Test method and device for humidity sensor temperature drift mechanism research

Abstract

The invention discloses a testing method and a testing device for researching a temperature drift mechanism of a humidity sensor, which are applied to the field of electronics and circuits and aim at solving the problem that the temperature drift mechanism of the humidity sensor is not comprehensively and accurately researched in the prior art. According to the invention, the impedance spectrum information of the humidity sensor is collected under different temperature conditions through a self-developed high-precision miniaturized impedance measuring instrument. Based on impedance spectrum information, an equivalent circuit model is fitted, circuit element parameters are quantified, and a temperature drift mechanism of the humidity sensor is deeply analyzed by combining equivalent circuit model combinations and circuit element parameter changes under different temperature conditions.

Description

Technical Field

[0001] The present invention belongs to the field of electronics and circuits, and particularly relates to a sensor temperature drift test technology and device. Background Art

[0002] The temperature drift phenomenon of a humidity sensor refers to the phenomenon that the output result of the sensor deviates due to the influence of environmental temperature changes. This phenomenon stems from the effect of temperature on the humidity-sensitive medium inside the humidity sensor. Studying the temperature drift mechanism of the humidity sensor aims to find out how temperature acts on the humidity-sensitive medium of the humidity sensor, thereby causing the temperature drift phenomenon. On the basis of clarifying the specific influence of temperature on the humidity-sensitive medium of the humidity sensor, targeted temperature drift suppression schemes can be adopted to reduce the temperature drift of the humidity sensor. Therefore, it is of great significance to study the temperature drift mechanism of the humidity sensor. Summary of the Invention

[0003] To solve the above technical problems, the present invention proposes a test method and device for studying the temperature drift mechanism of a humidity sensor; by measuring the impedance spectrum information of the humidity sensor at different temperatures, fitting an equivalent circuit model of the humidity sensor, and quantifying the circuit model component parameters. Combining the equivalent circuit model combinations and circuit component parameter information under different temperature conditions, analyze and study the temperature drift mechanism of the humidity sensor.

[0004] One of the technical solutions adopted by the present invention is: a test method for studying the temperature drift mechanism of a humidity sensor, including:

[0005] Set the initial relative humidity (RH i ) and temperature (T i ) of the test environment, and specify the initial test temperature (T a ) and the termination test temperature (T s );

[0006] The test device generates an excitation signal and inputs it into the humidity sensor measurement circuit;

[0007] Collect the output signal of the humidity sensor measurement circuit;

[0008] In the processor core unit of the test device, solve the above data to obtain impedance spectrum information;

[0009] Based on the impedance spectrum information, fit the equivalent circuit model of the humidity sensor and quantify its circuit component parameters;

[0010] If the current temperature (T i ) is lower (or higher) than the termination test temperature (T s ), then increase (or decrease) the environmental temperature by t°C and repeat the test;

[0011] When the temperature reaches the termination test temperature (T s ), the measurement ends;

[0012] Based on the equivalent circuit model combination and circuit element parameter information under different temperature conditions, analyze and study the temperature drift mechanism of the humidity sensor.

[0013] The second technical solution adopted by the present invention is: a test device for studying the temperature drift mechanism of a humidity sensor; mainly including: an FPGA module, a humidity sensor measurement circuit module, a temperature and humidity calibration module, and a display module.

[0014] The FPGA module is used for signal generation and the calculation of multi-frequency point impedance information; the humidity sensor measurement circuit measures the complex impedance of the humidity sensor; and the HMP110 sensor is used to perform standard calibration on the temperature and humidity of the test environment; the display module is used for data display and visual analysis of the data.

[0015] The humidity sensor measurement circuit includes: a power supply module, a digital-to-analog converter, a voltage follower, a self-balancing circuit, and an analog-to-digital converter. The power supply module supplies power to the self-balancing circuit. The digital-to-analog converter converts the input excitation signal from a digital quantity into an analog quantity and inputs it into the voltage follower. The voltage follower plays a role in isolating, buffering, and improving the load-carrying capacity of the front and rear circuits. The self-balancing circuit is an I / V conversion circuit containing the humidity sensor to be measured. After the input signal passes through the self-balancing circuit, the amplitude and phase will change. The analog-to-digital converter converts the changed analog output signal into a digital quantity and inputs it into the internal multiplier in the FPGA module for mixing processing.

[0016] The FPGA module includes: a dual-channel direct digital synthesizer (DDS) module, a fast Fourier transform (FFT) processing module, and a mixing module. The dual-channel DDS module generates a swept-frequency cosine excitation signal DDS1 as the input of the humidity sensor measurement circuit, and at the same time provides a known reference signal DDS2 for the mixer. The mixing module performs multiplier mixing processing on the signal with a frequency of f1 collected by the ADC and the signal with a frequency of f2 generated by DDS2 inside the FPGA, and the obtained output signal contains two frequencies: f1 + f2 and f1 - f2 respectively. By adjusting the signal frequency generated by the DDS2 module, the two frequencies f1 + f2 and f1 - f2 are located at the frequency points of the FFT processing, thereby reducing the influence brought by spectral leakage. The mixed signal is input into the FFT processing module for the calculation of multi-frequency point impedance information, and finally the impedance spectrum information of the humidity sensor is obtained.

[0017] Temperature and humidity calibration module: The HMP110 sensor is used to perform standard calibration on the temperature and humidity of the environment.

[0018] Advantages of the present invention: Through the self-developed high-precision miniaturized impedance measuring instrument, the impedance spectrum information of the humidity sensor is collected under different temperature conditions. Based on the impedance spectrum information, an equivalent circuit model is fitted and the circuit element parameters are quantified. Further, by combining the equivalent circuit model combinations and the changes in circuit element parameters under different temperature conditions, the temperature drift mechanism of the humidity sensor is analyzed in depth. The present invention provides reliable theoretical support for formulating the temperature compensation method of the humidity sensor. The present invention has the following advantages:

[0019] (1) By measuring the impedance spectrum information under different temperature conditions, fitting the equivalent circuit model and quantifying the circuit element parameters, and combining the equivalent circuit model combinations and circuit element parameters under different temperature conditions, the characteristics of the humidity sensor changing with temperature are more comprehensively characterized, and then the temperature drift mechanism of the humidity sensor is analyzed in depth.

[0020] (2) The impedance spectrum test device uses FFT processing for the calculation of impedance information at multiple frequency points: the processor core unit of the test device performs FFT processing on the mixed signal. This calculation method processes the data at high speed and in real time, greatly reducing the test delay. Description of the drawings

[0021] Figure 1 It is the structural block diagram of the humidity sensor impedance spectrum information measuring device provided by the present invention.

[0022] Figure 2 It is the specific implementation block diagram of the humidity sensor impedance spectrum information measuring device provided by the present invention.

[0023] Figure 3 It is the circuit logic diagram of the humidity sensor measurement circuit in the embodiment of the present invention.

[0024] Figure 4 (a) It is the impedance spectrum data measured by the humidity sensor Q1 in the embodiment of the present invention under the conditions of a temperature of 5°C and a relative humidity of 60%RH. Figure 4 (b) It is the equivalent circuit model of the humidity sensor fitted according to the Figure 4 impedance spectrum data in (a).

[0025] Figure 5 (a) It is the impedance spectrum data measured by the humidity sensor Q1 in the embodiment of the present invention under the conditions of a temperature of 25°C and a relative humidity of 60%RH. Figure 5 (b) It is the equivalent circuit model of the humidity sensor fitted according to the Figure 5 impedance spectrum data in (a).

[0026] Figure 6 (a) shows the impedance spectrum data of humidity sensor Q1 measured under the conditions of a temperature of 45 °C and a relative humidity of 60% RH in an embodiment of the present invention. Figure 6 (b) is the equivalent circuit model of the humidity sensor obtained by fitting the impedance spectrum data according to Figure 6 (a).

[0027] Figure 7 (a) shows the impedance spectrum data of humidity sensor Q1 measured under the conditions of a temperature of 65 °C and a relative humidity of 60% RH in an embodiment of the present invention. Figure 7 (b) is the equivalent circuit model of the humidity sensor obtained by fitting the impedance spectrum data according to Figure 7 (a).

[0028] Figure 8 It is a schematic diagram of a test method for studying the temperature drift mechanism of a humidity sensor provided by the present invention. Detailed implementation mode

[0029] To facilitate those skilled in the art to understand the technical content of the present invention, the content of the present invention will be further explained below with reference to the accompanying drawings.

[0030] As Figure 1 shown is a structural block diagram of a device for measuring the impedance spectrum information of a humidity sensor provided by the present invention. This device is used to measure the impedance spectrum information of the humidity sensor and provide data support for the fitting of the equivalent circuit model of the sensor. This test device includes: an FPGA module, a humidity sensor measurement circuit module, a temperature and humidity calibration module, a display module, and a peripheral interaction device.

[0031] As Figure 2 shown, the detailed processes of each module will be described:

[0032] This test device uses a processor core unit (FPGA, Field Programmable Gate Array) as the control center, and is equipped with a humidity sensor measurement circuit and a temperature and humidity calibration module to complete the impedance spectrum measurement of the humidity sensor. The generation of signals is completed by a dual-channel DDS. Both channel 1 and channel 2 of the DDS generate cosine signals but have different functions. In this embodiment, channel 1 of the DDS is denoted as DDS1, and channel 2 of the DDS is denoted as DDS2. Among them, the signal generated by DDS1 is used as the input of the humidity sensor measurement circuit, and the signal generated by DDS2 is used for multiplier mixing. When the device works, the signal generated by DDS1 is input into the humidity sensor measurement circuit. This signal is converted into an analog signal by a DAC (Digital to analog converter) and then input into a voltage follower 1 for signal buffering. The buffered signal is input into a self-balancing circuit containing the humidity sensor to be measured. At this time, the input signal after passing through the humidity sensor to be measured changes in amplitude and phase. After the changed signal is buffered by a voltage follower 2, it is collected by an ADC (Analog-to-Digital Converter). The collected signal is subjected to multiplier mixing processing with the signal generated by DDS2 inside the FPGA, and the processed data is input into the processor core unit of the test device for FFT calculation, and finally the impedance spectrum information of the humidity sensor is obtained. In addition, in this embodiment, an HMP110 sensor is used to perform standard calibration on the temperature and humidity of the test environment. Finally, the impedance spectrum information of the humidity sensor and the standard temperature and humidity information of the environment can be viewed through the upper computer.

[0033] As Figure 3 shown, the circuit logic diagram of the humidity sensor measurement circuit in the embodiment of the present invention is given; assuming that the excitation signal voltage input by DDS1 is V in , the signal voltage output through the humidity sensor to be measured is V out , the current passing through the voltage follower 1 and the humidity sensor to be measured is I1, and the current passing through the automatic balancing circuit is I2, where the expressions of I1 and I2 are as follows:

[0034]

[0035] The current in the entire branch is the same, that is, I1 = I2. Therefore, the impedance expression of the humidity sensor to be measured is:

[0036]

[0037] Since the humidity sensor to be measured presents different impedance values (Z x) When the impedance value of the humidity sensor to be measured is large, the amplitude of the output signal voltage is lower than the minimum resolution of the ADC. When the impedance value of the humidity sensor to be measured is small, the amplitude of the output signal voltage is higher than the range of the ADC, making it difficult for the ADC to accurately collect. To ensure that the signal can stably and accurately fall within the effective sampling range of the ADC, this measurement system uses a shifting operation, that is, switching different feedback resistors so that the impedance measurement range of the humidity sensor can be from 500Ω - 500kΩ.

[0038] Feedback resistor R f According to the magnitude of the output voltage V out for switching. The purpose of switching R f is to change the gear to prevent the amplitude of the output signal V out from being too low or too high, ensuring that the ADC accurately collects the output signal passing through the humidity sensor to be measured.

[0039] As Figure 3 shown, which includes three feedback resistors with different resistance values: R f1 、R f2 、R f3 , with values of 1kΩ, 10kΩ, and 100kΩ respectively. In this embodiment, the amplitude of the input excitation signal V in is 1V, a 12-bit ADC is used, the working voltage is 5V, the minimum resolution of the ADC is 1.22mV, and the measurement range of the ADC is -5V to 5V. When using R f1 , if the output voltage V out is lower than the minimum resolution of the ADC, 1.22mV, it will automatically switch to R f2 ; if R f2 still cannot meet the sampling requirements, it will switch to R f3 . If the output voltage V f3 is still lower than the minimum input range of the ADC, 1.22mV, under the condition of R out , it indicates that the impedance of the humidity sensor to be measured exceeds the upper limit of the system measurement range. Conversely, when using R f1 , if the output voltage V out exceeds the maximum input range of the ADC, 5V, it indicates that the impedance of the humidity sensor to be measured is lower than the lower limit of the system measurement range.

[0040] Figure 4 (a), Figure 5 (a), Figure 6 (a), Figure 7 (a) is the impedance spectrum of the humidity sensor at different temperatures in the embodiment of the present invention; Figure 4 (b), Figure 5 (b), Figure 6 (b), Figure 7(b) is the equivalent circuit model obtained by fitting the impedance spectra of the humidity sensor at different temperatures in the embodiments of the present invention.

[0041] In Figure 4 (b), Figure 5 (b), Figure 6 In the equivalent circuit model components of (b), R represents resistance, C represents capacitance, and Z w represents the diffusion Warburg impedance. The formula for the Warburg impedance is: When quantifying the parameters of the equivalent circuit components, the Warburg impedance is represented by three parameters, namely W-R (representing R in the Warburg impedance formula), W-T (representing T in the Warburg impedance formula), and W-P (representing P in the Warburg impedance formula): where W-R represents the resistance factor, reflecting the resistance of electrons or ions passing through the interface during the diffusion process; W-T represents the time constant, reflecting the time required for diffusion; W-P represents the power exponent, used to adjust the phase angle of the Warburg impedance.

[0042] In addition, in Figure 7 (b) also includes a constant phase element (CPE) for describing non-ideal capacitive behavior. The formula for the CPE impedance is: When quantifying the parameters of the equivalent circuit components, the CPE impedance is represented by two parameters, namely CPE-T (representing T in the CPE impedance formula) and CPE-P (representing P in the CPE impedance formula): where CPE-T represents the main parameter of the CPE impedance, similar to the capacitance value but not equivalent to an ideal capacitor; CPE-P represents the phase factor, determining the phase angle of the CPE and thus characterizing the non-ideal capacitive characteristics.

[0043] As Figure 8 shown is the test method of the present invention, and the specific steps are as follows:

[0044] (1) Place the humidity sensor to be tested in a thermostatic and humidistatic chamber, set the relative humidity of the test environment to 60%RH and the temperature to 5°C, and set the starting minimum test temperature T a1 to 5°C and the ending maximum test temperature T h to 65°C according to the operating temperature range of common temperature sensors on the market. After setting the relevant test temperature and humidity, make the test device generate a swept-frequency cosine excitation signal with a frequency of 20Hz to 300kHz and an amplitude of 1V. The frequency interval of the excitation signal increases exponentially as f(x) = 20.975×e 0.0476x and the frequency points include 20.9751Hz, 21.9977Hz, 23.0702Hz, 24.195Hz, 25.3746Hz, etc. And input this signal into the humidity sensor measurement circuit.

[0045] (2)Collect the output signal of the humidity sensor measurement circuit and obtain impedance data at 200 fixed frequency points with exponentially increasing frequency intervals. At this time, the ambient humidity output by the test device is 60.3%RH, and the temperature is 5.2°C.

[0046] (3)Perform FFT processing on the impedance data at 200 frequency points obtained in step (2) in the processor core unit of the test device to obtain impedance spectrum information. The specific impedance spectrum data is as Figure 4 (a) shown.

[0047] (4)Fit an equivalent circuit model according to the impedance spectrum data. The specific circuit model is as Figure 4 (b) shown. And quantify the component parameters. The specific component parameter information is shown in the second row of Table 1.

[0048] Table 1 Component parameters of the circuit model at different temperatures with a humidity of 60%RH

[0049]

[0050] (5)The currently set ambient temperature is 5°C, which is lower than the termination maximum test temperature of 65°C. Therefore, increase the ambient temperature by 20°C. At this time, the ambient temperature is 25°C. And repeat the above operation (1) to make the test device generate a swept-frequency cosine excitation signal with a frequency of 20 Hz to 300 kHz and an amplitude of 1 V, and input it into the humidity sensor measurement circuit.

[0051] (6)Collect the output signal of the humidity sensor measurement circuit and obtain impedance data at 200 fixed frequency points with exponentially increasing frequency intervals. At this time, the ambient humidity output by the test device is 60.3%RH and the temperature is 25.1°C.

[0052] (7)Perform FFT processing on the impedance data at 200 frequency points obtained in step (6) in the processor core unit of the test device to obtain impedance spectrum information. The specific impedance spectrum data is as Figure 5 (a) shown.

[0053] (8)Fit an equivalent circuit model according to the impedance spectrum data. The specific circuit model is as Figure 5 (b) shown. And quantify the component parameters. The specific component parameter information is shown in the third row of Table 1.

[0054] (9)The currently set ambient temperature is 25°C, which is lower than the termination maximum test temperature of 65°C. Therefore, increase the ambient temperature by 20°C. At this time, the ambient temperature is 45°C. And repeat the above operation (1) to make the test device generate a swept-frequency cosine excitation signal with a frequency of 20 Hz to 300 kHz and an amplitude of 1 V, and input it into the humidity sensor measurement circuit.

[0055] (10)Collect the output signal of the humidity sensor measurement circuit and obtain the impedance data of 200 fixed frequency points with exponentially increasing frequency intervals. At this time, the ambient humidity output by the test device is 60.3%RH and the temperature is 45.1°C.

[0056] (11)Perform FFT processing on the impedance data of the 200 frequency points obtained in step (10) in the processor core unit of the test device to obtain impedance spectrum information. The specific impedance spectrum data is as Figure 6 (a) shown.

[0057] (12)Fit an equivalent circuit model according to the impedance spectrum data. The specific circuit model is as Figure 6 (b) shown. And quantify the component parameters. The specific component parameter information is shown in the fourth row of Table 1.

[0058] (13)The currently set ambient temperature is 45°C, which is lower than the termination maximum test temperature of 65°C. Therefore, increase the ambient temperature by 20°C. At this time, the ambient temperature is 65°C. And repeat the above operation (1) to make the test device generate a swept-frequency cosine excitation signal with a frequency of 20Hz to 300kHz and an amplitude of 1V, and input it into the humidity sensor measurement circuit.

[0059] (14)Collect the output signal of the humidity sensor measurement circuit and obtain the impedance data of 200 fixed frequency points with exponentially increasing frequency intervals. At this time, the ambient humidity output by the test device is 60.3%RH and the temperature is 65.3°C.

[0060] (15)Perform FFT processing on the impedance data of the 200 frequency points obtained in step (14) in the processor core unit of the test device to obtain impedance spectrum information. The specific impedance spectrum data is as Figure 7 (a) shown.

[0061] (16)Fit an equivalent circuit model according to the impedance spectrum data. The specific circuit model is as Figure 7 (b) shown. And quantify the component parameters. The specific component parameter information is shown in the fifth row of Table 1.

[0062] (17)The currently set ambient temperature is 65°C, which is equal to the termination maximum test temperature of 65°C. End the measurement.

[0063] (18)Finally, based on a series of humidity sensor equivalent circuit combination models and circuit component parameter information fitted under different temperature conditions, analyze and study the temperature drift mechanism of the humidity sensor. In this embodiment, when the temperature is 5°C, 25°C, 45°C, and 65°C, the equivalent circuit models are respectively as Figure 4(b), 5(b), 6(b), and 7(b) show that the circuit element parameters are as shown in Table 1. The changes in the circuit element parameters in the equivalent circuit model of the humidity sensor indicate that as the temperature increases, the overall resistance R shows a downward trend, and the overall Warburg impedance also shows a downward trend. When the temperature is between 5 °C and 45 °C, the change in temperature has little effect on the capacitance. At 65 °C, the capacitance effect gradually weakens, showing a non-ideal capacitance form and presenting the characteristics of a constant phase element.

[0064] In this embodiment, the humidity sensor Q1 uses graphene oxide quantum dots as the humidity-sensitive material. The surface of graphene oxide quantum dots contains abundant hydroxyl groups (-OH) and carboxyl groups (-COOH), and these groups act as proton acceptors and donors. As the temperature increases, the proton hopping conduction speed between the groups on the surface of the humidity-sensitive material speeds up, which is reflected in the circuit element parameters as a decrease in the Warburg impedance. In addition, when the relative humidity (RH) remains unchanged, an increase in temperature will cause an increase in the saturated water vapor partial pressure in the air, resulting in an increase in the actual water vapor partial pressure in the air under the same RH condition, an increase in the density of water vapor per unit volume, and thus an increase in the number of water molecules on the sensor surface. A continuous water layer gradually appears on the surface of the humidity-sensitive material, and a large number of hydronium ions (H3O + ) will be generated under the action of an electric field. At this time, the Grotthuss chain reaction mechanism (H2O + H3O + →H3O + + H2O) begins to dominate. In this case, the conduction characteristics of the humidity-sensitive material are significantly enhanced, the conductivity of the humidity sensor increases, and therefore, in the circuit element parameters, it is reflected as a downward trend in the resistance R. Therefore, the change in temperature affects the humidity-sensitive medium of the humidity sensor, changing its ability to adsorb, diffuse, and permeate moisture. The above-mentioned influence of temperature on the inside of the humidity-sensitive material of the humidity sensor is finally reflected in the change of the equivalent circuit model combination of the humidity sensor and its element parameters. Specifically, when the temperature is 5 °C, 25 °C, 45 °C, and 65 °C, the equivalent circuit models are respectively as shown in Figure 4 (b), 5(b), 6(b), and 7(b). The circuit element parameters are as shown in Table 1. The data in the table show that as the temperature increases, the overall resistance R shows a downward trend, corresponding to a significant enhancement of the conduction characteristics of the humidity-sensitive material inside the humidity sensor and an increase in the conductivity of the humidity sensor. The overall Warburg impedance also shows a downward trend, corresponding to an increase in the proton hopping conduction speed between the groups on the surface of the humidity-sensitive material.

[0065] Those of ordinary skill in the art will realize that the embodiments described herein are provided to assist the reader in understanding the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. Various modifications and variations can be made to the present invention for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A test device for studying the temperature drift mechanism of a humidity sensor, characterized in that, Including: FPGA module, humidity sensor measurement circuit module; The humidity sensor measurement circuit includes: power supply module, digital-to-analog converter, first voltage follower, self-balancing circuit with the humidity sensor to be measured, second voltage follower, analog-to-digital converter; the power supply module supplies power to the self-balancing circuit with the humidity sensor to be measured; The FPGA module includes: dual-channel digital synthesizer module, fast Fourier transform processing module, mixing module; the dual-channel digital synthesizer module generates a swept-frequency cosine excitation signal as the input of the humidity sensor measurement circuit; meanwhile, it provides a known reference signal for the mixing module; The digital-to-analog converter converts the input excitation signal from digital quantity to analog quantity and inputs it into the first voltage follower for signal buffering. The buffered signal is input into the self-balancing circuit with the humidity sensor to be measured; the input signal changes in amplitude and phase after passing through the humidity sensor to be measured. The signal output by the self-balancing circuit with the humidity sensor to be measured is buffered by the second voltage follower, and the analog-to-digital converter collects the signal buffered by the second voltage follower and inputs the collected signal into the mixing module; The mixed signal is input into the FFT processing module to calculate the impedance information at multiple frequency points, and finally the impedance spectrum information of the humidity sensor is obtained.

2. The test device for studying the temperature drift mechanism of a humidity sensor according to claim 1, characterized in that, Denote the signal frequency collected by the analog-to-digital converter as f1, and denote the frequency of the reference signal as f2; the mixing module performs multiplier mixing processing on the signal with frequency f1 collected by the analog-to-digital converter and the reference signal with frequency f2 inside the FPGA, and the output signal obtained contains two frequencies: f1 + f2 and f1 - f2 respectively; by adjusting the reference signal frequency, make these two frequencies f1 + f2 and f1 - f2 be at the frequency points of the FFT processing.

3. The test device for studying the temperature drift mechanism of a humidity sensor according to claim 2, characterized in that, The self-balancing circuit with the humidity sensor to be measured includes a humidity sensor, an amplifier, a first feedback resistor, a second feedback resistor, a third feedback resistor, a first switch, a second switch, and a third switch; the input end of the humidity sensor is used as the input end of the self-balancing circuit with the humidity sensor to be measured, the output end of the humidity sensor is connected to the inverting input end of the amplifier, the non-inverting input end of the amplifier is grounded, the output end of the humidity sensor is also respectively connected to the first end of the first feedback resistor, the first end of the second feedback resistor, and the first end of the third feedback resistor. The second end of the first feedback resistor is connected to the output end of the amplifier through the first switch, the second end of the second feedback resistor is connected to the output end of the amplifier through the second switch, the second end of the third feedback resistor is connected to the output end of the amplifier through the third switch, and the output end of the amplifier is used as the output end of the self-balancing circuit with the humidity sensor to be measured.

4. The test device for studying the temperature drift mechanism of a humidity sensor according to claim 3, characterized in that, The calculation process of the impedance of the humidity sensor to be measured is as follows: Assume that the voltage of the swept-frequency cosine excitation signal is V in , and the signal voltage output by the humidity sensor to be measured is V out . The current passing through the first voltage follower and the humidity sensor to be measured is I1, and the current passing through the automatic balance circuit is I2, where the expressions of I1 and I2 are as follows: The current in the whole branch is the same, that is, I1 = I2. Therefore, the impedance expression of the humidity sensor to be measured is: Among them, R f represents the feedback resistance of the humidity sensor measurement circuit.

5. A test method for studying the temperature drift mechanism of a humidity sensor, characterized in that, Including: S1. Set the initial relative humidity and temperature of the test environment, and set the initial test temperature and the termination test temperature; S2. The test device generates excitation signals at several different frequency points and inputs them into the humidity sensor measurement circuit; S3. Collect the output signal of the humidity sensor measurement circuit; and based on the input signal, output signal of the humidity sensor measurement circuit, and feedback resistor, obtain impedance data corresponding to excitation signals at several different frequency points; S4. In the processor core unit of the test device, calculate the several impedance data obtained in step S3 to obtain impedance spectrum information; S5. Based on the impedance spectrum information, fit the equivalent circuit model of the humidity sensor and quantify its circuit element parameters; S6. If the current test temperature is less than the termination test temperature, add the set interval value to the current test temperature and return to step S2; otherwise, execute step S7; S7. Analyze the temperature drift mechanism of the humidity sensor according to the element parameters in the equivalent circuit model fitted under different temperature conditions.

6. The test method for studying the temperature drift mechanism of a humidity sensor according to claim 5, characterized in that, The test device generates a swept-frequency cosine excitation signal with a frequency of 20 Hz to 300 kHz and an amplitude of 1 V.

7. A test method for studying the temperature drift mechanism of a humidity sensor according to claim 6, characterized in that, If the current test temperature is less than the termination test temperature, the equivalent circuit model of the humidity sensor fitted in step S5 includes: a diffusion Warburg impedance, a resistor, and a capacitor. The first end of the capacitor is connected to the first end of the resistor through the diffusion Warburg impedance, and the second end of the resistor is connected to the second end of the capacitor.

8. The test method for studying the temperature drift mechanism of a humidity sensor according to claim 6, characterized in that, If the current test temperature is equal to the termination test temperature, the equivalent circuit model of the humidity sensor fitted in step S5 includes: a diffusion Warburg impedance, a resistor, and a constant phase element. The first end of the constant phase element is connected to the first end of the resistor through the diffusion Warburg impedance, and the second end of the resistor is connected to the second end of the constant phase element.

9. The test method for studying the temperature drift mechanism of a humidity sensor according to claim 6, characterized in that, Step S7 is specifically: when the humidity sensor uses graphene oxide quantum dots as the humidity-sensitive material, as the test temperature increases, in the equivalent circuit model of the humidity sensor fitted, the overall resistance shows a downward trend, corresponding to a significant enhancement of the conduction characteristics of the humidity-sensitive material, and the overall Warburg impedance also shows a downward trend, corresponding to an accelerated proton hopping conduction speed between the groups on the surface of the humidity-sensitive material.

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