TWI228591B - Solution concentration detection device of fuel cell and solution concentration detection method thereof - Google Patents

Abstract

The direct methanol fuel cell of the present invention comprises: a cell body and a solution concentration detection device. The cell body has a fuel tank, the fuel tank contains aqueous methanol solution. The solution concentration detection device has two oscillation circuits, a difference frequency circuit and a computation module. The first oscillation circuit has the first capacitor, the capacitor is immerged in the sealed reference solution, which can output a first oscillation signal. The second oscillation circuit has a second capacitor immerged in the aqueous methanol solution, which can output a second oscillation signal. The difference frequency circuit of the solution concentration detection device forms a difference frequency signal between the first oscillation signal and the second oscillation signal. The computation module can measure the frequency of the difference frequency signal, and then compute the methanol concentration in the solution according to the relationship of the preset difference frequency with respect to the concentration.

Description

1228591 Case No. 92112654 Amendment V. Description of the Invention (1) Technical Field of the Invention The present invention relates to a solution concentration detection device and a detection method thereof, particularly a detection device for obtaining an unknown solution concentration by using an oscillation frequency, and the same Fuel cell system of detection device. In the prior art, the concentration of fuel is often a very important parameter in the reaction process. For example, in the internal combustion engine, the concentration of the additive in the fuel will affect the ignition time; in the fuel cell of the liquid fuel, the concentration of the fuel will affect Power and efficiency of power generation. Therefore, a simple and accurate method to measure fuel concentration is the most important issue in the control of reaction procedures. Known methods for measuring fuel concentration, as disclosed in U.S. Patent Nos. 4, 4 3, 8 and 7 9 are based on the principle that under different solution concentrations, the optical refractive index of a solution is different, so a light source can be used. With a light sensing circuit, measuring the change in its refractive index, the concentration of the solution can be known. However, the main disadvantage of this measurement method is that the device structure of the optical method is complex and expensive, which is less suitable for commercial applications. In addition, U.S. Patent No. 6,4 6 2,5 6 2 also discloses a method for obtaining the concentration of a solution through voltage measurement, and its structure is shown in FIG. 1. One of the detection capacitors 18 is placed in a solution to be measured, and the other capacitor 16 is a standard capacitor of known capacitance. The measurement method is to use different conductivity constants in solutions of different concentrations to make each The capacitance value of the capacitor is different, and the obtained output voltage ν. Differences in size may also be used to measure solution concentration. The main disadvantages of using this method are: a. This method uses the output voltage generated by the current difference (12-I i) through the resistor 2 2 to determine the relative concentration of the solution to be measured, and the output voltage is relatively low

Page 6 1228591 _Case No. 92Π2654_Year Month and Day__ V. Description of the invention (2) Easy to measure and susceptible to external electromagnetic wave interference, noise immunity is poor. b. The circuit required to measure the voltage signal is more complicated, the measurement error is larger, and the difference caused by temperature changes cannot be corrected. c. The analog voltage signal measured by this method requires an analog-to-digital circuit to digitize the signal, which is difficult to apply. SUMMARY OF THE INVENTION In view of this, the object of the present invention is to provide a simple solution concentration detection method and device, and at the same time improve the shortcomings of the past using optical, voltage, current and other signals to measure the solution concentration, so that it has better noise immunity Force, high resolution and accuracy, and overcome the problem of temperature drift during concentration measurement. Another object of the present invention is to simplify the circuit of the concentration detection device, reduce the manufacturing cost, and make it applicable to fuel cells that generally use liquid fuel and other devices that require concentration detection and control. Another object of the present invention is to provide a concentration detection device that uses an oscillation circuit to generate different frequencies in a test solution and a standard concentration solution, and correspondingly finds the concentration of an unknown solution. In order to achieve the above object, the present invention provides a solution concentration detection method suitable for detecting a predetermined compound concentration in a test solution, which includes the following steps: first, providing a preset difference frequency frequency to concentration relationship according to experimental data, and then Provide a reference solution with a fixed concentration. A first oscillating circuit is provided, wherein the first oscillating circuit has a first capacitor immersed in the reference solution and can output a first oscillating signal; a second oscillating circuit is provided, wherein the second oscillating circuit has an immersed in the The second capacitor in the test solution can output a second oscillating signal. Then with the first oscillating signal and the first

1228591 Case No. 92112654 Amendment V. Description of the invention (3) Two-oscillation signal, and then according to the predetermined compound concentration in a relatively oscillating signal, the method of chemical combination and interpolation and the second oscillation in the solution of the present invention has to be tested. The first difference between the electrical output solutions is set to a degree. Jiashi is obtained by mixing the two components, namely the circuit capacitance, the oscillating capacitor circuit, and the difference frequency of the second device with the difference frequency. The difference signal is based on the preset concentration. In a better container, and after the formation of the difference frequency, the frequency can be changed: Η 疋 供 To provide a certain, difference signal, you can use the calculation mode of the container to calculate the difference frequency and measure the frequency versus the concentration. The difference signal in the relationship is that the combined signal is filtered and the frequency of the difference signal is measured according to a preset difference frequency. The first oscillating signal and the first in the solution to be measured are calculated; and the frequency pair in the solution to be tested is Concentration relationship, the liquid concentration path and the frequency capacitance of the immersion immersion solvent; the second vibration output and the first vibration exhaustion group can be used to detect the concentration degree. The solvent calculation mode is closed and the circuit is oscillated. And the first excess measurement system calculation device liquid concentration group. The stored solution has a signal of two vibrations and a differential frequency solution, and the applicability test is the first vibration of the reference solution and an immersion. In the signal of the solution oscillating signal, the frequency of the difference between the concentration of tritium in the oscillating liquid in the detection device is used to determine the frequency of each road. The alcohol can be detected and formed. The temperature error of the complex is RC oscillation. Circuit or oscillating electrical circuit, the first embodiment of the ceramic plane is the LC component capacitors, capacitors, capacitors, reference solution and immersed in the solution to be tested, the first oscillating electrical oscillating circuit, in which the gas characteristics are equal. It is a flat capacitor or the electrode can be sealed by a conductive material. The first capacitor is hermetically sealed in to eliminate the measurement path and the second oscillation circuit. The first oscillation circuit and the second are ceramic planar capacitors. The material is formed by coating.

Page 8 1228591 _ Case No. 92112654 _ Month and Day __ 5. Description of the invention (4), easier to assemble. In a preferred embodiment, the frequency difference circuit includes a frequency mixing circuit and a filter circuit. The frequency mixing circuit is configured to receive the first oscillation signal and the second oscillation signal, and form a combined frequency with the frequency of the two oscillation signals. Signal, and a difference frequency signal formed by the difference between the two oscillating signals. In addition, the frequency mixing circuit is preferably an X 0 R digital logic gate, and the filter circuit is a low-pass chirp signal, which is a vibration-plus signal with frequency division. In addition, the difference frequency circuit further includes a level resolution circuit, so that the output difference frequency signal forms an accurate square wave. The level resolution circuit may be a Schmitt trigger circuit, an inverter, or a voltage level comparator. In a preferred embodiment, the computing module includes a memory and a calculation unit. The memory stores a preset difference frequency-to-concentration relationship, and the calculation unit can use the difference signal according to the preset difference frequency-to-concentration relationship. Calculate the concentration of a given compound in the test solution. The computing module further includes a counter and a timer. The counter counts the number of waveforms of the differential frequency signal, and then obtains the frequency of the differential frequency signal through the computing unit. In addition, the present invention further provides a fuel cell, which includes a battery body and a solution concentration detection device as described above. The battery body has a fuel tank. The fuel tank contains a test solution having a predetermined compound, and the container sealing the reference solution and the first capacitor is immersed in the test solution of the fuel tank. Through the above configuration, the solution concentration detection device The fuel concentration in the fuel cell can be detected immediately. In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below in conjunction with the accompanying drawings, and described in detail as follows:

1228591 _Case No. 92Π2654_ Years and Months Revisions__ 5. Description of the Invention (5) Embodiments Due to the different dielectric constants of the solution at different concentrations, the sensors placed in the solution will have different impedances; therefore, in Capacitors with the same electrical characteristics are set in solutions with different concentrations, and their capacitance values are also different. If an oscillating circuit is formed with this capacitor, the oscillation frequency will be different accordingly. The solution concentration detection device provided by the present invention And the method is to make use of this characteristic, by analyzing the frequency generated by the vibrating circuit in the test solution and the known reference solution, the concentration of the test solution can be measured correspondingly.

FIG. 2 is a flowchart of a solution concentration detection method according to the present invention. As shown in FIG. 2, the solution concentration detection method of the present invention is suitable for detecting a predetermined compound concentration in a test solution, and includes the following steps: First, a preset difference frequency-to-concentration relationship is provided according to experimental data (S 2 1), and then provide a reference solution (S 2 2) with a fixed concentration, such as: pure water, 10 wt% solution or other fixed concentration solution.

Next, a first oscillating circuit is provided, wherein the first oscillating circuit has a first capacitor immersed in a reference solution, and can output a first oscillating signal (S23); and a second oscillating circuit is further provided, wherein the second oscillating circuit A second capacitor immersed in the solution to be tested can output a second oscillating signal (S 2 4). Then use the absolute value of the frequency difference between the first oscillation signal and the second oscillation signal to form a difference frequency signal (S 2 5), and measure the frequency or period (S 2 6) of the difference frequency signal, and finally according to the preset The relationship between the difference frequency and the concentration can obtain the predetermined compound concentration (S 2 7) in the test solution. As shown in FIG. 3, the solution concentration detecting device 20 of the present invention includes a first oscillation circuit 21, a second oscillation circuit 22, a difference frequency circuit 23, and an operation module 27, respectively. The first oscillating circuit 21 has a reference solution 282

Page 10 1228591 _Case No. 92112654_ Year Month Date__ V. Description of the Invention (6) The first capacitor 211 made of a dielectric material, and the reference solution 282 and the electrode of the first capacitor are sealed and sealed in a container 2 8 1. A first oscillating signal fi can be output. The second oscillating circuit 22 has a second capacitor 221 using the test solution 2 8 3 as a dielectric material, and can output a second oscillating signal dagger. The difference frequency circuit 23 of the solution concentration detection device 20 can form a difference frequency signal fd from the input first oscillation signal dagger and the second oscillation signal d2, and the arithmetic module can measure the frequency of the difference frequency signal fd and then According to the preset difference frequency-to-concentration relationship, the predetermined compound concentration in the test solution 2 8 3 is calculated by interpolation. Secondly, the container 2 8 1 containing the reference solution 2 8 2 is immersed in the solution to be measured 2 8 3, which can eliminate the temperature error during the measurement. As shown in FIG. 3, the difference frequency circuit 23 of the solution concentration detection device 20 has a mixing circuit 24 and a filtering circuit 25. The mixing circuit 24 receives the first oscillation signal I and the second oscillation from the two oscillation circuits. The signal dagger, the sum of the frequencies of the two oscillating signals forms a combined frequency signal (fi + h), and the difference between the frequencies of the two oscillating signals forms a differential frequency signal (fi-h). The frequency signal fm is input to the filter circuit 25. The filter circuit 25 is a low-pass filter for filtering high-frequency oscillating signals (combined signals) and outputting low-frequency difference-frequency signals (f i-h). When the oscillating signal generated by the two oscillating circuits is mixed and then filtered and attenuated, the sent signal fdl is a lower frequency square wave or a triangular wave. In order to allow the signal to be accurately judged, the solution concentration detection of the present invention The difference frequency circuit 23 of the device 20 further includes a level resolution circuit 26, which can make the output difference frequency signal closer to the digital waveform of the binary level (binary 1 eve 1). In addition, the level resolution circuit 26 can be achieved simply by an inverter or a voltage level comparator, or by a logic circuit including a Schmitt trigger.

1228591

The solution concentration detection device 2 of the present invention further includes a computing module 27. The computing module 27 may be a microprocessor, which includes a computing unit 271, a memory 2 7 2, a counter 2 7 3, and a timer.器 2 74. The device 2 74. In the record & body 272, as shown in Figure 4, one of the preset differential frequency-to-concentration relationships obtained in advance can be stored. The counter 2 7 3 can be used with the timer 274 to calculate the number of waveforms of the differential frequency signal fd within a given time. , And then the calculation unit obtains the frequency of the difference frequency signal f. Finally, the calculation unit 271 may interpolate the concentration of the predetermined compound in the test solution 283 from the frequency fd of the difference signal according to a preset difference frequency frequency-to-concentration relationship (as shown in FIG. 4). Fig. 5A of the first embodiment is a circuit diagram of the solution concentration detection device according to the first embodiment of the present invention. As shown in Fig. 5A, the first oscillation circuit 21 and the second oscillation circuit 22 may be formed by a concentration of a roll valley structure. {RC1, C2, a resistor r 1 r 2 and an inverter U1A, U2A composed of RC oscillation: circuit structure, the first capacitor C 1 and the second capacitor C 2 have the same structure and electrical Characteristics, resistors R1 and R2 have the same resistance value. The first oscillating circuit 21 and the second oscillating surplus circuit 22 use RC repeated charging and discharging to achieve the oscillating operation, and output vibration-free signals. The frequency of the oscillation signal is related to the resistance values R 1 and R 2 in the circuit and the capacitance values C 1 and C 2, and the capacitance value of the concentration detector is approximately proportional to the concentration of the solution. Therefore, via the vibration surplus circuit 2 1 The frequency of the vibration i can be used to know the degree of the solution. Secondly, in order to make the first oscillation circuit 21 and the second oscillation circuit 22 output relatively stable waveforms, an inverter is respectively provided between the first oscillation circuit 21 and the second oscillation surplus circuit 22 and the mixing circuit. U 1 B, U 2 B for load buffering. The mixer 24 of the first embodiment of the present invention is an X 〇 logic gate, and X q r logic

Page 121228591 _Case No. 92112654_Year Month Date__ V. Description of the invention (8) The gate can combine the two-frequency sum signal and the two-frequency difference signal of the first oscillation signal 1 and the second oscillation signal. The formation output of the carrier is to output a mixed signal fm formed by a combined signal and a difference frequency signal. When the mixed signal passes the low-pass filter circuit 25, a difference frequency signal fdi of a lower frequency can be obtained.

Figure 5B is the waveform of each signal of the solution concentration detection device. As shown in Figure 5B, when the mixed signal fm is low-pass filtered, the output difference frequency signal fdl is an irregular triangle wave at a lower frequency. In order to allow the differential frequency signal fdl to be accurately judged, the differential frequency circuit 23 of the first embodiment further includes a signal amplifier circuit 29 and a level resolution circuit 26. The level resolution circuit 26 is simply composed of an inverter U The composition of 1 C can obtain better square wave difference frequency signal fd after filtering high-frequency noise, and can also make the microprocessor 2 7 obtain better measurement results. Fig. 5C of the second embodiment is a circuit diagram of the solution concentration detection device of the second embodiment of the present invention. As shown in Fig. 5C, the circuit of the second embodiment is similar to the first embodiment, except that the first oscillating circuit 21 and The second oscillating circuit 22 may be constituted by an LC oscillating circuit composed of a concentration detector C1, C2, an inductor L1, L2, and an inverter U1A, U2A. The first capacitor C1 and The second capacitor C 2 also has the same structure and electrical characteristics, and the inductors L 1 and L 2 have the same inductance value. The first oscillating circuit 21 'and the second oscillating circuit 22' use an LC charging and discharging method to achieve an oscillating operation and output an oscillating signal.

In addition to the low-pass filter, the filter circuit 25 of the second embodiment can also be designed by means of band-pass filter circuits, transistor circuits, logic circuits, etc. The breakpoint frequency of the filter circuit is set to the oscillation frequency of the two oscillation circuits. The higher frequency combined signal is filtered, and the lower frequency difference frequency fd is passed. Second, the level resolution circuit of the second embodiment is a Schmitt trigger circuit.

Page 13 1228591 Case No. 92112654 Rev. V. Description of the invention (9) The structure can also obtain a more accurate square wave difference frequency signal fd as shown in Figure 5B. FIG. 6 of the third embodiment is a sectional view of a fuel cell having a solution concentration detection device according to the present invention. The solution concentration detection device mentioned in the first and second embodiments of the present invention has a simple measurement circuit and can be applied to general Fuel cells using liquid fuels, such as Direct Fuel Cells (D irect Meth η 1 Fuel Cell, DMFC). As shown in FIG. 6, the direct methanol fuel cell includes a membrane electrode group 3 2, and the membrane electrode group 32 is formed by thermocompression lamination of a proton conductive membrane 321, an anode catalyst electrode 3 2 2 and a cathode catalyst electrode 3 2 3 On the anode catalyst electrode 3 2 2 side, there is a fuel tank 31 containing an aqueous methanol solution of unknown concentration, and on the cathode catalyst electrode 3 2 3 it is directly in contact with air. The solution concentration detection device 20 shown in FIG. 3 is set beside the fuel tank 3 1, and the second capacitor 2 2 1 of the second oscillation circuit is immersed in the methanol solution to be measured, and the reference solution and the first capacitor 2 are sealed. The 1 1 container 2 8 1 is also immersed in the methanol solution to be measured, thereby eliminating errors caused by temperature during measurement. As mentioned above, the oscillation signal generated by the solution concentration detection device can be measured after mixing, filtering, and calibrating the frequency value of a difference frequency signal, and then the concentration is measured by a preset difference frequency preset in a microprocessor. The relationship is that the methanol concentration in the methanol solution can be obtained by interpolation. Figures 7A to 7C are diagrams of capacitor structures suitable for the solution concentration detection device of the present invention. The first capacitor and the second capacitor used in the solution concentration detection device may be composed of two opposite electrode plates 41, with a predetermined distance d in the middle for the alcohol solution to pass through (FIG. 7A). To help the solution flow,

Page 14 1228591 _Case No. 92112654_Year Month__ V. Description of the invention (10) A through hole 5 2 may be formed on the plate 51 to promote the flow of the solution (Figure 7B). In addition, the first capacitor and the second capacitor can also be coated with a conductive material on two sets of electrodes 6 2 and 6 3 on an insulating substrate 61 to form a planar capacitor (Figure 7C). In this embodiment, the reference solution is pure water, and the methanol aqueous solution is the test solution. The relationship between the frequency difference and the concentration is shown in Figure 4. The solution concentration detection method proposed by the present invention can accurately measure the frequency difference change caused by the methanol concentration change, and the measurement frequency can be accurate to one thousandth or one thousandth, and the frequency measurement is not easy. Affected by external noise, the overall detection of the wire is also simple, so it is better than other measurement methods. In addition, the solution concentration detection device of the present invention can directly convert the vibration i-frequency signal into a digital signal acceptable to the microprocessor, and can be simply used with a programmable single chip for subsequent control and use. Although the present invention has been disclosed in the preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and retouching without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be determined by the scope of the attached patent application.

1228591 _Case No. 92112654_ 年月 日 __ Brief Description of Drawings Figure 1 is a circuit diagram of a conventional solution concentration detection method. Figure 2 is a flow chart of the solution concentration detection method of the present invention. Fig. 3 is a block diagram of a solution concentration detection device of the present invention. Fig. 4 is a graph showing the relationship between the frequency difference and the methanol concentration in the embodiment. Fig. 5A is a circuit diagram of a solution concentration detecting device according to the first embodiment of the present invention. Figure 5B is a signal waveform diagram of the solution concentration detection device. Fig. 5C is a circuit diagram of a solution concentration detecting device according to a second embodiment of the present invention.

Fig. 6 is a sectional view of a fuel cell having a solution concentration detecting device according to the present invention. Figure 7A is a schematic diagram of one of the first capacitor and the second capacitor of the present invention. Figure 7B is another schematic diagram of the first capacitor and the second capacitor of the present invention. Fig. 7C is another schematic diagram of the first capacitor and the second capacitor of the present invention. Explanation of symbols 10 Conventional solution concentration detection device 12

14 Transformer circuit 16 Standard capacitor 18 Sense capacitor 1 9 1 Amplifier 1 9 2 Resistance

Page 16 1228591 __Case No. 92112654_Year Month Day_Modified illustration of the diagram 2 0 The solution concentration detection device 2 of the present invention 2 1 The first oscillating circuit 211 the first capacitor 22 the second oscillating circuit 22 1 the second capacitor 2 3 Differential frequency circuit 2 4 Mixer circuit 2 5 Filter circuit 26 Level resolution circuit 2 7 Operation module

2 7 1 Calculation unit 2 7 2 Memory 2 7 3 Counter 2 74 Timer 2 8 1 Container 2 8 2 Reference solution 2 8 3 Solution to be tested 29 Amplifying circuit 30 Fuel cell with solution concentration detection device 3 1 Fuel tank

3 2 Membrane electrode group 3 2 1 Proton conductive membrane 3 2 2 Anode catalyst electrode 3 2 3 Cathode catalyst electrode 40, 50, 60 Capacitor 4 1, 5 1 Electrode plate

Page 17 1228591 _Case No. 92112654_Year Month Day_A simple explanation of the revised diagram 5 2 through hole 6 1 insulating substrate 6 2, 6 3 electrode d predetermined distance f! First vibration signal f2 second oscillation signal fra mixing Signal fdi, fd difference frequency signal win, methanol alcohol flow direction gin air entry direction

Rl, R2, R4, R6, R8 resistors

Cl, C2, C4, C6, C8 Resistors U1A, U2A, U1B, U2B, U1C Inverter U4AX0R Logic Gate Q1 Transistor

Page 18

Claims (1)

1228591 _ Case No. 92112654_ 年月 日 _Character_ 6. Application scope 1. A solution concentration detection method is suitable for detecting the concentration of a given compound in a test solution. The solution concentration detection method includes the following steps: Provide a A reference solution having a fixed concentration; providing a first oscillating circuit, wherein the first oscillating circuit has a first capacitor using the reference solution as a dielectric material for outputting a first oscillating signal; providing a second oscillating circuit Wherein the second oscillating circuit has a second capacitor using the solution to be measured as a dielectric material for outputting a second oscillating signal; Forming a difference frequency signal by using the first oscillation signal and the second oscillation signal, wherein the frequency of the difference frequency signal is an absolute value of the frequency difference between the first oscillation signal and the second oscillation signal; and measuring the difference frequency signal Frequency, providing a relationship between a preset difference frequency and concentration; and calculating the concentration of a predetermined compound in the test solution based on the frequency of the difference signal according to the relationship between the preset difference frequency and concentration. 2. A solution concentration detection device adapted to detect a predetermined compound concentration in a test solution, the solution concentration detection device comprising: a first oscillating circuit having a first capacitor using the reference solution as a dielectric material, For outputting a first oscillating signal; A second oscillating circuit having a second capacitor using the test solution as a dielectric material to output a second oscillating signal; a differential frequency circuit connected to the first oscillating circuit and the second oscillating circuit, The difference frequency circuit is formed by the first oscillation signal and the second oscillation signal Page 19 1228591 _Case No. 92112654_Year Month Date__ VI. Patent application scope-a differential frequency signal, wherein the frequency of the differential frequency signal is the absolute value of the frequency difference between the first oscillation signal and the second oscillation signal; and An arithmetic module is connected to the differential frequency circuit and calculates a predetermined compound concentration of the solution to be tested by measuring the frequency of the differential frequency signal. 3. The solution concentration detection device according to item 2 of the scope of the patent application, wherein the first capacitor is immersed in the reference solution. 4. The solution concentration detection device according to item 2 of the scope of the patent application, wherein the second capacitor is immersed in the solution to be measured. 5. The solution concentration detection device according to item 3 of the scope of patent application, wherein the reference solution is packaged in a closed container. 6. The solution concentration detection device according to item 5 of the scope of the patent application, wherein the closed container is immersed in the solution to be measured. 7. The solution concentration detection device according to item 3 of the scope of patent application, wherein the first capacitor and the second capacitor have the same geometric structure. 8. The solution concentration detection device according to item 7 of the scope of the patent application, wherein the first capacitor and the second capacitor each have two conductive plates spaced a predetermined distance apart, and the conductive plates have a plurality of through holes for the solution. by. 9. The solution concentration detection device according to item 7 in the scope of the patent application, wherein the first capacitor and the second capacitor are both planar capacitors, each of which includes an insulating substrate and is disposed on the same surface of the insulating substrate without contacting each other. Of two electrodes. 10. The solution concentration detection device according to item 9 of the scope of the patent application, wherein the insulating substrates respectively have a grounded conductive layer on opposite sides of the electrodes. 1228591 Case No. 92112654 λ_a. Amendment VI. Patent application scope 1 1. The solution concentration detection device described in item 7 of the patent application scope, wherein the first oscillation circuit and the second oscillation circuit are both RC oscillation circuits. 1 2. The solution concentration detection device according to item 11 of the scope of patent application, wherein the first oscillating circuit has a first resistance, the second oscillating circuit has a second resistance, and the first resistance and The design resistance of the second resistor is the same. 1 3. The solution concentration detection device according to item 7 of the scope of patent application, wherein the first oscillation circuit and the second oscillation circuit are both LC oscillation circuits. 1 4. The solution concentration detection device according to item 13 of the scope of patent application, wherein the first oscillating circuit has a first inductance, the second oscillating circuit has a second inductance, and the first inductance and The inductance of the second inductor is the same. 1 5. The solution concentration detection device according to item 2 of the scope of the patent application, wherein the differential frequency circuit includes a digital logic exclusive OR gate, which uses the first oscillation signal and the second oscillation The signal produces a mixed signal. 16. The solution concentration detection device according to item 2 of the scope of patent application, wherein the difference frequency circuit further includes a low-pass filter for taking out the difference frequency signal from the signal generated by the difference frequency signal processing. 1 7. The solution concentration detection device according to item 2 of the scope of patent application, wherein the difference frequency circuit further includes a level resolution circuit to make the waveform of the difference frequency signal closer to the binary level (binary 1 eve). 1) Digital waveform Page 21 1228591 Case No. 92112654 _η Amendment 6. Scope of patent application 1 8. The solution concentration detection device described in item 17 of the scope of patent application, wherein the level resolution circuit is a Schmitt trigger circuit. 19. The solution concentration detection device according to item 2 of the scope of patent application, wherein the computing module includes a memory and a calculation unit, and a preset difference frequency frequency-to-concentration relationship is stored in the memory, and the calculation unit The difference signal is used to calculate the predetermined compound concentration in the test solution according to the preset difference frequency-to-concentration relationship. 20. The solution concentration detection device according to item 19 of the scope of the patent application, wherein the operation module further includes a counter and a timer, and the counter counts a number of pulse waves generated by the differential frequency circuit within a predetermined time, The frequency of the difference frequency signal is obtained through the calculation unit. 2 1. A fuel cell having a fuel solution concentration detection device, comprising: a battery body having a fuel tank containing a test solution having a predetermined compound in the fuel tank; a container containing a fixed concentration of Reference solution; a first oscillating circuit having a first capacitor using the reference solution as a dielectric material to output a first oscillating signal; a second oscillating circuit having a solution to be tested as a dielectric material A second capacitor for outputting a second oscillating signal; a differential frequency circuit connected to the first oscillating circuit and the second oscillating circuit, the differential frequency circuit being formed by the first oscillating signal and the second oscillating signal A difference frequency signal, wherein the frequency of the difference frequency signal is an absolute value of the frequency difference between the first oscillation signal and the second oscillation signal; and Page 22 1228591 Case No. 92112654_Year_Month__ VI. Patent application scope An arithmetic module is connected to the differential frequency circuit and calculates the predetermined compound concentration of the test solution by measuring the frequency of the differential frequency signal. 2 2. The fuel cell having a fuel solution concentration detection device as described in item 21 of the scope of the patent application, wherein the container is immersed in the test solution. Page 23