Current measuring device, impedance measuring device, current measuring method, and impedance measuring method

Abstract

To measure a current flowing through a measurement target object with high accuracy even when the measurement target object and a non-measurement target object are connected in parallel via a connection line and a large DC current flows through the connection line.SOLUTION: Current sensors 4 measure current values I1 to I3 of a measurement AC current Im and also a current value Ip of the measurement AC current Im supplied to a power supply device PD, and a processing unit 5 obtains a current value obtained by dividing the current value I1 by the sum of the current values I1 to I3 and the current value Ip, and multiplying this value by the current value Io of the measurement AC current Im measured by a current sensor 4-m, as a supply current value for a measurement target object DUT1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a current measuring device and a current measuring method capable of measuring the current flowing through an object to be measured when the object to be measured and an object not to be measured are connected in parallel via a connection line such as a bus bar, and an impedance measuring device and an impedance measuring method capable of measuring the impedance of the object to be measured using the measured current value. [Background technology]

[0002] The impedance measuring device disclosed in the following patent document is known as an impedance measuring device capable of measuring the impedance of a measurement object when the measurement object is connected in parallel with the non-measurement object via a connection line. This impedance measuring device is configured to measure the internal impedance of a secondary battery when a load as a measurement object is connected in parallel with the secondary battery as the measurement object via a power line as a connection line. Specifically, this impedance measuring device is configured to include an AC current supply unit, an AC voltage detection unit, an AC current detection unit, an A / D conversion unit, and an arithmetic control unit. In this case, the AC current detection unit is configured to include a clamp-type current sensor.

[0003] When measuring the internal impedance of a secondary battery using this impedance measuring device, first, a power line is inserted through the opening of the clamp-type current sensor in the AC current detection unit. In this state, the AC current supply unit supplies a measurement AC current between the power lines. As a result, a portion of the measurement AC current flows through the secondary battery. Meanwhile, the remaining portion of the measurement AC current flows through the load, along with a DC current output from the secondary battery. In this case, the current sensor in the AC current detection unit detects the AC current flowing through the power line inserted through the opening and outputs a negative feedback current corresponding to the AC current value. At this time, the flow of the feedback current generates an AC voltage across the detection resistor. Next, the A / D conversion unit A / D converts the detected AC current into AC current data indicating the AC current value and outputs the data to the calculation control unit. Furthermore, the AC voltage detection unit detects the voltage across the secondary battery and outputs AC voltage data indicating the voltage value to the calculation control unit. Next, the calculation control unit calculates the internal impedance of the secondary battery based on the AC current value indicated by the input AC current data and the voltage value across the secondary battery indicated by the input AC voltage data. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-251625 A (pages 3-8, Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-described impedance measuring device has the following problems. Specifically, for example, when measuring a large fuel cell or electrolyzer, a wide bus bar may be used as the connection line because a large DC current flows through the connection line. In such cases, it is extremely difficult to clamp the wide bus bar with a clamp-type current sensor. Furthermore, because a large DC current flows through the connection line, when a high-precision current sensor with a small dynamic range is used, it becomes difficult to measure the measurement AC current due to magnetic saturation of the current sensor. On the other hand, when a current sensor with a wide dynamic range is used, the measurement accuracy decreases when measuring a small measurement AC current.

[0006] In this case, using a Rogowski coil with a wide dynamic range as a current sensor makes it possible to grasp the bus bar and avoid magnetic saturation. However, because the Rogowski coil has poor gain and phase characteristics in the low frequency band, there is a problem in that the current detection accuracy drops significantly when a low-frequency AC current is used for measurement.

[0007] The present invention has been made in consideration of these problems, and its main object is to provide a current measuring device and current measuring method that can accurately measure the current flowing through an object to be measured, even when the object to be measured and the object not to be measured are connected in parallel via a connection line and a large DC current is flowing through the connection line, as well as an impedance measuring device and impedance measuring method that can accurately measure the impedance of the object to be measured using the measured current value. [Means for solving the problem]

[0008] In order to achieve the above object, a current measuring device according to the present invention is a current measuring device in which N (N is an integer of 1 or more) objects to be measured and objects not to be measured are connected in parallel via connection lines and object to be measured currents are supplied to each of the objects to be measured and the objects not to be measured via the connection lines, the current measuring device comprising: a first non-contact current sensor that can measure the object to be measured current flowing through the connection lines by inserting the connection lines into an opening; and a processing unit that calculates a supply current value of the object to be measured current that is supplied to one of the N objects to be measured based on a measurement value obtained by the first current sensor, and the sum of the object to be measured currents supplied to the N objects to be measured and the objects not to be measured is calculated as The first current sensor is an air-core AC current sensor capable of measuring AC current, and measures the currents of the objects to be measured supplied to each of the N objects to be measured and the currents of the objects to be measured supplied to the non-objects to be measured. The processing unit calculates the supply current value for the one object to be measured by multiplying the sum of the currents of the objects to be measured measured by the second current sensor by the sum of the measurement values ​​of the N objects to be measured measured by the first current sensor and the measurement values ​​of the non-objects to be measured measured by the first current sensor.

[0009] Furthermore, in order to achieve the above object, a current measurement method according to the present invention is a current measurement method in which, in a state in which N (N is an integer of 1 or more) measurement targets and non-measurement targets are connected in parallel via connection lines and a measurement target current is supplied to each of the measurement targets and non-measurement targets via the connection lines, the connection lines are inserted into an opening of a first current sensor to measure the measurement target current flowing through the connection lines, and a supply current value of the measurement target current supplied to one of the N measurement targets based on the measurement value by the first current sensor is measured, and a sum of the measurement target currents supplied to the N measurement targets and the non-measurement targets is calculated as a first current value. The currents to be measured supplied to the N objects to be measured and the currents to be measured supplied to the non-objects to be measured are measured by the first current sensor, which is an air-core AC current sensor capable of measuring AC current, and the measurement value for one object to be measured measured by the first current sensor is divided by the sum of the measurement values ​​for each of the N objects to be measured measured by the first current sensor and the measurement value for the non-objects to be measured measured by the first current sensor, and the result is multiplied by the sum of the currents to be measured measured by the second current sensor to measure the supply current value for one object to be measured.

[0010] According to this current measuring device and current measuring method, when a Rogowski coil-type first current sensor having poor gain and phase characteristics in the low frequency band is used to measure the supply current value when a low-frequency current to be measured flows through the object to be measured, the influence (measurement error) of the characteristics (gain and phase characteristics) of the first current sensor on the accuracy of current measurement can be eliminated, thereby enabling the supply current value of the current to be measured flowing through the object to be measured with high accuracy.

[0011] In the current measuring device according to the present invention, the second current sensor measures the current to be measured with higher accuracy in gain characteristics and phase characteristics than the first current sensor.

[0012] In the current measuring method according to the present invention, the current to be measured is measured using the second current sensor, which has higher accuracy in gain characteristics and phase characteristics than the first current sensor.

[0013] According to this current measuring device and current measuring method, by using a second current sensor that has higher accuracy in gain characteristics and phase characteristics than the first current sensor, the current to be measured can be measured more accurately, and as a result, the supply current value of the current to be measured that is supplied to the object to be measured can be measured more accurately.

[0014] In addition, the current measuring device of the present invention includes (N+1) first current sensors configured to have the same characteristics, and the (N+1) first current sensors measure the measurement object currents flowing through the N measurement objects and the non-measurement objects, respectively.

[0015] In addition, the current measurement method of the present invention measures the measurement object currents flowing through the N measurement objects and the non-measurement objects using (N+1) first current sensors configured to have the same characteristics.

[0016] According to this current measuring device and current measuring method, the current value of the current to be measured flowing through the object to be measured and the current value of the current to be measured flowing through non-objects to be measured can be measured at the same time, so that measurement errors caused by changes over time in the current measurement of the current to be measured flowing through the object to be measured and non-objects to be measured can be eliminated, and as a result, the value of the supply current flowing through the object to be measured can be measured with high accuracy.

[0017] In addition, in a current measuring device according to the present invention, the current measuring device measures the current flowing through the object to be measured, which is configured by electrically connecting electrochemical cells that cause electrochemical reactions in series. In addition, in a current measuring device according to the present invention, the object to be measured is configured by stacking electrolytic cells as the electrochemical cells, and the current measuring device measures the current flowing through the object to be measured in an operating state using power output from a power source as the object to be measured. In addition, in a current measuring device according to the present invention, the object to be measured is configured by stacking either fuel cell cells or battery cells as the electrochemical cells, and the current measuring device measures the current flowing through the object to be measured when a load as the object to be measured is consuming the power output from the object to be measured.

[0018] A current measurement method according to the present invention measures the current flowing through a measurement object configured by electrically connecting electrochemical cells that cause electrochemical reactions in series. The current measurement method according to the present invention measures a device configured by stacking electrolytic cells as the electrochemical cells, and measures the current flowing through the measurement object in an operating state using power output from a power source as the non-measurement object. The current measurement method according to the present invention measures a device configured by stacking either fuel cells or battery cells as the electrochemical cells, and measures the current flowing through the measurement object when a load as the non-measurement object is consuming the power output from the measurement object.

[0019] This current measuring device and current measuring method can accurately measure the current flowing through the object to be measured when the object to be measured and non-object to be measured are operating and a large DC current is flowing through the connection line.

[0020] Furthermore, the impedance measuring device of the present invention comprises the above-described current measuring device, a measurement current supply unit that supplies a measurement current as the measurement object current to the N measurement objects and the non-measurement objects via the connection line, and a voltage measuring unit that measures the end-to-end voltage across one of the measurement objects, and the processing unit calculates the impedance of the one measurement object based on the calculated supply current value for the one measurement object and the end-to-end voltage across the one measurement object measured by the voltage measuring unit.

[0021] In addition, the impedance measurement method of the present invention supplies a measurement current as the measurement object current to the N measurement objects and the non-measurement objects via the connection line, executes the current measurement method, measures the end-to-end voltage across one measurement object, and measures the impedance of the one measurement object based on the calculated supply current value for the one measurement object and the measured end-to-end voltage across the one measurement object.

[0022] According to this impedance measuring device and impedance measuring method, when a Rogowski coil type first current sensor having poor gain and phase characteristics in the low frequency band is used to measure the supply current value when a low frequency current to be measured flows through the object to be measured, the influence (measurement error) of the characteristics (gain and phase characteristics) of the first current sensor on the current measurement accuracy can be eliminated, so that the supply current value of the current to be measured flowing through the object to be measured can be measured with high accuracy, and as a result, the impedance of the object to be measured can be measured with high accuracy.

[0023] In the impedance measuring device according to the present invention, the measurement current supply section is configured by a current source.

[0024] In the impedance measuring method according to the present invention, the measuring AC current is supplied from a current source.

[0025] According to this impedance measuring device and impedance measuring method, the output impedance of the current source is extremely large, so that even when a large DC current is output from an object not to be measured, the current does not flow to the current source but flows only to the object to be measured. Therefore, according to this impedance measuring device and impedance measuring method, magnetic saturation of the second current sensor caused by the flow of a large DC current can be avoided, and a high-precision current sensor with a small dynamic range can be used, thereby enabling the supply current value of the current to be measured with high precision.

[0026] In the impedance measuring device according to the present invention, the current source is configured as an electronic load.

[0027] In the impedance measuring method according to the present invention, the measuring AC current is supplied from the current source constituted by an electronic load.

[0028] According to this impedance measuring device and impedance measuring method, the electronic load consumes the DC current output from the non-measured object to generate the current to be measured, making it possible to generate a large current to be measured. Therefore, according to this impedance measuring device and impedance measuring method, the current value and voltage value can be made large, making it possible to accurately measure (calculate) the supply current value of the current to be measured flowing through the object to be measured, and also to accurately measure (calculate) the impedance of the object to be measured.

[0029] In addition, in the impedance measuring device of the present invention, the measurement current supply unit is configured to be able to vary the frequency of the measurement current in accordance with a frequency control signal, and the processing unit acquires the frequency characteristics of the impedance of the object to be measured by outputting the frequency control signal to the measurement current supply unit and varying the frequency of the measurement current.

[0030] Furthermore, the impedance measuring method according to the present invention acquires the frequency characteristics of the impedance of the measurement object by varying the frequency of the measurement current.

[0031] According to this impedance measuring device and impedance measuring method, the frequency characteristics of the impedance of the object to be measured can be obtained by varying the frequency of the current to be measured, thereby making it possible to determine the performance and deterioration state of the object to be measured.

[0032] In the impedance measuring device according to the present invention, the processing unit acquires either a Cole-Cole plot or a Bode diagram as the frequency characteristics.

[0033] In addition, the impedance measuring method according to the present invention obtains either a Cole-Cole plot or a Bode diagram as the frequency characteristics.

[0034] According to this impedance measuring device and impedance measuring method, by acquiring either a Cole-Cole plot or a Bode diagram as the frequency characteristic, it is possible to determine the performance and degradation state of the object to be measured with high accuracy.

[0035] In the impedance measuring device according to the present invention, the processing unit records the acquired frequency characteristics in a recording unit.

[0036] In addition, in the impedance measuring method according to the present invention, the acquired frequency characteristics are recorded in a recording unit.

[0037] According to this impedance measuring device and impedance measuring method, the acquired frequency characteristics are recorded in the recording section, thereby realizing the function of a recording device. [Effects of the Invention]

[0038] The current measuring device and current measuring method according to the present invention can eliminate the influence of the characteristics of the first current sensor on current measurement accuracy (measurement error), thereby enabling the supply current value of the current to be measured flowing through the object to be measured to be measured with high accuracy.Furthermore, the impedance measuring device and impedance measuring method according to the present invention can eliminate the influence of the characteristics of the first current sensor on current measurement accuracy (measurement error), thereby enabling the supply current value of the current to be measured flowing through the object to be measured to be measured with high accuracy, and as a result, the impedance of the object to be measured with high accuracy. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a configuration diagram of an impedance measuring device 1. [Figure 2] This is a frequency characteristic diagram showing the conceptual frequency characteristics of the gain characteristic CHGR and phase characteristic CHPR for current value measurement when using a Rogowski coil type current sensor, and the conceptual frequency characteristics of the gain characteristic CHGC and phase characteristic CHPC for current value measurement when using a clamp type current sensor 4-m. [Figure 3] 1 is an explanatory diagram illustrating the principle by which the current value of a measurement AC current Im can be measured with high accuracy using Rogowski coil type current sensors 4-1 and 4-p and a clamp type current sensor 4-m. [Figure 4] FIG. 1 is a configuration diagram of an impedance measuring device 1A. DETAILED DESCRIPTION OF THE INVENTION

[0040] Hereinafter, embodiments of a current measuring device, a current measuring method using the current measuring device, an impedance measuring device, and an impedance measuring method using the impedance measuring device will be described with reference to the accompanying drawings.

[0041] 1 is an example of an impedance measurement device that performs an impedance measurement method, and is configured to be able to measure the impedance of N measurement targets DUT1, DUT2, and DUT3 (hereinafter, also referred to as "measurement targets DUTs" when no distinction is needed) in a state where the DUTs are connected in parallel with a power supply device PD as a non-measurement target via a bus bar Bb that serves as a connection line. In this case, "N" is an integer equal to or greater than 1, and in this example, an example where "N=3" is described as an example, but "N" may of course be 1, 2, 4 or more.

[0042] Examples of DUTs to be measured include electrolysis devices (electrolysis devices) in which multiple electrochemical cells (an example of impedance elements) are electrically connected in series to form a stack; electrolysis reduction devices (electrolytic reduction devices) in which multiple electrolyte membranes (an example of impedance elements) are electrically connected in series to form a stack; devices using ion exchange membranes in which multiple ion exchange membranes (an example of impedance elements) are electrically connected in series to form a stack; fuel cells in which multiple power generation cells (an example of impedance elements) are electrically connected in series to form a stack; and lithium ion batteries and lead-acid batteries in which multiple battery cells (an example of impedance elements) are electrically connected in series to form a stack. Non-measurement targets include power supply devices such as inverters and converters, various loads such as electronic devices, and various power generation devices such as operating or non-operating fuel cells. Known electrolytic reduction devices include organic electrolytic reduction devices used in the production of MCH (methylcyclohexane), a hydrogen carrier (see JP 2022-30943 A).

[0043] However, the impedance measuring device 1 is not limited to this, and is configured to be suitable for accurately measuring the current under test that flows through the DUT under test and the impedance of the DUT under test when a large DC current flows through the bus bar Bb, forming an active line. Below, as an example, a description will be given of an example in which an electrolytic device is the DUT under test and a power supply device PD that supplies power to drive the DUT under test is not the object of measurement.

[0044] First, the DUT under measurement will be described. As shown in Fig. 1, in this example, the DUT under measurement is an electrolysis device in which a plurality of electrochemical cells C1 to C5 (hereinafter, also referred to as "electrochemical cells C" when not distinguishing between them) are electrically connected in series to form a stack. Note that, although an electrolysis device is actually configured with tens to hundreds of electrochemical cells C connected in series, for ease of understanding, the DUT under measurement is illustrated as being configured with five electrochemical cells C1 to C5 electrically connected in series. In this case, the DUT under measurement is provided with a pair of input terminals T1, T2 and terminals (not shown) that are connected to the connection points of the electrochemical cells C, C, respectively.

[0045] (First Example) Next, the configuration of the impedance measuring device 1 will be described. As shown in Fig. 1, the impedance measuring device 1 is configured to include a measurement current supply unit 2, a voltage measurement unit 3, current sensors 4-1, 4-2, 4-3, 4-p, and 4-m, a processing unit 5, an output unit 6, a recording unit 7, voltage detection probes P1 and P2, and measurement current supply probes Pi1 and Pi2. When there is no need to distinguish between the current sensors 4-1 to 4-3 and 4-p, they will hereinafter also be referred to as "current sensors 4." The current sensors 4-1 to 4-3, 4-p, and 4-m and the processing unit 5 form a current measuring device 10.

[0046] The measurement current supply unit 2 functions as a current source that supplies a measurement AC current Im as a measurement current to the DUT under test and the power supply device PD. In accordance with instructions from the processing unit 5, the measurement current supply unit 2 generates and outputs the measurement AC current Im, which is a sinusoidal AC signal for measuring the impedance of the DUT under test. Measurement current supply lines Li are connected to one output terminal and the other output terminal of the measurement current supply unit 2. Therefore, the measurement current supply unit 2 outputs (supplies) the measurement AC current Im to the DUT under test and the power supply device PD by outputting the measurement AC current Im to the bus bar Bb via the measurement current supply lines Li and Li and the probes Pi1 and Pi2. The measurement current supply unit 2 is configured to be able to vary the frequency of the measurement AC current Im, and sweeps (varies) the frequency of the measurement AC current Im and outputs it in accordance with a frequency control signal Sf output from the processing unit 5. In this case, because the measurement current supply unit 2 functions as a current source, the output impedance of the measurement current supply unit 2 is extremely large.

[0047] The voltage measurement unit 3 measures the voltage (end-to-end voltage V1) generated between the pair of probes P1 and P2 in accordance with instructions from the processing unit 5, and outputs voltage value data Dv indicating the measurement value (voltage value of end-to-end voltage V1) to the processing unit 5. Note that Fig. 1 shows, as an example, a state in which the voltage measurement unit 3 is connected via the probes P1 and P2 to a bus bar Bb that is connected to the input terminals T1 and T2 of the DUT 1.

[0048] The current sensor 4 is an air-core AC current sensor capable of measuring AC current and functions as a non-contact first current sensor. For example, a Rogowski coil-type current sensor without a core, such as that disclosed in Japanese Patent Application Laid-Open No. 2019-27970, can be used as the current sensor 4. These current sensors 4-1, 4-2, 4-3, and 4-p are configured to have the same characteristics. That is, the current sensors 4-1, 4-2, 4-3, and 4-p have the same gain characteristic CHGR and phase characteristic CHPR with respect to the frequency of the AC current shown in FIG. 2. In this case, the current sensor 4 is configured, for example, by winding a coil around a resin former. The former has a circular cross section and is formed in a doughnut shape with a slit, allowing for the formation of an openable and closable loop (opening 4o). The current sensor 4 measures the current value (supply current value) of the measurement AC current Im supplied via the bus bar Bb inserted through the opening 4o as the current to be measured, and outputs current value data indicating the measured current value. Note that the current sensor 4 is not limited to a Rogowski coil type current sensor, and can be appropriately selected from air-core type AC current sensors capable of measuring AC current.

[0049] As shown in FIG. 1, for example, current sensor 4-1 is attached to bus bar Bb connecting power supply device PD and measurement target DUT1, and outputs current value data Di1 indicating the current value of measurement AC current Im flowing through measurement target DUT1. Current sensor 4-2 is attached to bus bar Bb connecting power supply device PD and measurement target DUT2, and outputs current value data Di2 indicating the current value of measurement AC current Im flowing through measurement target DUT2. Current sensor 4-3 is attached to bus bar Bb connecting power supply device PD and measurement target DUT3, and outputs current value data Di3 indicating the current value of measurement AC current Im flowing through measurement target DUT3. Current sensor 4-p is attached to bus bar Bb connecting power supply device PD and each measurement target DUT, and outputs current value data DiP indicating the current value of measurement AC current Im flowing through power supply device PD. Note that hereinafter, when the current value data Di1 to Di3 and DiP are not to be distinguished from one another, they will also be referred to as "current value data Di."

[0050] As shown in FIG. 2, current sensor 4-m measures (detects) currents over a wide frequency range from DC to high frequencies with high gain characteristics CHGC and flat phase characteristics CHPC. That is, current sensor 4-m functions as a second current sensor that measures the measurement AC current Im with higher accuracy than current sensor 4 (first current sensor) in terms of gain characteristics CHGC and phase characteristics CHPC. In this case, because the output impedance of the measurement current supply unit 2, which functions as a current source, is extremely high, the large DC current output from the power supply device PD does not flow through the measurement current supply unit 2. Therefore, because magnetic saturation caused by the flow of a large DC current does not occur, a current sensor with a small dynamic range but capable of high-accuracy current measurement can be used as current sensor 4-m.

[0051] For example, the current sensor 4-m may be a current sensor such as that disclosed in Japanese Patent Application Laid-Open No. 2014-235045, and is configured as a clamp-type ammeter capable of contactlessly clamping a conductor such as a coated metal conductor. Specifically, the current sensor 4-m is configured with two semicircular magnetic cores 4a and 4b and a magnetic detection element 4c formed, for example, by a Hall element or a fluxgate element, and functions as a clamp-type contactless current sensor configured such that the clamp on the clamped conductor can be released (opened and closed) by operating an operation unit (not shown) to bring the magnetic cores 4a and 4b close to each other to form an annular opening 4d, through which the conductor can be clamped (inserted). The operation unit can be operated to move the magnetic cores 4a and 4b apart from each other to release the clamp on the clamped conductor. In addition, in this current sensor 4-m, the magnetic detection element 4c detects the magnetic flux generated in the magnetic cores 4a and 4b when a current flows through the conductor inserted into the opening 4d, thereby measuring (detecting) the current value of the current flowing through the conductor at frequencies ranging from direct current to high frequencies, and outputs current value data DiO indicating the measured current value.

[0052] In this case, as shown in Fig. 1, when the measurement current supply line Li is inserted into the opening 4d, the current sensor 4-m outputs the current values ​​of all the measurement AC currents Im output from the measurement current supply unit 2 as current value data DiO. That is, in the state of Fig. 1, the current sensor 4-m outputs the sum of the current values ​​of the measurement AC currents Im flowing through the measurement targets DUT1 to DUT3 and the power supply device PD as current value data DiO. Also, instead of a clamp-type current sensor, a shunt resistor with higher accuracy than the current sensor 4 in terms of gain characteristics and phase characteristics, or a current sensor configured to be unopenable using an annular core, can be used as the current sensor 4-m.

[0053] The processing unit 5 is configured, for example, by a CPU and controls the impedance measuring device 1. Specifically, during impedance measurement, the processing unit 5 controls the measurement current supply unit 2 to generate and output a measurement AC current Im. During impedance measurement, the processing unit 5 also controls each current sensor 4 to measure the current flowing through the bus bar Bb inserted into the opening 4o of the current sensor 4 and output current value data Di, and controls the current sensor 4-m to measure the measurement AC current Im flowing through the measurement current supply line Li inserted into the opening 4d of the current sensor 4-m and output current value data DiO. The processing unit 5 also controls the voltage measurement unit 3 to measure the voltage V1 across the probes P1 and P2 and output voltage value data Dv.

[0054] The processing unit 5 also receives the current value data Di output from the current sensor 4 and the current value data DiO output from the current sensor 4-m. The processing unit 5 also receives the voltage value data Dv output from the voltage measurement unit 3. The processing unit 5 measures (calculates) the current value of the measurement AC current Im flowing through the DUT under test and the impedance of the DUT under test, based on the received current value data Di, DiO and voltage value data Dv.

[0055] Specifically, when the measurement target DUT1 is taken as an example, the processing unit 5 calculates the current value (I: supply current value) of the measurement AC current Im flowing through the measurement target DUT1 based on the amplitude of the measurement AC current Im included in the current value data Di1, as described below, and also calculates the voltage V1 across the AC voltage at both ends of the measurement target DUT1 as a voltage value (V) based on the amplitude of the measurement AC current Im included in the voltage value data Dv. Furthermore, the processing unit 5 calculates the phase difference (θ) between the AC current of the measurement AC current Im and the AC voltage of the measurement AC current Im, i.e., the phase difference (θ) between the AC current flowing through the measurement target DUT1 and the AC voltage generated across the measurement target DUT1, based on the current value data Di1 and the voltage value data Dv. Furthermore, the processing unit 5 measures (calculates) the impedance (impedance Z=V / I, R=Z·cosθ, X=Z·sinθ) of the measurement target DUT1, which is the measurement target, based on the current value (I) of the measurement AC current Im, the voltage value (V) of the measurement AC current Im, and the phase difference (θ) calculated in this manner.

[0056] In this case, the frequency characteristic diagram of the Rogowski coil type current sensor 4 shows frequency characteristics in which the gain decreases and the phase is not flat at low frequencies, as shown in Figure 2. Therefore, it is usually difficult to accurately measure the current value of the measurement AC current Im using a current sensor 4 with such frequency characteristics, and it is also difficult to create a Cole-Cole plot or Bode diagram for the DUT under test based on the impedance measured by sweeping the frequency of the measurement AC current Im.

[0057] Therefore, in this impedance measuring device 1, the processing unit 5 performs the following process, thereby enabling accurate measurement of the current value of the measurement AC current Im flowing through the DUT under test. This will be specifically described below with reference to FIG. 3.

[0058] 3 shows a state in which the measurement current supply unit 2, the DUT 1 under test, and the power supply device PD are connected in parallel, and a measurement AC current Im is supplied to the DUT 1 under test and the power supply device PD from the measurement current supply unit 2. In this case, it is assumed that the measurement current supply unit 2 outputs a measurement AC current Im with a current value Io, a measurement AC current Im with a current value I1 is supplied to the DUT 1 under test, and a measurement AC current Im with a current value Ip is supplied to the power supply device PD.

[0059] Furthermore, when a measurement AC current Im with a current value I1 flows through current sensor 4-1, it outputs a voltage output SI1 proportional to the magnitude of the current value I1. The transfer characteristic of current sensor 4-1 at this time is defined as "G1." When a current value Ip flows through current sensor 4-p, it outputs a voltage output SIp proportional to the magnitude of the current value Ip. The transfer characteristic of current sensor 4-p at this time is defined as "Gp." At this time, the voltage output of each current sensor 4 is expressed by the following equation. In this case, "G1" and "Gp" represent complex transimpedances. SI1=G1·I1 SIp=Gp·Ip

[0060] Furthermore, current sensors 4-1 and 4-p have the same gain and phase characteristics. Therefore, transfer characteristics G1 and Gp are equal to each other, and therefore, hereinafter, transfer characteristics G1 and Gp are also referred to as transfer characteristic G. As a result, the voltage output of each of the current sensors 4 is expressed by the following equation: SI1=G·I1 SIp=G·Ip

[0061] In this case, because the current sensor 4 is a Rogowski coil, the transfer characteristic G has a low gain and a large phase lead, resulting in an uneven characteristic in the low frequency band including DC. Therefore, when the frequency of the measurement AC current Im is in the low frequency band, it is difficult for the current sensor 4 to accurately measure the current value of the measurement AC current Im. On the other hand, the current sensor 4-m has a higher measurement accuracy in terms of gain and phase characteristics than the current sensor 4. Therefore, the current sensor 4-m accurately measures the current value Io of the measurement AC current Im output from the measurement current supply unit 2. Therefore, because the current value Io is accurate and known, the current value I1 flowing through the DUT1 can be accurately calculated (measured) using the following equation (1): I1=SI1 / (SI1+SIp)×Io (1) formula

[0062] Here, the current value I1 can be calculated (measured) with high accuracy by using equation (1) for the following reason: That is, the right side of equation (1) can be expressed by the following equation (2). Right side of equation (1) = SI1 / (SI1+SIp)×Io (2)

[0063] In this case, since the transfer characteristic of the current sensors 4-1 and 4-p is expressed as "G", equation (2) is transformed as follows: SI1 / (SI1+SIp)×Io =G·I1 / (G·I1+G·Ip)×Io =I1 / (I1+Ip)×Io =I1 / (Io)×Io =I1···(3) formula

[0064] As a result, according to equation (3), the value (I1) on the left side of equation (1) is equal to the value (I1) on the right side, and therefore, equation (1) is a correct equation. In other words, by having the processing unit 5 calculate the current value I1 of the measurement AC current Im flowing through the measurement target DUT1 according to equation (1), the transfer characteristics G1 of current sensor 4-1 and the transfer characteristics Gp of current sensor 4-p, which have the same characteristics, can be eliminated (cancelled) from the calculation formula for determining the current value I1. Therefore, it can be understood that the current value I1 of the measurement AC current Im flowing through the measurement target DUT1 can be accurately measured based on the current values ​​measured by current sensor 4-1, current sensor 4-p, and current sensor 4-m, even in the low-frequency band of the measurement AC current Im.

[0065] Note that equation (1) means that the current value Io measured by current sensor 4-m is multiplied by the value obtained by dividing the current value of the measurement AC current Im flowing through the measurement object DUT1 connected in parallel, measured by current sensor 4-1, by the sum (total) current value of the measurement AC current Im flowing through the power supply device PD, measured by current sensor 4-p.

[0066] For the same reason, when N (N is an integer of 2 or more) measurement targets DUT1 to DUTn are connected in parallel with the power supply device PD, the current value Ij of the measurement AC current Im flowing through the measurement target DUTj can be calculated according to the following equation (4). In this case, when the measurement target is the measurement target DUTj, current sensor 4j is a current sensor 4 that measures the measurement AC current Im supplied to the measurement target DUTj and outputs the current value of the measurement AC current Im flowing through the measurement target DUTj. Furthermore, "j" is any one integer from 1 to N. Furthermore, current sensor 4i is one of the N current sensors 4. Furthermore, when the measurement targets DUT1 to DUTn are not distinguished from one another, they are also referred to as "measurement targets DUTs." Current value Ij = (measured value of the measurement AC current Im flowing through the target DUTj) / ((total of measured values ​​of the measurement AC current Im flowing through each of the target DUT1 to DUTn) + current value Ip of the measurement AC current Im output from current sensor 4-p) × Io (Equation 4)

[0067] In this case, the calculation does not necessarily have to be performed according to the above equation (4), but can be performed according to an equation obtained by modifying equation (4) and equivalently modifying it to have the same meaning as equation (4). In other words, the accurate supply current value (Ij) of the measurement AC current Im for the measurement target DUTj as one measurement target can be equivalently obtained by multiplying the current value (measurement value) of the measurement AC current Im for the measurement target DUTj as one measurement target measured by current sensor 4j by the sum current value (addition value) of each current value (measurement value) of the measurement AC current Im for the N measurement targets DUTj, respectively, measured by the N current sensors 4, and the current value (measurement value) of the measurement AC current Im for the power supply device PD, which is a non-measurement target, measured by current sensor 4-p, by the current value Io (total) of the measurement AC current Im measured by current sensor 4-m, which is a second current sensor.

[0068] Therefore, when calculating the impedance of one DUTj under test, the processing unit 5 uses the current value found for the DUTj under test as the current value (I) for that DUTj under test. The processing unit 5 also calculates the impedance of the DUTj under test based on the current value (I), the voltage value (V) that is the voltage V1 across the DUTj under test measured by the voltage measurement unit 3, and the phase difference (θ) between the AC current Im under test flowing through the DUTj under test and the voltage V1 across the DUTj under test. This allows the processing unit 5 to accurately measure the current value of the AC current Im under test flowing through the DUTj under test and the impedance of the DUTj under test.

[0069] In addition, in accordance with instructions from an operation unit (not shown), processing unit 5 outputs a frequency control signal Sf to measurement current supply unit 2 to sweep the frequency of measurement AC current Im between a low frequency band and a high frequency band. Processing unit 5 also outputs display data Dd to output unit 6 for displaying the measured impedance of the DUT under test and the frequency characteristics of the impedance such as a Cole-Cole plot and a Bode plot. Processing unit 5 also outputs measurement data Dm indicating the measured impedance of the DUT under test and the frequency characteristics of the impedance such as a Cole-Cole plot and a Bode plot to recording unit 7 for recording.

[0070] The output unit 6 is, for example, a display device such as a liquid crystal panel or an organic EL panel, and receives the display data Dd output from the processing unit 5 to display the impedance of the DUT under test and the frequency characteristics of that impedance on a screen. Instead of a display device, the output unit 6 may be configured as an interface device that communicates data with an external device, and output impedance data indicating the impedance of the DUT under test and the frequency characteristics of that impedance to the external device. The recording unit 7 is, for example, a hard disk, and receives the measurement data Dm output from the processing unit 5 to record the measured impedance of the DUT under test and the frequency characteristics of the impedance, such as a Cole-Cole plot and a Bode diagram.

[0071] The probes P1 and P2 are configured as contact-type probes whose tips are connected (contacted) to terminals T of the DUT to be measured, respectively, to measure the AC voltage as the voltage across terminals T, T when an AC current Im to be measured is supplied to the DUT to be measured. The probes Pi1 and Pi2 are also configured as contact-type probes whose tips are connected (contacted) to bus bars Bb, respectively, to supply the AC current Im to be measured.

[0072] Next, with reference to the drawings, a current measurement method for measuring (calculating) the measurement AC current Im flowing through the DUT under test and an impedance measurement method for measuring (calculating) the impedance of the DUT under test will be described using the impedance measurement device 1. It is assumed that the power supply device PD and each DUT under test are connected in advance by a bus bar Bb.

[0073] First, each current sensor 4 is attached to measure the measurement AC current Im flowing through each DUT under test and the power supply device PD. Specifically, current sensor 4-1 is attached to the bus bar Bb connecting the power supply device PD and the DUT under test 1, current sensor 4-2 is attached to the bus bar Bb connecting the power supply device PD and the DUT under test 2, current sensor 4-3 is attached to the bus bar Bb connecting the power supply device PD and the DUT under test 3, and current sensor 4-p is attached to the bus bar Bb connecting the power supply device PD and each DUT under test. Also, to measure the current value Io, which is the sum of the measurement AC currents Im output from the measurement current supply unit 2, current sensor 4-m is attached to the measurement current supply line Li connected to the measurement current supply unit 2. In other words, the measurement current supply line Li is clamped by the current sensor 4-m. Next, when the measurement object DUT1 is to be measured, probe P1 is connected (contacted) to bus bar Bb connected to input terminal T1 of measurement object DUT1, and probe P2 is connected (contacted) to bus bar Bb connected to input terminal T2 of measurement object DUT1.

[0074] Next, a measurement start switch (not shown) is operated. This causes the processing unit 5 to output a frequency control signal Sf to control the measurement current supply unit 2 to output a measurement AC current Im. At this time, the measurement current supply unit 2 outputs a measurement AC current Im of predetermined amplitude, frequency, and phase in accordance with the frequency control signal Sf.

[0075] Each current sensor 4 measures the current value of the measurement AC current Im flowing through the bus bar Bb inserted through the opening 4o, and outputs current value data Di1 to Di3, DiP to the processing unit 5. Further, the current sensor 4-m measures the current value Io of the measurement AC current Im output from the measurement current supply unit 2, and outputs current value data DiO to the processing unit 5.

[0076] In this case, because the output impedance of the measurement current supply unit 2 is extremely large, the large DC current output from the power supply device PD does not flow through the measurement current supply unit 2, but flows only through the measurement targets DUT1 to DUT3. Therefore, current sensor 4-m does not experience magnetic saturation due to the flow of a large DC current, and therefore measures the current value Io of the measurement AC current Im with high accuracy. Meanwhile, because each current sensor 4 is a Rogowski coil, magnetic saturation due to the flow of a large DC current does not occur, and so measures the current values ​​I1 to I3, Ip of the measurement AC current Im flowing through the measurement target DUT according to the gain and phase characteristics of the Rogowski coil.

[0077] Furthermore, the voltage measurement unit 3 measures a voltage V1 across both ends of the DUT 13 under test and outputs voltage value data Dv to the processing unit 5.

[0078] Next, the processing unit 5 receives the current value data Di1 to Di3, DiP output from each current sensor 4, the current value data DiO output from the current sensor 4-m, and the voltage value data Dv output from the voltage measurement unit 3. The processing unit 5 also measures (calculates) the impedance of the measurement target DUT1 based on the received current value data Di1 to Di3, DiP, DiO and voltage value data Dv.

[0079] In this case, first, the processing unit 5 calculates the current value (I) flowing through the DUT1 under test. Specifically, based on the current value data Di1-Di3, DiP, and DiO, the processing unit 5 calculates the current values ​​I1-I3 of the measurement AC current Im flowing through each of the DUT1-DUT3 under test, the current value Ip of the measurement AC current Im flowing through the power supply device PD, and the current value Io of the measurement AC current Im output from the measurement current supply unit 2. Furthermore, based on the voltage value data Dv, the processing unit 5 calculates the voltage V1 across the DUT1 under test. In this case, the current values ​​I1-I3, Ip, and Io and the voltage V1 are all expressed as complex numbers.

[0080] Next, in accordance with equation (4) above, the processing unit 5 calculates a current value (I: supply current value) for the DUT1 under test by multiplying the current value Io by the sum of the current values ​​(measured values ​​for current values ​​I1, I2, I3) and the current value (measured value for current value Ip) divided by the current value (measured value for current values ​​I1, I2, I3), and calculates the voltage V1 across the DUT1 under test as a voltage value (V). Next, the processing unit 5 calculates the phase difference (θ) between the AC current and AC voltage of the measurement AC current Im, and measures (calculates) the impedance (impedance Z=V / I, R=Z cos θ, X=Z sin θ) of the DUT1 under test, based on the current value (I), voltage value (V), and phase difference (θ) of the measurement AC current Im.

[0081] The processing unit 5 also sweeps the frequency of the measurement AC current Im by outputting a frequency control signal Sf to the measurement current output unit 2. The processing unit 5 then measures (calculates) each impedance of the DUT 1 under test at multiple frequencies as described above. Next, the processing unit 5 acquires the frequency characteristics of the impedance of the DUT 1 under test at multiple frequencies. In this case, the processing unit 5 acquires, as frequency characteristics, a Cole-Cole plot showing the impedance characteristics of the DUT 1 under test with respect to frequency, and a Bode plot showing the gain characteristics and phase characteristics with respect to frequency. The processing unit 5 then outputs display data Dd to the output unit 6, causing the display device of the output unit 6 to display each measured impedance of the DUT 1 under test and the acquired Cole-Cole plot and Bode plot. The processing unit 5 also outputs measurement data Dm to the recording unit 7, recording the acquired Cole-Cole plot and Bode plot. This completes the processing for measuring the impedance of the DUT 1 under test, which is the measurement target. Similarly, when measuring the impedance of another DUT under test, the processing unit 5 performs the same impedance measurement processing as described above.

[0082] In this embodiment, an electrolysis device is described as the DUT under test, and a power supply device PD that supplies power to the DUT under test is described as the non-measurement object. However, the DUT under test can also be a fuel cell formed by electrically connecting multiple power generation cells in series to form a stack, or a lithium-ion battery or lead-acid battery formed by electrically connecting multiple battery cells in series to form a stack, and various loads such as power supply devices (inverters, converters, etc.) and electronic devices can be described as the non-measurement object. Furthermore, various power generation devices, such as fuel cells, whether in operation or not, can be described as the non-measurement object instead of the power supply device PD. In other words, when a DC current is supplied from the non-measurement object to the DUT under test, or conversely, when a DC current is supplied from the DUT under test to the non-measurement object, the current measuring device 10 and the impedance measuring device 1 can be used to accurately measure the current value of the measurement AC current Im flowing through the DUT under test and the impedance of the DUT under test, in the same manner as the current measuring method and impedance measuring method described above.

[0083] In this way, in this current measuring device 10 and current measuring method, the sum of the measurement AC currents Im supplied to N (three in this example) measurement targets DUT1 to DUT3 and the non-measurement target power supply device PD is measured by current sensor 4-m, the measurement AC currents Im supplied to each of the three measurement targets DUT1 to DUT3 and the measurement AC current Im supplied to the power supply device PD are measured by current sensor 4, and the supply current value (current value I1) for one measurement target DUT1 measured by current sensor 4-1 is divided by the sum of the current values ​​(measured values ​​for each current value I1 to I3) for the three measurement targets DUT1 measured by current sensor 4 (measured values ​​for each current value I1 to I3) and the current value for the power supply device PD measured by current sensor 4-p (measured value for current value Ip) to measure the supply current value (current value I1) for one measurement target DUT1.

[0084] Therefore, with this current measuring device 10 and current measuring method, when a Rogowski coil-type current sensor 4 with poor gain and phase characteristics in the low frequency band is used to measure the current value I1 when a low-frequency measurement AC current Im flows through the DUT 1, it is possible to eliminate the influence (measurement error) of the characteristics (gain characteristics and phase characteristics) of the current sensor 4 on current measurement accuracy, and therefore it is possible to accurately measure the current value I1 of the measurement AC current Im flowing through the DUT 1. As a result, with the impedance measuring device 1 and impedance measuring method equipped with this current measuring device 10, it is possible to accurately measure the impedance of the DUT 1 based on the current value I1 of the measured measurement AC current Im.

[0085] Furthermore, according to this current measuring device 10 and current measuring method, by using a current sensor 4-m that has higher accuracy in gain characteristics and phase characteristics than the current sensor 4, the measurement AC current Im can be measured more accurately, and as a result, the current value of the measurement AC current Im supplied to the DUT to be measured can be measured more accurately.

[0086] Furthermore, with this current measuring device 10 and current measuring method, (N+1) (four in this example) current sensors 4 are arranged on each bus bar Bb that connects the measurement current supply unit 2 with N (three in this example) DUTs under test and the power supply device PD, and current values ​​I1 to I3 for the three DUTs under test and current value Ip for the power supply device PD are measured. Therefore, with this current measuring device 10 and current measuring method, current values ​​I1 to I3 of the measurement AC current Im flowing through each of the measurement targets DUT1 to DUT3 and current value Ip of the measurement AC current Im flowing through the power supply device PD can be measured simultaneously, which makes it possible to eliminate measurement errors caused by changes over time in the current measurement of the measurement AC current Im flowing through each of the measurement targets DUT1 and the power supply device PD, and as a result, current value I1 flowing through the measurement target DUT1 can be measured with high accuracy.

[0087] The current measuring device 10 and current measuring method measure a measurement AC current Im flowing through a DUT (device under test) configured by electrically connecting electrochemical cells that cause electrochemical reactions in series. The current measuring device 10 and current measuring method measure a device configured by stacking electrolytic cells as electrochemical cells, and measure the measurement AC current Im flowing through the DUT (device under test) in an operating state using power output from a power supply device PD (non-target device). The current measuring device 10 and current measuring method measure a device configured by stacking either fuel cell cells or battery cells as electrochemical cells, and measure the impedance of the DUT (device under test) when a load (non-target device) is consuming the power output from the DUT (device under test).

[0088] Therefore, with this current measuring device 10 and current measuring method, it is possible to accurately measure the measurement AC current Im flowing through the measurement target DUT when the measurement target DUT and non-measurement targets such as the power supply device PD are operating and a large DC current is flowing through the bus bar Bb.

[0089] Furthermore, in this impedance measuring device 1 and impedance measuring method, a measurement AC current Im is supplied to N (three in this example) measurement targets DUT1 to DUT3 and a power supply device PD that is not a measurement target via a bus bar Bb, a voltage V1 across both ends of one measurement target DUT1 is measured, and the impedance of the measurement target DUT1 is measured based on the calculated current value I1 of the measurement AC current Im for one measurement target DUT1 and the measured voltage V1 across both ends of the measurement target DUT1.

[0090] Therefore, according to this impedance measuring device 1 and impedance measuring method, when a Rogowski coil type current sensor 4 having poor gain and phase characteristics in the low frequency band is used to measure the current value I1 when a low frequency measurement AC current Im flows through the measurement target DUT1, the influence (measurement error) of the characteristics (gain characteristics and phase characteristics) of the current sensor 4 on the current measurement accuracy can be eliminated, so that the current value I1 of the measurement AC current Im flowing through the measurement target DUT1 can be measured with high accuracy, and as a result, the impedance of the measurement target DUT1 can be measured with high accuracy.

[0091] Furthermore, in this impedance measuring device 1 and impedance measuring method, the measurement AC current Im is supplied from the measurement current supply unit 2 configured as a current source. Therefore, with this impedance measuring device 1 and impedance measuring method, the output impedance of the measurement current supply unit 2 is extremely large, so that even when a large DC current is output from the power supply device PD (not being measured), the current does not flow to the measurement current supply unit 2 but can flow only to the DUT under test. Therefore, with this impedance measuring device 1 and impedance measuring method, magnetic saturation of the current sensor 4-m caused by the flow of a large DC current can be avoided, and a high-precision current sensor with a small dynamic range can be used, making it possible to measure the current value Io of the measurement AC current Im with high precision.

[0092] Furthermore, according to this impedance measuring device 1 and impedance measuring method, the frequency characteristics of the impedance of the DUT to be measured can be obtained by varying the frequency of the measurement AC current Im, thereby making it possible to determine the performance and degradation state of the DUT to be measured.

[0093] Furthermore, according to this impedance measuring device 1 and impedance measuring method, by acquiring either a Cole-Cole plot or a Bode plot as the frequency characteristics, it is possible to determine the performance and degradation state of the DUT under measurement with high accuracy.

[0094] Furthermore, according to the impedance measuring device 1 and the impedance measuring method, the acquired frequency characteristics are recorded in the recording section 7, thereby realizing the function of a recording device.

[0095] (Second Example) Next, the impedance measuring apparatus 1A will be described with reference to Fig. 4. Note that components and operations similar to those of the impedance measuring apparatus 1 are given the same reference numerals and redundant description will be omitted.

[0096] This impedance measuring device 1A is an example of an impedance device that performs an impedance measurement method, and unlike the impedance measuring device 1, it is equipped with a measurement current supply unit 2A consisting of an electronic load that functions as a current source, instead of the measurement current supply unit 2.

[0097] In this impedance measuring device 1A, at the start of impedance measurement, the processing unit 5 outputs a frequency control signal Sf to the measurement current output unit 2A, causing the measurement current output unit 2A to operate as an AC load. At this time, in accordance with the frequency control signal Sf, the measurement current output unit 2A consumes the DC current output from the power supply device PD as a load, thereby supplying a measurement AC current Im of the specified frequency to the DUT under test and the power supply device PD via the bus bar Bb. In this state, similar to the impedance measuring device 1, the processing unit 5 measures the current value of the measurement AC current Im flowing through the DUT under test and the impedance of the DUT under test.

[0098] In this impedance measuring device 1A, the measurement current output section 2A is configured as an electronic load, and the electronic load consumes the DC current output from the power supply device PD to generate the measurement AC current Im, making it possible to generate a large measurement AC current Im. Therefore, with this impedance measuring device 1A and impedance measuring method, the above-mentioned current value (I) and voltage value (V) can be increased, making it possible to accurately measure (calculate) the current value of the measurement AC current Im flowing through the measurement target DUT, and also to accurately measure (calculate) the impedance of the measurement target DUT.

[0099] The present invention is not limited to the above-described embodiments and can be modified as appropriate. For example, in the above-described embodiments, a configuration in which a current sensor 4 is attached to each of the bus bars Bb connected to the DUTs 1 to 3 and the power supply device PD has been described. However, the present invention is not limited to this. For example, it is also possible to use only one current sensor 4 to sequentially measure the current value of the measurement AC current Im flowing through each DUT and the current value of the measurement AC current Im flowing through the power supply device PD. However, in a state in which the current value of the measurement AC current Im flowing through each DUT is constantly fluctuating, attaching a current sensor 4 to each DUT and the power supply device PD and simultaneously measuring the fluctuating current value of the measurement AC current Im flowing through each DUT can accurately measure the current value of the measurement AC current Im flowing through the DUT and the impedance of the DUT.

[0100] In the above embodiment, the current sensor 4-m serving as the second current sensor is configured as a clamp-type non-contact current sensor configured to be openable and closable, but the current sensor 4-m can also be configured as a current sensor configured to be non-openable and closable using a shunt resistor or an annular core. In this case, the current value Io of the measurement AC current Im can be measured with high accuracy by placing a shunt resistor at the connection between the measurement current supply unit 2 and the measurement current supply line Li or by inserting the measurement current supply line Li into the opening of the current sensor configured to be non-openable and closable.

[0101] In the above embodiment, an example has been described in which a single Rogowski coil-type current sensor is used as each of the current sensors 4-1 to 4-3, 4-p, but this is not limiting. For example, when the power supply device PD and each DUT under test are connected by multiple bus bars Bb, a configuration can be adopted in which a current sensor is attached to each of the multiple bus bars Bb to form a single current sensor 4 as a whole. In this case, the current sensors 4-1 to 4-3, 4-p, each made up of multiple current sensors, are specified so that their gain characteristics and phase characteristics are identical to each other.

[0102] Although the example in which the current sensor 4 outputs the current value data Di has been described, it is also possible to adopt a configuration in which the current sensor 4 outputs a current measurement signal that is an analog signal, and the processing unit 5 measures (calculates) the current flowing through the DUT under test or the impedance of the DUT under test based on the input current measurement signal. Similarly, it is also possible to adopt a configuration in which the voltage measurement unit 3 outputs a voltage measurement signal that is an analog signal, and the processing unit 5 measures (calculates) the impedance of the DUT under test based on the input voltage measurement signal.

[0103] Furthermore, although the above embodiment has been described as an example of measuring the impedance of the DUT under test, this is not limiting. For example, probes P1 and P2 may be connected to terminals that are respectively connected to the connection points of the electrochemical cells C and C that make up the DUT under test, and a voltage V1 across both ends of one or multiple electrochemical cells C under test that are connected in series may be measured, and the impedance of the electrochemical cell C under test may be measured based on the current value I1 of the measurement AC current Im thus determined and the measured voltage V1 across both ends. [Industrial Applicability]

[0104] According to the present invention, the influence (measurement error) of the characteristics (gain characteristics and phase characteristics) of the first current sensor on current measurement accuracy can be eliminated, making it possible to accurately measure the supply current value of the current flowing through the object to be measured, and as a result, to accurately measure the impedance of the object to be measured. As a result, the present invention can be widely applied to such current measurement devices and current measurement methods for current measurement, and impedance measurement devices and impedance measurement methods for impedance measurement. [Explanation of symbols]

[0105] 1. Impedance measuring device 2 Measurement current supply section 3 Voltage measurement section 4-1 to 4-3, 4-m, 4-p Current Sensor 5 Processing section 7 Recording section 10 Current measuring device Bb busbar C1~C5 Electrochemical Cells Di1~Di3,DiO,DiP current value data DUT1 to DUT3 measurement target Dv voltage value data PD power supply

Claims

1. a first non-contact current sensor that is capable of measuring the current of the object to be measured flowing through the connection line by inserting the connection line into an opening, in a state in which N (N is an integer of 1 or more) objects to be measured and non-objects to be measured are connected in parallel via connection lines and a current of the object to be measured is supplied to each of the objects to be measured and non-objects to be measured via the connection lines; a processing unit that calculates a supply current value of the object-of-measurement current supplied to one of the N objects-of-measurement based on a measurement value by the first current sensor, a second current sensor for measuring a sum of the currents to be measured supplied to the N number of objects to be measured and the non-object to be measured; the first current sensor is an air-core AC current sensor capable of measuring AC current, and measures the currents to be measured supplied to the N measurement targets and the currents to be measured supplied to the non-measurement targets; The processing unit is a current measuring device that calculates the supply current value for one measurement object by multiplying the sum of the measurement values ​​for the N measurement objects measured by the first current sensor and the measurement values ​​for the non-measurement objects measured by the first current sensor by the sum of the measurement values ​​for the N measurement objects measured by the first current sensor.

2. The current measuring device according to claim 1 , wherein the second current sensor measures the current to be measured with higher accuracy in gain characteristics and phase characteristics than the first current sensor.

3. 2. The current measuring device according to claim 1, comprising (N+1) first current sensors configured to have identical characteristics, and the (N+1) first current sensors measure the measurement object currents flowing through the N measurement objects and the N non-measurement objects, respectively.

4. 3. The current measuring device according to claim 2, further comprising (N+1) first current sensors configured to have identical characteristics, wherein the (N+1) first current sensors measure the currents flowing through the N objects to be measured and the N non-objects to be measured, respectively.

5. The current measuring device according to any one of claims 1 to 4, wherein the current measuring device measures the current flowing through the object to be measured, which is configured by electrically connecting electrochemical cells that cause electrochemical reactions in series.

6. the measurement object is configured by stacking electrolytic cells as the electrochemical cells, The current measuring device according to claim 5 , wherein the current measuring device measures the current flowing through the object to be measured in an operating state by utilizing power output from a power supply serving as the object to be measured.

7. the measurement object is configured by stacking either fuel cell cells or battery cells as the electrochemical cells, The current measuring device according to claim 5 , wherein the current measuring device measures the current flowing through the object to be measured when the load as the non-object to be measured is consuming the power output from the object to be measured.

8. A current measuring device according to any one of claims 1 to 4, a measurement current supply unit that supplies a measurement current as the object-of-measurement current to the N objects-of-measurement and the non-object-of-measurement via the connection line; a voltage measurement unit for measuring a voltage across both ends of the one measurement object, The processing unit calculates the impedance of the one object to be measured based on the calculated supply current value for the one object to be measured and the voltage across the one object to be measured measured by the voltage measurement unit.

9. 9. The impedance measuring device according to claim 8, wherein the measurement current supply section is composed of a current source.

10. 10. The impedance measuring device according to claim 9, wherein the current source is configured as an electronic load.

11. the measurement current supply unit is configured to be able to vary the frequency of the measurement current in accordance with a frequency control signal; 9. The impedance measuring device according to claim 8, wherein the processing unit outputs the frequency control signal to the measurement current supply unit to vary the frequency of the measurement current, thereby acquiring the frequency characteristics of the impedance of the measurement object.

12. The impedance measuring device according to claim 11 , wherein the processing unit acquires one of a Cole-Cole plot and a Bode diagram as the frequency characteristics.

13. The impedance measuring device according to claim 11 , wherein the processing unit records the acquired frequency characteristics in a recording unit.

14. In a state in which N (N is an integer of 1 or more) measurement targets and non-measurement targets are connected in parallel via connection lines and measurement target currents are supplied to the measurement targets and non-measurement targets via the connection lines, the connection lines are inserted into openings of a first current sensor to measure the measurement target currents flowing through the connection lines; A current measurement method for measuring a supply current value of the object-of-measurement current supplied to one of the N objects-of-measurement based on a measurement value by the first current sensor, comprising: measuring a sum of the currents to be measured supplied to the N number of objects to be measured and the non-object to be measured by a second current sensor; measuring the currents to be measured supplied to the N measurement targets and the currents to be measured supplied to the non-measurement targets by the first current sensor configured as an air-core AC current sensor capable of measuring AC current; A current measurement method for measuring the supply current value for one measurement object by multiplying the sum of the measurement values ​​for the N measurement objects measured by the first current sensor and the measurement value for the non-measurement object measured by the first current sensor by the sum of the measurement values ​​for the N measurement objects measured by the first current sensor.

15. The current measuring method according to claim 14, wherein the current to be measured is measured using the second current sensor having higher accuracy in gain characteristics and phase characteristics than the first current sensor.

16. 15. The current measurement method according to claim 14, wherein the (N+1) first current sensors configured to have the same characteristics are used to measure the currents flowing through the N objects to be measured and the N non-objects to be measured, respectively.

17. 16. The current measurement method according to claim 15, wherein the (N+1) first current sensors configured to have the same characteristics are used to measure the currents flowing through the N objects to be measured and the N non-objects to be measured, respectively.

18. 18. The current measuring method according to claim 14, wherein the current flowing through the object to be measured is measured by electrically connecting electrochemical cells that cause an electrochemical reaction in series.

19. The measurement target is an apparatus configured by stacking electrolytic cells as the electrochemical cell, The current measuring method according to claim 18, wherein the current flowing through the object to be measured in an operating state is measured by utilizing power output from a power supply serving as the object to be measured.

20. The measurement object is a device configured by stacking either fuel cells or battery cells as the electrochemical cells, 19. The current measuring method according to claim 18, wherein the current flowing through the object to be measured is measured in a state in which the load as the non-object to be measured is consuming the power output from the object to be measured.

21. supplying a measurement current as the object-of-measurement current to the N objects-of-measurement and the non-object-of-measurement via the connection line; Implementing the current measurement method according to any one of claims 14 to 17, measuring a voltage across both ends of the one measurement target; An impedance measurement method for measuring the impedance of one object to be measured based on the calculated supply current value for the object to be measured and the measured voltage across the object to be measured.

22. 22. The impedance measuring method according to claim 21, wherein the measuring AC current is supplied from a current source.

23. The impedance measuring method according to claim 22, wherein the measuring AC current is supplied from the current source constituted by an electronic load.

24. 22. The impedance measuring method according to claim 21, wherein the frequency characteristic of the impedance of the measurement object is obtained by varying the frequency of the measurement current.

25. The impedance measuring method according to claim 24, wherein one of a Cole-Cole plot and a Bode plot is obtained as the frequency characteristics.

26. The impedance measuring method according to claim 24, wherein the acquired frequency characteristics are recorded in a recording unit.

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