JP2003223918A - Resistance measurement equipment and diagnostic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide resistance measurement equipment which can measure effective resistance of a fuel cell efficiently in a short time. <P>SOLUTION: The diagnostic equipment 1, which measures the effective resistance of the fuel cell BT, has a signal generation section 11 that generates signals for measurement including a 1st alternate current signal for measurement for measuring membrane resistance, which forms a part of the effective resistance, and a 2nd alternate current signal for measurement for measuring a reaction resistance, which forms a part of the effective resistance, and has a measurement section 12 that obtains a resistance value of the membrane resistance based on a current value of the 1st alternate current signal for measurement flowing in the membrane resistance in a state where the signal for measurement is impressed on the fuel cell BT, and voltage which is generated in the membrane, and also obtains the resistance value of the reaction resistance based on the current value of the 2nd alternate current signal for measurement flowing in the reaction resistance, and the voltage which is generated in the reaction resistance. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance measuring device suitable for measuring the effective resistance of a polymer electrolyte fuel cell according to the four-terminal method, and a diagnostic device equipped with the resistance measuring device. is there.

[0002]

2. Description of the Related Art Generally, the internal resistance (impedance) of a polymer electrolyte fuel cell (hereinafter also referred to as "fuel cell")
As the effective resistance, among them, the resistance of the electrolyte membrane that constitutes the fuel cell, the resistance of the catalyst, the resistance of the electrodes and the like, and the contact resistance thereof (these are referred to as “membrane resistance” in this specification).
Defined) and the reaction resistance due to the reaction of the catalyst and the fuel gas. In this case, for the effective resistance component (hereinafter, also referred to as “effective resistance”) in the internal resistance of the fuel cell, an AC signal for measurement (hereinafter also referred to as “measurement signal”) is applied to the fuel cell according to the four-terminal method. To measure. At this time, when the applied measurement signal has a high frequency, the membrane resistance is measured as an effective resistance, and when the measurement signal has a low frequency, the reaction resistance is measured as an effective resistance. The relationship between the effective resistance component and the imaginary number component in the internal resistance of the fuel cell using the frequency of the measurement signal as a parameter is represented by the Cole-Cole plot shown in FIG. 2 as an example. In this case, "R1" represents the membrane resistance when the fuel cell is in a normal state, and "R2" represents the reaction resistance in that state. On the other hand, for example, when the fuel cell is internally short-circuited, the membrane resistance shows a resistance value smaller than the resistance value R1, and when the fuel cell is exhausted, the membrane resistance shows the resistance value as shown in FIG. A resistance value R3 larger than R1 is shown. When the reaction state between the catalyst and the fuel gas is poor, the reaction resistance is the resistance value R as shown in FIG.
The resistance value R4 is larger than 2. Therefore, the quality of the fuel cell can be determined by measuring the membrane resistance and the reaction resistance and comparing each measured value with a predetermined reference value.

A resistance measuring device 6 shown in FIG. 3 is used as a resistance measuring device for measuring the effective resistance of a fuel cell according to the four-terminal method.
1 is conventionally known. When measuring the effective resistance of the fuel cell BT to be measured using this resistance measuring device 61, the frequency of the measurement signal to be applied is changed to measure the membrane resistance and the reaction resistance. Specifically, as shown in the figure, first, after setting the resistance value of the variable load 62 to a resistance value according to the electromotive force of the fuel cell BT, the variable load 62 is connected to the fuel cell via the probes P1 and P2. Connect to both electrodes of BT. Further, a current detection sensor (current transformer) CT that detects the current value of the measurement signal flowing through the fuel cell BT is arranged between the probe P1 and the variable load 62, and the current detection sensor CT and the sensor signal input of the resistance measuring device 61 are input. Connect with the terminal. Further, the probes P3 and P5 are connected to one electrode of the fuel cell BT and the probes P4 and P6 are connected.
Is connected to the other electrode. Then, after setting the measurement signal to a predetermined frequency (for example, a low frequency of 1 mHz), the measurement signal is applied to the fuel cell BT through the probes P3 and P4, and the measurement signal flows through the probes P5 and P6. The AC voltage generated in the internal resistance of the fuel cell BT is input by. At the same time, the detection voltage of the current detection sensor CT is input.

In this case, the resistance measuring device 61 calculates the effective resistance of the fuel cell BT based on the AC voltage generated in the internal resistance and the detection voltage detected by the current detection sensor CT. Then, the frequency of the measurement signal is changed to a higher frequency in predetermined frequency steps, and the effective resistance of the fuel cell BT is calculated in the same manner. In this way, the effective resistance is calculated while gradually changing the frequency of the measurement signal to a high frequency up to several tens of kHz. As a result, FIG.
The Cole-Cole plot shown in is created. In this case, the membrane resistance (R
1) is obtained, and the reaction resistance (R2) shown in the same figure is obtained with a low-frequency measurement signal, and the quality of the fuel cell BT can be determined by confirming the magnitudes of the membrane resistance and the reaction resistance. it can.

[0005]

However, the conventional resistance measuring device 61 has the following problems. That is, in the conventional resistance measuring device 61, the frequency of the measurement signal is gradually changed and the effective resistance is measured each time. In this case, when measuring the effective resistance, it is necessary to continue to apply the measurement signal to the fuel cell BT for a time corresponding to at least one cycle. Will be required.
On the other hand, in order to measure the membrane resistance R1 and the reaction resistance R2 of the fuel cell, it is necessary to apply measurement signals of high frequency and low frequency to measure. Therefore, the measurement that requires a long time is performed many times, and there is a problem that the measurement work is complicated and inefficient.

The present invention has been made in view of the above problems, and is based on a resistance measuring device capable of efficiently measuring the effective resistance of a fuel cell in a short time, and an effective resistance measured by the resistance measuring device. The main object of the present invention is to provide a diagnostic device capable of efficiently diagnosing the quality of a fuel cell.

[0007]

In order to achieve the above object, a resistance measuring device according to claim 1 is a measuring device for measuring an effective resistance of a fuel cell, the film resistance forming a part of the effective resistance. A first measuring alternating current signal for measuring and a second measuring current resistance for forming a part of the effective resistance.
A measurement signal generator that generates a measurement signal including a measurement AC signal, and a current value of the first measurement AC signal that flows through the membrane resistance in a state where the measurement signal is applied to the fuel cell and The resistance value of the membrane resistance is calculated based on the voltage generated in the membrane resistance, and the resistance value of the reaction resistance is calculated based on the current value of the second measuring AC signal flowing through the reaction resistance and the voltage generated in the reaction resistance. And a measuring unit for determining.

A resistance measuring device according to a second aspect is the first aspect.
In the resistance measuring device described above, the measuring unit responds to a current value of the first measuring AC signal flowing through the membrane resistance when a voltage corresponding to a current value of the measuring signal flowing through the fuel cell is input. And a voltage corresponding to the current value of the first measuring AC signal, which is generated by the membrane resistance. A first synchronous rectification circuit that detects a voltage, and a resistance value of the membrane resistance is obtained by dividing the voltage detected by the first synchronous rectification circuit by a voltage according to a current value of the first measurement AC signal. A first divider and a second voltage input according to a current value of the measurement signal flowing through the fuel cell, and a voltage output according to a current value of the second measurement AC signal flowing through the reaction resistance. With bandpass filter A second synchronous rectification circuit for synchronously detecting the voltage generated between the electrodes of the fuel cell and the voltage corresponding to the current value of the second measuring AC signal to detect the voltage generated in the reaction resistance; A second divider that obtains the resistance value of the reaction resistance by dividing the voltage detected by the second synchronous rectification circuit by the voltage corresponding to the current value of the second measurement AC signal. There is.

The diagnostic device according to claim 3 is a diagnostic device for diagnosing the quality of a fuel cell, wherein the resistance measuring device according to claim 1 or 2 and whether the resistance value of the membrane resistance is within a predetermined range or not. And a determination unit that determines whether or not the resistance value of the reaction resistance is less than or equal to a predetermined upper limit value.

According to a fourth aspect of the present invention, in the diagnostic apparatus according to the third aspect, the judging section determines that the resistance value of the membrane resistance is out of the predetermined range or the resistance value of the reaction resistance is When the predetermined upper limit is exceeded, the fuel cell to be diagnosed is determined to be defective.

A diagnostic device according to a fifth aspect is the diagnostic device according to the third or fourth aspect, further comprising a display section for displaying the determination result of the determination section.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a resistance measuring device and a diagnostic device according to the present invention will be described below with reference to the accompanying drawings. The same components as those in the configuration shown in FIG. 3 are designated by the same reference numerals, and redundant description will be omitted.

First, regarding the configuration of the diagnostic device 1, FIG.
Will be described with reference to.

The diagnostic device 1 is a diagnostic device for measuring the effective resistance of the fuel cell to be measured and diagnosing the quality of the fuel cell based on the measured value. As shown in FIG. The measurement unit 12, the determination unit 13, and the display unit 14 are provided. The signal generator 11 includes the oscillator 2
1, 22, an amplifier 23 and resistors 24 to 26. In this case, the oscillator 21 has a frequency (for example, 10 kHz) at which the membrane resistance of the fuel cell BT to be measured can be measured.
Of the second measurement AC signal having a frequency (a frequency lower than the frequency of the first measurement AC signal: eg, 10 Hz) at which the oscillator 22 can measure the reaction resistance of the fuel cell BT. To generate. The amplifier 23 and the resistors 24 to 26 mix the first measurement AC signal and the second measurement AC signal generated by the oscillators 21 and 22 to generate a measurement signal.

The measuring section 12 includes a bandpass filter 31,
41, synchronous detection circuits 32 and 42, low-pass filter 3
3, 43, dividers 34, 44 and comparator 35,
It is configured with 45. In this case, the band pass filter 31, the synchronous detection circuit 32, the low pass filter 33
And a divider 34 measures the membrane resistance. Specifically, the bandpass filter 31 corresponds to the first bandpass filter in the present invention, and when the sensor signal output from the current detection sensor CT is input, it corresponds to the current value of the first measurement AC signal. Output voltage V2. Synchronous detection circuit 32
Corresponds to the first synchronous rectification circuit in the present invention, and the voltage V1 and the voltage V2 generated in the internal resistance of the fuel cell BT by the flow of the measurement signal are synchronously detected, so that both ends of the membrane resistance are equivalently detected. A voltage V3 including a voltage corresponding to the voltage generated at is generated. In this case, the voltage V1 may be input to the bandpass filter 31, and the sensor signal output from the current detection sensor CT may be input to the synchronous detection circuit 32 instead of the voltage V1 (in a reaction resistance measuring circuit described later). The same). The low-pass filter 33 has a resistor 3
6 and the capacitor 37, the high frequency component is removed from the voltage V3 to output only the DC voltage V4 corresponding to the voltage generated across the membrane resistance. The divider 34 has a voltage V
By dividing 4 by the voltage V2, a voltage V5 having a voltage value proportional to the effective resistance value of the film resistance is output.

On the other hand, the bandpass filter 41, the synchronous detection circuit 42, the lowpass filter 43 and the divider 44 measure the reaction resistance. Specifically, the bandpass filter 4
1 corresponds to the second bandpass filter in the present invention, and when the sensor signal output from the current detection sensor CT is input, the voltage V1 corresponding to the current value of the second measurement signal is input.
2 is output. The synchronous detection circuit 42 corresponds to the second synchronous rectification circuit in the present invention, and is equivalently equivalent to the synchronous detection by the voltage V1 and the voltage V12 generated in the internal resistance of the fuel cell BT when the measurement signal flows. A voltage V1 including a voltage corresponding to the voltage generated across the reaction resistance
3 is generated. The low-pass filter 43, in combination with the resistor 46 and the capacitor 47, removes a high frequency part from the voltage V13 and outputs only a DC voltage V14 corresponding to the voltage generated across the reaction resistor. The divider 44 has a voltage V
A voltage V15 proportional to the effective resistance value of the reaction resistance is output by dividing 14 by the voltage V12.

The comparator 35 includes a lower limit judgment power source 38.
Lower limit voltage V6 and upper limit determination power supply 39 output from
Comparing the upper limit voltage V7 and the voltage V5 output from
When the voltage V5 is out of the voltage range (predetermined range) from the lower limit voltage V6 to the upper limit voltage V7, the detection signal is output.
In this case, the lower limit voltage V6 is a voltage corresponding to the minimum effective resistance value (for example, 70% of the resistance value R1 shown in FIG. 2) of the membrane resistance in the non-defective fuel cell BT which is not internally short-circuited. Corresponding to, the upper limit voltage V7 is the maximum effective resistance value allowable as the film resistance of the non-defective fuel cell BT (for example, 130% of the resistance value R1 shown in FIG. 2).
Corresponds to the voltage corresponding to. In addition, the comparator 45
Is the upper limit voltage V16 output from the upper limit determination power supply 48.
And the voltage V15 are compared, and the voltage V15 is the upper limit voltage V1.
When it exceeds 6, the detection signal is output. in this case,
The upper limit voltage V16 corresponds to a voltage corresponding to the maximum effective resistance value (for example, 130% of the resistance value R2 shown in FIG. 2) that is allowable as the reaction resistance of the non-defective fuel cell BT. Therefore, by monitoring the detection signals of the comparators 35 and 45, the effective resistance value of the membrane resistance falls within ± 30% of the resistance value R1, and the effective resistance value of the reaction resistance becomes the resistance value R2. On the other hand, when it is within + 130% or less, it is possible to determine that the fuel cell BT is in a normal reaction state without causing an internal short circuit. Regarding the lower limit of the effective resistance value of the reaction resistance,
Since the internal short circuit can be discriminated based on the detection signal of the comparator 35, its setting is unnecessary.

The determination unit 13 determines the quality of the fuel cell BT based on the detection signals output by the comparators 35 and 45, and outputs the determination result to an external device (not shown) and displays it on the display unit 14. Specifically, the determination unit 1
3 is an external device, for example, a comparator 35,
The NG signal is output when the detection signal is output from at least one of the 45, and the OK signal is output when the detection signal is not input from any of the 45. In addition, the determination unit 13 converts the voltage values of the voltages V5 and V15 into effective resistance values of the membrane resistance and the reaction resistance of the fuel cell BT, and then calculates the display unit 1
No. 4, each effective resistance value is displayed, and when an OK signal is output, a message indicating “non-defective product” is displayed.
When outputting the signal, a message indicating "defective product" is displayed. The display unit 14 displays the effective resistance values of the membrane resistance and the reaction resistance of the fuel cell BT based on the display data output by the determination unit 13, and also displays the quality.

Next, the fuel cell BT by this diagnostic device 1
The method of measuring the effective voltage and the pass / fail diagnosis operation will be described with reference to FIG.

Prior to the measurement, as shown in FIG.
A load 2 having a predetermined resistance value corresponding to the electromotive force of the fuel cell BT is connected to both electrodes of the fuel cell BT via the probes P1 and P2. Next, a current detection sensor CT that detects the current flowing through the fuel cell BT is arranged so as to surround the probe P1 connected to the positive electrode side of the fuel cell BT, and the current detection sensor CT and the sensor signal input terminal of the diagnostic device 1 are arranged. And connect.

The probe P3 is connected to the probe P1 (or the positive electrode of the fuel cell BT), and the probe P4 is connected to the negative electrode of the fuel cell BT. Further, the probe P5 is connected to the positive electrode of the fuel cell BT, and the probe P6 is connected to the negative electrode of the fuel cell BT. As a result, the measurement signal is applied to the fuel cell BT, and the sensor signal corresponding to the voltage corresponding to the current value of the measurement signal flowing through the fuel cell BT is output from the current detection sensor CT to the sensor signal input terminal of the diagnostic device 1. In addition to being output, the voltage V1 generated between both electrodes of the fuel cell BT is output via the probe P5 to the sense H terminal (the input section of the measuring section 12) of the diagnostic device 1.

The sensor signal output from the current detection sensor CT is input to the measuring unit 12 via the sensor signal input terminal, divided into two, and input to the bandpass filters 31 and 41, respectively. At this time, the bandpass filter 31
Extracts a voltage V2 proportional to (corresponding to) the current value of the first measuring AC signal from the input sensor signal and outputs the voltage V2 to the synchronous detection circuit 32. Next, the synchronous detection circuit 32 synchronously detects the voltage V2 and the voltage V1 to generate and output the voltage V3, and subsequently, the low-pass filter 33 removes a high frequency component included in the voltage V3, A voltage V4 proportional to the voltage generated in the effective resistance of the membrane resistance is output. Next, the divider 34 outputs the voltage V5 proportional to the effective resistance value of the film resistance to the comparator 35 and the determination unit 13 by dividing the voltage V4 by the voltage V2. On the other hand, the bandpass filter 41 has a voltage V12 proportional (according to) the current value of the second measurement AC signal from the input sensor signal.
Is extracted and output to the synchronous detection circuit 42. Next, the synchronous detection circuit 42 synchronously detects the voltage V12 and the voltage V1 to generate and output the voltage V13, and subsequently, the low-pass filter 43 removes a high frequency portion included in the voltage V13, The voltage V14 proportional to the voltage generated in the effective resistance of the reaction resistance is output. Next, the divider 44 outputs the voltage V15 proportional to the effective resistance value of the reaction resistance to the comparator 45 and the determination unit 13 by dividing the voltage V14 by the voltage V12. Thereby, the effective resistance values of the membrane resistance and the reaction resistance are simultaneously measured.

Subsequently, the comparator 35 causes the voltage V5
And the lower limit voltage V6 input from the lower limit determination power supply 38 and the upper limit voltage V7 input from the upper limit determination power supply 39 are compared, and when the voltage V5 is out of the range of both voltages, a detection signal is output. On the other hand, the comparator 45
15 and the upper limit voltage V1 input from the upper limit determination power supply 48
6, the detection signal is output when the voltage V15 exceeds the upper limit voltage V16. Subsequently, the determination unit 13 determines the quality of the fuel cell BT based on the detection signals output from the comparators 35 and 45, respectively. in this case,
The determination unit 13 outputs the voltages V5 and V15 from the dividers 34 and 44.
Is output for a predetermined time, and when a detection signal is output from at least one of the comparators 35 and 45, the fuel cell BT is determined to be defective, an NG signal is output, and the detection signal is output from both. If not, it is judged to be normal and an OK signal is output. Thereby, the quality of the fuel cell BT is diagnosed based on the measurement results of the membrane resistance and the reaction resistance. In addition, the determination unit 13 digitizes the voltage V5 output from the divider 34 and the voltage V15 output from the divider 44, and displays each numerical value (measured value) and the pass / fail determination result of the fuel cell BT. It is displayed on the section 14. As a result, the measurement person is notified of the measured values of the membrane resistance and reaction resistance of the fuel cell BT and the diagnostic result.

As described above, according to the diagnostic device 1, the measurement is performed by mixing the first measurement signal and the second measurement signal for measuring the effective resistance values of the membrane resistance and the reaction resistance of the fuel cell BT. With the configuration including the signal generation unit 11 that generates the use signal and the measurement unit 12 that measures each effective resistance value of the membrane resistance and the reaction resistance,
Each effective resistance value of the membrane resistance and the reaction resistance can be measured at the same time. Therefore, since the time required for measurement can be shortened, the effective resistance of the fuel cell BT can be efficiently measured. Further, since the determination unit 13 is provided, it is possible to automatically diagnose the quality of the fuel cell. Furthermore, by providing the display unit 14, the measurer can visually and surely recognize the determination result and can easily confirm the measured value.

The present invention is not limited to the above-described embodiments of the present invention. For example, in the diagnostic device 1 described above, the example in which the signal generation unit 11 is configured by including the oscillators 21 and 22 that generate a signal of a fixed frequency has been described.
The signal generation unit can also be configured by including a DDS or PLL circuit whose frequency can be set arbitrarily. In addition, the diagnostic device 1
Can also be incorporated into the fuel cell to be measured. In this case, for example, a self-diagnosis of the fuel cell BT can be performed periodically and automatically by providing a timer for measuring the measurement start time. Further, by providing a recording device for recording the measured value, it is possible to grasp the transition of the measured value and predict the life of the fuel cell based on this.

[0026]

As described above, according to the resistance measuring device of the first aspect, the first measuring AC signal for measuring the membrane resistance and the second measuring AC signal for measuring the reaction resistance are used. And a resistance value of the membrane resistance based on the current value of the first measurement AC signal flowing through the membrane resistance and the voltage generated at the membrane resistance and the reaction resistance flowing through the reaction resistance. A second measuring alternating current signal and a measuring unit for determining the resistance value of the reaction resistance based on the voltage generated in the reaction resistance, so that the effective resistance values of the membrane resistance and the reaction resistance are simultaneously measured. Because you can
The effective resistance value of the fuel cell can be efficiently measured in a short time.

According to the resistance measuring device of the second aspect, the first bandpass filter, the second bandpass filter, the first synchronous rectifying circuit, the second synchronous rectifying circuit, the first divider and the second divider. By configuring the measuring unit with the above, it is possible to measure each effective resistance value of the membrane resistance and the reaction resistance simultaneously and accurately.

According to the diagnostic device of the present invention, the resistance measuring device determines whether the effective resistance value of the membrane resistance is within a predetermined range, and the effective resistance value of the reaction resistance is a predetermined upper limit. Since the determination unit that determines whether the value is less than or equal to the value is provided, the quality of the fuel cell can be efficiently and automatically diagnosed.

According to the measuring device of claim 5,
Since the display unit that displays the determination result of the determination unit is provided, it is possible to reliably notify the measurer of the quality of the fuel cell.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing configurations of a diagnostic device 1 and a fuel cell BT according to an embodiment of the present invention.

FIG. 2 is a Cole-Cole plot diagram showing the internal resistance of a general fuel cell, in which the solid line is a non-defective fuel cell BT.
Shows a Cole-Cole plot diagram in Figure 3, and the broken line shows a Cole-Cole plot diagram in the defective fuel cell BT.

FIG. 3 is a circuit diagram showing configurations of a conventional resistance measuring device 61 and a fuel cell BT.

[Explanation of symbols]

1 Diagnostic device 2 load 11 Signal generator 12 Measuring section 13 Judgment section 14 Display 21,22 oscillator 31,41 bandpass filter 32,42 Synchronous detection circuit 34,44 divider 35, 45 comparator 38 Lower limit power supply 39,48 Power supply for upper limit judgment BT Fuel cell BT CT current detection sensor R1, R3 Membrane resistance R2, R4 reaction resistance

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G028 AA02 BE04 CG02 DH05 DH11                       DH14 DH16 FK01 FK02 FK08                       GL03 HN11 HN16                 2G036 AA03 AA27 BB08 CA06                 5H026 AA06 CX05                 5H027 AA06 KK51

Claims (5)

[Claims] 1. A measuring device for measuring an effective resistance of a fuel cell, comprising: a first measuring AC signal for measuring a membrane resistance forming a part of the effective resistance; and a part of the effective resistance. Measuring signal generating section for generating a measuring signal including a second measuring AC signal for measuring a reaction resistance, and the first signal flowing through the membrane resistance in a state where the measuring signal is applied to the fuel cell. 1 The resistance value of the membrane resistance is obtained based on the current value of the measurement AC signal and the voltage generated in the membrane resistance, and the current value of the second measurement AC signal flowing through the reaction resistance and the resistance value of the second measurement AC signal are generated in the reaction resistance. A resistance measuring device comprising: a measuring unit that obtains a resistance value of the reaction resistance based on a voltage. 2. The measurement unit, when a voltage corresponding to a current value of the measurement signal flowing through the fuel cell is input, a voltage corresponding to a current value of the first measurement AC signal flowing through the membrane resistance. A first band-pass filter for outputting the voltage, a voltage generated between both electrodes of the fuel cell, and a voltage corresponding to the current value of the first measurement AC signal, and a voltage generated in the membrane resistance is detected synchronously. A first synchronous rectification circuit for detecting, and a first value for obtaining a resistance value of the membrane resistance by dividing a voltage detected by the first synchronous rectification circuit by a voltage according to a current value of the first measurement AC signal. A divider and a second bandpass for inputting a voltage corresponding to the current value of the measuring signal flowing through the fuel cell and outputting a voltage corresponding to the current value of the second measuring AC signal flowing through the reaction resistance. Filter and the fuel cell A second synchronous rectification circuit that synchronously detects a voltage generated between the electrodes and a voltage corresponding to a current value of the second measurement AC signal to detect a voltage generated in the reaction resistance; A second method for obtaining the resistance value of the reaction resistance by dividing the voltage detected by the rectifier circuit by a voltage corresponding to the current value of the second measuring AC signal.
The resistance measuring device according to claim 1, further comprising a divider. 3. A diagnostic device for diagnosing the quality of a fuel cell, wherein the resistance measuring device according to claim 1 or 2 is used to determine whether or not the resistance value of the membrane resistance is within a predetermined range, and the reaction resistance. And a determination unit that determines whether or not the resistance value of is less than or equal to a predetermined upper limit value. 4. The determination unit, when the resistance value of the membrane resistance is out of the predetermined range or when the resistance value of the reaction resistance exceeds the predetermined upper limit value, the diagnosis target The diagnostic device according to claim 3, wherein the fuel cell is determined to be defective. 5. The diagnostic device according to claim 3, further comprising a display unit that displays a determination result of the determination unit.