection voltage. The voltage is converted to Vd3 and output from the output unit 32 as an output voltage Vo. In the present example, as an example, the voltage conversion unit 6c as the first voltage conversion unit includes a third detection resistor 33 having a predetermined resistance value R3 (for example, 5Ω). One end of the third detection resistor 33 is connected to the input unit 31 and the output unit 32, and the other end is connected to a reference potential portion (ground G) in the current sensor 1D. With this configuration, the voltage conversion unit 6c converts the negative feedback current I2 input to the input unit 31 into a third detection voltage Vd3 (= I2 × R3) using the third detection resistor 33 (resistance value R3). The output unit 12 outputs the output voltage Vo as it is. The third detection voltage Vd3 is represented as (I1 × R3 / n) using a third detection rate (R3 / n) defined by the resistance value R3 and the number of turns n. In this example, since R3 = 5Ω and n = 50, the voltage conversion unit 6c converts the detection current I1 to the third detection voltage Vd3 at the third detection rate (numerical value “0.1”). .

  With this configuration, in the current sensor 1D, the first detection rate (numerical value “1”) and the second detection rate (numerical value “10”) of the current sensors 1A and 1B are changed to the third detection rate (numerical value “0”). ..1 ”), the negative feedback current I2 can be converted to the output voltage Vo by switching to any one of the three detection rates. Therefore, according to the current sensor 1D, the three detection rates can be switched, and two of the detection rates (the first detection rate and the third detection rate) do not include the amplifier, that is, the amplifier is not used. The detection current I1 can be converted into the first detection voltage Vd1 or the third detection voltage Vd3 and output without being affected by the generated noise. Also, in the current sensor 1D, similarly to the current sensor 1B, the heat generation in the voltage-current conversion circuit 5 and the heat generation in the first detection resistor 13 and the third detection resistor 33 are distributed to different units. Therefore, both the temperature rise in the relay unit 53 and the temperature rise in the terminal unit 52 can be suppressed low. Further, it is possible to avoid an influence on the voltage-current conversion circuit 5 due to heat generated by the first detection resistor 13 and the third detection resistor 33.

  Next, a current sensor 1E configured to be able to switch three detection rates based on the current sensor 1C will be described with reference to FIG. Hereinafter, a configuration of the terminal unit 52 different from the current sensor 1C will be described.

  The terminating unit 52 houses a voltage converter 6c (another first voltage converter) and a second switching unit 8 (hereinafter, also simply referred to as a switching unit 8) in addition to the voltage conversion unit 6a and the output terminal 9. Have been. The switching unit 8 is composed of switching circuits 8a and 8b having a one-circuit and two-contact structure, like the switching unit 7. The switching switch 8a is connected to the second connection cable CB2 and the input unit 11 of each of the voltage conversion units 6a and 6c. , 31, and the changeover switch 8 b is disposed between the output terminals 12, 32 of the voltage converters 6 a, 6 c and the output terminal 9. With this configuration, the switching unit 8 is configured such that any one second element of the two voltage conversion units 6a and 6c is connected to the second connection cable CB2 and the output terminal by switching the changeover switches 8a and 8b in conjunction with each other. The connection state is switched to the connection state connected to the communication terminal 9. The voltage converter 6c has the same configuration as the above-described current sensor 1D.

  In the current sensor 1E having this configuration, the switching unit 7 has a current-to-voltage conversion circuit configured to convert the negative feedback current I2 output from the other end 4b of the feedback winding 4 into the second detection resistor 23 and the amplifier 24. It switches to and outputs (supplies) any one of the first elements of the voltage conversion unit 6b and the transmission line TL1, and switches the signal output from the one first element via the second connection cable CB2. 8 (supply). Further, the switching unit 8 converts the signal supplied from the switching unit 7 into an arbitrary second element of the first detection resistor 13 (the voltage conversion unit 6a) and the third detection resistor 33 (the voltage conversion unit 6c). And a signal output from the second element is output to the output terminal 9.

  Specifically, the current sensor 1E is in a switching state in which the switching unit 7 has switched to the transmission line TL1 as one of the first elements, and the switching unit 8 has switched to the first detection resistor 13 as one of the second elements. In the state, the first detection resistor 13 converts the negative feedback current I2 supplied from the transmission line TL1 into the first detection voltage Vd1, and outputs the first detection voltage Vd1 to the output terminal 9 as the output voltage Vo. Further, the current sensor 1E is in a switching state in which the switching unit 7 has switched to the voltage conversion unit 6b (a current-voltage conversion circuit including the second detection resistor 23 and the amplifier 24) as one of the first elements, and 8 is switched to the first detection resistor 13 as one of the second elements, the voltage conversion section 6b and the first detection resistor 13 cause the negative feedback current I2 to have a resistance value R2 larger than that of the first detection resistor 13. The voltage is converted into a voltage and amplified by the second detection resistor 23, converted into a second detection voltage Vd 2, and output to the output terminal 9 as the output voltage Vo. The current sensor 1E is in a switching state in which the switching unit 7 switches to the transmission line TL1 as one first element, and in a switching state in which the switching unit 8 switches to the third detection resistor 33 as one second element. The third detection resistor 33 converts the negative feedback current I2 into the third detection voltage Vd3 by the third detection resistor 33 having a resistance value R3 smaller than that of the first detection resistor 13, and outputs the third detection voltage Vd3 to the output terminal 9 as the output voltage Vo.

  With this configuration, in the current sensor 1E, the first detection rate (numerical value “1”) and the second detection rate (numerical value “10”) of the current sensor 1C are changed to the third detection rate (numerical value “0.1”). )), The detection current I1 can be converted into the output voltage Vo by switching to any one of the three detection rates.

  Also in the current sensor 1E, the detection rate can be switched in the same manner as the current sensor 1C, and the two detection rates (the first detection rate and the third detection rate) do not include an amplifier. That is, the detection current I1 can be converted into the first detection voltage Vd1 or the third detection voltage Vd3 and output without being affected by noise generated in the amplifier. Also in the current sensor 1E, similarly to the current sensor 1C, the heat generation in the voltage-current conversion circuit 5 and the heat generation in the first detection resistor 13 and the third detection resistor 33 are distributed to different units. Therefore, both the temperature rise in the relay unit 53 and the temperature rise in the terminal unit 52 can be suppressed low. Further, according to the current sensor 1E, the voltage-current conversion circuit 5 and the current-voltage conversion circuit (a circuit composed of the second detection resistor 23 and the amplifier 24: the voltage conversion unit 6b) include the first detection resistor 13 and the third Since it is housed in the relay unit 53 different from the detection resistor 33, it is housed in the terminal unit 52 in which the average temperature tends to be higher due to the heat generated by the first detection resistor 13 and the third detection resistor 33. Unlike the above configuration, it is possible to avoid the influence of the heat generated by the first detection resistor 13 on the voltage-current conversion circuit 5 and the amplifier 24 of the current-voltage conversion circuit.

  Further, as described in the current sensor 1A, the other current sensors 1B to 1E are also provided with a processing unit (not shown) including a CPU, an A / D converter, and the like. , And a process of switching the switching unit 7 (and further, in the current sensor 1E, the switching unit 8) based on the detected voltage value of the output voltage Vo (the detection rate is automatically set). Automatic switching of the detection rate to be switched) may be executed.

  Further, for the current sensors 1A to 1E, a processing unit including a D / A converter is provided in addition to the CPU and the A / D converter. An offset adjustment process for adjusting the offset of the operational amplifier constituting the current conversion circuit 5 and the offset of the operational amplifier constituting the amplifier 24 can also be executed. Hereinafter, a current sensor 1F including the processing unit based on the current sensor 1E will be described with reference to FIG. The same components as those of the current sensor 1E are denoted by the same reference numerals, and redundant description will be omitted.

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

  The processing unit 17 includes a CPU 17a, an A / D converter (simply referred to as “A / D” in FIG. 7) 17b, and two D / A converters (simply “D / A” in FIG. 7). 17c, 17d). The A / D converter 17b converts a voltage output from the buffer 16 (for example, a voltage having the same voltage value as the voltage of the second connection cable CB2) into voltage data D1 indicating the voltage value and outputs the same to the CPU 17a. I do.

  The CPU 17a outputs a control signal S1 for switching the switching unit 7 and a control signal S2 for switching the switching unit 8 in the automatic switching process of the detection rate. The control signal S2 is output to the terminal unit 52 via the second connection cable CB2. In the offset adjustment process, the CPU 17a outputs adjustment data D2 for adjusting the offset of the operational amplifier included in the voltage-current conversion circuit 5 to the D / A converter 17c, and outputs the offset of the operational amplifier included in the amplifier 24. Is output to the D / A converter 17d. The D / A converter 17c converts the adjustment data D2 input from the CPU 17a into an adjustment voltage S3, and outputs the adjustment voltage S3 to an offset adjustment terminal of an operational amplifier included in the voltage / current conversion circuit 5. The D / A converter 17d converts the adjustment data D3 input from the CPU 17a into an adjustment voltage S4, and outputs the adjustment voltage S4 to an offset adjustment terminal of an operational amplifier included in the amplifier 24.

  Next, the offset adjustment processing will be specifically described.

  First, the offset adjustment of the 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 magnetic core 2, the CPU 17a first outputs a control signal S1 for switching to the transmission line TL1 to the switching unit 7, and switches to the voltage conversion unit 6a. Control signal S2 is output to the switching unit 8. Thereby, the negative feedback current I2 caused by 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, and then output to the terminal unit 52 via the relay unit 53. Thus, the voltage is converted to the first detection voltage Vd1 by the voltage conversion unit 6a.

  The CPU 17a detects the voltage value of the first detection voltage Vd1 based on the voltage data D1 input via the buffer 16 and the A / D converter 17b, and reduces the voltage value of the first detection voltage Vd1 to zero. The adjustment data D2 for the adjustment voltage S3 is changed and output to the D / A converter 17c so as to approach. The D / A converter 17c converts the adjustment data D2 into an adjustment voltage S3 and outputs the same to an offset adjustment terminal of an operational amplifier included in the voltage / current conversion circuit 5. The CPU 17a repeatedly changes the adjustment data D2 to the D / A converter 17c until the detected voltage value of the first detection voltage Vd1 becomes zero. Further, the CPU 17a stores the adjustment data D2 at the time when the voltage value of the first detection voltage Vd1 becomes zero, and continues to output the adjustment data D2 to the D / A converter 17c. As a result, the voltage value of the adjustment voltage S3 to the offset adjustment terminal of the operational amplifier included in the voltage-current conversion circuit 5 is maintained at the voltage value at the time when the voltage value of the first detection voltage Vd1 becomes zero. That is, the offset of the operational amplifier forming 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.

  The first detection voltage Vd1 (of the voltage data D1) detected by the CPU 17a via the buffer 16 and the A / D converter 17b includes not only the offset of the operational amplifier constituting the voltage-current conversion circuit 5 but also the offset. Since the voltage generated due to the offset generated in the magneto-electric conversion unit 3 is also included, in the offset adjustment of the operational amplifier configuring the voltage-current conversion circuit 5, as a result, the operation configuring the voltage-current conversion circuit 5 is performed. The offset adjustment in the amplifier and the entire magnetoelectric conversion unit 3 is completed.

  Next, the 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 in the operational amplifier and the magnetoelectric conversion unit 3 as a whole constituting the voltage-current conversion circuit 5 is completed, and the detected electric wire 61 is not inserted into the magnetic core 2, The CPU 17a first outputs a control signal S1 for switching to the voltage conversion unit 6b to the switching unit 7, and outputs a control signal S2 for switching to the voltage conversion unit 6a to the switching unit 8. Thereby, the voltage conversion unit 6b converts the negative feedback current I2 output from the voltage-current conversion circuit 5 in the state where the offset adjustment is completed into the second detection voltage Vd2, and outputs the second detection voltage Vd2. Since the negative feedback current I2 at this time is zero amperes, the second detection voltage Vd2 is a voltage resulting from the offset of the operational amplifier constituting the amplifier 24.

  The CPU 17a detects the voltage value of the second detection voltage Vd2 based on the voltage data D1 input via the buffer 16 and the A / D converter 17b, and reduces the voltage value of the second detection voltage Vd2 to zero. The adjustment data D3 for the adjustment voltage S4 is changed and output to the D / A converter 17d so as to approach. The D / A converter 17d converts the adjustment data D3 into an adjustment voltage S4, and outputs the adjustment voltage S4 to an offset adjustment terminal of an operational amplifier included in the amplifier 24. The CPU 17a repeats the change of the adjustment data D3 to the D / A converter 17d until the detected voltage value of the second detection voltage Vd2 becomes zero. The CPU 17a stores the adjustment data D3 at the time when the voltage value of the second detection voltage Vd2 becomes zero, and continues to output the adjustment data D3 to the D / A converter 17d. Thereby, the voltage value of the adjustment voltage S4 to the offset adjustment terminal of the operational amplifier included in the amplifier 24 is maintained at the voltage value at the time when the voltage value of the second detection voltage Vd2 becomes zero. That is, the offset of the operational amplifier constituting the amplifier 24 is maintained at zero. Thereby, the offset adjustment of the operational amplifier constituting the amplifier 24 is completed.

  Next, the detection rate automatic switching process will be specifically described. The current sensor 1F based on the current sensor 1E has a third detection rate when the negative feedback current I2 is supplied to the voltage converter 6c in the terminal unit 52 via the transmission line TL1 of the relay unit 53. (Numerical value “0.1”) and the first detection rate (numerical value “1”) when the negative feedback current I2 is supplied to the voltage converter 6a in the termination unit 52 via the transmission line TL1 of the relay unit 53. And a second detection rate (numerical value) when the negative feedback current I2 is supplied to the voltage converter 6b of the relay unit 53 and the voltage output from the voltage converter 6b is supplied to the voltage converter 6a in the termination unit 52. There are three detection rates of “10”). Therefore, the current sensor 1F has the detection range of the lowest third detection rate (the maximum detection range in which the largest detection current I1 can be detected) and the detection range of the second lowest detection rate (the second largest detection rate). It has three detection ranges: an intermediate detection range in which the current I1 can be detected; and a detection range of the highest second detection rate (a minimum detection range in which the smallest detection current I1 can be detected).

  In the automatic switching process of the detection rate, the CPU 17a determines the detection voltages (the detection voltages Vd1, Vd2, and Vd3) in the current detection range based on the voltage data D1 input via the buffer 16 and the A / D converter 17b. Is detected, and the detected voltage is set to a predetermined range-up voltage range (for example, a voltage range in which the maximum voltage value of the output voltage Vo is 90% or more) or the range of the output voltage Vo. It is determined whether or not the voltage falls within a down voltage range (for example, a voltage range in which the output voltage Vo is 10% or less of the maximum voltage value).

  As a result of this determination, the CPU 17a outputs the control signal S1 to the switching unit 7 when the detection voltage is included in the range-up voltage range and the detection range is higher than the current detection range, The control signal S2 is output to the switching unit 8, and the switching unit 7 and the switching unit 8 are switched in an interlocked manner so that the detection range becomes higher (the detection rate is lowered by one step). Further, as a result of this determination, when the detected voltage is included in the range down voltage range and the detection range below the current detection range exists, the CPU 17a outputs the control signal S1 to the switching unit 7. At the same time, a control signal S2 is output to the switching unit 8, and the switching unit 7 and the switching unit 8 are switched in an interlocked manner so that the detection range becomes lower (the detection rate is increased by one step). Also, as a result of this determination, when the detected voltage is not included in any of the range-up voltage range and the range-down voltage range, the CPU 17a outputs the control signal S1 output to the switching unit 7 and the control signal S1 output to the switching unit 8. The current detection range is maintained (that is, the current detection rate is maintained) by maintaining the current control signal S2 in the current state (that is, without switching the switching unit 7 and the switching unit 8).

  In the current sensor 1F, as described above, the buffer 16 and the processing unit 17 are disposed in the relay unit 53 in which the voltage-current conversion circuit 5 and the amplifier 24 are housed, so that the relay unit 53 and the terminal unit 52 are connected. The signal line of the second connection cable CB2 need only be a signal line for the control signal S2 in addition to the signal line for transmitting the negative feedback current I2 and the detection voltage (one of the detection voltages Vd1, Vd2, and Vd3). Can be.

  Further, in each of the above-described current sensors 1A, 1B, 1C, 1E, and 1F, the resistance value R1 of the first detection resistor 13 and the resistance value R2 of the second detection resistor 23 are set to 50Ω as an example. Reference numeral 13 functions as a terminating resistor of a line (hereinafter also referred to as a first line for distinction) from the other end 4b of the feedback winding 4 to the voltage converter 6a including the first detection resistor 13, and a second detection terminal. The resistor 23 functions as a terminating resistor of a line (hereinafter, also referred to as a second line for distinction) from the other end 4b of the feedback winding 4 to the voltage conversion unit 6b including the second detection resistor 23, so that the impedance For the purpose of matching, it is defined to be equal to the characteristic impedance (50Ω) of the first line and the second line.

  In this case, in the current sensor 1A shown in FIGS. 1 and 2, the first line is connected to the changeover switch 7a (the current sensor 1A is divided into a sensor unit 51 and a termination unit 52) from the other end 4b of the feedback winding 4. Therefore, when they are connected to each other by the connection cable CB, they reach the input unit 11 of the voltage conversion unit 6a via the connection cable CB and the changeover switch 7a (substantially the first detection resistor of the voltage conversion unit 6a). 13). Further, the second line extends from the other end 4b of the feedback winding 4 to the input unit 21 of the voltage conversion unit 6b via the changeover switch 7a (or the connection cable CB and the changeover switch 7a) (substantially). This is a line up to the second detection resistor 23 of the voltage converter 6b.

  In the current sensor 1B shown in FIG. 3 and the current sensor 1D shown in FIG. 5, the first line is connected to the first connection cable CB1, the transmission line TL1, and the second connection cable CB2 from the other end 4b of the feedback winding 4. , And a line extending to the input unit 11 of the voltage conversion unit 6a via the changeover switch 7a. Further, the second line is the input terminal 21 of the voltage converter 6b from the other end 4b of the feedback winding 4 via the first connection cable CB1, the transmission line TL1, the second connection cable CB2, and the switch 7a. It is a railroad leading to.

  Further, in the current sensor 1C shown in FIG. 4, the first line is connected from the other end 4b of the feedback winding 4 to the first connection cable CB1, the changeover switch 7a, the transmission line TL1, the changeover switch 7b, and the second connection cable. This is a line extending to the input unit 11 of the voltage conversion unit 6a via the CB2. The second line is a line from the other end 4b of the feedback winding 4 to the input unit 21 of the voltage conversion unit 6b via the first connection cable CB1 and the changeover switch 7a.

  In the current sensor 1E shown in FIG. 6 and the current sensor 1F shown in FIG. 7, the first line is connected from the other end 4b of the feedback winding 4 to the first connection cable CB1, the changeover switch 7a, the transmission line TL1, This is a line extending to the input unit 11 of the voltage conversion unit 6a via the switch 7b, the second connection cable CB2, and the changeover switch 8a. The second line is a line from the other end 4b of the feedback winding 4 to the input unit 21 of the voltage conversion unit 6b via the first connection cable CB1 and the changeover switch 7a.

  With this configuration, according to the above-described current sensors 1A, 1B, 1C, 1D, 1E, and 1F, the resistance value R1 of the first detection resistor 13 that converts the negative feedback current I2 to the first detection voltage Vd1 is equal to the resistance value of the first detection resistor 13. Since the characteristic impedance (50Ω) of the first line that supplies the negative feedback current I2 to the first detection resistor 13 is specified, the waveform distortion of the first detection voltage Vd1 can be suppressed low. When the detection current I1 is an AC signal, the negative feedback current I2 becomes an AC signal having the same frequency as the detection current I1, and when a stray capacitance exists between the first line and the ground G, the first detection current I2 becomes the first detection current. The combined impedance of the resistor 13 and the parallel circuit of the stray capacitance is converted to the first detection voltage Vd1. In this case, the conversion to the first detection voltage Vd1 in this parallel circuit depends on the influence of a parameter represented by a multiplication value (C · R1) of the capacitance value C of the stray capacitance and the resistance value R1 of the first detection resistor 13. Accordingly, as the frequency of the negative feedback current I2 increases, the voltage value of the first detection voltage Vd1 decreases (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 first detection resistor 13 constituting the parallel circuit is a low value of 50Ω, the multiplication value (C The influence of the limitation of the detection band by R1) can be reduced, and the detection band of the negative feedback current I2 can be extended to a higher frequency.

  According to each of the current sensors 1A, 1B, 1C, 1D, 1E, 1F, the second detection resistor 23 (the second line) included in the voltage converter 6b that converts the negative feedback current I2 into the second detection voltage Vd2. The resistance value R2 of the second detection resistor 23 is defined as the characteristic impedance (50Ω) of the second line that supplies the negative feedback current I2 to the second detection resistor 23. As a result, the waveform distortion of the second detection voltage Vd2 output from the voltage conversion unit 6b can be suppressed low.

  Further, in each of the current sensors 1A, 1B, 1C, 1D, 1E, 1F, at the first detection rate, the first detection voltage Vd1 is directly output as the output voltage Vo from the output terminal 9 to the outside. Waveform distortion of the output voltage Vo at one detection rate can be suppressed low. Further, in each of the current sensors 1A, 1B, and 1D, at the second detection rate, the second detection voltage Vd2 is directly output from the output terminal 9 to the outside as the output voltage Vo. Waveform distortion of the output voltage Vo can be suppressed low.

  Further, in each of the current sensors 1C, 1E, 1F, at the second detection rate, the second detection voltage Vd2 is output from the output terminal 9 via the line terminated by the first detection resistor 13 as another resistor. However, as shown in FIG. 4, in the current sensor 1C, the output signal from the output unit 22 of the voltage conversion unit 6b is transmitted through the changeover switch 7b and the second connection cable CB2 to the first line. As shown in FIGS. 6 and 7, in the current sensors 1E and 1F, the line extends to the detection resistor 13, and from the output unit 22 of the voltage conversion unit 6b via the changeover switch 7b, the second connection cable CB2, and the changeover switch 8a. 4 to 6, which is referred to as a voltage transmission line in order to distinguish the first line and the second line that transmit the negative feedback current I2. Sea urchin, substantially overlaps with a portion of the first line described above. For this reason, the characteristic impedance of this voltage transmission line is defined to be equal to the characteristic impedance of the first line. Therefore, the second detection voltage Vd2 output from the voltage conversion unit 6b to this line is transmitted to the first detection resistor 13 in a state where the waveform distortion is kept low, and is output as the output voltage Vo. Therefore, in each of the current sensors 1C, 1E, and 1F, the waveform distortion of the output voltage Vo at the second detection rate can be suppressed.

  In each of the current sensors 1C, 1E, and 1F, when the resistance value Ro of the output resistor 25 of the voltage conversion unit 6b is specified to be equal to the characteristic impedance of the voltage transmission line (50Ω in this example), the voltage conversion unit The output impedance of 6b matches the characteristic impedance of the voltage transmission line. Therefore, according to the current sensors 1C, 1E, and 1F having this configuration, at the second detection rate (R2 / n × k × R1 / (R1 + Ro)), the second detection output from the voltage conversion unit 6b is performed. The voltage Vd2 can be transmitted to the first detection resistor 13 via the voltage transmission line in a state where the waveform distortion is further suppressed.

  In addition, regarding the above-mentioned voltage transmission line, the characteristic impedance at a portion that does not overlap with a part of the first line (the portion from the output unit 22 of the voltage conversion unit 6b to the changeover switch 7b) is defined as the characteristic impedance of the first line. Even when it is inevitable to adopt a configuration that cannot be made equivalent, since the main part (the second connection cable CB2) is common, it is possible to suppress the waveform distortion of the output voltage Vo low.

  Further, in the current sensors 1D, 1E, and 1F of the present example, as described above, the line through which the negative feedback current I2 is transmitted at the third detection rate (from the other end 4b of the feedback winding 4 to the third detection resistor 33). The line up to the voltage conversion unit 6c including the following. For the sake of distinction, the line is hereinafter also referred to as a third line), and substantially overlaps the entire first line through which the negative feedback current I2 is transmitted at the first detection rate. Therefore, the characteristic impedance is equal to the characteristic impedance (50Ω) of the first line. On the other hand, the resistance value R3 of the third detection resistor 33 functioning as a terminating resistor of the third line is 5Ω in this example. Therefore, at the time of the third detection rate, the resistance value R3 of the third detection resistor 33 is not matched with the characteristic impedance of the third line.

  However, if the reduction of the waveform distortion of the output voltage Vo at the third detection rate is more important than the reduction of the waveform distortion of the output voltage Vo at the first detection rate or the second detection rate, the third detection Of course, a configuration in which the resistance value R3 of the resistor 33 is defined as the characteristic impedance (50Ω) of the third line may be adopted.

1A, 1B, 1C, 1D, 1E, 1F Current sensor
2 Magnetic core
3 Magnetoelectric converter
4 Feedback winding
5 Voltage-current converter 6a, 6b Voltage converter
7 First switching unit
8 Second switching unit
9 Output terminal 13 First detection resistor 23 Second detection resistor 33 Third detection resistor 61 Detection conductor I1 Detection current I2 Negative feedback current Vd1 First detection voltage Vd2 Second detection voltage Vd3 Third detection voltage Vo Output voltage

Claims (14)

A magnetic core through which the detection conductor is inserted, a magnetoelectric converter disposed on the magnetic core, a feedback winding wound around the magnetic core, and a magnetic flux generated in the magnetic core when a detection current flows through the detection conductor A voltage-current conversion circuit that generates a negative feedback current that cancels the voltage based on the voltage output from the magnetoelectric conversion unit and supplies the generated negative feedback current to one end of the feedback winding, and a current sensor including an output terminal,
Converting the detection current into a first detection voltage at a first detection rate by converting the negative feedback current output from the other end of the feedback winding into a voltage using a first detection resistor; Alternatively, the detected current is larger than the first detection rate by converting the negative feedback current into a voltage using a second detection resistor and amplifying the voltage with an amplifier using two or more first voltage conversion units. One or more second voltage conversion units that convert the voltage to a second detection voltage at the second detection rate and output the converted voltage;
An arbitrary one of the one or more first voltage converters and the one or more second voltage converters is switched to a connection state in which the one or more elements are connected between the other end and the output terminal. A current sensor including a switching unit.   The resistance value of the detection resistor included in the arbitrary one element of the first detection resistor and the second detection resistor is a characteristic of a line from the other end of the feedback winding to the arbitrary one element. 2. The current sensor according to claim 1, wherein the current sensor is defined by impedance. A sensor unit in which the magnetic core, the magnetoelectric converter and the feedback winding are housed,
A relay unit in which the voltage-current conversion circuit and the transmission line are housed,
A termination unit in which the switching unit, the first voltage conversion unit, the second voltage conversion unit, and the output terminal are housed;
A first connection cable;
A second connection cable,
The sensor unit and the relay unit are connected via the first connection cable, and the voltage / current conversion circuit connects the magneto-electric conversion unit and the feedback winding via a wire forming the first connection cable. Connected to the one end, and one end of the transmission path is connected to the other end of the feedback winding via another wiring constituting the first connection cable,
The relay unit and the terminating unit are connected via the second connection cable, and the switching unit is connected to the other end of the transmission path connected via a wire configuring the second connection cable, and The current sensor according to claim 1, wherein the current sensor is switched to a connection state in which the arbitrary one element is connected to an output terminal. A magnetic core through which the detection conductor is inserted, a magnetoelectric converter disposed on the magnetic core, a feedback winding wound around the magnetic core, and a magnetic flux generated in the magnetic core when a detection current flows through the detection conductor A voltage-current conversion circuit that generates a negative feedback current that cancels the voltage based on the voltage output from the magnetoelectric conversion unit and supplies the generated negative feedback current to one end of the feedback winding, and a current sensor including an output terminal,
A first detection resistor for converting the supplied current to a voltage, a second detection resistor for converting the supplied current to a voltage, an amplifier for amplifying and outputting the voltage converted by the second detection voltage, a transmission line, and switching Part
The switching unit converts the negative feedback current output from the other end of the feedback winding to any one of a current-voltage conversion circuit configured by the second detection resistor and the amplifier and the transmission line. While switching and supplying to the element, supplying a signal output from the one element to the first detection resistor,
In a switching state in which the switching unit switches to the transmission line as the one element, the first detection resistor converts the negative feedback current into a voltage, thereby detecting the detection current at a first detection rate. Converted to voltage and output to the output terminal,
In the switching state in which the switching unit switches to the current-voltage conversion circuit as the one element, the current-voltage conversion circuit and the first detection resistor convert the negative feedback current into a voltage and amplify the voltage. A current sensor for converting a detection current into a second detection voltage at a second detection rate larger than the first detection rate and outputting the second detection voltage to the output terminal.   The resistance value of the first detection resistor is defined as a characteristic impedance of a line from the other end of the feedback winding to the first detection resistor in a switching state in which the switching unit switches to the transmission path as the one element. The current sensor according to claim 4, wherein   The resistance value of the second detection resistor is 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. The current sensor according to claim 4, wherein the current sensor is defined as follows.   7. The current sensor according to claim 6, wherein a resistance value of the first detection resistor is defined as a characteristic impedance of a line from the current-voltage conversion circuit to the first detection resistor. A sensor unit in which the magnetic core, the magnetoelectric converter and the feedback winding are housed,
A relay unit in which the voltage-current conversion circuit, the transmission line, the current-voltage conversion circuit, and the switching unit are housed;
A termination unit in which the first detection resistor and the output terminal are housed;
A first connection cable;
A second connection cable,
The sensor unit and the relay unit are connected via the first connection cable, and the voltage / current conversion circuit connects the magneto-electric conversion unit and the feedback winding via a wire forming the first connection cable. Connected to the one end, and the switching unit is connected to the other end of the feedback winding via another wiring constituting the first connection cable,
The relay unit and the terminating unit are connected via the second connection cable, and the switching unit is connected to the feedback winding connected via the other wiring constituting the first connection cable. 8. A connection state in which the one element is connected between the other end and the first detection resistor connected via a wiring configuring the second connection cable. Current sensor. A magnetic core through which the detection conductor is inserted, a magnetoelectric converter disposed on the magnetic core, a feedback winding wound around the magnetic core, and a magnetic flux generated in the magnetic core when a detection current flows through the detection conductor A voltage-current conversion circuit that generates a negative feedback current that cancels the voltage based on the voltage output from the magnetoelectric conversion unit and supplies the generated negative feedback current to one end of the feedback winding, and a current sensor including an output terminal,
A first detection resistor for converting the supplied current to a voltage, a second detection resistor for converting the supplied current to a voltage, an amplifier for amplifying and outputting the voltage converted by the second detection voltage, and a supplied current Has a third detection resistor that converts the signal into a voltage, a transmission line, a first switching unit and a second switching unit,
The first switching unit is configured to convert the negative feedback current output from the other end of the feedback winding into a current-voltage conversion circuit configured by the second detection resistor and the amplifier and any of the transmission path. While switching and supplying to one of the first elements, a signal output from the one of the first elements is supplied to the second switching unit,
The second switching unit switches the signal supplied from the first switching unit to an arbitrary one of the first detection resistor and the third detection resistor and supplies the signal. And outputting a signal output from the second element to the output terminal.
In a switching state in which the first switching unit switches to the transmission line as the one first element, and in a switching state in which the second switching unit switches to the first detection resistor as the one second element, A detection resistor converts the negative feedback current into a voltage, converts the detection current into a first detection voltage at a first detection rate, and outputs the first detection voltage to the output terminal;
In a switching state in which the first switching unit switches to the current-voltage conversion circuit as the one first element, and in a switching state in which the second switching unit switches to the first detection resistor as the one second element, The current-voltage conversion circuit and the first detection resistor convert the negative feedback current into a voltage and amplify the voltage, thereby converting the detection current to a second detection voltage at a second detection rate larger than the first detection rate. Convert and output to the output terminal,
In a switching state in which the first switching unit switches to the transmission line as the one first element, and a switching state in which the second switching unit switches to the third detection resistor as the one second element, A current sensor that converts the negative feedback current into a voltage, converts the negative current into a third detection voltage at a third detection rate smaller than the first detection rate, and outputs the third detection voltage to the output terminal. .   The resistance value of the first detection resistor is a switching state in which the first switching unit switches to the transmission line as the one first element, and the second switching unit determines the resistance of the first detection as the one second element. The current sensor according to claim 9, wherein the current sensor is defined by a characteristic impedance of a line from the other end of the feedback winding to the first detection resistor in a switching state in which the resistance is switched.   The resistance value of the second detection resistor is a switching state in which the first switching unit has switched to the current-voltage conversion circuit as the one first element, and the second switching unit has the second switching element as the one second element. The current sensor according to claim 9, wherein the current sensor is defined by a characteristic impedance of a line from the other end of the feedback winding to the current-to-voltage conversion circuit in a switching state in which switching is performed to one detection resistor.   The current sensor according to claim 11, wherein a resistance value of the first detection resistor is defined as a characteristic impedance of a line from the current-voltage conversion circuit to the first detection resistor.   The resistance value of the third detection resistor is a switching state in which the first switching unit has switched to the transmission line as the one first element, and the second switching unit has the third detection value as the one second element. The current sensor according to claim 9, wherein the current sensor is defined by a characteristic impedance of a line from the other end of the feedback winding to the third detection resistor in a switching state in which the resistance is switched. A sensor unit in which the magnetic core, the magnetoelectric converter and the feedback winding are housed,
A relay unit accommodating the voltage-current conversion circuit, the transmission line, the current-voltage conversion circuit, and the first switching unit;
A terminal unit in which the first detection resistor, the third detection resistor, the second switching unit, and the output terminal are housed;
A first connection cable;
A second connection cable,
The sensor unit and the relay unit are connected via the first connection cable, and the voltage / current conversion circuit connects the magneto-electric conversion unit and the feedback winding via a wire forming the first connection cable. Connected to the one end, and the first switching unit is connected to the other end of the feedback winding via another wiring constituting the first connection cable,
The relay unit and the terminal unit are connected via the second connection cable,
The first switching unit is connected to the other end of the feedback winding connected via the other wiring forming the first connection cable and the wiring connected to the second connection cable. Switching to a connection state in which the one first element is connected to the second switching unit;
14. The device according to claim 9, wherein the second switching unit switches to a connection state in which the one second element is connected between the wiring configuring the second connection cable and the output terminal. Current sensor.

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