Current measurement device, impedance measurement device, current measurement method, and impedance measurement method

Abstract

The present invention accurately measures a current flowing through a measurement object even when the measurement object and a non-measurement object are connected in parallel via a connection line, and a large direct current is flowing through the connection line.　Current sensors 4 measure current values I1 to I3 of alternating current Im for measurement and measure a current value Ip of the alternating current Im for measurement that is supplied to a power supply device PD. A processing unit 5 calculates, as a supply current value for a measurement object DUT 1, a current value by dividing the current value I1 by a summed current value of the current values I1 to I3 and the current value Ip, and multiplying the thus obtained quotient by a current value Io of the alternating current Im for measurement measured by a current sensor 4-m.

Description

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

[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.

[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 the non-measurement object is connected in parallel with the secondary battery 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.

[0004] JP 2004-251625 A (pages 3-8, Figure 1)

[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.

[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 system further includes a second current sensor for measuring the currents of the N objects to be measured, the first current sensor being an air-core AC current sensor capable of measuring AC current, and measuring 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, and 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 value 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 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 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 having 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 voltage across both ends of 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 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 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 measurement AC current 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.

[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 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 with high accuracy, and as a result, the impedance of the object to be measured with high accuracy.

[0039] Fig. 1 is a configuration diagram of an impedance measuring device 1. Fig. 2 is a frequency characteristic diagram showing the conceptual frequency characteristics of the gain characteristic CHGR and the phase characteristic CHPR for current value measurement when a Rogowski coil type current sensor is used, and the conceptual frequency characteristics of the gain characteristic CHGC and the phase characteristic CHPC for current value measurement when a clamp type current sensor 4-m is used. Fig. 3 is an explanatory diagram for explaining 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, 4-p and a clamp type current sensor 4-m. Fig. 4 is a configuration diagram of an impedance measuring device 1A.

[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) connected in parallel to 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 of 1 or more, 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 the DUT to be measured include an electrolysis device (electrolysis device) in which multiple electrochemical cells (an example of an impedance element) are electrically connected in series to form a stack; an electrolysis reduction device (electrolytic reduction device) in which multiple electrolyte membranes (an example of an impedance element) are electrically connected in series to form a stack; an ion exchange membrane device in which multiple ion exchange membranes (an example of an impedance element) are electrically connected in series to form a stack; a fuel cell in which multiple power generation cells (an example of an impedance element) are electrically connected in series to form a stack; and a lithium ion battery or lead-acid battery in which multiple battery cells (an example of an impedance element) are electrically connected in series to form a stack. Non-measurement targets include power supply devices such as inverter devices and converter devices, various loads such as electronic devices, and various power generation devices such as operating or non-operating fuel cells. An example of an electrolytic reduction device is an organic electrolytic reduction device 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 and the bus bar Bb becomes an active line. As an example, the following will describe an example in which the electrolysis device is the DUT under test and the power supply device PD that supplies power to drive the DUT under test is not the object of measurement.

[0044] First, the DUT under test will be described. As shown in FIG. 1 , in this example, the DUT under test is an electrolysis device configured by electrically connecting multiple electrochemical cells C1 to C5 (hereinafter, referred to as "electrochemical cells C" when not distinguishing between them) in a stacked configuration. While an electrolysis device is actually configured by connecting tens to hundreds of electrochemical cells C in series, for ease of understanding, the DUT under test is illustrated as being configured by electrically connecting five electrochemical cells C1 to C5 in series. In this case, the DUT under test is provided with a pair of input terminals T1 and T2 and terminals (not shown) connected to the connection points of each of the electrochemical cells C and C.

[0045] First Example Next, the configuration of an 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." Furthermore, 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. A measurement current supply line Li is 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 measured 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 wrapping a coil winding around a resin former. The former has a circular cross section and is formed in a donut shape with a slit, allowing for the formation of a freely openable and closable loop (opening 4o). The current sensor 4 measures the AC current Im supplied via the bus bar Bb inserted through the opening 4o as the current to be measured (supplied current value) and outputs current value data indicating the measured current value. The current sensor 4 is not limited to a Rogowski coil type current sensor, and can be selected appropriately 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 DUT 1, and outputs current value data Di1 indicating the current value of measurement AC current Im flowing through DUT 1. Current sensor 4-2 is attached to bus bar Bb connecting power supply device PD and DUT 2, and outputs current value data Di2 indicating the current value of measurement AC current Im flowing through DUT 2. Current sensor 4-3 is attached to bus bar Bb connecting power supply device PD and DUT 3, and outputs current value data Di3 indicating the current value of measurement AC current Im flowing through DUT 3. Current sensor 4-p is attached to bus bar Bb connecting power supply device PD and each DUT, and outputs current value data DiP indicating the current value of measurement AC current Im flowing through power supply PD. In the following description, 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 a high gain characteristic CHGC and a flat phase characteristic CHPC. In other words, 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 the gain characteristic CHGC and phase characteristic 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 clamping a conductor such as a coated metal conductor in a non-contact manner. 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 non-contact current sensor configured to be able to release (open and close) the clamp on the clamped conductor by operating an operation unit (not shown) to bring the magnetic cores 4a and 4b close to each other and to separate the magnetic cores 4a and 4b from each other. 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 Figure 1, when the measurement current supply line Li is inserted through the opening 4d, the current sensor 4-m outputs the current values ​​of all of the measurement AC currents Im output from the measurement current supply unit 2 as current value data DiO. That is, in the state shown in Figure 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. Furthermore, 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 non-openable using an annular core, can also 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 overall. 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 DUT 1 is used as the measurement target, the processing unit 5 calculates the current value (I: supply current value) of the measurement AC current Im flowing through the measurement target DUT 1 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 of the AC voltage across the measurement target DUT 1 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 DUT 1 and the AC voltage generated across the measurement target DUT 1, 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·cos θ, X=Z·sin θ) of the DUT 1, which is the object to be measured, 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 non-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 the current value of the measurement AC current Im flowing through the DUT to be measured to be measured with high accuracy. 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 the current sensor 4-1, it outputs a voltage output SI1 proportional to the magnitude of the current value I1. The transfer characteristic of the current sensor 4-1 at this time is "G1". When a current value Ip flows through the current sensor 4-p, it outputs a voltage output SIp proportional to the magnitude of the current value Ip. The transfer characteristic of the current sensor 4-p at this time is "Gp". At this time, the voltage output of each current sensor 4 is expressed by the following equation. In this case, "G1" and "Gp" mean complex transimpedances. SI1 = G1·I1 SIp = Gp·Ip

[0060] Furthermore, current sensors with the same gain and phase characteristics are used for current sensor 4-1 and current sensor 4-p. 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 equations: 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, since the current value Io is an accurate and known value, the current value I1 flowing through the DUT 1 can be accurately calculated (measured) using the following equation (1): I1 = SI1 / (SI1 + SIp) × Io (1)

[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) x Io (2)

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

[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, so it can be seen that equation (1) is the 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 DUT 1 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 seen that even in the low-frequency band of the measurement AC current Im, the current value I1 of the measurement AC current Im flowing through the measurement target DUT 1 can be accurately measured based on the current values ​​measured by current sensor 4-1, current sensor 4-p, and current sensor 4-m.

[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 target DUT1 connected in parallel, measured by current sensor 4-1, by the sum (sum) of the 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 greater than or equal to 2) 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 measurement target DUTj, current sensor 4j is a current sensor 4 that measures the measurement AC current Im supplied to measurement target DUTj and outputs the current value of the measurement AC current Im flowing through 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 measurement targets DUT1 to DUTn are not distinguished, they are also referred to as "measurement targets DUT." 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 DUTs 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 dividing 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 DUTs measured by the N current sensors 4, respectively, and the current value (measurement value) of the measurement AC current Im for the power supply device PD as a non-measurement target measured by current sensor 4-p, and multiplying this value by the current value Io (sum) of the measurement AC current Im measured by current sensor 4-m, which is the second current sensor.

[0068] Therefore, when calculating the impedance of one DUTj under test, the processing unit 5 uses the current value determined for the DUTj under test as the above-mentioned current value (I) for that DUTj under test. The processing unit 5 also calculates the impedance of one 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 measurement AC current Im flowing through the DUTj under test and the voltage V1 across the DUTj under test. As a result, the processing unit 5 can accurately measure the current value of the measurement AC current Im 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), the processing unit 5 outputs a frequency control signal Sf to the measurement current supply unit 2 to sweep the frequency of the measurement AC current Im between a low frequency band and a high frequency band. The processing unit 5 also outputs display data Dd to the 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. The 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 the 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 AC voltage as a voltage across terminals T, T when a measurement AC current Im 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 measurement AC current Im.

[0072] Next, a current measurement method for measuring (calculating) the measurement AC current Im flowing through a DUT under test and an impedance measurement method for measuring (calculating) the impedance of the DUT under test using the impedance measurement device 1 will be described with reference to the drawings. 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 power supply PD. Specifically, current sensor 4-1 is attached to the bus bar Bb connecting power supply PD and DUT under test 1, current sensor 4-2 is attached to the bus bar Bb connecting power supply PD and DUT under test 2, current sensor 4-3 is attached to the bus bar Bb connecting power supply PD and DUT under test 3, and current sensor 4-p is attached to the bus bar Bb connecting power supply PD and each DUT under test. Furthermore, 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 current sensor 4-m. Next, when the measurement target DUT1 is the measurement target, probe P1 is connected (contacted) to bus bar Bb connected to input terminal T1 of measurement target DUT1, and probe P2 is connected (contacted) to bus bar Bb connected to input terminal T2 of measurement target 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. 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] 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 inputs 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 DUT 1 based on the input current value data Di1 to Di3, DiP, DiO and voltage value data Dv.

[0079] In this case, the processing unit 5 first calculates the current value (I) flowing through the DUT 1 under test. Specifically, based on the current value data Di1 to Di3, DiP, and DiO, the processing unit 5 calculates the current values ​​I1 to I3 of the measurement AC current Im flowing through each of the DUTs under test 1 to DUT 3, 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. The processing unit 5 also calculates the voltage V1 across the DUT 1 under test based on the voltage value data Dv. In this case, the current values ​​I1 to I3, Ip, Io, and the voltage V1 are all expressed as complex numbers.

[0080] Next, in accordance with the above equation (4), the processing unit 5 calculates a current value (I: supply current value) for the DUT 1 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 DUT 1 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 DUT 1 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 at multiple frequencies as described above. Next, the processing unit 5 acquires the frequency characteristics of the impedance of the DUT 1 at multiple frequencies. In this case, the processing unit 5 acquires, as frequency characteristics, Cole-Cole plots showing the impedance characteristics of the DUT 1 with respect to frequency, and Bode plots 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 the measured impedances of the DUT 1 and the acquired Cole-Cole plots and Bode plots. The processing unit 5 also outputs measurement data Dm to the recording unit 7, recording the acquired Cole-Cole plots and Bode plots. This completes the impedance measurement process of the DUT 1, which is the measurement target, performed by the processing unit 5. Similarly, when measuring the impedance of another DUT under test, the processing unit 5 executes the same impedance measurement process as described above.

[0082] In this embodiment, an electrolysis device is used as the DUT under test, and the power supply device PD that supplies power to the DUT under test is used as the non-measurement object. However, the DUT under test can also be a fuel cell in which multiple power generation cells are electrically connected in series to form a stack, or a lithium-ion battery or lead-acid battery in which multiple battery cells are electrically connected in series to form a stack, and various loads such as power supply devices such as inverters and converters, and electronic devices can be used as the non-measurement object. Furthermore, various power generation devices, such as fuel cells, whether in operation or not, can be used 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 measurement device 10 and current measurement method, the total 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 ​​for the three measurement targets DUT1 (measured values ​​for each of current values ​​I1 to I3) measured by current sensor 4 and the current value for the power supply device PD measured by current sensor 4-p (measured value for current value Ip), and the supply current value (current value I1) for one measurement target DUT1 is measured by multiplying this value by the total sum (current value Io) of the measurement AC currents Im measured by current sensor 4-m.

[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 measurement device 10 and current measurement method, (N+1) current sensors 4 (four in this example) are arranged on each bus bar Bb connecting the measurement current supply unit 2 to 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 measurement device 10 and current measurement method, current values ​​I1 to I3 of the measurement AC current Im flowing through each of the DUTs under test 1 to DUT 3 and current value Ip of the measurement AC current Im flowing through the power supply device PD can be measured simultaneously, thereby eliminating measurement errors caused by changes over time in the measurement of the measurement AC current Im flowing through each of the DUTs under test and the power supply device PD, and as a result, current value I1 flowing through the DUT under test 1 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 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.

[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 DUT 1, 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 the current value I1 of the measurement AC current Im flowing through the measurement target DUT 1 can be measured with high accuracy, and as a result, the impedance of the measurement target DUT 1 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, in 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 (device under test). Therefore, in 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, allowing the current value Io of the measurement AC current Im to be measured 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 deterioration 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 to be measured 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 Embodiment Next, an 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 denoted by 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 to operate the measurement current output unit 2A as an AC load. At this time, the measurement current output unit 2A consumes the DC current output from the power supply device PD as a load in accordance with the frequency control signal Sf, 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, as with 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, since the measurement current output section 2A is configured as an electronic load, 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 measurement 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 DUT under test, and to accurately measure (calculate) the impedance of the DUT under test.

[0099] The present invention is not limited to the above-described embodiment and can be modified as appropriate. For example, in the above-described embodiment, 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, a single current sensor 4 can be used to sequentially measure the current value of the measurement AC current Im flowing through each DUT and 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 a clamp-type non-contact current sensor configured to be openable and closable, but the current sensor 4-m can also be configured using a shunt resistor or a current sensor configured to be non-openable and closable using 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 was described in which a single Rogowski coil-type current sensor was used for each of the current sensors 4-1 to 4-3, 4-p, but this is not limited to this. 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 overall current sensor 4. In this case, the gain characteristics and phase characteristics of each of the current sensors 4-1 to 4-3, 4-p, each composed of multiple current sensors, are specified to be 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, C that constitute 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.

[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.

[0105] REFERENCE SIGNS LIST 1 Impedance measuring device 2 Measurement current supply unit 3 Voltage measuring unit 4-1 to 4-3, 4-m, 4-p Current sensor 5 Processing unit 7 Recording unit 10 Current measuring device Bb Bus bar C1 to C5 Electrochemical cells Di1 to Di3, DiO, DiP Current value data DUT1 to DUT3 Measurement object Dv Voltage value data PD Power supply device

Claims

1. A current measuring device comprising: N (N is an integer of 1 or more) measurement objects and non-measurement objects connected in parallel via connection lines, with measurement object currents being supplied to each of the measurement objects and non-measurement objects via the connection lines; a non-contact first current sensor capable of inserting the connection lines into an opening and measuring the measurement object current flowing through the connection lines; and a processing unit that calculates a supply current value of the measurement object current being supplied to one of the N measurement objects based on the measurement value of the first current sensor; and a second current sensor that measures the sum of the measurement object currents supplied to the N measurement objects and the non-measurement objects, and the first current sensor is an air-core AC current sensor that can measure AC currents, and measures the measurement object currents supplied to each of the N measurement objects and the measurement object currents supplied to the non-measurement objects, 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. The current measuring device according to claim 1, comprising (N+1) first current sensors configured to have the same characteristics, and the (N+1) first current sensors respectively measure the currents flowing through the N objects to be measured and the N non-objects to be measured.

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

5. A current measuring device according to any one of claims 1 to 4, which 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. A current measuring device according to claim 5, wherein the object to be measured is constructed by stacking electrolytic cells as the electrochemical cells, and the current measuring device measures the object to be measured current flowing through the object to be measured in an operating state by utilizing power output from a power source as the object not to be measured.

7. A current measuring device as described in claim 5, wherein the object to be measured is configured by stacking cells, either fuel cells or battery cells, as the electrochemical cells, and the current measuring device measures the object to be measured current flowing through the object to be measured when the power output from the object to be measured is consumed by a load, as the non-object to be measured.

8. An impedance measuring device comprising: 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 measurement object current to the N measurement objects and the non-measurement objects via the connection lines; and a voltage measuring unit that measures the voltage across both ends of one measurement object, wherein 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 voltage across both ends of the one measurement object measured by the voltage measuring unit.

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

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

11. An impedance measuring device according to claim 8, wherein 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 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 object to be measured.

12. The impedance measuring device according to claim 11, wherein the processing unit acquires either a Cole-Cole plot or 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. A current measurement method 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 connection lines are inserted into an opening of a first current sensor to measure the object to be measured current flowing through the connection lines, and the supply current value of the object to be measured current supplied to one of the N objects to be measured based on the measurement value by the first current sensor, wherein the sum of the object to be measured currents supplied to the N objects to be measured and the object to be measured current supplied to the object to be measured is measured by a second current sensor, and the object to be measured current supplied to each of the N objects to be measured and the object to be measured current supplied to the object to be measured is measured by the first current sensor, which is 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 measurement method according to claim 14, wherein 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.

16. A 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. A 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. A current measurement method according to any one of claims 14 to 17, wherein the current flowing through the object to be measured is measured, the object being configured by electrically connecting electrochemical cells that cause electrochemical reactions in series.

19. A current measurement method as claimed in claim 18, wherein the measurement object is a device constructed by stacking electrolytic cells as the electrochemical cells, and the measurement object current flowing through the measurement object in an operating state is measured using power output from a power source as the non-measurement object.

20. A current measurement method as claimed in claim 18, wherein the measurement object is a device constructed by stacking either fuel cell cells or battery cells as electrochemical cells, and the measurement object current flowing through the measurement object is measured when the power output from the measurement object is consumed by a load as the non-measurement object.

21. An impedance measurement method comprising: 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 lines; executing the current measurement method according to any one of claims 14 to 17; measuring a voltage across both ends of one object-of-measurement; and measuring the impedance of the one object-of-measurement based on the calculated supply current value for the one object-of-measurement and the measured voltage across the one object-of-measurement.

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. The impedance measuring method according to claim 21, wherein the frequency characteristics of the impedance of the object to be measured are obtained by varying the frequency of the measuring current.

25. The impedance measuring method according to claim 24, wherein either a Cole-Cole plot or 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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