JP2015143622A - Zero magnetic flux control current sensor, and zero adjustment method for zero magnetic flux control current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce magnetization of a magnetic core when a magnetoelectric transducer is switched to an ON state.SOLUTION: A processing section performs: stop-time zero adjustment processing (53, 54) of identifying a stop-time zero adjustment voltage data value Dad1 indicating a stop-time zero adjustment voltage value Vad1 of a voltage for adjustment Vad such that a detection voltage V2 is zero when a Hall element 3 is in a stop state; first demagnetization processing (55); and operation-time zero adjustment processing (58, 59) of identifying an operation-time zero adjustment voltage data value Dad2 indicating an operation-time zero adjustment voltage value Vad2 of the voltage for adjustment Vad such that a detection voltage V2 is zero when the Hall element 3 is in an operation state. Thereafter, the processing section starts regular zero adjustment processing, that means, the processing section performs stop processing (60, 61) of stopping the Hall element 3 with the voltage for adjustment Vad of the stop-time zero adjustment voltage value Vad1 being outputted to a negative feedback current generating section 7, and second demagnetization processing (62), and then starts driving of the Hall element 3 (63) and outputs the voltage for adjustment Vad of the operation-time zero adjustment voltage value Vad2 to the negative feedback current generating section 7.

Description

  The present invention relates to a zero flux control type (zero flux type) current sensor and a zero adjustment method for the zero flux control type current sensor.

  As this type of current sensor and this type of zero adjustment method, the present applicant has already proposed a current sensor and a zero adjustment method disclosed in Patent Document 1 below. This current sensor amplifies a detection signal from an annular magnetic core that can enclose a conductor to be measured, a magnetoelectric converter (Hall element) that detects a magnetic flux generated in the magnetic core as an electric signal, and a magnetoelectric converter. An amplifier, and a feedback coil wound around the magnetic core between the output side of the amplifier and an output terminal including an output resistor are provided. As a result, this current sensor is configured as a zero magnetic flux control type current sensor that detects the current of the conductor to be measured by amplifying the detection signal of the magnetoelectric conversion unit with an amplifier and negatively feeding it back to the magnetic core via the feedback coil. Has been. In this current sensor, a zero adjustment method for adjusting the zero point of the current sensor to an unbiased state is performed by demagnetizing the magnetic core in a state in which the conductor to be measured is not included to a state without magnetism.

  In this zero adjustment method, in a state where the magnetic core is not included in the conductor to be measured and the negative feedback operation loop including the amplifier and the feedback coil is a closed loop, the input side of the amplifier (the amplifier is connected to the power of the preceding amplifier and the subsequent stage). By demagnetizing the magnetic core by applying a demagnetizing AC attenuation signal with a voltage amplitude higher than the coercive force of the magnetic core to the input side of the previous stage amplifier when configured with an amplifier, the zero point of the current sensor is adjust. According to this zero adjustment method, since the negative feedback operation loop is always kept in the “closed loop”, there is no demagnetization due to a transient phenomenon accompanying the switching operation or the influence of the offset voltage when shifting to the “open loop”. Completeness can be avoided, and the zero point can be adjusted without deviation.

Japanese Unexamined Patent Publication No. 7-110345 (page 2-3, FIG. 1)

  However, the zero adjustment method for the zero magnetic flux control type current sensor and the zero magnetic flux control type current sensor has the following problems to be improved. That is, the zero magnetic flux control type current sensor and the zero adjustment method employ a configuration in which the magnetic core is demagnetized by supplying the demagnetizing AC attenuation signal amplified by the amplifier to the feedback coil in a closed loop state. For this reason, this zero magnetic flux control type current sensor and the zero adjustment method for the zero magnetic flux control type current sensor are compared with the configuration in which the magnetic core is demagnetized by supplying the demagnetizing AC attenuation signal to the feedback coil in the open loop state. Even when AC demagnetization signals with the same amplitude are supplied, there is a problem to be solved that the demagnetization of the magnetic core may be incomplete as a result of the lower magnetic flux level generated in the magnetic core. doing.

  The present invention has been made to improve such a problem, and can reduce the magnetization of the magnetic core when the magnetoelectric conversion element is turned from the off state to the on state, so that the magnetoelectric conversion element in the off state can be reduced. It is a main object of the present invention to provide a zero magnetic flux control type current sensor capable of executing demagnetization of a magnetic core and a zero adjustment method for the zero magnetic flux control type current sensor.

  In order to achieve the above object, a zero magnetic flux control type current sensor according to claim 1 includes a magnetic core into which a measurement object is inserted, a magnetoelectric transducer disposed in the magnetic core, and a magnetic core wound around the magnetic core. A negative feedback coil, a negative feedback current generator for outputting a negative feedback current to cancel the magnetic flux in the magnetic core to the negative feedback coil based on an output voltage of the magnetoelectric conversion element, and a negative feedback coil connected to the negative feedback coil A zero-flux control type current sensor that includes a current-voltage conversion unit that converts the negative feedback current into a voltage and outputs it as a sensor output, and inputs the adjustment data and the voltage value indicated by the adjustment data The negative feedback includes: a D / A conversion unit that outputs a voltage for adjustment in step A; an A / D conversion unit that inputs output of the sensor output and outputs output data indicating a voltage value of the sensor output; and a processing unit. Current The generator is configured to input the adjustment voltage together with the output voltage of the magnetoelectric transducer, and to generate the negative feedback current based on the output voltage and the adjustment voltage. By gradually changing the adjustment voltage to the positive side and the negative side gradually by changing the adjustment data in the first stop process for shifting the magnetoelectric conversion element to the stop state and the stop state of the magnetoelectric conversion element. A first degaussing process for demagnetizing the magnetic core by attenuating the fluctuation range, a first operating process for shifting the magnetoelectric conversion element from a stopped state to an operating state, and the D / A in the operating state of the magnetoelectric conversion element The voltage value of the sensor output indicated by the output data while outputting the adjustment data to the conversion unit and changing the adjustment data to adjust the voltage value of the adjustment voltage Zero adjustment processing during operation for specifying the data value of the adjustment data indicating the zero adjustment voltage value during operation of the adjustment voltage that becomes zero volts as the zero adjustment voltage data value during operation, and the magnetoelectric transducer from the operating state. By changing the adjustment data in the second stop process for shifting to the stop state and the magnetoelectric conversion element in the stop state, the fluctuation range is gradually increased while changing the adjustment voltage alternately to the positive side and the negative side. A second degaussing process for demagnetizing the magnetic core, causing the magnetoelectric conversion element to shift from a stopped state to an operating state, and supplying the adjustment data of the zero adjustment voltage data value during operation to the D / A converter. A voltage output process of outputting and outputting the adjustment voltage of the operating zero adjustment voltage value to the negative feedback current generator is sequentially executed.

  The zero magnetic flux control type current sensor according to claim 2 is the zero magnetic flux control type current sensor according to claim 1, wherein the processing unit is configured to perform the first degaussing process after the execution of the first stop process. In the stop state of the magnetoelectric conversion element before execution, the output data is output while adjusting the voltage value of the adjustment voltage by outputting the adjustment data to the D / A converter and changing the adjustment data. The zero value at the time of stop which specifies the data value of the adjustment data indicating the zero adjustment voltage value at the time of stop of the adjustment voltage as the zero adjustment voltage data value at the time of stop In the second stop process, the magnetoelectric conversion is performed with the adjustment data set to the stop zero adjustment voltage data value and the adjustment voltage set to the stop zero adjustment voltage value. It shifts the child from the operating state to the stopped state.

  A zero-flux control type current sensor according to claim 3 is the zero-flux control type current sensor according to claim 2, wherein the sensor output and a reference voltage of zero volts are input and the sensor output and the reference voltage are included. The processing unit includes a change-over switch that outputs any one of the A / D conversion unit to the A / D conversion unit, and the processing unit executes control on the change-over switch before executing the stop time zero adjustment process, and sets the reference voltage to the A / D conversion unit. A data value of the output data that is output when the A / D conversion unit inputs the reference voltage and obtains as a 0th AD data value, and in the stop zero adjustment process, The data value of the output data output by the A / D converter when outputting the first DA data value as the data value of the adjustment data to the D / A converter The data of the output data that is acquired as the first AD data value and output by the A / D converter when the second DA data value is output as the data value of the adjustment data to the D / A converter And the sensor output is zero volts based on the 0th AD data value, the 1st DA data value, the 1st AD data value, the 2nd DA data value, and the 2nd AD data value. A zero output data specifying process for specifying the data value of the adjustment data to be a zero output data value, and the data value of the adjustment data is positive and negative with reference to the zero output data value The sensor output is set to zero volts while gradually attenuating the fluctuation range while fluctuating alternately.

  A zero magnetic flux control type current sensor according to claim 4 is the zero magnetic flux control type current sensor according to claim 1 or 2, wherein the sensor output and a reference voltage of zero volts are inputted and the sensor output and the reference voltage are inputted. A switching switch that outputs any one of them to the A / D conversion unit, and the processing unit executes control on the switching switch before the operation zero adjustment processing to execute the reference voltage. A data value of the output data that is output when the A / D conversion unit inputs the reference voltage and acquires the data value of the output data as the 0th AD data value, and the zero adjustment process during operation The A / D converter outputs the first DA data value as the data value of the adjustment data to the D / A converter. The A / D converter outputs the data value as the first AD data value and outputs the second DA data value as the data value of the adjustment data to the D / A converter. The data value of data is acquired as a second AD data value, and the sensor is based on the 0th AD data value, the first DA data value, the first AD data value, the second DA data value, and the second AD data value A zero output data specifying process is performed for specifying the data value of the adjustment data whose output is zero volts as a zero output data value, and the data value of the adjustment data is corrected with reference to the zero output data value. The sensor output is set to zero volts while gradually varying the fluctuation range while alternately fluctuating between the negative side and the negative side.

  Further, the zero magnetic flux control type current sensor according to claim 5 is the zero magnetic flux control type current sensor according to any one of claims 1 to 4, wherein the processing unit performs the second stop process after the second stop process. (2) Before executing the degaussing process, the adjustment data is output to the D / A converter in the stop state of the magnetoelectric conversion element, and the data value of the adjustment data is started from the zero adjustment voltage data value at the stop. And adjusting the voltage value of the adjustment voltage with the zero adjustment voltage value at the time of stop as a starting point, while adjusting the voltage of the adjustment voltage at the second stop when the sensor output indicated by the output data becomes zero volts A secondary stop zero adjustment process that specifies a data value of the adjustment data indicating a voltage value as a secondary stop zero adjustment voltage data value is executed. In the second demagnetization process, the magnetoelectric conversion element is stopped. Previous The adjustment data is gradually converged to the zero adjustment voltage data value at the secondary stop while the data value of the adjustment data is alternately changed to the positive side and the negative side based on the secondary adjustment zero adjustment voltage data value. While the voltage value of the working voltage is alternately changed positively and negatively with respect to the secondary adjustment zero adjustment voltage value as a reference, the fluctuation range is gradually attenuated to converge to the secondary adjustment zero adjustment voltage value. As a result, the magnetic core is demagnetized.

  According to a sixth aspect of the present invention, there is provided a zero adjustment method for a zero magnetic flux control type current sensor, wherein a magnetic core into which a measurement object is inserted is inserted, a magnetoelectric transducer disposed in the magnetic core, and a magnetic core wound around the magnetic core. A negative feedback coil, a negative feedback current generator for outputting a negative feedback current to cancel the magnetic flux in the magnetic core to the negative feedback coil based on an output voltage of the magnetoelectric conversion element, and a negative feedback coil connected to the negative feedback coil A current-voltage conversion unit that converts the negative feedback current into a voltage and outputs it as a sensor output, and the negative feedback current generation unit inputs an adjustment voltage together with the output voltage of the magnetoelectric conversion element, and outputs the output A zero adjustment method for a zero magnetic flux control type current sensor configured to be able to generate the negative feedback current based on a voltage and the adjustment voltage, wherein the magnetoresistive conversion element is shifted to a stop state. And a first degaussing process for demagnetizing the magnetic core by gradually attenuating the fluctuation range while alternately changing the adjustment voltage to the positive side and the negative side, and changing the magnetoelectric conversion element from the stopped state to the operating state. The first operation process to be transferred, and the adjustment voltage is output to the negative feedback current generator in the operation state of the magnetoelectric conversion element, and the sensor output becomes zero volts while adjusting the adjustment voltage. An operation zero adjustment process that specifies the voltage value of the operating voltage as an operation zero adjustment voltage value; a second stop process that shifts the magnetoelectric transducer from an operation state to a stop state; A second demagnetization process for demagnetizing the magnetic core by gradually attenuating the fluctuation range while alternately fluctuating to the side, and moving the magnetoelectric conversion element from a stopped state to an operating state, and causing the negative feedback current generator to Performing a voltage output processing for outputting the adjustment voltage of the zero-adjusting voltage value during movement in order.

  In the zero adjustment method for the zero-flux control type current sensor according to claim 1 and the zero-flux control type current sensor according to claim 6, in the process up to the start of the second stop process (temporary zero adjustment process), the magnetoelectric conversion element In the operation state (closed loop state), the operation zero adjustment voltage data value (operation zero adjustment voltage value) that can make the negative feedback current substantially zero ampere is obtained, and in the processing after the second stop processing (this zero adjustment processing), When moving the magnetoelectric conversion element to the operating state, the adjustment voltage of the zero adjustment voltage value during operation is output to the negative feedback current generator.

  Therefore, according to the zero adjustment method for the current sensor and the zero magnetic flux control type current sensor, when the measurement target is not inserted in the magnetic core, the negative current is changed when the magnetoelectric transducer is shifted from the stopped state to the activated state. Since the negative feedback current output from the feedback current generator can be forced to zero amperes, an unnecessary negative feedback current is supplied to the negative feedback coil when the magnetoelectric conversion element is shifted to the operating state. It is possible to avoid the occurrence of a situation where the magnet is magnetized. As a result, the magnetic core is completely demagnetized by executing the second demagnetization process in a state where the magnetoelectric conversion element is stopped, and a new magnetization of the magnetic core when the magnetoelectric conversion element is shifted to the operating state is avoided. However, the current sensor can be shifted to a measurable state (with normal zero adjustment).

  In the zero magnetic flux control type current sensor according to claim 2, when the magnetoelectric conversion element is shifted from the operation state to the stop state in the zero adjustment process, the zero adjustment at the stop time specified in the stop zero adjustment process of the temporary zero adjustment process is performed. The voltage data value is output to the D / A converter, and the adjustment voltage of the zero adjustment voltage value at the time of stop is output to the negative feedback current generator.

  Therefore, according to this zero magnetic flux control type current sensor, when the measurement target is not inserted in the magnetic core, the zero feedback control type current sensor is output from the negative feedback current generator when the magnetoelectric conversion element is shifted from the operating state to the stopped state. The negative feedback current can be forced to zero ampere, so that an unnecessary negative feedback current is supplied to the negative feedback coil and the magnetic core becomes magnetized when the magnetoelectric transducer is shifted to the stop state. Can be avoided. As a result, when the second degaussing process is performed in a state where the magnetoelectric conversion element is stopped, the magnetic core can be demagnetized from a state with less magnetism, so that the magnetic core is demagnetized to a state with very little magnetism. Can do.

  In the zero magnetic flux control type current sensor according to claim 3, in the zero adjustment processing at the time of stop, the negative feedback current output from the negative feedback current generator becomes a current value close to zero ampere (the sensor output is a voltage close to zero volt). Stops by gradually attenuating the fluctuation range and converging to this voltage value while alternately changing the voltage to the positive and negative sides with reference to the voltage value of the adjustment voltage to the negative feedback current generator. Adjust the sensor output to approximately zero volts in the state.

  In the zero magnetic flux control type current sensor according to claim 4, in the zero adjustment process during operation, the negative feedback current output from the negative feedback current generator becomes a current value close to zero ampere (the sensor output is a voltage close to zero volt). With reference to the voltage value of the adjustment voltage to the negative feedback current generator, the fluctuation range is gradually attenuated while converging to this voltage value. Adjust the sensor output to approximately zero volts in the state.

  Therefore, according to these zero magnetic flux control type current sensors, the voltage value of the adjustment voltage to the negative feedback current generator is immediately (stepwise) changed to a voltage value at which the negative feedback current becomes a current value close to zero amperes. Unlike the configuration and method to be changed, the magnitude of the magnetic flux generated in the magnetic core due to the negative feedback current flowing in the negative feedback coil can be gradually attenuated to zero while the direction is alternately reversed. The magnetism generated in the magnetic core by changing the voltage value of the adjustment voltage can be greatly reduced.

  According to the zero magnetic flux control type current sensor according to claim 5, after executing the second stop process, executing the secondary stop zero adjustment process before executing the second degaussing process, the previous stop zero adjustment. The zero value at the time of secondary stop indicating the zero adjustment voltage value at the time of secondary stop where the current value of the negative feedback current becomes closer to zero ampere than the zero value voltage value at the time of stop specified by the zero adjustment voltage data value at stop The adjustment voltage data value can be specified. Therefore, according to this zero magnetic flux control type current sensor, the magnetic core can be demagnetized from a state with less magnetization in the second demagnetization process to be performed thereafter, so that the magnetic core is in a state with less magnetization (magnetization is reduced). It can be demagnetized to an extremely close state (zero).

1 is a configuration diagram of a current sensor 1. FIG. It is a flowchart for demonstrating the zero adjustment process 50 (zero adjustment method) which the current sensor 1 performs. FIG. 6 is an explanatory diagram for explaining the operation of the current sensor 1. 5 is a flowchart added to FIG. 2 for explaining another operation of the current sensor 1; It is a block diagram of 1 A of current sensors.

  Hereinafter, embodiments of a zero magnetic flux control type current sensor and a zero adjustment method for the zero magnetic flux control type current sensor will be described with reference to the accompanying drawings.

  First, the configuration of a zero magnetic flux control type current sensor 1 (hereinafter also referred to as “current sensor 1”) shown in FIG. 1 as an example of a zero magnetic flux control type current sensor will be described. For example, the current sensor 1 includes a magnetic core 2, a magnetoelectric conversion element 3, a bias power supply 4, a switch 5, a negative feedback coil 6 (hereinafter also referred to as a coil 6), a negative feedback current generation unit 7, a current-voltage conversion unit 8, A measuring object including a D / A conversion unit 9, a changeover switch 10, an A / D conversion unit 11, and a processing unit 12, configured as a zero-flux control type (zero-flux method) current sensor, and inserted through the magnetic core 2. The measurement current I1 flowing through the measurement circuit 100 is detected, and a detection voltage V2 whose voltage value changes in proportion to the current value of the measurement current I1 is output as a sensor output.

  As an example, the magnetic core 2 has an annular shape as a whole, and is formed in a split type that can be opened and closed with a base end portion (lower end portion in FIG. 1) as a center, and can clamp the measurement circuit 100 in a live state. (The measurement electric circuit 100 can be inserted inside). In addition, about the magnetic core 2, it is not limited to a split type, It can also be a penetration type (non-split type).

  In this example, the magnetoelectric conversion element 3 is constituted by a Hall element (hereinafter also referred to as “Hall element 3”) as an example, and is disposed in the gap formed in the magnetic core 2 (or in the vicinity of the gap). Yes. The Hall element 3 detects a magnetic flux generated inside the magnetic core 2 in an operating state in which the bias current Ib is supplied, and a voltage corresponding to the magnetic flux density (specifically, proportional or almost proportional) A value output voltage V1 is output. In this case, the magnetic flux generated inside the magnetic core 2 includes a magnetic flux φ1 generated when the current I1 to be measured flows through the measurement circuit 100 inserted through the magnetic core 2, and a negative feedback current I2 described later in the coil 6. This is a magnetic flux of a difference (φ1−φ2) from the magnetic flux φ2 generated by flowing. In addition to the Hall element, a fluxgate magnetic detection element or the like can be used for the magnetoelectric conversion element 3.

  The bias power supply 4 outputs a bias current Ib for operating the Hall element 3. The switch 5 is configured as a two-pole single-throw switch, for example, and is disposed between the Hall element 3 and the bias power supply 4, and its on / off state is controlled by the processing unit 12. Then, supply / stop of supply of the bias current Ib from the bias power source 4 to the Hall element 3 is executed.

  The coil 6 is formed by winding a wire around the magnetic core 2. The coil 6 has one end 6 a connected to the output terminal 7 d of the negative feedback current generator 7 and the other end 6 b connected to the current-voltage converter 8.

  The negative feedback current generator 7 inputs the output voltage V1 from the Hall element 3 from the pair of input terminals 7a and 7b and also inputs the adjustment voltage Vad output from the D / A converter 9 from the adjustment terminal 7c. The negative feedback current I2 is generated based on the output voltage V1 and the adjustment voltage Vad, and is output from the output terminal 7d to one end 6a of the coil 6. In this case, the negative feedback current generator 7 has a magnetic flux density of the magnetic flux (φ1-φ2) generated in the magnetic core 2 detected in the Hall element 3 so that the output voltage V1 becomes zero volts. The current value of the negative feedback current I2 is controlled to be zero (in other words, so as to cancel the magnetic flux φ1 with the magnetic flux φ2).

  In this example, as an example, the negative feedback current generator 7 includes a differential amplifier (instrumentation amplifier) 21, an adder circuit 22, and a current generator circuit 23 as shown in FIG. Receives and amplifies the output voltage V <b> 1 from the Hall element 3 and outputs the amplified voltage to the adder circuit 22. The adder circuit 22 adds the voltage signal output from the differential amplifier 21 and the adjustment voltage Vad and outputs the result to the current generation circuit 23. The current generation circuit 23 converts the voltage signal input from the addition circuit 22 (that is, the addition voltage of the output voltage V1 and the adjustment voltage Vad) into a negative feedback current I2 and outputs the negative feedback current I2.

  As an example in this example, the current-voltage conversion unit 8 includes a termination resistor connected between the other end 6b of the coil 6 and the ground (reference potential of zero volts) G (hereinafter referred to as “termination resistor 8”). ”). With this configuration, the termination resistor 8 converts the negative feedback current I2 flowing through the coil 6 into the detection voltage V2 and outputs it as a sensor output.

  The D / A conversion unit 9 receives the adjustment data D1 output from the processing unit 12 and converts it into an adjustment voltage Vad as an analog signal and outputs it. In this case, the D / A converter 9 outputs the adjustment voltage Vad as a voltage value indicated by the data value of the adjustment data D1.

  The change-over switch 10 is constituted by a one-pole double-throw switch, for example, and is disposed between the termination resistor 8 and the A / D conversion unit 11, and the contact state thereof is controlled by the processing unit 12. Thus, any one of the detection voltage V2 output from the termination resistor 8 and the potential of the ground G is selectively output to the A / D conversion unit 11 as the monitor voltage Vm. The A / D converter 11 receives the monitor voltage Vm, converts it into voltage data (output data) D2 indicating the voltage value of the monitor voltage Vm, and outputs it.

  The processing unit 12 includes a CPU and a memory (both not shown), and executes a zero adjustment process 50 shown in FIG. In the zero adjustment processing 50, the processing unit 12 cancels the offset of the Hall element 3 and the negative feedback current generation unit 7 constituting the negative feedback loop of the current sensor 1, as will be described later. By specifying the voltage value (adjustment data D1 indicating this voltage value) of the adjustment voltage Vad to be output to the magnetic core 2 and executing degaussing on the magnetic core 2, the current sensor 1 outputs the measured current I1 at zero amperes. Adjustment is made so that the voltage value of the output detection voltage V2 is exactly zero volts (zero adjustment).

  Next, a zero adjustment method for the current sensor 1 together with the operation of the current sensor 1 will be described with reference to the drawings.

  In the current sensor 1, the zero adjustment method is performed by the processing unit 12 executing the zero adjustment processing 50 shown in FIG. 2 in a state where the measurement electric circuit 100 is not inserted into the magnetic core 2.

  In the zero adjustment process 50, the processing unit 12 first executes a zero volt value detection process (step 51). In the zero volt value detection process, the processing unit 12 first executes control on the changeover switch 10 to output the ground G voltage (zero volt) to the A / D conversion unit 11 as the monitor voltage Vm. The A / D conversion unit 11 converts the monitor voltage Vm into voltage data D2 and outputs the voltage data D2 to the processing unit 12. In this case, the processing unit 12 acquires the data value of the voltage data D2 indicating zero volt input from the A / D conversion unit 11 as the 0th AD data value AD0 (data value indicating the zero volt value) and stores it in the memory. . Next, the processing unit 12 performs control on the changeover switch 10 and switches the changeover switch 10 so that the detection voltage V2 is output to the A / D conversion unit 11 as the monitor voltage Vm. Thereby, the zero volt value detection process is completed. The 0th AD data value AD0 acquired in the zero volt value detection process is a data value used in the primary coarse adjustment in the stop zero adjustment process and the secondary coarse adjustment in the operation zero adjustment process, as will be described later. It is. For this reason, this zero volt value detection process is not limited to the configuration that is executed immediately after the start of the zero adjustment process 50 as in this example, but at any timing before the execution of the zero adjustment process at the time of stop. Just do it.

  Next, the processing unit 12 controls the switch 5 to shift to an off state, and stops the supply of the bias current Ib from the bias power supply 4 to the magnetoelectric conversion element 3, thereby stopping the driving of the Hall element 3. The first stop process is executed (step 52). As the Hall element 3 is shifted from the operating state to the stopped state, the output voltage V1 output from the Hall element 3 changes, and is output from the negative feedback current generator 7 due to the change in the output voltage V1. The current value of the negative feedback current I2 may also change. Therefore, in the magnetic core 2, in addition to the magnetic component that originally existed, a magnetic magnetization is generated due to a change in the negative feedback current I <b> 2 that is generated due to the Hall element 3 being stopped.

  Next, the processing unit 12 performs a stop-time zero adjustment process. In the stop-time zero adjustment process, the processing unit 12 first performs the primary coarse adjustment of the negative feedback current generation unit 7 (step 53). In this primary coarse adjustment, the processing unit 12 first sets the detection voltage V2 generated in the termination resistor 8 by the negative feedback current I2 output from the negative feedback current generation unit 7 to zero volts when the Hall element 3 is stopped. The process of specifying the adjustment voltage Vad that becomes the zero-adjustment voltage value Vad1 at the time of stop, that is, the adjustment voltage Vad of the zero-adjustment voltage value Vad1 at the time of the detection voltage V2 becoming zero volts is output from the D / A converter 9 The zero output data specifying process for specifying the data value (zero output data value) of the adjustment data D1 to be executed is executed. In this example, the processing unit 12 includes a data value (primary 0th DA data value) DA01 for the adjustment data D1 for the D / A conversion unit 9 to output the adjustment voltage Vad of the zero adjustment voltage value Vad1 at the time of stop. Is specified as the zero output data value.

  Specifically, the processing unit 12 outputs voltage data output from the A / D conversion unit 11 when the data value of the adjustment data D1 output to the D / A conversion unit 9 is the first DA data value DA1. D2 (in this case, voltage data indicating the detection voltage V2) is acquired as the first AD data value AD1 and stored in the memory. The processing unit 12 also outputs voltage data D2 output from the A / D conversion unit 11 when the data value of the adjustment data D1 is the second DA data value DA2 (in this case, voltage data indicating the detection voltage V2). Is acquired as the second AD data value AD2 and stored in the memory.

  In this case, since the Hall element 3 is in the stopped state, the output voltage V1 output from the Hall element 3 is zero volts, so the negative feedback current generator 7 is substantially output from the D / A converter 9. Only the adjustment voltage Vad is converted into a negative feedback current I2 and output. For this reason, the detection voltage V2 that the termination resistor 8 converts and outputs the negative feedback current I2 is a voltage that changes only by the adjustment voltage Vad. Therefore, the data value of the voltage data D2 indicating the detection voltage V2 output from the A / D conversion unit 11 is a data value that changes only by the adjustment data D1 output from the processing unit 12 to the D / A conversion unit 9. It has become.

  In the current sensor 1 of this example, the D / A conversion unit 9 linearly converts the input adjustment data D1 into the adjustment voltage Vad, and the negative feedback current generation unit 7 is amplified by the differential amplifier 21. The addition voltage of the output voltage V1 and the adjustment voltage Vad is linearly converted into a negative feedback current I2, the termination resistor 8 linearly converts the negative feedback current I2 into a detection voltage V2, and the A / D conversion unit 11 The monitor voltage Vm (the detection voltage V2 or the potential of the ground G) is linearly converted into voltage data D2. For this reason, in the current sensor 1 in which the Hall element 3 is in a stopped state, a graph indicated by an alternate long and short dash line in FIG. 3 (an orthogonal coordinate system graph in which the horizontal axis is the adjustment data D1 and the vertical axis is the voltage data D2). As described above, the adjustment data D1 output to the D / A conversion unit 9 and the voltage data D2 output from the A / D conversion unit 11 are linear according to the data value of the adjustment data D1. It is a changing relationship.

Therefore, on the graph shown in FIG. 3, the point defined by the first DA data value DA1 and the first AD data value AD1, the point defined by the second DA data value DA2, and the second AD data value AD2. P2 is plotted. The 0th AD data value that is the data value of the voltage data D2 output from the A / D converter 11 when the monitor voltage Vm input to the A / D converter 11 is set to the potential of the ground G (zero volts). When the point P0 defined by AD0 and the 0th DA data value DA01, which is the data value of the adjustment data D1 for setting the detection voltage V2 to zero volts, is also plotted on the graph, the following is between each data value: The following relational expression (1) holds.
(AD2-AD0): (AD2-AD1)
= (DA2-DA01) :( DA2-DA1) (1)

Further, the 0th DA data value DA01 shown in the following formula (2) is specified (calculated) from the relational formula (1).
DA01 = DA2 × (AD0−AD1) / (AD2−AD1)
+ DA1 × (AD2-AD0) / (AD2-AD1) (2)

Note that one of the first DA data value DA1 that defines the point P1 and the second DA data value DA2 that defines the point P2 is zero, and one of the points P1 and P2 (for example, the first DA data value DA1 is zero). When the point P1) is defined on the intersection point Px between the graph and the vertical axis, this graph is expressed by the following equation (3).
D2 = D1 × (AD2-AD1) / DA2 + AD1 (3)
Therefore, the 0th DA data value DA01 shown in the following formula (4) is specified (calculated) from the formula (3).
DA01 = DA2 × (AD0−AD1) / (AD2−AD1) (4)

  In the primary coarse adjustment of the negative feedback current generation unit 7 in the stop zero adjustment process, the processing unit 12 sets the data value of the adjustment data D1 to the 0th DA data value DA01, as indicated by the symbol A in FIG. As a reference, it converges to the 0th DA data value DA01 while gradually attenuating the fluctuation range while alternately and periodically fluctuating between the positive side (the side with the large data value) and the negative side (the side with the small data value). As a result, the negative feedback current I2 output from the negative feedback current generator 7 also periodically and alternately varies positively and negatively with zero ampere as a reference in synchronization with the change in the data value of the adjustment data D1. The fluctuation range (current value) gradually attenuates and converges to zero amperes. As a result, the detection voltage V2 output from the termination resistor 8 also periodically fluctuates alternately on the positive side and the negative side with reference to zero volts, and gradually fluctuates to converge to zero volts. As a result, the voltage data D2 output from the A / D conversion unit 11 also periodically and alternately fluctuates between the positive side and the negative side with reference to the 0th AD data value AD0, as indicated by reference numeral B in FIG. It converges to the 0th AD data value AD0 while gradually attenuating the fluctuation range. Thereby, the primary coarse adjustment of the negative feedback current generator 7 is completed. In this case, when the negative feedback current generation unit 7 (specifically, the current generation circuit 23) is saturated, the detection voltage V2 may be asymmetric between the positive side and the negative side, and demagnetization may be incomplete. Therefore, the maximum value of the fluctuation range of the detection voltage V2 is defined as a level at which the negative feedback current generator 7 is not saturated.

  A method of immediately outputting the identified 0th DA data value DA01 as the adjustment data D1 to the D / A converter 9 as in this primary coarse adjustment (a method of stepping the adjustment data D1 to the 0th DA data value DA01) ), Instead of the 0th DA data value DA01 as a reference, the 0th DA data value is obtained by gradually attenuating the fluctuation range (current value) while periodically varying the data value alternately to the positive side and the negative side. By adopting the method of shifting to DA01, it is possible to significantly reduce the magnetization of the magnetic core 2 during the primary coarse adjustment. Even if the method of immediately outputting the specified 0th DA data value DA01 as the adjustment data D1 to the D / A converter 9 is adopted, even if the magnetism of the magnetic core 2 is hardly generated or the magnetization is generated. Of course, this method may be adopted when the level is negligible.

  The 0th DA data value DA01 obtained as described above is obtained when the D / A converter 9, the negative feedback current generator 7, the termination resistor 8, and the A / D converter 11 all operate in an ideal linear state. Since this is an assumed value, and in practice, each of these components operates in a substantially linear state, the ideal value (a value at which the detection voltage V2 can be accurately set to zero volts) is not The value is slightly shifted.

  Next, the processing unit 12 performs the primary fine adjustment of the negative feedback current generating unit 7 in the stop-time zero adjustment process (step 54). In the primary fine adjustment, the processing unit 12 finely adjusts the data value of the adjustment data D1 output to the D / A conversion unit 9 while monitoring the voltage data D2 output from the A / D conversion unit 11. Thus, the data value of the adjustment data D1 at which the detection voltage V2 indicated by the voltage data D2 becomes zero volts is specified, and this specified data value is stored as the stop zero adjustment voltage data value Dad1 (stop zero adjustment) The zero adjustment voltage value Vad1 at the time of stopping the adjustment voltage Vad corresponding to the voltage data value Dad1 may be stored. Thus, the stop zero adjustment process for obtaining the stop zero adjustment voltage data value Dad1 (stop zero adjustment voltage value Vad1) that can make the negative feedback current I2 zero ampere in the stop state (open loop state) of the Hall element 3 is completed. To do.

  Subsequently, the processing unit 12 executes a first degaussing process (step 55). In the first degaussing process, the processing unit 12 periodically and alternately changes the positive side and the negative side with reference to the stop zero adjustment voltage data value Dad1 specified in the primary fine adjustment of the stop zero adjustment process. By gradually converging to the zero adjustment voltage data value Dad1 at the time of stop, the voltage value of the adjustment voltage Vad output from the D / A converter 9 to the negative feedback current generator 7 is used as a reference for the zero adjustment voltage value Vad1 at the time of stop. As shown in FIG. 4, the fluctuation range is gradually attenuated while periodically fluctuating between the positive side and the negative side to converge to the zero adjustment voltage value Vad1 at the time of stop. As a result, the negative feedback current generator 7 converges the current value of the negative feedback current I2 gradually to zero amperes while periodically changing the current value of the negative feedback current I2 alternately to the positive side and the negative side around the zero ampere. The demagnetization is caused by the magnetic flux φ2 generated in the magnetic core 2 by such a negative feedback current I2 flowing through the coil 6 (the magnetic flux that gradually decreases in magnitude while being reversed in direction and finally becomes zero). Is done.

  In this case, since the first demagnetization process is executed in the stopped state of the Hall element 3, the output of the negative feedback current generator 7 is compared with the case where the first demagnetization process is executed in the operating state of the Hall element 3. Even in a state where the amplitude of the voltage output to the terminal 7d is smaller, the negative feedback current I2 sufficient for demagnetization can be supplied to the coil 6, thereby demagnetizing the magnetic core 2 in a more nearly complete state. It is possible.

  Next, the processing unit 12 executes a first operation process (step 56). In the first operation process, the processing unit 12 executes the control for the switch 5 to shift to the on state, and starts the supply of the bias current Ib from the bias power source 4 to the magnetoelectric conversion element 3. 3 is started. Further, the processing unit 12 performs D / A conversion on the adjustment data D1 of the zero adjustment voltage data value Dad1 at the time of stop within an extremely short time (immediately after entering the closed loop state) after the driving of the Hall element 3 is started. The output is output to the unit 9, and the D / A conversion unit 9 causes the negative feedback current generation unit 7 to start outputting the adjustment voltage Vad of the stop zero adjustment voltage value Vad1 (step 57). In step 57, the processing unit 12 uses the stop-time zero adjustment voltage data value Dad1 as the initial value of the adjustment data D1 output to the D / A conversion unit 9. A catalog value in which the D / A converter being used outputs zero volts as the adjustment voltage Vad can also be used.

  In this case, the Hall element 3 starts to operate upon receiving the supply of the bias current Ib, and starts outputting the output voltage V1. Thereby, the negative feedback loop of the current sensor 1 shifts to a closed state (becomes a closed loop state). The output voltage V1 at this time is in a state in which the measurement circuit 100 is not inserted into the magnetic core 2 and the magnetic core 2 is not magnetized, but includes the offset of the Hall element 3. Therefore, although it is not an exact zero volt, the voltage value is close to zero volt.

  Further, the negative feedback current generator 7 is slightly different from the adjustment voltage Vad that can make the current value of the negative feedback current I2 zero ampere in the closed loop state, but when the Hall element 3 is stopped (that is, the output) When the voltage V1 is zero volts and the negative feedback loop of the current sensor 1 is in an open state (open loop state), the adjustment voltage of the zero adjustment voltage value Vad1 at the time of stopping to make the current value of the negative feedback current I2 zero ampere Vad is output from the D / A converter 9.

  For this reason, the amount of change in the current value of the negative feedback current I2 output from the negative feedback current generator 7 when the Hall element 3 is shifted from the stopped state to the operating state is small, and the negative feedback current I2 is the coil 6 Since the amount of change in the magnetic flux φ2 generated in the magnetic core 2 by flowing through the magnetic field 2 is small, the magnetic core 2 is magnetized by shifting the Hall element 3 from the stopped state to the operating state (moving to the closed loop state). However, the magnetization amount is small.

  Subsequently, the processing unit 12 performs an operation zero adjustment process. In the zero adjustment process during operation, the processing unit 12 first performs secondary coarse adjustment of the negative feedback current generation unit 7 (step 58). In this secondary coarse adjustment, the processing unit 12 first sets the detection voltage V2 generated in the termination resistor 8 to zero volts by the negative feedback current I2 output from the negative feedback current generation unit 7 in the operating state of the Hall element 3. The process of specifying the adjustment voltage Vad that becomes the operation zero adjustment voltage value Vad2, that is, the adjustment voltage Vad of the operation zero adjustment voltage value Vad2 at which the detection voltage V2 becomes zero volts is output from the D / A converter 9 The zero output data specifying process for specifying the data value (zero output data value) of the adjustment data D1 to be executed is executed. In this example, the processing unit 12 has a data value (secondary 0th DA data value) DA02 of the adjustment data D1 for the D / A conversion unit 9 to output the adjustment voltage Vad of the operating zero adjustment voltage value Vad2. Is specified as the zero output data value.

  Specifically, the processing unit 12 converts the data value of the adjustment data D1 output to the D / A conversion unit 9 to the first DA data value DA1 (the data value in step 53) in the same manner as in step 53. The voltage data D2 output from the A / D converter 11 is acquired as the first AD data value AD1 and stored in the memory. Further, when the processing unit 12 sets the data value of the adjustment data D1 as the second DA data value DA2 (may be the same as or different from the data value in step 53), the processing unit 12 starts from the A / D conversion unit 11. The output voltage data D2 is acquired as the second AD data value AD2 and stored in the memory.

  In this case, the measurement circuit 100 is not inserted into the magnetic core 2, but due to the offset of the Hall element 3, the magnetization of the magnetic core 2 when the Hall element 3 shifts to the operating state, and the like, The activated Hall element 3 outputs an output voltage V1 that is close to zero volts but is not exactly zero volts. The negative feedback current generator 7 converts the addition voltage of the output voltage V1 and the adjustment voltage Vad output from the D / A converter 9 into a negative feedback current I2 and outputs the negative feedback current I2. The negative feedback current I2 output from the negative feedback current generator 7 is superimposed with a current corresponding to the output voltage V1, but is output when the measurement circuit 100 is not inserted into the magnetic core 2. The voltage V1 is constant. For this reason, the negative feedback current I2, and thus the detection voltage V2 that the termination resistor 8 converts and outputs the negative feedback current I2, is a voltage that changes only by the adjustment voltage Vad. Thereby, the data value of the voltage data D2 indicating the detected voltage V2 output from the A / D conversion unit 11 is a data value that changes only by the adjustment data D1 output from the processing unit 12 to the D / A conversion unit 9. It has become.

Accordingly, in the same manner as in step 53, the point P1 defined by the first DA data value DA1 and the first AD data value AD1, the second DA data value DA2, and the second AD data value are displayed on the graph shown in FIG. Plot the point P2 defined by AD2. The 0th AD data value that is the data value of the voltage data D2 output from the A / D converter 11 when the monitor voltage Vm input to the A / D converter 11 is set to the potential of the ground G (zero volts). When the point P0 defined by AD0 and the second-order 0th DA data value DA02 that is the data value of the adjustment data D1 for setting the detection voltage V2 to zero volts is also plotted on the graph, the following relational expression ( 5) holds.
(AD2-AD0): (AD2-AD1)
= (DA2-DA02): (DA2-DA1) (5)

Further, the 0th DA data value DA02 shown in the following equation (6) is specified (calculated) from the relational equation (5).
DA02 = DA2 × (AD0−AD1) / (AD2−AD1)
+ DA1 × (AD2-AD0) / (AD2-AD1) (6)

Note that one of the first DA data value DA1 that defines the point P1 and the second DA data value DA2 that defines the point P2 is zero, and one of the points P1 and P2 (for example, the first DA data value DA1 is zero). When the point P1) is defined on the intersection point Px between the graph and the vertical axis, this graph is expressed by the following equation (7).
D2 = D1 × (AD2-AD1) / DA2 + AD1 (7)
For this reason, the 0th DA data value DA02 shown in the following equation (8) is specified (calculated) from the equation (7).
DA02 = DA2 × (AD0−AD1) / (AD2−AD1) (8)

  In the secondary coarse adjustment of the negative feedback current generation unit 7 in this operation zero adjustment process, the processing unit 12 sets the data value of the adjustment data D1 to the 0th DA data value DA02, as indicated by the symbol A in FIG. As a reference, the data is shifted to the 0th DA data value DA02 while the fluctuation range is gradually attenuated while alternately fluctuating alternately between the positive side (the side with the larger data value) and the negative side (the side with the smaller data value). As a result, the negative feedback current I2 output from the negative feedback current generator 7 also periodically and alternately varies positively and negatively with zero ampere as a reference in synchronization with the change in the data value of the adjustment data D1. The fluctuation range (current value) gradually attenuates and shifts to zero amperes. As a result, the detection voltage V2 output from the termination resistor 8 also periodically and fluctuates alternately on the positive side and the negative side with reference to zero volts, and the fluctuation range gradually attenuates and shifts to zero volts. As a result, the voltage data D2 output from the A / D conversion unit 11 also periodically and alternately fluctuates between the positive side and the negative side with reference to the 0th AD data value AD0, as indicated by reference numeral B in FIG. Shifting to the 0th AD data value AD0 while gradually attenuating the fluctuation range. Thereby, the secondary coarse adjustment of the negative feedback current generator 7 in the zero adjustment process during operation is completed. In this case, when the negative feedback current generation unit 7 (specifically, the current generation circuit 23) is saturated, the detection voltage V2 may be asymmetric between the positive side and the negative side, and demagnetization may be incomplete. Therefore, the maximum value of the fluctuation range of the detection voltage V2 is defined as a level at which the negative feedback current generator 7 is not saturated.

  In this secondary coarse adjustment, as in the case of the primary coarse adjustment described above, the specified 0th DA data value DA02 is not directly output to the D / A converter 9 as the adjustment data D1, but for adjustment. By adopting a method of gradually attenuating the fluctuation range while shifting the data value of the data D1 alternately to the positive side and the negative side alternately with the 0th DA data value DA02 as a reference and shifting to the 0th DA data value DA02. It is possible to greatly reduce the magnetization of the magnetic core 2 during the secondary coarse adjustment. Even if the method of immediately outputting the specified 0th DA data value DA02 as the adjustment data D1 to the D / A converter 9 is adopted, even if the magnetic core 2 is hardly magnetized or the magnetism is generated. Of course, this method may be adopted when the level is negligible.

  The 0th DA data value DA02 obtained as described above is obtained when the D / A converter 9, the negative feedback current generator 7, the termination resistor 8, and the A / D converter 11 all operate in an ideal linear state. Since this is an assumed value, and in practice, each of these components operates in a substantially linear state, the ideal value (a value at which the detection voltage V2 can be accurately set to zero volts) is not The value is slightly shifted.

  Next, the processing unit 12 performs secondary fine adjustment of the negative feedback current generating unit 7 in the zero adjustment process during operation (step 59). In the secondary fine adjustment, the processing unit 12 finely adjusts the data value of the adjustment data D1 output to the D / A conversion unit 9 while monitoring the voltage data D2 output from the A / D conversion unit 11. Thus, the data value of the adjustment data D1 at which the detected voltage V2 indicated by the voltage data D2 is accurately zero volts is specified, and this specified data value is stored as the operation zero adjustment voltage data value Dad2. The zero adjustment voltage value Vad2 during operation of the adjustment voltage Vad corresponding to the zero adjustment voltage data value Dad2 may be stored). Thus, the operation zero adjustment process for obtaining the operation zero adjustment voltage data value Dad2 (operation zero adjustment voltage value Vad2) that can make the negative feedback current I2 zero ampere in the operation state (closed loop) of the Hall element 3 is completed. Accordingly, the above-described zero adjustment voltage data value Dad1 at the time of stop (the data value of the adjustment data D1 to the D / A converter 9 that can make the detection voltage V2 a voltage value close to zero volts in the open loop state) , And a zero adjustment voltage data value Dad2 during operation (data value of adjustment data D1 to the D / A converter 9 that can make the detection voltage V2 zero volts in the closed loop state) (temporary zero adjustment process) ) Is completed.

  In this temporary zero adjustment processing, in step 57 after starting the driving of the hall element 3 in step 56 (in a closed loop state), an adjustment voltage that can make the current value of the negative feedback current I2 zero ampere in the closed loop state. Zero adjustment voltage value Vad1 at the time of stop slightly different from the voltage value of Vad (zero adjustment voltage value at the time of stop Vad1 that makes the current value of the negative feedback current I2 zero ampere when the Hall element 3 is in the stop state (open loop state)) The adjustment voltage Vad is output to the negative feedback current generator 7. For this reason, as described above, in the magnetic core 2, when the Hall element 3 is put into an operating state, a magnetization is generated although the magnetization amount is small.

  Subsequently, the processing unit 12 performs the zero adjustment process. In this zero adjustment process, the processing unit 12 first executes a second stop process for stopping the driving of the Hall element 3. In the second stop process, the processing unit 12 first outputs the stop-time zero adjustment voltage data value Dad1 to the D / A conversion unit 9, and outputs the stop-time zero adjustment voltage value Vad1 to the D / A conversion unit 9. The output of the adjustment voltage Vad to the negative feedback current generator 7 is started (step 60). Further, the processing unit 12 is in the output state of the adjustment voltage Vad of the stop zero adjustment voltage value Vad1 (specifically, within a very short time after the output of the stop zero adjustment voltage value Vad1 is started). Then, the second stop process is executed to stop the driving of the Hall element 3 by executing the control for the switch 5 to shift to the OFF state and stopping the supply of the bias current Ib from the bias power source 4 to the Hall element 3. (Step 61).

  When the Hall element 3 is shifted from the operating state to the stopped state, the voltage value of the output voltage V1 output from the Hall element 3 may slightly fluctuate, but when the Hall element 3 is in the stopped state (that is, the current When the negative feedback loop of the sensor 1 is in an open state (open loop), the adjustment voltage Vad of the zero-adjustment voltage value Vad1 at the time of stoppage that can make the current value of the negative feedback current I2 substantially zero amperes is obtained from the D / A converter 9. It is output to the negative feedback current generator 7. For this reason, the amount of change in the current value of the negative feedback current I2 output from the negative feedback current generator 7 when the Hall element 3 is shifted from the operating state to the stopped state can be greatly reduced. The change of the magnetic flux φ2 generated in the magnetic core 2 due to the fluctuation of the current value of the feedback current I2 can be greatly reduced. As a result, when the Hall element 3 is shifted from the operating state to the stopped state (open loop) The magnetic quantity of the magnetic core 2 at the time of transition to (1) can be extremely reduced.

  Next, the processing unit 12 executes a second degaussing process (step 62). In the second degaussing process, the processing unit 12 sends the adjustment data D1 to the D / A converter 9 on the positive side with reference to the zero adjustment voltage data value Dad1 at the time of stop as in the first degaussing process. The adjustment voltage Vad output from the D / A conversion unit 9 to the negative feedback current generation unit 7 is gradually converged to the zero adjustment voltage data value Dad1 at the time of stop while changing periodically and negatively. While the voltage value is periodically and alternately varied positively and negatively with reference to the zero adjustment voltage value Vad1 at stop, the fluctuation range is gradually attenuated to converge to the zero adjustment voltage value Vad1 at stop. As a result, the current value of the negative feedback current I2 is gradually converged to zero amperes while being periodically changed alternately to the positive side and the negative side with zero amperes as a reference (center), thereby demagnetizing the magnetic core 2.

  In this case, since the second demagnetization process is performed in the stopped state of the Hall element 3, the output of the negative feedback current generator 7 is compared with the case where the second demagnetization process is performed in the activated state of the Hall element 3. Even in a state where the amplitude of the voltage output to the terminal 7d is smaller, the negative feedback current I2 sufficient for demagnetization can be supplied to the coil 6, thereby demagnetizing the magnetic core 2 in a more nearly complete state. It is possible.

  Next, the processing unit 12 executes a second operation process (step 63). In the second operation process, the processing unit 12 controls the switch 5 to shift to the on state, and starts supplying the bias current Ib from the bias power supply 4 to the magnetoelectric conversion element 3, thereby causing the Hall element to be turned on. 3 is started. Further, the processing unit 12 executes the voltage output process within a very short time after the driving of the Hall element 3 is started (Step 64). In this voltage output process, the processing unit 12 outputs the operation zero adjustment voltage data value Dad2 to the D / A conversion unit 9, and the D / A conversion unit 9 outputs the operation zero to the negative feedback current generation unit 7. The output of the adjustment voltage Vad having the adjustment voltage value Vad2 is started.

  In this case, the Hall element 3 starts to operate upon receiving the supply of the bias current Ib, and starts outputting the output voltage V1. As a result, the current sensor 1 shifts to a closed loop state. The output voltage V1 at this time is in a state in which the measurement circuit 100 is not inserted into the magnetic core 2 and the magnetic core 2 is not magnetized, but includes the offset of the Hall element 3. Therefore, although it is not an exact zero volt, the voltage value is close to zero volt.

  The negative feedback current generator 7 outputs the negative feedback current I2 to be output to zero ampere (that is, when the output voltage V1 is output from the Hall element 3 and the current sensor 1 is in the closed loop state). An adjustment voltage Vad of an operation zero adjustment voltage value Vad2 that can make the detection voltage V2 output from the terminating resistor 8 zero) is output from the D / A converter 9.

  For this reason, the current sensor 1 generates a new magnetism generated in the magnetic core 2 (the magnetic core 2 demagnetized to a very small state by the second demagnetization process) when the Hall element 3 shifts from the stopped state to the activated state. Transition to a closed loop state with very few states.

  Subsequently, the processing unit 12 executes a secondary operation zero adjustment process (step 65). In a state where the zero adjustment process at the time of the secondary operation is to be executed, as described above, the output voltage V1 output from the Hall element 3 is substantially zero volts, and the negative feedback current is generated from the D / A converter 9. Since the adjustment voltage Vad of the zero adjustment voltage value Vad2 at the time of operation that can make the negative feedback current I2 zero ampere is output to the unit 7, the detection voltage that the termination resistor 8 converts and outputs this negative feedback current I2 V2 is also very close to zero volts. Further, the magnetic core 2 has a very small magnetization (a state very close to zero). For this reason, in this secondary operation zero adjustment process, unlike the above-described stop zero adjustment process and operation zero adjustment process, the processing unit 12 omits coarse adjustment and fine adjustment (of the negative feedback current generating unit 7). Only tertiary fine adjustment) is executed.

  Specifically, in the third fine adjustment, the processing unit 12 monitors the voltage data D2 output from the A / D conversion unit 11 while monitoring the data value of the adjustment data D1 output to the D / A conversion unit 9. Is finely adjusted starting from the zero adjustment voltage data value Dad2 during operation to adjust the voltage value of the adjustment voltage Vad starting from the zero adjustment voltage value Vad2 during operation, and the detection voltage V2 indicated by the voltage data D2 is accurately Try to be zero volts. Thereby, the zero adjustment process at the time of secondary operation is completed, and the zero adjustment process 50 for the current sensor 1 is completed. As described above, the state before the execution of the secondary operation zero adjustment process is such that the detection voltage V2 is very close to zero volts and the magnetic core 2 has very little magnetization (zero). Therefore, when this state is sufficient, the zero adjustment process during secondary operation can be omitted.

 After the zero adjustment process 50 is completed, the current sensor 1 is demagnetized so that the magnetic core 2 is extremely demagnetized, and the adjustment data D1 output from the processing unit 12 to the D / A conversion unit 9 is used. Since the offsets of the closed loop components (Hall element 3 and negative feedback current generator 7) are completely canceled, the current sensor 1 is accurately zero-adjusted. Therefore, the current sensor 1 accurately detects the measured current I1 flowing in the measurement circuit 100 in this state, and outputs a detection voltage V2 whose voltage value changes in proportion to the current value of the measured current I1 as a sensor output. It is possible to do.

  As described above, in the zero adjustment method for the current sensor 1 and the zero magnetic flux control type current sensor, the zero adjustment during operation of the temporary zero adjustment processing is performed when the Hall element 3 is shifted from the stop state to the operation state in the zero adjustment processing. The operation zero adjustment voltage data value Dad2 specified in the processing is output to the D / A converter 9 and the adjustment voltage Vad of the operation zero adjustment voltage value Vad2 is output to the negative feedback current generator 7.

  Therefore, according to the zero adjustment method for the current sensor 1 and the zero magnetic flux control type current sensor, the Hall element 3 is shifted from the stopped state to the activated state when the measurement object 100 is not inserted into the magnetic core 2. At this time, the negative feedback current I2 output from the negative feedback current generator 7 can be forced to zero ampere, so that an unnecessary negative feedback current I2 is applied to the coil 6 when the Hall element 3 is shifted to the operating state. Occurrence of a situation where the magnetic core 2 is magnetized by being supplied can be avoided. As a result, the magnetic core 2 is completely demagnetized by executing the second demagnetization process in a state where the Hall element 3 is stopped, and a new magnetization of the magnetic core 2 when the Hall element 3 is shifted to the operating state is obtained. While avoiding, the current sensor 1 can be shifted to a measurable state.

  Further, in the zero adjustment method for the current sensor 1 and the zero magnetic flux control type current sensor, when the Hall element 3 is shifted from the operating state to the stopped state in the zero adjustment processing, The specified stop zero adjustment voltage data value Dad1 is output to the D / A converter 9 and the adjustment voltage Vad of the stop zero adjustment voltage value Vad1 is output to the negative feedback current generator 7.

  Therefore, according to the zero adjustment method for the current sensor 1 and the zero magnetic flux control type current sensor, the Hall element 3 is shifted from the operating state to the stopped state when the measuring object 100 is not inserted into the magnetic core 2. In this case, the negative feedback current I2 output from the negative feedback current generator 7 can be forced to zero ampere, so that an unnecessary negative feedback current I2 is applied to the coil 6 when the Hall element 3 is shifted to the stop state. Occurrence of a situation where the magnetic core 2 is magnetized by being supplied can be avoided. Thus, when the second degaussing process is performed in a state where the Hall element 3 is stopped, the magnetic core 2 can be demagnetized from a state with less magnetization, and therefore the magnetic core 2 is demagnetized to a state with very little magnetization. can do.

  Further, in the zero adjustment method for the current sensor 1 and the current sensor 1, the current is output from the negative feedback current generator 7 in the primary coarse adjustment in the stop zero adjustment process and the secondary coarse adjustment in the operation zero adjustment process. The negative feedback current I2 has a current value close to zero ampere (that is, the detection voltage V2 output from the termination resistor 8 based on the negative feedback current I2 becomes a voltage value close to zero volts) to the negative feedback current generator 7 With reference to the voltage value of the adjustment voltage Vad (zero adjustment voltage value Vad at stop in the first order coarse adjustment, zero adjustment voltage value Vad2 in operation in the second order coarse adjustment), it periodically and alternately fluctuates between the positive side and the negative side. The fluctuation range is gradually attenuated while being converged to this voltage value (zero adjustment voltage value Vad at stop for primary coarse adjustment, zero adjustment voltage value Vad2 at operation for secondary coarse adjustment). When the state Each adjusting the detected voltage V2 is a sensor output of the current sensor 1 to approximately zero volts.

  Therefore, according to this current sensor 1 and the zero adjustment method for the current sensor 1, the voltage value of the adjustment voltage Vad to the negative feedback current generator 7 is immediately (stepwise) immediately adjusted to the above voltage value (primary coarse adjustment). Unlike the configuration and the method of changing to the zero adjustment voltage value Vad at the time of stop 1 and the zero adjustment voltage value Vad2 at the time of operation in the secondary coarse adjustment, the magnetic flux generated in the magnetic core 2 by the negative feedback current I2 flowing through the coil 6. Since the magnitude of φ2 can be gradually attenuated to zero while alternately reversing its direction, the magnetism generated in the magnetic core 2 by changing the voltage value of the adjustment voltage Vad is greatly reduced. Can do.

  It is assumed that the method of immediately changing the voltage value of the adjustment voltage Vad to the voltage value described above (the zero adjustment voltage value Vad at the stop in the first order coarse adjustment, the zero adjustment voltage value Vad2 in the operation in the second order coarse adjustment) is adopted. In the case where the magnetic core 2 is hardly magnetized or is at a level that can be ignored even if magnetism is generated, the primary coarse adjustment of the stop zero adjustment process and the secondary coarse adjustment of the operation zero adjustment process are performed. In any one of them, the above method (a method of immediately changing the voltage value of the adjustment voltage Vad) can be adopted, and the primary coarse adjustment of the zero adjustment process at the time of stop and the secondary of the zero adjustment process at the time of operation. This method can also be adopted for both coarse adjustment.

  Further, as shown in FIG. 4, after the execution of step 61 and before the execution of the second degaussing process (step 62), the zero adjustment process during stop, the zero adjustment process during operation, and the zero adjustment process during secondary operation. It is also possible to adopt a configuration in which a secondary adjustment zero adjustment process (rough adjustment of the negative feedback current generation unit 7 (step 61a) and fine adjustment of the negative feedback current generation unit 7 (step 61b)) is performed. . The coarse adjustment and fine adjustment of the negative feedback current generation unit 7 in this configuration are substantially the same as the primary coarse adjustment and negative primary adjustment in step 54 for the negative feedback current generation unit 7 in step 53. Only the differences will be described.

  This difference is that, in the rough adjustment at step 61a, the processing unit 12 sets the adjustment voltage Vad output from the D / A conversion unit 9 to the negative feedback current generation unit 7 to be positive with respect to the zero adjustment voltage value Vad1 at the time of stop. The voltage data D2 output from the A / D conversion unit 11 is monitored in the fine adjustment at step 61b while gradually converging to the zero adjustment voltage value Vad1 at the time of stop while changing periodically to the negative side and the negative side. On the other hand, by finely adjusting the data value of the adjustment data D1 output to the D / A conversion unit 9, the voltage value (secondary stop) of the adjustment voltage Vad at which the detection voltage V2 indicated by the voltage data D2 becomes zero volts. Time zero adjustment voltage value Vad3) (specifically, the data value of adjustment data D1 for outputting the secondary stop zero adjustment voltage value Vad3 from the D / A converter 9 is specified) Identified It lies in storing over data value as a secondary stop zero-adjusting voltage data value DAD3.

  Thus, in the second degaussing process (step 62) after the secondary stop zero adjustment process, the adjustment voltage Vad is set to the positive side based on the secondary stop zero adjustment voltage value Vad3 specified in the fine adjustment in step 61b. The fluctuation range is gradually attenuated while alternately and periodically changing to the negative side to converge to the zero adjustment voltage value Vad3 at the time of secondary stop.

  By performing this secondary stop zero adjustment process immediately before the second demagnetization process (step 62) of the zero adjustment process 50 shown in FIG. 2, the adjustment voltage Vad that is alternately changed in the second demagnetization process. Can be set to the secondary stop zero adjustment voltage value Vad3 in which the current value of the negative feedback current I2 is closer to zero amperes than the stop zero adjustment voltage value Vad1 specified in step 54. . For this reason, in the second demagnetization process, the magnetic core 2 can be demagnetized from a state with less magnetism, and as a result, the magnetic core 2 can be demagnetized to a state with less magnetism (a state in which the magnetism is extremely close to zero). .

  Further, like the current sensor 1 </ b> A shown in FIG. 5, the current generation circuit 23 of the negative feedback current generation unit 7 uses another adjustment terminal 7 e that is input from an adjustment terminal 7 e that is different from the voltage output from the addition circuit 22. An addition circuit 23a that adds and outputs the voltage (voltage for adjusting the current value) Viad, and a current conversion circuit 23b that converts the voltage output from the addition circuit 23a into a current and outputs the current. In some cases, with respect to the negative feedback current generation unit 7, the circuits up to the differential amplifier 21 and the addition circuit 22 and the current generation circuit 23 can be separated, and zero adjustment can be performed in each circuit.

  Specifically, the feedback current generator 7 is provided with a monitor terminal 7f for monitoring the voltage output from the adder circuit 22 together with the adjustment terminal 7e. Further, the current sensor 1A includes another D / A conversion unit 13 that outputs the adjustment voltage Viad based on the adjustment data D3 output from the processing unit 12, and the addition circuit 22 that is output from the monitor terminal 7f. Is provided with another A / D converter 14 that converts the voltage (added voltage) Vadd into other voltage data D4 and outputs it to the processing unit 12. In addition, about the component which has the function similar to the current sensor 1, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  In the current sensor 1A, the processing unit 12 is a voltage indicating the voltage Vadd output from the monitor terminal 7f of the negative feedback current generating unit 7 in the stop zero adjustment processing or the operation zero adjustment processing of the zero adjustment processing 50 described above. By adjusting the data value of the adjustment data D1 while monitoring the data D4, coarse adjustment of the circuit composed of the differential amplifier 21 and the addition circuit 22 (by the above-described primary coarse adjustment and secondary coarse adjustment). Execute adjustment in the same way as the adjustment that was made. Next, the processing unit 12 finely adjusts the data value of the adjustment data D1 while monitoring the voltage data D4, so that the voltage Vadd is reduced to zero volt for the circuit constituted by the differential amplifier 21 and the addition circuit 22. The fine adjustment for accurately obtaining the adjustment data D1 is executed.

  In addition, the processing unit 12 outputs the adjustment data D1 at which the voltage Vadd obtained for the circuit constituted by the differential amplifier 21 and the addition circuit 22 is zero volts to the D / A conversion unit 9 and outputs the A / D By adjusting the data value of the other adjustment data D3 while monitoring the voltage data D2 output from the conversion unit 11, a rough adjustment (above the current generation circuit 23 (the addition circuit 23a and the current conversion circuit 23b)) is performed. The adjustment performed in the same manner as the adjustment performed in the primary coarse adjustment or the secondary coarse adjustment is performed. Next, the processing unit 12 finely adjusts the data value of the adjustment data D3 while monitoring the voltage data D2, so that the negative feedback current I2 becomes zero ampere (output from the termination resistor 8) for the current generation circuit 23. The detected voltage V2 is zero volts). Fine adjustment for accurately obtaining the adjustment data D3 is executed.

  Thereby, also in the zero adjustment method for the current sensor 1A and the current sensor 1A, the Hall element 3 is stopped in the zero adjustment process of the zero adjustment process 50 in the same manner as the zero adjustment method for the current sensor 1 and the current sensor 1. When the transition from the state to the operation state is performed, the adjustment voltage Vad is supplied to the negative feedback current generation unit 7 with the voltage value finely adjusted in the operation zero adjustment process of the temporary zero adjustment process (in the operation state of the Hall element 3). At the same time, by outputting another adjustment voltage Viad to the negative feedback current generator 7 with the voltage value finely adjusted in the operation zero adjustment process (in the operation state of the Hall element 3), the Hall element 3 Is switched from the stopped state to the activated state, the negative feedback current I2 output from the negative feedback current generator 7 is forcibly set to zero ampere, and the Hall element 3 is Negative feedback current I2 unnecessary when shifting the dynamic state can be avoided occurrence of a situation that is supplied to the coil 6 the magnetic core 2 is magnetized by. As a result, the magnetic core 2 is completely demagnetized by executing the second demagnetization process in a state where the Hall element 3 is stopped, and a new magnetization of the magnetic core 2 when the Hall element 3 is shifted to the operating state is obtained. While avoiding, the current sensor 1 can be shifted to a measurable state.

  Further, in the zero adjustment method for the current sensor 1A and the current sensor 1A, the Hall element 3 is operated in the zero adjustment process of the zero adjustment process 50 in the same manner as the zero adjustment method for the current sensor 1 and the current sensor 1. When the transition to the stop state is made, the adjustment voltage Vad is output to the negative feedback current generator 7 with the voltage value finely adjusted in the stop zero adjustment process of the temporary zero adjustment process (in the stop state of the Hall element 3). At the same time, another adjustment voltage Viad is output to the negative feedback current generator 7 with the voltage value finely adjusted in the stop zero adjustment process (in the stop state of the Hall element 3). When shifting from the operating state to the stopped state, the negative feedback current I2 output from the negative feedback current generator 7 is forcibly set to zero ampere, and the Hall element 3 is stopped. It can be negative feedback current I2 unnecessary when shifting to avoid the occurrence of a situation in which the magnetic core 2 is supplied to the coil 6 is magnetized to. Thus, when the second degaussing process is performed in a state where the Hall element 3 is stopped, the magnetic core 2 can be demagnetized from a state with less magnetization, and therefore the magnetic core 2 is demagnetized to a state with very little magnetization. can do.

  Further, according to the current sensor 1A and the zero adjustment method for the current sensor 1A, in the present zero adjustment processing, when the Hall element 3 is shifted to the operating state, the voltage value that has been finely adjusted in the operating state of the Hall element 3 Then, the adjustment voltage Vad is output to the negative feedback current generation unit 7, and another adjustment voltage Viad is output to the negative feedback current generation unit 7 with the voltage value finely adjusted in the operating state of the Hall element 3. When executing the zero adjustment process at the time of the next operation, the voltage value of one of the adjustment voltage Vad and the adjustment voltage Viad is fixed to the voltage value that has been finely adjusted when the Hall element 3 is stopped. In this case, the detected voltage is adjusted while adjusting the voltage value of the other voltage value with the voltage value finely adjusted in the stopped state of the Hall element 3 as described above for the other voltage value. By 2 to zero volts, it is possible to adjust the adjustment voltage Vad so as to detect the voltage V2 to zero volt with may cancel the offset of the Hall element 3 and the negative feedback current generator 7.

  Also, according to the current sensor 1A, unlike the current sensor 1, the negative feedback current generation unit 7 is separated from the circuit including the differential amplifier 21 and the adder circuit 22 and the current generation circuit 23, which constitute the negative feedback current generation unit 7. Since it is possible to perform zero adjustment in each circuit (independently), the offset of each circuit can be canceled individually, thereby using the dynamic range of each circuit without waste can do.

1 Current sensor
2 Magnetic core
3 Hall element
6 coils
7 Negative feedback current generator
8 Terminal resistance
9 D / A converter 11 A / D converter 100 Measurement circuit D1 Adjustment data D2 Voltage data I2 Negative feedback current V1 Output voltage V2 Detection voltage Vad Adjustment voltage φ1, φ2 Magnetic flux

Claims (6)

A magnetic core into which a measurement target is inserted, a magnetoelectric conversion element disposed in the magnetic core, a negative feedback coil wound around the magnetic core, and the negative feedback based on an output voltage of the magnetoelectric conversion element A negative feedback current generator that outputs a negative feedback current that cancels the magnetic flux in the magnetic core to the coil; and a current-voltage converter that is connected to the negative feedback coil and converts the negative feedback current into a voltage and outputs it as a sensor output A zero magnetic flux control type current sensor comprising:
A D / A converter that inputs the adjustment data and outputs the adjustment voltage at the voltage value indicated by the adjustment data;
An A / D converter that inputs the sensor output and outputs output data indicating a voltage value of the sensor output;
A processing unit,
The negative feedback current generator is configured to input the adjustment voltage together with the output voltage of the magnetoelectric conversion element, and to generate the negative feedback current based on the output voltage and the adjustment voltage,
The processor is
A first stop process for shifting the magnetoelectric conversion element to a stop state;
By changing the adjustment data while the magnetoelectric conversion element is stopped, the fluctuation voltage is gradually attenuated while the adjustment voltage is changed alternately between the positive side and the negative side, thereby demagnetizing the magnetic core. Degaussing treatment,
A first operation process for shifting the magnetoelectric conversion element from a stop state to an operation state;
The adjustment data is output to the D / A conversion unit in an operating state of the magnetoelectric conversion element, and the adjustment data is changed to adjust the voltage value of the adjustment voltage and to be indicated by the output data. A zero adjustment process during operation for specifying the data value of the adjustment data indicating the zero adjustment voltage value during operation of the adjustment voltage when the voltage value of the sensor output is zero volts, as the zero adjustment voltage data value during operation;
A second stopping process for shifting the magnetoelectric conversion element from an operating state to a stopping state;
By changing the adjustment data in the stopped state of the magnetoelectric conversion element, the adjustment voltage is changed alternately between the positive side and the negative side, and the fluctuation range is gradually attenuated to demagnetize the magnetic core. Degaussing treatment,
The magnetoelectric conversion element is shifted from a stopped state to an operating state, and the adjustment data of the operation zero adjustment voltage data value is output to the D / A conversion unit to output the adjustment voltage of the operation zero adjustment voltage value. A zero-flux control type current sensor that sequentially executes voltage output processing for causing the negative feedback current generator to output the voltage. The processing unit outputs the adjustment data to the D / A conversion unit in the stop state of the magnetoelectric conversion element after the execution of the first stop process and before the execution of the first degaussing process. Indicates the zero adjustment voltage value when the adjustment voltage is stopped when the voltage value of the sensor output indicated by the output data becomes zero volts while changing the adjustment data to adjust the voltage value of the adjustment voltage Execute zero stop adjustment processing that specifies the data value of the adjustment data as stop zero adjustment voltage data value,
In the second stop process, in the state where the adjustment data is set to the stop zero adjustment voltage data value and the adjustment voltage is set to the stop zero adjustment voltage value, the magnetoelectric conversion element is moved from the operating state. The zero flux control type current sensor according to claim 1, wherein the zero flux control type current sensor is shifted to the stop state. A switch for inputting the sensor output and a reference voltage of zero volts and outputting any one of the sensor output and the reference voltage to the A / D converter,
The processor is
When the control for the changeover switch is executed and the reference voltage is output to the A / D converter before the zero adjustment processing at the time of stop is executed, and the reference voltage is input to the A / D converter A data value of the output data to be output to the 0th AD data value,
In the stop zero adjustment process, the data of the output data output by the A / D converter when the first DA data value is output as the data value of the adjustment data to the D / A converter A value is acquired as a first AD data value, and the output data output by the A / D converter when the second DA data value is output as the data value of the adjustment data to the D / A converter. The sensor value is acquired as a second AD data value, and the sensor output is based on the zeroth AD data value, the first DA data value, the first AD data value, the second DA data value, and the second AD data value. Performing zero output data specifying processing for specifying the data value of the adjustment data to be zero volts as a zero output data value, and the data of the adjustment data Positive and zero flux-controlling current sensor according to claim 2 wherein the zero volts the sensor output while gradually attenuating the fluctuation range while varying alternately on the negative side as a reference the zero-output data values. A switch for inputting the sensor output and a reference voltage of zero volts and outputting any one of the sensor output and the reference voltage to the A / D converter,
The processor is
When the control for the changeover switch is executed before the zero adjustment process at the time of operation is executed to output the reference voltage to the A / D conversion unit and the A / D conversion unit inputs the reference voltage A data value of the output data to be output to the 0th AD data value,
In the operation zero adjustment process, the data of the output data output by the A / D converter when the first DA data value is output as the data value of the adjustment data to the D / A converter A value is acquired as a first AD data value, and the output data output by the A / D converter when the second DA data value is output as the data value of the adjustment data to the D / A converter. The sensor value is acquired as a second AD data value, and the sensor output is based on the zeroth AD data value, the first DA data value, the first AD data value, the second DA data value, and the second AD data value. Performing zero output data specifying processing for specifying the data value of the adjustment data to be zero volts as a zero output data value, and the data of the adjustment data Claim 1 or 2 zero flux-controlling current sensor according to zero volts the sensor output while gradually attenuating the fluctuation range while varying alternately positive and negative sides relative to the said zero-output data values. The processing unit outputs the adjustment data to the D / A conversion unit in a stopped state of the magnetoelectric conversion element and before the execution of the second degaussing process after the execution of the second stop process. The sensor output indicated by the output data while changing the data value of the data from the zero adjustment voltage data value at the time of stop and adjusting the voltage value of the adjustment voltage from the zero adjustment voltage value at the time of stop The secondary stop zero adjustment process is performed to specify the data value of the adjustment data indicating the zero adjustment voltage value at the secondary stop of the adjustment voltage at which the adjustment voltage becomes zero volts as the zero adjustment voltage data value at the secondary stop. ,
In the second degaussing process, the data value of the adjustment data is gradually changed to a positive side and a negative side with reference to the secondary adjustment zero adjustment voltage data value in a stopped state of the magnetoelectric conversion element. The voltage value of the adjustment voltage is converged to the zero-adjustment voltage data value at the time of secondary stop, and gradually fluctuates while the voltage value of the adjustment voltage is alternately changed positively and negatively with reference to the zero-adjustment voltage value at the time of secondary stop. The zero magnetic flux control type current sensor according to any one of claims 1 to 4, wherein the magnetic core is demagnetized by attenuating and converging to a zero adjustment voltage value at the time of secondary stop. A magnetic core into which a measurement target is inserted, a magnetoelectric conversion element disposed in the magnetic core, a negative feedback coil wound around the magnetic core, and the negative feedback based on an output voltage of the magnetoelectric conversion element A negative feedback current generator that outputs a negative feedback current that cancels the magnetic flux in the magnetic core to the coil; and a current-voltage converter that is connected to the negative feedback coil and converts the negative feedback current into a voltage and outputs it as a sensor output And the negative feedback current generator is configured to receive the adjustment voltage together with the output voltage of the magnetoelectric conversion element, and to generate the negative feedback current based on the output voltage and the adjustment voltage. A zero adjustment method for a zero magnetic flux control type current sensor,
A first stop process for shifting the magnetoelectric conversion element to a stop state;
A first degaussing process of demagnetizing the magnetic core by gradually attenuating the fluctuation range while alternately changing the adjustment voltage to the positive side and the negative side;
A first operation process for shifting the magnetoelectric conversion element from a stop state to an operation state;
In the operating state of the magnetoelectric conversion element, the adjustment voltage is output to the negative feedback current generator, and the voltage value of the adjustment voltage at which the sensor output becomes zero volts while adjusting the adjustment voltage is Zero adjustment processing during operation that specifies the zero adjustment voltage value;
A second stopping process for shifting the magnetoelectric conversion element from an operating state to a stopping state;
A second degaussing process of demagnetizing the magnetic core by gradually attenuating the fluctuation range while alternately changing the adjustment voltage to the positive side and the negative side;
A zero magnetic flux control type current sensor that sequentially executes a voltage output process for causing the magnetoelectric conversion element to shift from a stopped state to an operating state and causing the negative feedback current generator to output the adjustment voltage of the zero adjustment voltage value during operation. Zero adjustment method for.

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