Display device, impedance measurement device, and display method

Abstract

Provided is a display device capable of accurately grasping an operating state or performance evaluation of a measurement subject by utilizing a current-voltage characteristic graph or the like.　The display device comprises a processing unit 4 for causing a display screen to display at least one characteristic graph among: a current-voltage characteristic graph indicating the characteristic of a voltage value of a direct current voltage between terminals T1, T2 with respect to a current value of a direct current inputted / outputted through a measurement subject DUT1 via the terminals; a current-power characteristic graph indicating the characteristic of a power value of power inputted / outputted via the terminals with respect to the current value of the direct current that is inputted / outputted; and a current-impedance characteristic graph indicating the characteristic of the impedance of the measurement subject DUT1 with respect to the current value of the direct current that is inputted / outputted. When one measurement point among a plurality of measurement points on one characteristic graph displayed on the display screen is selected, the processing unit 4 displays, on the display screen, a Cole–Cole plot of the measurement subject DUT1 when a direct current of a current value corresponding to the selected measurement point is flowing.

Description

Display device, impedance measuring device and display method

[0001] The present invention relates to a display device and display method suitable for understanding the operating state and performance evaluation of a measurement object, using at least one of a current-voltage characteristic graph (a characteristic graph showing the relationship between the current values ​​of input and output currents and the voltage values ​​of input and output voltages; hereinafter also referred to as an "IV characteristic graph"), a current-power characteristic graph (a characteristic graph showing the relationship between the current values ​​of input and output currents and the power values ​​of input and output power; hereinafter also referred to as an "IP characteristic graph"), and a current-impedance characteristic graph (a characteristic graph showing the relationship between the current values ​​of input and output currents and the impedance of the measurement object; hereinafter also referred to as an "IZ characteristic graph") obtained from the measurement object, such as a fuel cell or an electrolysis apparatus (hereinafter also referred to as an "electrolysis apparatus"). The present invention also relates to an impedance measuring apparatus equipped with the display device.

[0002] For example, a method for determining the performance of a fuel cell as a measurement target is known, as disclosed in Patent Document 1 below. This method measures each current value of the direct current output from the fuel cell and the voltage value of the output voltage of the fuel cell when the direct current is output at each current value, and uses an IV characteristic graph that shows the relationship between the voltage value and the current value, created based on the measured values. Specifically, an IV characteristic graph obtained at the initial manufacturing stage of the fuel cell is compared with an IV characteristic graph obtained from a fuel cell that has deteriorated over time through use, and a determination is made that the fuel cell has deteriorated if there is a large decrease in the average output voltage of the fuel cell.

[0003] JP 2022-155485 A (pages 4-15, Figure 7)

[0004] As described above, the degradation characteristics of a fuel cell can be evaluated using an IV characteristic graph. However, in order to fully evaluate the performance of a fuel cell, many other evaluation factors are required in addition to the degradation characteristics described above. For example, when maximizing the output efficiency, a fundamental evaluation factor for a fuel cell, it is generally considered preferable to operate the fuel cell at an operating point with a larger output current and a higher output voltage. However, it is difficult to determine whether a fuel cell is operating in an optimal state simply by using an IV characteristic graph. Specifically, for example, if the water content of the electrolyte membrane in the fuel cell is insufficient, if there is an excess or deficiency of the platinum catalyst used in the fuel cell, or if there is an excess or deficiency of oxygen or hydrogen supplied to the fuel cell, it becomes difficult to operate the fuel cell in a state with sufficient output efficiency. However, it is extremely difficult to determine the actual operating state of the fuel cell at each measurement point on the IV characteristic graph simply by using an IV characteristic graph. For this reason, there is a need for an apparatus and method that can fully understand the operating state and performance evaluation of a measurement object such as a fuel cell using an IV characteristic graph.

[0005] Furthermore, there are numerous evaluation factors for fully evaluating the performance of an electrolysis device. For example, when it is desired to maximize output efficiency, a fundamental evaluation factor for an electrolysis device, it is generally considered preferable to operate the device at an operating point that allows the greatest output of hydrogen and oxygen. However, it is difficult to determine whether an electrolysis device is operating at an optimal operating state simply by using an IV characteristic graph. Specifically, for example, if the water content of the electrolyte membrane in the electrolysis device is insufficient, if there is an excess or deficiency of the platinum catalyst or iridium catalyst used in the electrolysis device, or if there is an excess or deficiency in the amount of water supplied to the electrolysis device, it becomes difficult to operate the electrolysis device at a state where output efficiency is sufficient. However, it is extremely difficult to determine the actual operating state of the electrolysis device at each measurement point on the IV characteristic graph simply by using an IV characteristic graph. For this reason, there is a need for a device or method that can fully grasp the operating state and performance evaluation of a measurement object, such as an electrolysis device, using an IV characteristic graph. Similarly, there is a need for a device or method that can fully grasp the operating state and performance evaluation of a fuel cell or electrolysis device using an IP characteristic or an IZ characteristic.

[0006] The present invention has been made in consideration of these problems, and its main object is to provide a display device, an impedance measuring device, and a display method that make it possible to accurately grasp the operating state and performance evaluation of the object to be measured using a current-voltage characteristic graph or the like.

[0007] In order to achieve the above object, the display device of the present invention is a display device that includes a processing unit that displays on a display screen at least one of the following characteristic graphs: a current-voltage characteristic graph that shows the characteristic of the voltage value of the DC voltage between a pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; a current-power characteristic graph that shows the characteristic of the power value of the power input / output via the pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; and a current-impedance characteristic graph that shows the characteristic of the impedance of the object to be measured versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; and when one of a plurality of measurement points on one characteristic graph displayed on the display screen is selected, the processing unit displays on the display screen a Cole-Cole plot of the object to be measured when the DC current of the current value corresponding to the selected measurement point is flowing.

[0008] Furthermore, in order to achieve the above-mentioned object, the display method of the present invention displays at least one of the following characteristic graphs on a display screen: a current-voltage characteristic graph showing the characteristic of the voltage value of the DC voltage between a pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; a current-power characteristic graph showing the characteristic of the power value of the power input / output via the pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; and a current-impedance characteristic graph showing the characteristic of the impedance of the object to be measured versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; and when one of a plurality of measurement points on one characteristic graph displayed on the display screen is selected, a Cole-Cole plot of the object to be measured when the DC current of the current value corresponding to the selected measurement point is flowing is displayed on the display screen.

[0009] Furthermore, in order to achieve the above-mentioned object, a display device according to the present invention is a display device including a processing unit that displays on a display screen at least one of a current-voltage characteristic graph showing the characteristics of the voltage value of the DC voltage between a pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, a current-power characteristic graph showing the characteristics of the power value of the power input / output via the pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, and a current-impedance characteristic graph showing the characteristics of the impedance of the object to be measured versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, wherein the processing unit displays on the display screen a plurality of Cole-Cole plots of the object to be measured when the DC current is flowing, each of which has a current value corresponding to a plurality of measurement points on the single characteristic graph, and when one of the plurality of measurement points on the single characteristic graph displayed on the display screen is selected, the Cole-Cole plot corresponding to the selected measurement point is highlighted.

[0010] Furthermore, in order to achieve the above-mentioned object, a display method according to the present invention displays at least one of the following characteristics graphs on a display screen: a current-voltage characteristics graph showing the characteristics of the voltage value of the DC voltage between a pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; a current-power characteristics graph showing the characteristics of the power value of the power input / output via the pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; and a current-impedance characteristics graph showing the characteristics of the impedance of the object to be measured versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; the display screen displays a plurality of Cole-Cole plots of the object to be measured when a DC current flows, each of which has a current value corresponding to a plurality of measurement points on the single characteristics graph; and when one of the plurality of measurement points on the single characteristics graph displayed on the display screen is selected, the Cole-Cole plot corresponding to the selected measurement point is highlighted.

[0011] These display devices and display methods allow a user to select a measurement point on a characteristics graph, and thereby display each measurement point on the characteristics graph in conjunction with a Cole-Cole plot corresponding to that measurement point. Therefore, these display devices and display methods allow a user to accurately grasp the operating state and performance evaluation of the object to be measured by displaying the characteristics graph and the Cole-Cole plot in conjunction with each other.

[0012] An impedance measuring device according to the present invention includes the display device described above, an AC voltage measuring unit, and an AC current measuring unit, wherein the AC voltage measuring unit measures the voltage value of the AC voltage generated across the pair of terminals due to the measurement AC current flowing through the object to be measured, the AC current measuring unit measures the current value of the measurement AC current flowing through the object to be measured, and the processing unit acquires, at each measurement point where the current value of the DC current changes, the frequency characteristics of the complex impedance of the object to be measured, for displaying the Cole-Cole plot on the display screen, based on the frequency of the measurement AC current, the voltage value of the AC voltage measured by the AC voltage measuring unit, and the current value of the measurement AC current measured by the AC current measuring unit. Thus, in addition to the function of displaying the Cole-Cole plot, this impedance measuring device can also generate display data for displaying the Cole-Cole plot based on the frequency characteristics of the complex impedance of the object to be measured.

[0013] An impedance measuring device according to the present invention includes a DC current measuring unit and a DC voltage measuring unit, wherein the DC current measuring unit measures the current value of the DC current superimposed on the measurement AC current when the DC current inputs and outputs the DC current to and from the object to be measured, and the DC voltage measuring unit measures the voltage value of the DC voltage generated across the pair of terminals in response to a change in the current value of the DC current when the DC current superimposed on the measurement AC current inputs and outputs the DC current to and from the object to be measured via the pair of terminals, and the processing unit acquires display data for displaying at least one of the I-V characteristic graph and the I-P characteristic graph on the display screen based on the current value of the DC current measured by the DC current measuring unit and the voltage value of the DC voltage measured by the DC voltage measuring unit. Thus, this impedance measuring device not only has the function of displaying a Cole-Cole plot and the function of generating display data for displaying a Cole-Cole plot, but also can generate display data for displaying at least one of an I-V characteristic graph and an I-P characteristic graph.

[0014] Furthermore, an impedance measuring device according to the present invention includes a DC current measuring unit that measures the current value of the DC current on which the measurement AC current is superimposed when the DC current inputs and outputs the DC current to and from the object to be measured, and the processing unit acquires display data for displaying the IZ characteristics graph on the display screen based on the current value of the DC current measured by the DC current measuring unit and the frequency characteristics of the acquired complex impedance of the object to be measured. Thus, this impedance measuring device can generate display data for displaying an IZ characteristics graph in addition to the function of displaying a Cole-Cole plot and the function of generating display data for displaying the Cole-Cole plot.

[0015] The impedance measuring device according to the present invention also includes an AC current generating unit that generates the measurement AC current and superimposes it on the DC current. Therefore, this impedance measuring device can measure (calculate) the impedance of an object to be measured that supplies a DC current to a load that cannot output the measurement AC current, or that receives a DC current from a DC power supply that cannot output the measurement AC current, and can display a characteristic graph and a Cole-Cole plot of the object to be measured.

[0016] Furthermore, the impedance measuring device according to the present invention includes a non-contact current sensor that measures the current value of the DC current flowing through the object to be measured. Therefore, this impedance measuring device can prevent the internal mechanism of the current sensor from coming into contact with a power supply line or the like, making it possible to measure the current value of the DC current extremely safely.

[0017] In addition, in the impedance measuring device according to the present invention, the current sensor is a clamp-type current sensor that is configured to be able to open and close, and therefore, with this impedance measuring device, the current value of a DC current can be measured reliably and quickly while a power line remains connected between the measurement target and a load, etc.

[0018] The impedance measuring device according to the present invention also includes a non-contact current sensor that measures the current value of the measurement AC current flowing through the measurement object. Therefore, this impedance measuring device can prevent the internal mechanism of the current sensor from coming into contact with power lines, etc., and can therefore measure the current value of the measurement AC current extremely safely.

[0019] In addition, in the impedance measuring device according to the present invention, the current sensor is a clamp-type current sensor that is configured to be openable and closable, and therefore, with this impedance measuring device, the current value of the measurement AC current can be measured reliably and quickly while a power line remains connected between the measurement target and a load, etc.

[0020] The display device, impedance measuring device, and display method according to the present invention allow a user to select a measurement point on a characteristics graph, and thereby display each measurement point on the characteristics graph in conjunction with a Cole-Cole plot corresponding to that measurement point. Therefore, the display device, impedance measuring device, and display method allow a user to accurately grasp the operating state and performance evaluation of the object to be measured by displaying the characteristics graph and the Cole-Cole plot in conjunction with each other.

[0021] 1 is a diagram showing the configuration of an impedance measuring apparatus 1. FIG. 2 is a diagram showing the configuration of an impedance measuring apparatus 1A. FIG. 3 is a diagram showing the configuration of an impedance measuring apparatus 1B. FIG. 4 is a diagram showing the configuration of an impedance measuring apparatus 1C. FIG. 5 is a diagram showing a display screen in which an IV characteristic graph is displayed on an output unit 6 when a fuel cell is the measurement target DUT 1. FIG. 6 is an explanatory diagram showing a Cole-Cole plot corresponding to measurement point Po1 in the IV characteristic graph when a fuel cell is the measurement target DUT 1, and a Cole-Cole plot corresponding to measurement point Po11 in the IV characteristic graph when an electrolysis device is the measurement target DUT 2. FIG. 7 is an explanatory diagram showing a Cole-Cole plot corresponding to measurement point Po2 in the IV characteristic graph when a fuel cell is the measurement target DUT 1, and a Cole-Cole plot corresponding to measurement point Po12 in the IV characteristic graph when an electrolysis device is the measurement target DUT 2. 1 is an explanatory diagram showing a Cole-Cole plot corresponding to measurement point Po3 on an IV characteristics graph when a fuel cell is the measurement target DUT 1, and a Cole-Cole plot corresponding to measurement point Po13 on an IV characteristics graph when an electrolytic device is the measurement target DUT 2. FIG. 1 is an explanatory diagram showing a Cole-Cole plot corresponding to measurement point Po4 on an IV characteristics graph when a fuel cell is the measurement target DUT 1, and a Cole-Cole plot corresponding to measurement point Po14 on an IV characteristics graph when an electrolytic device is the measurement target DUT 2. FIG. 2 is a display screen diagram showing an IV characteristics graph when a fuel cell is the measurement target DUT 1, and a Cole-Cole plot corresponding to measurement point Po2 on the IV characteristics graph, displayed on output unit 6. FIG. 3 is a display screen diagram showing an IV characteristics graph when a fuel cell is the measurement target DUT 1, and a Cole-Cole plot corresponding to measurement point Po3 on the IV characteristics graph, displayed on output unit 6. FIG. 4 is an explanatory diagram for explaining the Cole-Cole plots of measurement target DUT 1 (fuel cell) and measurement target DUT 2 (electrolytic device). 1 is a diagram of a display screen in which an IP characteristics graph when a fuel cell is used as the measurement object DUT 1 is displayed on the output unit 6. FIG. 2 is a diagram of a display screen in which an IP characteristics graph when a fuel cell is used as the measurement object DUT 1 and a Cole-Cole plot corresponding to measurement point Po3 on the IP characteristics graph are displayed on the output unit 6.FIG. 1 is a display screen diagram showing an IZ characteristic graph displayed on the output unit 6 when a fuel cell is the DUT 1 under test. FIG. 1 is a display screen diagram showing an IZ characteristic graph displayed on the output unit 6 when a fuel cell is the DUT 1 under test, and a Cole-Cole plot corresponding to measurement point Po3 on the IZ characteristic graph. FIG. 2 is a display screen diagram showing an IV characteristic graph displayed on the output unit 6 when a fuel cell is the DUT 1 under test, and a single Cole-Cole plot obtained by superimposing four Cole-Cole plots corresponding to measurement points Po1 to Po4 on the IV characteristic graph. FIG. 3 is a display screen diagram showing an IV characteristic graph displayed on the output unit 6 when a fuel cell is the DUT 1 under test, and a Cole-Cole plot corresponding to measurement point Po3 on the IV characteristic graph that is highlighted on the output unit 6. FIG. 4 is a display screen diagram showing an IV characteristic graph displayed on the output unit 6 when an electrolysis device is the DUT 2 under test. FIG. 5 is a display screen diagram showing an IP characteristic graph displayed on the output unit 6 when an electrolysis device is the DUT 2 under test. FIG. 10 is a display screen diagram showing an IZ characteristics graph when the DUT 2 under measurement is an electrolytic device, displayed on the output unit 6. FIG. 11 is a display screen diagram showing an IV characteristics graph when the DUT 2 under measurement is an electrolytic device, and a Cole-Cole plot corresponding to measurement point Po3 on the IV characteristics graph, displayed (or highlighted) on the output unit 6. FIG. 10 is a display screen diagram showing an IV characteristics graph when the DUT 2 under measurement is an electrolytic device, and a single Cole-Cole plot formed by superimposing four Cole-Cole plots corresponding to measurement points Po11 to Po14 on the IV characteristics graph, displayed on the output unit 6.

[0022] Hereinafter, embodiments of a display device, an impedance measuring device, and a display method will be described with reference to the accompanying drawings.

[0023] The impedance measuring device 1 shown in FIG. 1 is an example of an impedance measuring device that performs an impedance measurement method. It is configured to measure the impedance of a measurement object, such as a fuel cell that generates electricity from supplied oxygen or hydrogen, or a water electrolysis device (electrolysis device) that operates using a large DC current as a driving current to generate large amounts of hydrogen or oxygen. The impedance measuring device 1 also acquires an IV characteristic graph (a characteristic graph showing the relationship between the voltage values ​​of input and output voltages and the current values ​​of input and output currents), an IP characteristic graph (a characteristic graph showing the relationship between the power values ​​of input and output power and the current values ​​of input and output currents), and an IZ characteristic graph (a characteristic graph showing the relationship between the impedance of the measurement object DUT and the current values ​​of input and output currents; hereinafter, when the three graphs are not distinguished, they are also referred to as "characteristic graphs") for the measurement object, and also acquires Cole-Cole plots corresponding to measurement points on each characteristic graph. The impedance measuring device 1 is also configured to display the acquired characteristic graphs and Cole-Cole plots when determining the operating state of the measurement object or evaluating the performance of the measurement object.

[0024] First, an example will be described in which a fuel system is used as the measurement target DUT 1. In this case, the measurement target DUT 1 has a pair of input terminals, i.e., a positive terminal T1 and a negative terminal T2, connected to the positive and negative input terminals of a load LD1 via a pair of power supply lines Lp, respectively. The load LD1 supplies (outputs) a DC current generated based on supplied oxygen and hydrogen to the load LD1. The load LD1 is configured as an electrical device or the like, and consumes the DC current output from the measurement target DUT 1 and is configured to superimpose a sinusoidal AC signal (measurement AC current Im) used to measure the impedance of the measurement target DUT 1 onto the DC current. The load LD1 sweeps (varies) the frequency of the AC signal (measurement AC current Im) and outputs it in accordance with a frequency control signal Sf1 output from an external device (in this example, a processing unit 4, described later).

[0025] Next, we will explain the configuration of the impedance measuring device 1. As shown in Fig. 1, the impedance measuring device 1 is configured with a voltage measurement unit 2, a current sensor 3, a processing unit 4, a memory 5, an output unit 6, and voltage detection probes P1 and P2. The processing unit 4, memory 5, and output unit 6 configure a display device 10.

[0026] The voltage measurement unit 2 functions as a DC voltage measurement unit and an AC voltage measurement unit. As shown in FIG. 1 , the voltage measurement unit 2 is configured to be able to measure the voltage of signals ranging from DC to high frequency, measures the value of a voltage V1 input via a pair of probes P1, P2 connected to terminals T1, T2 of the DUT under test, and outputs voltage value data Dv indicating the measured value (the voltage across terminals T1, T2) to the processing unit 4. In this case, when a measurement AC current Im flows through the DUT under test 1, the voltage measurement unit 2 measures the value of an AC voltage generated across terminals T1, T2 of the DUT under test 1 due to the flow of the measurement AC current Im.

[0027] The current sensor 3 functions as a DC current measuring unit and an AC current measuring unit. The current sensor 3 can be, for example, a current sensor such as that disclosed in Japanese Patent Application Laid-Open No. 2014-235045. It is configured as a clamp-type ammeter capable of non-contact clamping of a conductor such as a coated metal conductor. Specifically, the current sensor 3 includes two semicircular magnetic cores 3a and 3b and a magnetic detection element 3c, such as a Hall element or a fluxgate element. By operating an operating unit (not shown), the magnetic cores 3a and 3b are brought close to each other to form an annular opening 3d, through which the conductor can be clamped (inserted). By operating the operating unit to move the magnetic cores 3a and 3b apart from each other, the current sensor 3 functions as a clamp-type non-contact current sensor that can release (open and close) the clamped conductor. In addition, in this current sensor 3, the magnetic detection element 3c detects the magnetic flux generated in the magnetic cores 3a and 3b when a current flows through the conductor inserted through the opening 3d, thereby measuring (detecting) the current value of the current flowing through the conductor at frequencies ranging from DC to high frequencies, and outputting current value data Di indicating the measured current value. However, the current sensor 3 may be configured to use two current sensors: one type that can measure the current value of DC current, and another type that can measure the current value of high-frequency signals other than DC. Furthermore, instead of a clamp-type current sensor, the current sensor 3 may be configured to use a current sensor that cannot be opened or closed using an annular core.

[0028] The processing unit 4 is configured by, for example, a CPU, and performs overall control of the impedance measuring device 1. Specifically, the processing unit 4 acquires the above-mentioned three types of characteristic graphs and Cole-Cole plots to be displayed in association with each characteristic graph (hereinafter also referred to as "linked display"). Specifically, the processing unit 4 acquires display data Dd for displaying an I-V characteristic graph showing the characteristics of the voltage value of the DC voltage between the pair of terminals T1 and T2 versus the current value of the DC current input / output to / from the DUT1 via the pair of terminals T1 and T2 (in this example, output from the DUT1), an I-P characteristic graph showing the characteristics of the power value of the power input / output to / from the pair of terminals T1 and T2 (in this example, output from the DUT1) versus the current value of the DC current input / output to / from the DUT1 via the pair of terminals T1 and T2 (in this example, output from the DUT1), and an I-Z characteristic graph showing the characteristics of the impedance of the DUT1 versus the current value of the DC current input / output to / from the DUT2 via the pair of terminals T1 and T2 (in this example, output from the DUT1), and also acquires display data Dd for displaying a Cole-Cole plot as described below.

[0029] In this case, the processing unit 4 acquires display data Dd for displaying an I-V characteristic graph or an I-P characteristic graph by acquiring each current value of the DC current output from the DUT 1 measured by the current sensor 3 and each voltage value of the DC voltage measured by the voltage measurement unit 2 when the DC current of each current value is being output. The processing unit 4 also acquires each current value of the DC current output from the DUT 1 measured by the current sensor 3 and a Cole-Cole plot for the DUT 1 when the DC current of each current value is being output, and acquires display data Dd for displaying an I-Z characteristic graph by correlating each current value with the impedance (low frequency impedance (LFR: Low Frequency Resistance; hereinafter also referred to as "LFR") or high frequency impedance (HFR: High Frequency Resistance; hereinafter also referred to as "HFR")) in the Cole-Cole plot acquired at each current value. Although an example in which an IZ characteristic graph is displayed using LFR as impedance will be described below, an IZ characteristic graph may also be displayed using HFR as impedance.

[0030] Furthermore, when acquiring the Cole-Cole plot, the processing unit 4 changes the frequency of the measurement AC current Im by outputting a frequency control signal Sf1 to the load LD1 at each time point (measurement point) when the current value of the DC current output from the DUT 1 changes. Then, when the measurement AC current Im is output at each frequency, the processing unit 4 calculates the complex impedance of the DUT 1 based on each voltage value of the AC voltage (the AC voltage generated across the terminals T1 and T2 of the DUT 1 due to the flow of the measurement AC current Im) measured by the voltage measurement unit 2 and each current value of the measurement AC current Im measured by the current sensor 3. Furthermore, the processing unit 4 acquires the frequency characteristic of the complex impedance of the DUT 1 to display a Cole-Cole plot on the display screen of the output unit 6 based on the frequency of the measurement AC current Im and the complex impedance calculated at that frequency.

[0031] During impedance measurement, the processing unit 4 outputs a frequency control signal Sf1 to control the load LD1 to sweep the frequency of the measurement AC current Im and output the AC current Im superimposed on the DC current. The processing unit 4 also controls the voltage measurement unit 2 to measure the voltage between the probes P1 and P2 and output voltage value data Dv, and controls the current sensor 3 to measure the current flowing through the power supply line Lp (in this example, between the terminals T1 and T2) inserted into the opening 3d of the current sensor 3 and output current value data Di. The processing unit 4 also inputs the voltage value data Dv output from the voltage measurement unit 2 and the current value data Di output from the current sensor 3. The processing unit 4 then measures (calculates) the impedance of the measurement target DUT 1 (the impedance between the terminals T1 and T2) based on the input voltage value data Dv and current value data Di.

[0032] Specifically, the processing unit 4 calculates the AC voltage (voltage across both ends) between the terminals T1 and T2 of the DUT 1 under test as a voltage value (V) based on the amplitude of the measurement AC current Im (AC voltage) included in the voltage value data Dv, and calculates the current value (I: supply current value) of the measurement AC current Im flowing through the DUT 1 under test based on the amplitude of the AC current included in the current value data Di. The processing unit 4 also calculates the phase difference (θ) between the AC current and the AC voltage, i.e., the phase difference (θ) between the AC voltage generated between the terminals T1 and T2 of the DUT 1 under test and the AC current flowing through the DUT 1 under test, based on the voltage value data Dv and the current value data Di. The processing unit 4 also 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 voltage value (V) of the AC voltage, the current value (I) of the measurement AC current Im, and the phase difference (θ) calculated in this manner.

[0033] The processing unit 4 also stores display data Dd for displaying the acquired characteristic graph and Cole-Cole plot of the DUT 1 under test in the memory 5, and, in accordance with instructions from an operation unit not shown, outputs the display data Dd to display the characteristic graph and Cole-Cole plot on the display screen of the output unit 6. In this case, when one of the multiple measurement points on one characteristic graph displayed on the display screen is selected, the processing unit 4 displays on the display screen of the output unit 6 the Cole-Cole plot of the DUT 1 when a DC current having a current value corresponding to the selected measurement point is being output.

[0034] The memory 5 stores display data Dd for displaying the characteristic graph and Cole-Cole plot of the measurement target DUT 1 acquired by the processing unit 4. Specifically, when a fuel cell is the measurement target DUT 1, the memory 5 stores display data Dd for displaying the acquired characteristic graph (for example, an I-V characteristic graph) on the output unit 6 as shown in Fig. 5, and display data Dd for displaying Cole-Cole plots corresponding to four measurement points Po1 to Po4 (hereinafter, measurement points Po11 to Po14, described later, will also be referred to as "measurement points Po" when not being distinguished) on the I-V characteristic graph on the output unit 6 with the display contents shown in Figs. 6 to 9. Note that the Cole-Cole plot shown in Fig. 6 corresponds to measurement point Po1, the Cole-Cole plot shown in Fig. 7 corresponds to measurement point Po2, the Cole-Cole plot shown in Fig. 8 corresponds to measurement point Po3, and the Cole-Cole plot shown in Fig. 9 corresponds to measurement point Po4. In this case, display data Dd of Cole-Cole plots corresponding to many measurement points on the characteristics graph is actually stored in memory 5, but for ease of understanding, an example will be described in which four Cole-Cole plots are stored corresponding to four measurement points Po on the characteristics graph. Furthermore, when the measurement target is another device such as an electrolysis device, memory 5 stores display data Dd and the like for displaying an IV characteristics graph, an IP characteristics graph, an IZ characteristics graph, and a Cole-Cole plot corresponding to the measurement target.

[0035] The output unit 6 is, for example, configured as a touch panel using a display device (display) such as a liquid crystal panel or an organic EL panel. It inputs the display data Dd output from the processing unit 4 and displays on the screen the impedance of the DUT 1 under test, a characteristic graph of the DUT 1 under test, and Cole-Cole plots to be displayed in conjunction with each characteristic graph. When a measurement point Po on a characteristic graph displayed on the touch panel is touched with a fingertip or the like, the output unit 6 outputs pointing data Dp to the processing unit 4. Note that instead of or in addition to touching the touch panel, various pointing devices can be used to point to the measurement point Po on the characteristic graph. Alternatively, the output unit 6 can be configured as an interface device that communicates data with an external device instead of a display device, and by outputting the display data Dd, the external display device can display the data instead of the display by the output unit 6.

[0036] The probes P1 and P2 are contact-type probes whose tips are connected (contacted) to the terminals T1 and T2 of the measurement target DUT 1, respectively, and which measure the DC voltage output from the measurement target DUT 1 and the AC voltage as the voltage across the terminals T1 and T2 when the measurement AC current Im is output to the measurement target DUT 1.

[0037] Next, with reference to the drawings, we will explain an impedance measurement method for measuring (calculating) the impedance of the DUT 1 to be measured using the impedance measuring device 1, an acquisition method for acquiring a characteristic graph and Cole-Cole plot for the DUT 1 to be measured, and a display method for displaying the characteristic graph and Cole-Cole plot on the output unit 6.

[0038] The measurement target DUT1 and the load LD1 are connected in advance with their positive electrodes and negative electrodes connected with each other via a power supply line Lp.

[0039] First, probes P1 and P2 are connected to terminals T1 and T2 of the DUT 1 under test. One of the pair of power supply lines Lp is then clamped by the current sensor 3. In this case, because the current sensor 3 is non-contact, it is possible to avoid a short circuit with the power supply line Lp, and as a result, it can be safely attached to the power supply line Lp. Furthermore, because the current sensor 3 is a clamp-type current sensor, it can be attached to any position on the power supply line Lp.

[0040] Next, a measurement start switch (not shown) is operated. At this time, a DC current generated by the DUT 1 under test is supplied to the load LD1 via the power supply lines Lp, Lp. In other words, the power supply line Lp is an active line through which a DC current flows. Next, the processing unit 4 outputs a frequency control signal Sf1 to control the load LD1, thereby superimposing a measurement AC current Im (AC voltage) on the DC current supplied from the DUT 1 under test.

[0041] At this time, the voltage measurement unit 2 measures the voltage value (voltage across both ends) of the voltage V1 occurring between the terminals T1 and T2 of the DUT 1 under test, and outputs voltage value data Dv to the processing unit 4. Also, the current sensor 3 measures the current value of the current flowing through the power supply line Lp inserted (clamped) in the opening 3d. In this case, the current sensor 3 measures the current value of the DC current flowing through the power supply line Lp and the current value of the measurement AC current Im, and outputs current value data Di to the processing unit 4.

[0042] Next, the processing unit 4 inputs the voltage value data Dv output from the voltage measurement unit 2 and the current value data Di output from the current sensor 3. Furthermore, based on the input voltage value data Dv and current value data Di, the processing unit 4 acquires the voltage value (output voltage to the load LD1) and current value of the DC current output from the DUT 1 under test. As a result, the processing unit 4 acquires the current value at one measurement point (the measurement point at this time is referred to as "measurement point Po1") on the IV characteristics graph displayed at the top of the display screen of the output unit 6 as shown in FIG. 5 and the voltage value corresponding to that current value, thereby acquiring display data Dd for displaying the IV characteristics graph. The processing unit 4 then stores the acquired display data Dd in the memory 5. The processing unit 4 also obtains the display data Dd for displaying the IP characteristics graph by calculating the power value based on the current value and voltage value at the measurement point Po1 on the IP characteristics graph when displayed at the top of the display screen of the output unit 6 as shown in Figure 13 at this current value and obtaining the DC current value at the measurement point Po1 and the power value corresponding to that current value. The processing unit 4 then stores the obtained display data Dd in the memory 5.

[0043] Furthermore, the processing unit 4 sweeps the frequency of the measurement AC current Im at this measurement point Po1 by outputting a frequency control signal Sf1 to the load LD1, and at each frequency, acquires the frequency characteristics of the complex impedance of the measurement target DUT 1 based on the frequency of the measurement AC current Im, the voltage value of the voltage V1 measured by the voltage measurement unit 2 (input voltage value data Dv), and the current value of the measurement AC current Im measured by the current sensor 3 (input current value data Di). As a result, the processing unit 4 acquires display data Dd for displaying a Cole-Cole plot of the measurement target DUT 1 at the measurement point Po1 of each characteristic graph, as shown in FIG. The processing unit 4 also calculates the LFR in the acquired Cole-Cole plot (although the HFR may be used, as described above, an example of calculating the LFR will be described), and obtains the current value of the DC current at the measurement point Po1 on the IZ characteristics graph when displayed at the top of the display screen of the output unit 6 as shown in Figure 15, and the LFR corresponding to that current value, thereby obtaining display data Dd for displaying the IZ characteristics graph. Thereafter, the processing unit 4 stores the obtained display data Dd in the memory 5.

[0044] In FIG. 6, the solid arc indicates the Cole-Cole plot at measurement point Po1, and the dashed arcs indicate the Cole-Cole plots at other measurement points Po2 to Po4, which will be described later. However, in FIG. 6 and in FIGS. 7 to 9, dashed arcs corresponding to other measurement points may be omitted. Also, in FIGS. 6 to 9, the black circles on the solid arcs indicate points corresponding to frequencies at which the impedance of the DUT 1 under test was measured. In this case, impedance was actually measured at many frequencies, but for ease of understanding, an example of measurements at only a few points is shown. However, these black circles may also be omitted.

[0045] Next, in the same manner as the above process, the current sensor 3 measures the changed current value of the DC current flowing through the power supply line Lp and the current value of the measurement AC current Im, and outputs current value data Di to the processing unit 4. In addition, the voltage measurement unit 2 measures the DC voltage value and AC voltage value V1 between the terminals T1 and T2 of the DUT 1 under test, and outputs voltage value data Dv to the processing unit 4.

[0046] Next, the processing unit 4 acquires the current value at measurement point Po2 on the IV characteristics graph shown in Fig. 5 and the voltage value corresponding to that current value, thereby acquiring display data Dd for displaying the IV characteristics graph, and stores the acquired display data Dd in the memory 5. Furthermore, similar to the processing at measurement point Po1, the processing unit 4 acquires the current value at measurement point Po2 on the IP characteristics graph shown in Fig. 13 and the power value corresponding to that current value, thereby acquiring display data Dd for displaying the IP characteristics graph, and stores the acquired display data Dd in the memory 5.

[0047] At measurement point Po2, similar to the processing performed at measurement point Po1, the processing unit 4 sweeps the frequency of the measurement AC current Im by outputting a frequency control signal Sf1 to the load LD1, thereby acquiring the frequency characteristics of the complex impedance of the DUT 1 under test at each frequency. As a result, the processing unit 4 acquires display data Dd for displaying the Cole-Cole plot of the DUT 1 under test at measurement point Po2 on each characteristic graph, as shown in FIG. 7 . The processing unit 4 also calculates the LFR in the acquired Cole-Cole plot and acquires the current value of the DC current at measurement point Po2 on the IZ characteristic graph shown in FIG. 15 and the LFR corresponding to that current value, thereby acquiring the display data Dd for displaying the IZ characteristic graph. The processing unit 4 then stores the acquired display data Dd in memory 5. In this case, in FIG. 7 , the solid-line arc indicates the Cole-Cole plot at measurement point Po2, and the dashed-line arcs indicate the Cole-Cole plots at the other measurement points Po1, Po3, and Po4.

[0048] Similarly, the processing unit 4 executes the same processing as the above-described processing each time the current value of the DC current flowing through the power supply line Lp changes, thereby obtaining the current value at measurement point Po3 on the I-V characteristics graph shown in Fig. 5 and the voltage value corresponding to that current value, thereby obtaining display data Dd for displaying the I-V characteristics graph, and stores the obtained display data Dd in the memory 5. Similarly, the processing unit 4 obtains the current value at measurement point Po3 on the I-P characteristics graph shown in Fig. 13 and the power value corresponding to that current value, thereby obtaining display data Dd for displaying the I-P characteristics graph, and stores the obtained display data Dd in the memory 5.

[0049] Furthermore, in processing for measurement point Po3, similar to the processing for measurement point Po1, the processing unit 4 outputs a frequency control signal Sf1 to the load LD1 to sweep the frequency of the measurement AC current Im and acquire the frequency characteristics of the complex impedance of the DUT 1 under test at each frequency. As a result, the processing unit 4 acquires display data Dd for displaying a Cole-Cole plot of the DUT 1 under test at measurement point Po3 on the characteristics graph as shown in FIG. 8. The processing unit 4 also calculates the LFR in the acquired Cole-Cole plot and acquires the current value of the DC current at measurement point Po3 on the IZ characteristics graph shown in FIG. 15 and the LFR corresponding to that current value, thereby acquiring display data Dd for displaying the IZ characteristics graph. The processing unit 4 then stores the acquired display data Dd in memory 5. In this case, in FIG. 8, the solid-line arc indicates the Cole-Cole plot at measurement point Po3, and the dashed-line arcs indicate the Cole-Cole plots at the other measurement points Po1, Po2, and Po4.

[0050] Similarly, the processing unit 4 executes the same processing as the above-described processing each time the current value of the DC current flowing through the power supply line Lp changes, thereby obtaining the current value at measurement point Po4 on the I-V characteristics graph shown in Fig. 5 and the voltage value corresponding to that current value, thereby obtaining display data Dd for displaying the I-V characteristics graph, and stores the obtained display data Dd in the memory 5. Similarly, the processing unit 4 obtains the current value at measurement point Po4 on the I-P characteristics graph shown in Fig. 13 and the power value corresponding to that current value, thereby obtaining display data Dd for displaying the I-P characteristics graph, and stores the obtained display data Dd in the memory 5.

[0051] Furthermore, in processing for measurement point Po4, similar to the processing for measurement point Po1, the processing unit 4 outputs a frequency control signal Sf1 to the load LD1 to sweep the frequency of the measurement AC current Im and acquire the frequency characteristics of the complex impedance of the DUT 1 under test at each frequency. As a result, the processing unit 4 acquires display data Dd for displaying a Cole-Cole plot of the DUT 1 under test at measurement point Po4 on the characteristics graph as shown in FIG. 9 . The processing unit 4 also calculates the LFR in the acquired Cole-Cole plot and acquires the current value of the DC current at measurement point Po4 on the IZ characteristics graph shown in FIG. 15 and the LFR corresponding to that current value, thereby acquiring display data Dd for displaying the IZ characteristics graph. The processing unit 4 then stores the acquired display data Dd in memory 5. In this case, in FIG. 9 , the solid-line arc indicates the Cole-Cole plot at measurement point Po4, and the dashed-line arcs indicate the Cole-Cole plots at the other measurement points Po1 to Po3.

[0052] As a result, the memory 5 stores display data Dd for the IV characteristic graph shown in FIG. 5, display data Dd for the IP characteristic graph shown in FIG. 13, display data Dd for the IZ characteristic graph shown in FIG. 15, and display data Dd for the Cole-Cole plots at measurement points Po1 to Po4 shown in FIGS. 6 to 9.

[0053] Next, the process of displaying the characteristic graph and the Cole-Cole plot in conjunction with each other by the impedance measuring device 1 will be described.

[0054] When displaying an IV characteristic graph and a Cole-Cole plot in conjunction as a single characteristic graph, an instruction to display the IV characteristic graph is given via an operation unit (not shown). In this case, the processing unit 4 reads display data Dd for displaying the IV characteristic graph from the memory 5 and outputs it to the output unit 6. As a result, the output unit 6 displays the IV characteristic graph, as shown in FIG. 5 . In this case, an image is displayed on the output unit 6, with the horizontal axis representing the DC current value and the vertical axis representing the DC current voltage value. The black circles displayed in this figure and the letters of the measurement points Po1 to Po4 corresponding to each black circle may be displayed or hidden. This also applies to the figures described below.

[0055] In this case, when determining which measurement point (operating point) of the DUT1 is optimally operating using only the IV characteristics graph, it is common to select a measurement point with a large DC current and a high voltage. Therefore, users generally determine that it is preferable to operate the DUT1 at a measurement point between measurement points Po2 and Po3. However, if the water content of the electrolyte membrane in the DUT1 (a fuel cell) is insufficient, if there is an excess or deficiency of the platinum catalyst used in the DUT1, or if there is an excess or deficiency of oxygen or hydrogen supplied to the DUT1, it becomes difficult to operate the DUT1 with sufficient output efficiency. Therefore, a measurement point selected simply because it has a large DC current and a high voltage does not necessarily indicate the optimal operating state.

[0056] Therefore, when any one of the plurality of measurement points Po1 to Po4 on the I-V characteristics graph is selected by the touch panel or pointing device (assuming that measurement point Po2 is selected in this case), processing unit 4 inputs pointing data Dp output from output unit 6 to identify measurement point Po, reads display data Dd for displaying a Cole-Cole plot of DUT1 under test when a DC current of a current value corresponding to selected measurement point Po2 is flowing, and outputs this data to output unit 6. In this case, as shown in Fig. 10, output unit 6 displays the I-V characteristics graph in the upper part of the display screen, and displays a Cole-Cole plot for DUT1 under test when a DC current of a current value corresponding to measurement point Po2 is flowing in the lower part of the display screen.

[0057] In this case, while FIG. 10 also displays Cole-Cole plots corresponding to other measurement points Po (measurement points Po1, Po3, and Po4 in this example), the Cole-Cole plots corresponding to the other measurement points Po can also be hidden. However, it is preferable to also display the Cole-Cole plots corresponding to the other measurement points Po so that they can be compared. Also, in FIG. 10 , the processing unit 4 displays the Cole-Cole plot corresponding to the selected measurement point Po (measurement point Po2 in this example) with a thick line and the Cole-Cole plots corresponding to the other measurement points Po with thin lines, and displays a black circle in the Cole-Cole plot corresponding to the selected measurement point Po2 at a location corresponding to the frequency of the measurement AC current Im. However, this is not limiting, and it is sufficient if the Cole-Cole plot corresponding to the selected measurement point Po can be displayed in a way that allows the user to grasp it. For example, the Cole-Cole plots corresponding to measurement points Po1 to Po4 can be displayed with lines of the same thickness, and a black circle can be displayed only in the Cole-Cole plot corresponding to the selected measurement point Po2 at a location corresponding to the frequency of the measured measurement AC current Im. Alternatively, without displaying black circles, only the Cole-Cole plot corresponding to the selected measurement point Po2 may be displayed in a thick line, while the Cole-Cole plots corresponding to the other measurement points Po may be displayed in a thin line, thereby emphasizing the Cole-Cole plot corresponding to the selected measurement point Po2 relative to the Cole-Cole plots corresponding to the other measurement points Po. The Cole-Cole plot corresponding to the selected measurement point Po2 may also be highlighted by being displayed in a different color from the Cole-Cole plots corresponding to the other measurement points Po. Similar display methods can be used for other characteristic graphs, which will be described later.

[0058] This allows the user to understand the operating state of the DUT 1 under test by checking the Cole-Cole plot (frequency characteristics of complex impedance) of the DUT 1 under test at an arbitrary measurement point (measurement point Po2 in this example) on the IV characteristics graph. In this case, in the Cole-Cole plot, the HFR shown in FIG. 12 corresponds to the length between the point of zero on the Z' axis (the real part of the complex impedance) and the first intersecting point (also referred to as the "first intercept") with the first semicircle (also referred to as the "first semicircle") on the zero side of the Z' axis. The LFR corresponds to the length between the first intercept and the intersecting point (intercept) of the first semicircle (or, if another semicircle is adjacent to the first semicircle) on the infinity side of the Z' axis. The resistance value corresponding to the length on the Z' axis between the point of zero on the Z' axis and the next intersecting point (intercept) of the first semicircle with the Z' axis is defined as R1.

[0059] In this case, for the DUT 1 under test, the magnitude of the HFR indicates the ease of electronic and ionic conduction and is related to the water content in the electrolyte membrane. The resistance value obtained by subtracting the HFR from the resistance value R1 indicates the performance of the catalyst used in the DUT 1 under test and is related to the excess or deficiency of the platinum catalyst in the DUT 1 under test. The resistance value obtained by adding the HFR to the resistance value obtained by subtracting the resistance value R1 from the LFR indicates the amount of reactant supplied and is related to the amount of oxygen and hydrogen supplied to the DUT 1 under test. Therefore, to operate the DUT 1 under optimal operating conditions, small HFR and LFR are preferable.

[0060] Therefore, the user can find better operating conditions for the DUT 1 by selecting another measurement point Po on the IV characteristics graph. For example, assume that measurement point Po3, which is close to measurement point Po2, is selected. In this case, the processing unit 4 reads out display data Dd for displaying a Cole-Cole plot of the DUT 1 when a DC current having a current value corresponding to the selected measurement point Po3 is flowing, and outputs the display data Dd to the output unit 6. In this case, as shown in FIG. 11 , the output unit 6 displays the IV characteristics graph in the upper part of the display screen, and also displays a Cole-Cole plot of the DUT 1 when a DC current having a current value corresponding to measurement point Po3 on the IV characteristics graph is flowing in the lower part of the display screen.

[0061] At this time, the user can understand that the operating conditions of the DUT 1 under test at measurement point Po3 are better than the operating conditions of the DUT 1 under test at measurement point Po2. Similarly, by checking the Cole-Cole plots corresponding to measurement points Po1 and Po4, the user can understand that the operating conditions of the DUT 1 under test at measurement point Po3 are the best operating conditions for the DUT 1 under test.

[0062] Next, when the IP characteristics graph and the Cole-Cole plot are to be displayed in conjunction as a single characteristics graph, an instruction to display the IP characteristics graph is given by an operation unit (not shown). At this time, the processing unit 4 reads display data Dd for displaying the IP characteristics graph from the memory 5 and outputs it to the output unit 6. As a result, the output unit 6 displays the IP characteristics graph, as shown in Fig. 13. At this time, the output unit 6 displays an image in which the horizontal axis represents the DC current value and the vertical axis represents the DC power output from the DUT 1.

[0063] In this case, when determining which measurement point (operating point) is in the optimal operating state of the DUT1 under test using only the IP characteristics graph, it is common to select a measurement point with a large DC current value and a large power value. Therefore, the user generally determines that it is preferable to operate the DUT1 under test at a measurement point between measurement points Po3 and Po4. However, for the reasons described above, a measurement point selected simply because it has a large DC current value and a large power value is not necessarily the measurement point that indicates the optimal operating state.

[0064] Therefore, in the same way as when the I-V characteristic graph and the Cole-Cole plot are displayed in conjunction with each other, when any one of the plurality of measurement points Po1 to Po4 on the I-P characteristic graph is selected by the touch panel or pointing device (at this time, it is assumed that measurement point Po4 is selected), processing unit 4 reads out display data Dd for displaying the Cole-Cole plot of measurement target DUT 1 when a DC current of a current value corresponding to the selected measurement point Po4 is flowing, and outputs this to output unit 6. At this time, output unit 6 displays the I-V characteristic graph in the upper part of the display screen, and also displays the Cole-Cole plot of measurement target DUT 1 when a DC current of a current value corresponding to measurement point Po4 on the I-P characteristic graph is flowing in the lower part of the display screen.

[0065] Furthermore, the user can find better operating conditions for the DUT 1 under test by selecting another measurement point on the IP characteristics graph. For example, assume that measurement point Po3, which is close to measurement point Po4, is selected. In this case, the processing unit 4 reads out display data Dd for displaying a Cole-Cole plot of the DUT 1 under test when a DC current having a current value corresponding to the selected measurement point Po3 is flowing, and outputs the data to the output unit 6. In this case, as shown in FIG. 14 , the output unit 6 displays the IP characteristics graph in the upper part of the display screen, and also displays a Cole-Cole plot of the DUT 1 under test when a DC current having a current value corresponding to measurement point Po3 on the IP characteristics graph is flowing in the lower part of the display screen.

[0066] At this time, the user can understand that the operating conditions of the DUT 1 under test at measurement point Po3 are better than the operating conditions of the DUT 1 under test at measurement point Po4. Similarly, by checking the Cole-Cole plots corresponding to measurement points Po1 and Po2, the user can understand that the operating conditions of the DUT 1 under test at measurement point Po3 are the best operating conditions for the DUT 1 under test.

[0067] Next, when the IZ characteristic graph and the Cole-Cole plot are to be displayed in conjunction as a single characteristic graph, an instruction to display the IZ characteristic graph is given via an operation unit (not shown). At this time, the processing unit 4 reads display data Dd for displaying the IZ characteristic graph from the memory 5 and outputs it to the output unit 6. As a result, the output unit 6 displays the IZ characteristic graph in the upper part of the display screen, as shown in Fig. 15. At this time, the output unit 6 displays an image in which the horizontal axis represents the DC current value and the vertical axis represents the LFR in the Cole-Cole plot of DUT 1.

[0068] In this case, when using only the IZ characteristics graph to determine at which measurement point (operating point) the DUT1 under test is in its optimal operating state, it is common to select a measurement point where the DC current value is large and the impedance of the DUT1 is small. Therefore, the user generally determines that it is preferable to operate the DUT1 under test at a measurement point between measurement points Po3 and Po4. However, for the reasons described above, a measurement point selected simply because the DC current value is large and the impedance of the DUT1 is small is not necessarily the measurement point that indicates the optimal operating state.

[0069] Therefore, in the same way as when the IV characteristics graph and the Cole-Cole plot are displayed in conjunction with each other, when any one of the multiple measurement points Po1 to Po4 on the IZ characteristics graph is selected by the touch panel or pointing device (it is assumed that measurement point Po4 is selected at this time), processing unit 4 reads out display data Dd for displaying the Cole-Cole plot of DUT 1 under test when a DC current of a current value corresponding to the selected measurement point Po4 is flowing, and outputs this to output unit 6. In this case, output unit 6 displays the IZ characteristics graph in the upper part of the display screen, and also displays the Cole-Cole plot for DUT 1 under test when a DC current of a current value corresponding to measurement point Po4 on the IZ characteristics graph is flowing in the lower part of the display screen.

[0070] Furthermore, the user can find better operating conditions for the DUT 1 under test by selecting another measurement point on the IZ characteristics graph. For example, assume that measurement point Po3, which is close to measurement point Po4, is selected. In this case, the processing unit 4 reads out display data Dd for displaying a Cole-Cole plot of the DUT 1 under test when a DC current having a current value corresponding to the selected measurement point Po3 is flowing, and outputs the data to the output unit 6. In this case, as shown in FIG. 16 , the output unit 6 displays the IZ characteristics graph in the upper part of the display screen, and also displays a Cole-Cole plot of the DUT 1 under test when a DC current having a current value corresponding to measurement point Po3 on the IZ characteristics graph is flowing in the lower part of the display screen.

[0071] At this time, the user can understand that the operating conditions of the DUT 1 under test at measurement point Po3 are better than the operating conditions of the DUT 1 under test at measurement point Po4. Similarly, by checking the Cole-Cole plots corresponding to measurement points Po1 and Po2, the user can understand that the operating conditions of the DUT 1 under test at measurement point Po3 are the best operating conditions for the DUT 1 under test.

[0072] In the above description, an example was described in which, when one of the measurement points Po1 to Po4 on a characteristics graph displayed on the display screen is selected, a Cole-Cole plot of the DUT 1 is displayed on the display screen when a DC current having a current value corresponding to the selected measurement point Po is flowing. However, the present invention is not limited to this. It is also possible to simultaneously display on the display screen multiple Cole-Cole plots of the DUT 1 when DC currents having current values ​​corresponding to the multiple measurement points Po on the characteristics graph are flowing, and when one of the measurement points Po on the characteristics graph displayed on the display screen is selected, the Cole-Cole plot corresponding to the selected measurement point Po is highlighted. Below, an impedance measuring device 1 that performs this highlighting will be described. Since the configuration of the impedance measuring device 1 itself is the same as that described above, only the different display processing will be described.

[0073] When displaying an IV characteristic graph and Cole-Cole plots in a linked manner as a single characteristic graph, an instruction to display the IV characteristic graph and the Cole-Cole plots in a linked manner and highlight them is given via an operation unit (not shown). In this case, the processing unit 4 reads display data Dd for displaying the IV characteristic graph from the memory 5 and outputs it to the output unit 6, while simultaneously displaying on the display screen multiple Cole-Cole plots of the DUT 1 when DC currents of current values ​​corresponding to multiple measurement points Po on the IV characteristic graph are flowing. As a result, as shown in FIG. 17 , the output unit 6 displays the IV characteristic graph in the upper part of the display screen and the Cole-Cole plots in the lower part of the display screen. In this case, as shown in the same figure, the processing unit 4 outputs the display data Dd to display a single Cole-Cole plot in the lower part of the display screen of the output unit 6, in which four Cole-Cole plots corresponding to measurement points Po1 to Po4 are superimposed.

[0074] Next, when any one of the measurement points Po1 to Po4 on the IV characteristics graph is selected by the touch panel or pointing device (assuming that measurement point Po3 is selected in this case), processing unit 4 reads out display data Dd for highlighting the Cole-Cole plot of the DUT 1 under test when a DC current of a current value corresponding to the selected measurement point Po3 is flowing so that the Cole-Cole plot is distinguishable from the other Cole-Cole plots, and outputs the display data Dd to output unit 6. In this case, as shown in Fig. 18 , output unit 6 displays the IV characteristics graph in the upper part of the display screen, and also highlights and displays the Cole-Cole plot of the DUT 1 under test when a DC current of a current value corresponding to measurement point Po3 on the IV characteristics graph is flowing in the lower part of the screen.

[0075] 18 , as an example, the processing unit 4 displays the Cole-Cole plot corresponding to the selected measurement point Po (measurement point Po3 in this example) with a thick line, displays the Cole-Cole plots corresponding to the other measurement points Po (measurement points Po1, Po2, and Po4 in this example) with thin lines, and displays a black circle at the location corresponding to the frequency of the measurement AC current Im on the Cole-Cole plot corresponding to the selected measurement point Po3. However, this is not limited to this, and the Cole-Cole plots corresponding to measurement points Po1 to Po4 can be displayed with lines of the same thickness, and a black circle can be displayed only on the Cole-Cole plot corresponding to the selected measurement point Po at the location corresponding to the frequency of the measured measurement AC current Im. Alternatively, without displaying a black circle, the processing unit 4 can display only the Cole-Cole plot corresponding to the selected measurement point Po3 with a thick line, and display the Cole-Cole plots corresponding to the other measurement points Po1, Po2, and Po4 with thin lines, thereby highlighting the Cole-Cole plot corresponding to the selected measurement point Po.

[0076] Furthermore, the user can select other measurement points Po1, Po2, and Po4 on the IV characteristics graph in the same manner as described above, thereby finding the best operating conditions for the DUT 1 under test.

[0077] In addition, the processing unit 4 also processes the linked display of the IP characteristic graph and the Cole-Cole plot, and the linked display of the IZ characteristic graph and the Cole-Cole plot, in the same manner as the processing for the linked display of the IV characteristic graph and the Cole-Cole plot.

[0078] In this way, with the display device 10, the impedance measuring device 1, and the display method using the display device 10, when one of a plurality of measurement points Po (measurement points Po1 to Po4 in this example) on a single characteristic graph displayed on the display screen is selected, a Cole-Cole plot of the measurement object DUT 1 (measurement object: a fuel cell in this example) when a DC current of a current value corresponding to the selected measurement point Po is flowing is displayed on the display screen. Also, with the display device 10, the impedance measuring device 1, and the display method using the display device 10, a plurality of Cole-Cole plots of the measurement object DUT 1 (measurement object: a fuel cell in this example) when a DC current of a current value corresponding to each of a plurality of measurement points (measurement points Po1 to Po4 in this example) on a single characteristic graph displayed on the display screen is displayed on the display screen, and when one of the plurality of measurement points Po (measurement points Po1 to Po4 in this example) on a single characteristic graph displayed on the display screen is selected, the Cole-Cole plot corresponding to the selected measurement point Po is highlighted on the display screen. In this case, the display device 10, the impedance measuring device 1, and the display method using the display device 10 display an IV characteristic graph, an IP characteristic graph, and an IZ characteristic graph as characteristic graphs.

[0079] Therefore, according to this display device 10, impedance measuring device 1, and display method using the display device 10, by selecting a measurement point Po on the characteristic graph, each measurement point Po on the characteristic graph and the Cole-Cole plot corresponding to each measurement point Po can be displayed in conjunction with each other.

[0080] Therefore, the display device 10, the impedance measuring device 1, and the display method using the display device 10 display the characteristic graph and the Cole-Cole plot in conjunction with each other, allowing the user to accurately grasp the operating state and performance evaluation of the DUT 1. Specifically, the display device 10, the impedance measuring device 1, and the display method using the display device 10 allow the user to sequentially select each measurement point Po on the characteristic graph and sequentially check the corresponding Cole-Cole plots, and at the same time, check the magnitude of the HFR in the displayed Cole-Cole plot, thereby accurately grasping the operating state and performance evaluation, such as whether the water content of the electrolyte membrane in the DUT 1 is appropriate when a DC current of the selected current value is flowing. Furthermore, the display device 10, the impedance measuring device 1, and the display method using the display device 10 allow the user to check the magnitude of the resistance value obtained by subtracting the HFR from the resistance value R1 in the displayed Cole-Cole plot, thereby accurately grasping the operating state and performance evaluation, such as whether the amount of platinum catalyst used in the DUT 1 is appropriate. Furthermore, with this display device 10, impedance measuring device 1, and display method using the display device 10, the user can confirm the magnitude of the resistance value obtained by adding the HFR to the resistance value obtained by subtracting the resistance value R1 from the LFR in the displayed Cole-Cole plot, thereby allowing the user to accurately grasp the operating state and performance evaluation, such as whether the amount of oxygen and hydrogen supplied to the DUT 1 to be measured is appropriate.

[0081] The impedance measuring device 1 also includes a voltage measuring unit 2 (AC voltage measuring unit) and a current sensor 3 (AC current measuring unit), in which the voltage measuring unit 2 measures the voltage value of the AC voltage generated across a pair of terminals (terminals T1, T2) due to the flow of the measurement AC current Im through the DUT 1 under test, the current sensor 3 measures the current value of the measurement AC current Im flowing through the DUT 1 under test, and the processing unit 4 acquires, at each measurement point Po where the DC current value changes, the frequency characteristics of the complex impedance of the DUT 1 under test for displaying a Cole-Cole plot on the display screen based on the frequency of the measurement AC current Im, the voltage value of the AC voltage V1 measured by the voltage measuring unit 2, and the current value of the measurement AC current Im measured by the current sensor 3. Thus, in addition to the function of displaying the Cole-Cole plot, the impedance measuring device 1 can also generate display data Dd for displaying the Cole-Cole plot based on the frequency characteristics of the complex impedance of the DUT 1 under test.

[0082] Furthermore, this impedance measuring device 1 includes a voltage measuring unit 2 (DC voltage measuring unit) and a current sensor 3 (DC current measuring unit), and the voltage measuring unit 2 measures the voltage value of the DC voltage generated across the pair of terminals (terminals T1, T2) when the DC current on which the measurement AC current Im is superimposed inputs and outputs (in this example, when it is "output") the measurement target DUT 1 via the pair of terminals (terminals T1, T2) in response to the changed current value of the DC current, the current sensor 3 measures the current value of the DC current when the DC current on which the measurement AC current Im is superimposed inputs and outputs the measurement target DUT 1, and the processing unit 4 acquires display data Dd for displaying a characteristics graph on the display screen based on the voltage value of the DC voltage measured by the voltage measuring unit 2 and the current value of the DC current measured by the current sensor 3. Therefore, according to this impedance measuring device 1, in addition to the function of displaying a Cole-Cole plot and the function of generating display data Dd for displaying the Cole-Cole plot, it is also possible to generate display data Dd for displaying at least one of an IV characteristics graph and an IP characteristics graph.

[0083] Furthermore, this impedance measuring device 1 includes a current sensor 3 (DC current measuring unit), which measures the current value of the DC current when the DC current superimposed with the measurement AC current Im inputs / outputs (in this example, when it is "output") from / to the DUT 1 under test, and the processing unit 4 acquires display data Dd for displaying an IZ characteristics graph on the display screen based on the current value of the DC current measured by the voltage measuring unit 2 and the acquired frequency characteristics of the complex impedance of the DUT 1 under test. Therefore, this impedance measuring device 1 has the function of displaying a Cole-Cole plot and the function of generating display data Dd for displaying the Cole-Cole plot, as well as the ability to generate display data Dd for displaying the IZ characteristics graph.

[0084] Furthermore, this impedance measuring device 1 is equipped with a non-contact current sensor 3 that measures the current value of the DC current and measurement AC current Im that are input / output (in this example, "output") to / from the DUT 1 under measurement. This makes it possible to avoid contact of the internal mechanism of the current sensor 3 with the power supply line Lp, etc., and therefore makes it possible to measure the current value of the DC current extremely safely.

[0085] Furthermore, according to this impedance measuring device 1, the current sensor 3 is a clamp-type current sensor that is configured to be able to open and close, so that the current values ​​of the DC current and the measurement AC current Im can be measured reliably and quickly while the power supply line Lp remains connected between the measurement target DUT 1 and the load LD1, etc.

[0086] Second Embodiment Next, the configuration of an impedance measuring device 1A will be described with reference to FIG.

[0087] As shown in FIG. 2 , the impedance measuring apparatus 1A is configured to include the components of the impedance measuring apparatus 1, and further includes an AC current generator 7 that generates a measurement AC current Im. Therefore, this impedance measuring apparatus 1A is configured to measure the impedance of a DUT 1 that is connected via a power supply line Lp to a load LD2 that does not have the function of outputting a measurement AC current Im. In this case, the load LD2 is configured as an electrical device or the like and consumes the DC current output from the DUT 1. Note that, with regard to the configuration of the impedance measuring apparatus 1A and the impedance measuring apparatuses 1B and 1C described below, components that are similar to those of the impedance measuring apparatus 1 are designated by the same reference numerals, and redundant description will be omitted.

[0088] The AC current generator 7 generates the measurement AC current Im in accordance with the frequency control signal Sf2 output from the processing unit 4, and outputs the generated measurement AC current Im superimposed on the DC current output from the DUT 1. In this case, the AC current generator 7 can be configured as a general AC current source that can sweep (change) the frequency of an AC signal (measurement AC current Im) and output it in accordance with the frequency control signal Sf2 output from the processing unit 4. Alternatively, the AC current generator 7 can be configured as an electronic load that consumes DC power output from the DUT 1 as a load in accordance with the frequency control signal Sf2 to output the measurement AC current Im of a specified frequency. Note that a configuration of the AC current generator 7 using an electronic load consumes DC power output from the DUT 1 to generate the measurement AC current Im, thereby generating a large measurement AC current Im. Therefore, this impedance measuring device 1A can increase the calculated current value (I) and voltage value (V), thereby enabling accurate measurement (calculation) of the impedance of the DUT 1.

[0089] Next, an impedance measurement method will be described in which the impedance measurement device 1A is used to measure (calculate) the impedance of the DUT 1. Note that the method for acquiring a characteristic graph and Cole-Cole plot for the DUT 1 and the method for displaying the characteristic graph and Cole-Cole plot on the output unit 6 are the same as those in the impedance measurement device 1, so only the differences will be described and redundant explanations will be omitted.

[0090] In this impedance measuring device 1A, when a measurement start switch (not shown) is operated, a DC current generated by the DUT 1 under test is supplied to the load LD2 via the power supply lines Lp, Lp. Next, the processing unit 4 outputs a frequency control signal Sf2 to control the AC current generating unit 7, thereby superimposing a measurement AC current Im (AC voltage) on the DC current supplied from the DUT 1 under test. Next, the processing unit 4 executes the same processing as in the impedance measuring device 1 to acquire display data Dd for displaying an IV characteristic graph, an IP characteristic graph, an IZ characteristic graph, and a Cole-Cole plot, and then stores the acquired display data Dd in the memory 5. Thereafter, the processing unit 4 displays the characteristic graphs and the Cole-Cole plot on the display screen of the output unit 6 in accordance with a user's operating instructions.

[0091] Thus, in addition to the effects achieved by the impedance measuring device 1, the impedance measuring device 1A is provided with an AC current generating unit 7 that generates a measurement AC current Im and superimposes it on a DC current, making it possible to measure (calculate) the impedance of the measurement target DUT 1 that supplies a DC current to a load LD2 that cannot output the measurement AC current Im, and to display a characteristic graph and a Cole-Cole plot of the measurement target DUT 1.

[0092] Third Example Next, an impedance measurement device 1B using an electrolysis device as the DUT 2 to be measured will be described. In this case, as shown in FIG. 3 , the DUT 2 to be measured has a pair of input terminals, a positive terminal T11 and a negative terminal T12, which are connected to the positive output terminal and the negative output terminal of a DC power supply PD1 via a pair of power supply lines Lp, respectively. The DUT 2 to be measured operates using a DC current supplied from the DC power supply PD1 as a driving current to electrolyze supplied water to produce oxygen and hydrogen. The DC power supply PD1 generates and outputs a DC current and is also configured to superimpose a sinusoidal AC signal (measurement AC current Im) on the DC current, which is used to measure the impedance of the DUT 2 to be measured. The DC power supply PD1 also sweeps (varies) the frequency of the AC signal (measurement AC current Im) and outputs it in accordance with a frequency control signal Sf3 output from an external device (in this example, the processing unit 4).

[0093] The processing unit 4 acquires display data Dd for displaying an I-V characteristic graph showing the characteristics of the voltage value of the DC voltage between the pair of terminals T11, T12 versus the current value of the DC current input / output to / from the DUT 2 via the pair of terminals T11, T12 (input to the DUT 2 in this example), an I-P characteristic graph showing the characteristics of the power value of the power input / output to / from the pair of terminals T11, T12 (input to the DUT 2 in this example) versus the current value of the DC current input / output to / from the DUT 2 via the pair of terminals T11, T12 (input to the DUT 2 in this example), and an I-Z characteristic graph showing the characteristics of the impedance of the DUT 2 versus the current value of the DC current input / output to / from the DUT 2 via the pair of terminals T11, T12 (input to the DUT 2 in this example), and also acquires display data Dd for displaying a Cole-Cole plot as described above.

[0094] Next, a display process for displaying an IV characteristics graph and a Cole-Cole plot in conjunction as a single characteristics graph will be described. Note that the method for acquiring the characteristics graph and Cole-Cole plot for the DUT 2 under measurement and the method for displaying the characteristics graph and Cole-Cole plot on the output unit 6 are the same as those in the impedance measuring device 1, so only the differences will be described and redundant explanations will be omitted.

[0095] In this impedance measuring device 1B, when a measurement start switch (not shown) is operated, a DC current generated by a DC power supply PD1 is supplied to a DUT 2 under test via power supply lines Lp, Lp. Next, a processing unit 4 outputs a frequency control signal Sf2 to control the DC power supply PD1, thereby superimposing a measurement AC current Im (AC voltage) on the supplied DC current. Next, the processing unit 4 executes the same processing as in the impedance measuring device 1 to acquire display data Dd for displaying an I-V characteristic graph, an IP characteristic graph, an I-Z characteristic graph, and a Cole-Cole plot, and then stores the acquired display data Dd in memory 5. Thereafter, the processing unit 4 displays the characteristic graphs and the Cole-Cole plot on the display screen of the output unit 6 in accordance with a user's operating instructions.

[0096] In this case, when the acquired characteristic graphs for the DUT 2 under test are displayed on the output unit 6, the IV characteristic graph is displayed as shown in Fig. 19, the IP characteristic graph is displayed as shown in Fig. 20, and the IZ characteristic graph is displayed as shown in Fig. 21. Furthermore, when the acquired Cole-Cole plots for the DUT 2 under test are displayed on the output unit 6, similar to the Cole-Cole plots for the DUT 1 under test, the Cole-Cole plot at measurement point Po11 in each characteristic graph is displayed as shown in Fig. 6, the Cole-Cole plot at measurement point Po12 is displayed as shown in Fig. 7, the Cole-Cole plot at measurement point Po13 is displayed as shown in Fig. 8, and the Cole-Cole plot at measurement point Po14 is displayed as shown in Fig. 9. Note that when DC currents of the same current value are flowing, the Cole-Cole plots for the DUTs under test 1 and 2 under test will be approximately the same characteristic diagram.

[0097] Furthermore, this impedance measuring device 1B allows the user to accurately grasp the operating state and performance evaluation of the DUT 2 under test using a Cole-Cole plot. In this case, the magnitude of the HFR in the DUT 2 under test represents the ease of electronic and ionic conduction and is related to the water content in the electrolyte membrane. The resistance value obtained by subtracting the HFR from the resistance value R1 represents the performance of the catalyst used in the DUT 2 under test and is related to the excess or deficiency of the platinum catalyst or iridium catalyst in the DUT 1 under test. The resistance value obtained by adding the HFR to the resistance value obtained by subtracting the resistance value R1 from the LFR represents the amount of reactant supplied and is related to the amount of water supplied to the DUT 2 under test. Therefore, small HFR and LFR are preferable to operate the DUT 2 under optimal operating conditions.

[0098] Furthermore, when the characteristic graph and the Cole-Cole plot are displayed in a linked manner, they are displayed in the same manner as the linked display in the impedance measuring apparatus 1. As an example, when any one of the measurement points Po11 to Po14 on the IV characteristic graph is selected by a touch panel or pointing device (assuming that measurement point Po13 is selected in this case), the processing unit 4 reads out display data Dd for displaying a Cole-Cole plot of the DUT 2 under test when a DC current of a current value corresponding to the selected measurement point Po13 is flowing, and outputs the display data Dd to the output unit 6. In this case, as shown in FIG. 22 , in the same manner as the linked display in the impedance measuring apparatus 1, the output unit 6 displays the IV characteristic graph in the upper part of the display screen, and also displays a Cole-Cole plot for the DUT 2 under test when a DC current of a current value corresponding to measurement point Po13 on the IV characteristic graph is flowing in the lower part of the display screen.

[0099] When highlighting the Cole-Cole plot, the processing unit 4 reads display data Dd for displaying the characteristic graph from the memory 5 and outputs it to the output unit 6, in the same way as the linked display and highlighting of the characteristic graph and the Cole-Cole plot in the impedance measuring device 1, and simultaneously displays on the display screen multiple Cole-Cole plots of the DUT 2 when DC currents of current values ​​corresponding to multiple measurement points Po11 to Po14 on the characteristic graph are flowing. As a result, as shown in Figure 23, the output unit 6 displays the characteristic graph in the upper part of the display screen and the Cole-Cole plots in the lower part of the display screen. In this case, the processing unit 4 outputs the display data Dd to display one Cole-Cole plot in the lower part of the display screen of the output unit 6, which is obtained by superimposing four Cole-Cole plots corresponding to measurement points Po11 to Po14, respectively.

[0100] Next, when, for example, any one of the multiple measurement points on the IV characteristics graph is selected by the touch panel or pointing device (assuming that measurement point Po13 is selected in this case), processing unit 4 reads out display data Dd for highlighting the Cole-Cole plot of DUT 2 under test when a DC current of a current value corresponding to selected measurement point Po13 is flowing so that it can be distinguished from other Cole-Cole plots, and outputs this data to output unit 6. In this case, as shown in Fig. 22 , output unit 6 displays the IV characteristics graph in the upper part of the display screen, and highlights the Cole-Cole plot of DUT 2 under test when a DC current of a current value corresponding to measurement point Po13 on the IV characteristics graph is flowing in the lower part of the screen.

[0101] In this way, with the display device 10, the impedance measuring device 1B, and the display method using the display device 10, when one of the measurement points Po (measurement points Po11 to Po14 in this example) on a single characteristic graph displayed on the display screen is selected, a Cole-Cole plot of the measurement target DUT 2 (measurement target: in this example, an electrolytic device) is displayed on the display screen when a DC current of a current value corresponding to the selected measurement point Po is flowing. Also, with the display device 10, the impedance measuring device 1B, and the display method using the display device 10, multiple Cole-Cole plots of the measurement target DUT 2 (measurement target: in this example, an electrolytic device) are displayed on the display screen when DC currents of current values ​​corresponding to the multiple measurement points (measurement points Po1 to Po4 in this example) on a single characteristic graph displayed on the display screen are displayed on the display screen, and when one of the measurement points Po (measurement points Po11 to Po14 in this example) on a single characteristic graph displayed on the display screen is selected, the Cole-Cole plot corresponding to the selected measurement point Po is highlighted on the display screen. In this case, the display device 10, the impedance measuring device 1B, and the display method using the display device 10 display an IV characteristic graph, an IP characteristic graph, and an IZ characteristic graph as characteristic graphs.

[0102] Therefore, with this display device 10, impedance measuring device 1B, and display method using display device 10, by selecting a measurement point Po on the characteristic graph, it is possible to display each measurement point Po on the characteristic graph in conjunction with the Cole-Cole plot corresponding to each measurement point Po.

[0103] Therefore, with the display device 10, the impedance measuring device 1B, and the display method using the display device 10, the characteristic graph and the Cole-Cole plot are displayed in conjunction with each other, allowing the user to accurately grasp the operating state and performance evaluation of the DUT 2. Specifically, with the display device 10, the impedance measuring device 1B, and the display method using the display device 10, the user can sequentially select each measurement point Po on the characteristic graph and sequentially check the corresponding Cole-Cole plots, and at the same time, check the magnitude of the HFR in the displayed Cole-Cole plot, thereby accurately grasping the operating state and performance evaluation, such as whether the water content of the electrolyte membrane in the DUT 2 is appropriate when a DC current of the selected current value is flowing. Furthermore, with the display device 10, the impedance measuring device 1, and the display method using the display device 10, the user can accurately grasp the operating state and performance evaluation, such as whether the amount of platinum catalyst or iridium catalyst used in the DUT 2 is appropriate, by checking the magnitude of the resistance value R1 in the displayed Cole-Cole plot. Furthermore, with this display device 10, impedance measuring device 1, and display method using the display device 10, the user can confirm the magnitude of the resistance value obtained by adding the HFR to the resistance value obtained by subtracting the resistance value R1 from the LFR in the displayed Cole-Cole plot, thereby allowing the user to accurately grasp the operating state and performance evaluation, such as whether the amount of water supplied to the measurement target DUT 2 is appropriate.

[0104] Furthermore, the impedance measuring device 1B can achieve the same effects as the impedance measuring device 1.

[0105] Fourth Embodiment Next, the configuration of an impedance measuring device 1C will be described with reference to FIG.

[0106] 4, the impedance measuring apparatus 1C is configured to include an AC current generating unit 7 that generates a measurement AC current Im in addition to the configuration of the impedance measuring apparatus 1B. Therefore, this impedance measuring apparatus 1C is configured to be able to measure the impedance of a DUT 2 under test that is connected via a power supply line Lp to a DC power supply PD2 that does not have the function of outputting a measurement AC current Im. Note that, with regard to the configuration of the impedance measuring apparatus 1C, components that are similar to the configurations of the impedance measuring apparatuses 1, 1A, and 1B are assigned the same reference numerals and redundant explanations will be omitted.

[0107] Next, an impedance measurement method will be described in which the impedance measurement device 1C is used to measure (calculate) the impedance of the DUT 2. Note that the method for acquiring a characteristic graph and Cole-Cole plot for the DUT 2 and the method for displaying the characteristic graph and Cole-Cole plot on the output unit 6 are the same as those in the impedance measurement device 1, so only the differences will be described and redundant explanations will be omitted.

[0108] In this impedance measuring device 1C, when a measurement start switch (not shown) is operated, a DC current generated by a DC power supply PD2 is supplied to a DUT 2 under test via power supply lines Lp, Lp. Next, the processing unit 4 outputs a frequency control signal Sf4 to control the AC current generating unit 7, thereby superimposing a measurement AC current Im (AC voltage) on the DC current supplied from the DC power supply PD2. Next, the processing unit 4 executes the same processing as in the impedance measuring device 1 to acquire display data Dd for displaying an I-V characteristic graph, an IP characteristic graph, an I-Z characteristic graph, and a Cole-Cole plot, and then stores the acquired display data Dd in memory 5. Thereafter, the processing unit 4 displays the characteristic graphs and the Cole-Cole plot on the display screen of the output unit 6 in accordance with a user's operating instructions.

[0109] Thus, in addition to the effects achieved by the impedance measuring device 1B, the impedance measuring device 1C is provided with an AC current generating unit 7 that generates a measurement AC current Im and superimposes it on a DC current, making it possible to measure (calculate) the impedance of the measurement target DUT 2 to which a DC current is supplied from a DC power supply PD2 that is not capable of outputting the measurement AC current Im, and to display a characteristic graph and a Cole-Cole plot of the measurement target DUT 2.

[0110] The present invention is not limited to the configuration of the impedance measuring apparatus 1, 1A-1C described above and can be modified as appropriate. For example, the Cole-Cole plots of the DUT 1 (or the DUT 2) under test when DC currents of corresponding current values ​​are flowing through a plurality of measurement points Po on a single characteristic graph displayed on the display screen are displayed in an overlapping manner, and when one of the measurement points Po on the single characteristic graph is selected, the Cole-Cole plot corresponding to the selected measurement point Po is highlighted on the display screen. However, the present invention is not limited to this. It is also possible to display multiple Cole-Cole plots of the DUT 1 (or the DUT 2) under test when DC currents of corresponding current values ​​are flowing through a plurality of measurement points Po on a single characteristic graph displayed on the display screen without overlapping each other, and when one of the measurement points Po on the single characteristic graph is selected, the selected measurement point Po can be highlighted in the same way as described above so as to be distinguishable from the Cole-Cole plots corresponding to the other measurement points Po. At this time, the Cole-Cole plots corresponding to the other measurement points Po can also be hidden. Furthermore, as long as the Cole-Cole plot corresponding to the selected measurement point Po is displayed in a manner that allows it to be distinguished from the Cole-Cole plots corresponding to the other measurement points Po, it is also possible to adopt a configuration in which the Cole-Cole plot is highlighted, for example, by using a different display color or line type (solid line, dashed line, etc.) from the other Cole-Cole plots.

[0111] In the above embodiment, an example was described in which all three of the IV characteristics graph, IP characteristics graph, and IZ characteristics graph could be displayed, but this is not limiting. It is also possible to adopt a configuration in which one or two of the IV characteristics graph, IP characteristics graph, and IZ characteristics graph are displayed in conjunction with a Cole-Cole plot.

[0112] In the above embodiment, the characteristics graph is displayed in the upper part of the display screen of the output unit 6, and the Cole-Cole plot is displayed in the lower part of the display screen of the output unit 6, but the display manner is not limited to this and can be changed as appropriate. For example, the characteristics graph may be displayed in the lower part of the display screen of the output unit 6, and the Cole-Cole plot may be displayed in the upper part of the display screen of the output unit 6. Furthermore, the characteristics graph may be displayed on either the left or right side of the display screen of the output unit 6, and the Cole-Cole plot may be displayed on the other left or right side of the display screen of the output unit 6.

[0113] Furthermore, for example, an example has been described in which open / close clamp-type current sensors 3a and 3b are used, but a type of current sensor that is fixedly attached to the power supply line Lp can also be used, or a shunt resistor can also be used.

[0114] Although the above description concerns an example in which the voltage measurement unit 2 and the current sensor 3 output data (voltage value data Dv and current value data Di), it is also possible to employ a configuration in which the voltage measurement unit 2 outputs an analog voltage detection signal, the current sensor 3 outputs an analog current detection signal, and the processing unit 4 measures (calculates) the impedance by digital processing based on the input voltage detection signal and current detection signal. Similarly, it is also possible to employ a configuration in which either the voltage measurement unit 2 or the current sensor 3 outputs an analog detection signal, and the processing unit 4 measures (calculates) the impedance by digital processing based on the input analog detection signal and digital data.

[0115] According to the present invention, by displaying a characteristic graph and a Cole-Cole plot in conjunction with each other, the user can accurately grasp the operating state and performance evaluation of the object to be measured. As a result, the present invention can be widely applied to such display devices, impedance measuring devices, and display methods.

[0116] 1, 1A to 1C Impedance measuring device 2 Voltage measuring section 3 Current sensor 4 Processing section 5 Memory 6 Output section 7 AC current generating section Dv Voltage value data Di Current value data DUT1, DUT2 Measurement object

Claims

1. A display device having a processing unit that displays on a display screen at least one of the following characteristics graphs: a current-voltage characteristics graph showing the characteristics of the voltage value of the DC voltage between a pair of terminals versus the current value of the DC current input / output to the object to be measured via the pair of terminals; a current-power characteristics graph showing the characteristics of the power value of the power input / output via the pair of terminals versus the current value of the DC current input / output to the object to be measured via the pair of terminals; and a current-impedance characteristics graph showing the characteristics of the impedance of the object to be measured versus the current value of the DC current input / output to the object to be measured via the pair of terminals, wherein when one of a plurality of measurement points on one of the characteristics graphs displayed on the display screen is selected, the processing unit displays on the display screen a Cole-Cole plot of the object to be measured when the DC current of the current value corresponding to the selected measurement point is flowing.

2. A display device having a processing unit that displays at least one of the following characteristics graphs on a display screen: a current-voltage characteristics graph showing the characteristics of the voltage value of the DC voltage between a pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; a current-power characteristics graph showing the characteristics of the power value of the power input / output via the pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals; and a current-impedance characteristics graph showing the characteristics of the impedance of the object to be measured versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, wherein the processing unit displays on the display screen multiple Cole-Cole plots of the object to be measured when a DC current flows, the current values ​​of which correspond to multiple measurement points on the single characteristics graph, and when one of the multiple measurement points on the single characteristics graph displayed on the display screen is selected, the display device highlights the Cole-Cole plot corresponding to the selected measurement point.

3. The display device according to claim 1, wherein said one graph is a current-voltage characteristic graph.

4. The display device according to claim 1, wherein said one graph is a current-power characteristic graph.

5. The display device according to claim 1, wherein said one graph is a current-impedance characteristic graph.

6. The display device according to claim 2, wherein said one graph is a current-voltage characteristic graph.

7. The display device according to claim 2, wherein said one graph is a current-power characteristic graph.

8. The display device according to claim 2, wherein said one graph is a current-impedance characteristic graph.

9. An impedance measuring device comprising: a display device as defined in any one of claims 1 to 8, an AC voltage measuring unit, and an AC current measuring unit, wherein the AC voltage measuring unit measures a voltage value of an AC voltage generated across both ends of the pair of terminals due to the measurement AC current flowing through the measurement object, the AC current measuring unit measures a current value of the measurement AC current flowing through the measurement object, and the processing unit acquires, at each measurement point where the current value of the DC current changes, a frequency characteristic of the complex impedance of the measurement object to display the Cole-Cole plot on the display screen based on the frequency of the measurement AC current, the voltage value of the AC voltage measured by the AC voltage measuring unit, and the current value of the measurement AC current measured by the AC current measuring unit.

10. An impedance measuring device as claimed in claim 9, comprising a DC voltage measuring unit and a DC current measuring unit, wherein the DC voltage measuring unit measures a voltage value of the DC voltage generated across both ends of the pair of terminals for a changed current value of the DC current when the DC current on which the measurement AC current is superimposed inputs and outputs to the object to be measured via the pair of terminals, and the DC current measuring unit measures a current value of the DC current when the DC current on which the measurement AC current is superimposed inputs and outputs to the object to be measured, and the processing unit obtains display data for displaying at least one of the I-V characteristic graph and the I-P characteristic graph on the display screen based on the voltage value of the DC voltage measured by the DC voltage measuring unit and the current value of the DC current measured by the DC current measuring unit.

11. An impedance measuring device as described in claim 9, further comprising a DC current measuring unit which measures a current value of the DC current on which the measurement AC current is superimposed when the DC current inputs and outputs to the object to be measured, and the processing unit acquires display data for displaying the I-Z characteristics graph on the display screen based on the current value of the DC current measured by the DC current measuring unit and the acquired frequency characteristics of the complex impedance of the object to be measured.

12. The impedance measuring device according to claim 9, further comprising an AC current generating section for generating the measuring AC current and superimposing the AC current on the DC current.

13. The impedance measuring device according to claim 9, further comprising a non-contact current sensor for measuring the current value of the DC current input / output to the object to be measured.

14. The impedance measuring device according to claim 13, wherein the current sensor is a clamp-type current sensor that is configured to be openable and closable.

15. The impedance measuring device according to claim 9, further comprising a non-contact current sensor for measuring the current value of the measurement AC current flowing through the object to be measured.

16. The impedance measuring device according to claim 15, wherein the current sensor is a clamp-type current sensor that is configured to be openable and closable.

17. A display method for displaying on a display screen at least one of a current-voltage characteristic graph showing the characteristics of the voltage value of the DC voltage between a pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, a current-power characteristic graph showing the characteristics of the power value of the power input / output via the pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, and a current-impedance characteristic graph showing the characteristics of the impedance of the object to be measured versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, wherein, when one of a plurality of measurement points on one characteristic graph displayed on the display screen is selected, a Cole-Cole plot of the object to be measured when the DC current of the current value corresponding to the selected measurement point is flowing is displayed on the display screen.

18. A display method for displaying on a display screen at least one of a current-voltage characteristic graph showing the characteristics of the voltage value of the DC voltage between a pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, a current-power characteristic graph showing the characteristics of the power value of the power input / output via the pair of terminals versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, and a current-impedance characteristic graph showing the characteristics of the impedance of the object to be measured versus the current value of the DC current input / output to / from the object to be measured via the pair of terminals, wherein the display screen displays a plurality of Cole-Cole plots of the object to be measured when a DC current flows, the current values ​​of which respectively correspond to a plurality of measurement points on the single characteristic graph, and when one of the plurality of measurement points on the single characteristic graph displayed on the display screen is selected, the Cole-Cole plot corresponding to the selected measurement point is highlighted.

Images