An automated testing system and method for standardizing marine electric field electrodes

Abstract

This invention relates to the field of sensors and discloses a standardized automated testing system and method for marine electric field electrodes. The testing system includes: a three-electrode system, a water tank assembly, a pre-signal acquisition circuit, an electromagnetic shielding box, a signal generator, a signal processing circuit, and a computer. The testing method includes: S1: immersion of the electrode; S2: electrode source impedance testing; S3: electrode range potential testing; S4: noise testing; S5: potential drift testing; S6: electric field response performance testing; S7: calibration testing of the electrode under test. This invention's testing system and method can uniformly and automatically test the source impedance, range potential, noise, potential drift, and electric field response of marine electric field electrodes. It also utilizes a reference electrode as a benchmark to calibrate and construct a set of performance evaluation models for marine electric field electrodes, significantly improving the efficiency and accuracy of marine electric field electrode testing.

Description

Technical Field

[0001] This invention relates to the field of sensors, and more particularly to an automated testing system and method for standardizing marine electric field electrodes. Background Technology

[0002] The electric fields generated by targets such as ships in the ocean have excellent propagation and identification characteristics in seawater. Therefore, ocean electric field detection has unique advantages in non-acoustic ship positioning and has become a hot technology in the field of marine military research in recent years. Ocean electric field sensors, as key components of ocean electromagnetic methods, also play an important role in the field of seabed resource exploration. Because different dielectric layers exist beneath the seabed, the electrical differences at the interfaces between these two phases provide electrical evidence for the application of ocean electromagnetic methods, contributing to the accurate acquisition of seabed reservoir physical property information.

[0003] Sensing electrodes are the front-end devices and the core components of marine electric field sensing; their performance directly affects the accuracy and stability of measurement results. Sensing electrodes possessing characteristics such as low self-noise, high sensitivity, and good long-term stability are the foundation and prerequisite for realizing marine electric field detection equipment. The main physical indicators reflecting these characteristics include: source impedance, range potential, noise, potential drift, and electric field response. Source impedance is generally measured using an impedance meter or multimeter, which is costly and prone to damaging the electrode. Range potential and potential drift are generally tested using an electrochemical workstation, but the testing accuracy is low. Noise testing typically involves amplification before testing with an oscilloscope; this method is susceptible to environmental noise interference and has poor accuracy. Most current testing schemes measure only one type of data at a time; different data tests require changing testing equipment, resulting in an inefficient testing process.

[0004] Chen Jialin et al. from the State Key Laboratory of Marine Science and Technology in Qingdao proposed an integrated testing system in their published invention patent application (application number: 202011538064.9, title: Marine Electric Field Sensor Testing System and Testing Method). However, this system is not automated and lacks electromagnetic shielding, making it difficult to maintain a standardized testing environment. Furthermore, it lacks calibration of the electrodes under test and the construction of data models, resulting in a lack of unified standards for evaluating electrode performance. Currently, research in the field of marine electric field electrodes in China remains relatively disorganized, with various teams operating independently and lacking unified standards. Specifically, there is no clear and rational solution for constructing a standard testing environment, and no universally applicable standard for evaluating electrode performance. Summary of the Invention

[0005] This invention addresses the shortcomings of existing marine electric field electrode testing by proposing a standardized and automated testing system and method for marine electric field electrodes. This testing system can automatically test the source impedance, range potential, noise, potential drift, and electric field response of marine electric field electrodes in a unified manner. It also uses a reference electrode as a benchmark to calibrate and construct a performance evaluation model for marine electric field electrodes, which can greatly improve the efficiency and accuracy of marine electric field electrode testing and establish a standardized testing system for research in the field of marine electric field electrodes.

[0006] The specific technical solution of this invention is as follows:

[0007] In a first aspect, the present invention provides an automated testing system for standardizing marine electric field electrodes, comprising:

[0008] Three-electrode systems include:

[0009] First electrode to be tested;

[0010] The second electrode to be tested;

[0011] The reference electrode has a fixed potential; it is used to reference the potential of the electrode under test and to calibrate the test data for different electrodes under test, ensuring the standard universality of the system.

[0012] Water tank assembly, including:

[0013] A water bath tank filled with water bath solution; used to maintain the temperature of the simulated seawater in the test tank close to the actual seawater temperature.

[0014] The test tank is equipped with simulated seawater and is placed inside a water bath. Two opposing plate-shaped electrodes are placed in the simulated seawater. The plate-shaped electrodes are connected to the signal generator respectively. The area between the two plate-shaped electrodes is the placement area for the reference electrode and the electrode to be tested.

[0015] The pre-amplifier signal acquisition circuit is connected to the three-electrode system.

[0016] The electromagnetic shielding box, the three-electrode system and the water tank assembly are located inside the electromagnetic shielding box to shield external electromagnetic signals and avoid various interferences.

[0017] The signal generator is connected to two plate-shaped electrodes in the test tank to generate low-frequency sine wave signals.

[0018] The signal processing circuit is connected to the pre-amplifier signal acquisition circuit.

[0019] The computer is connected to the signal processing circuitry.

[0020] Preferably, the reference electrode is a quartz tube containing an Ag / AgCl electrode wire, with a potassium chloride solution inside, and a porous ceramic seal at the bottom. This porous ceramic seal provides a complete circuit while ensuring environmental sealing.

[0021] Preferably, the pre-amplifier signal acquisition circuit includes: a first single-pole double-throw switch, a second single-pole double-throw switch, a third single-pole double-throw switch, a first amplifier, and a second amplifier.

[0022] The first input terminal of the first amplifier is connected to the third single-pole double-throw switch. The two terminals of the third single-pole double-throw switch are connected to the first electrode under test (DUT) and the second electrode under test, respectively. The second input terminal of the first amplifier is connected to the reference electrode. The two terminals of the first single-pole double-throw switch are connected to the second single-pole double-throw switch and the circuit directly connected to the three-electrode system, respectively. The first and second input terminals of the second amplifier are connected to the second electrode under test and the first electrode under test, respectively. The two terminals of the second single-pole double-throw switch are connected to the first amplifier and the second amplifier, respectively. The third single-pole double-throw switch is directly connected to the first amplifier. The two terminals of the third single-pole double-throw switch are connected to the first electrode under test and the second electrode under test, respectively. When the first single-pole double-throw switch is connected to the circuit directly connected to the three-electrode system, source impedance testing is performed. When connected to the second single-pole double-throw switch, range potential, noise, potential drift, and electric field response testing are performed.

[0023] As a further preferred embodiment, both the first amplifier and the second amplifier are low-noise chopper amplifiers, including a chopper, an AC amplification unit, a demodulator, a low-pass filter, a DC amplification unit, and a power supply connected in sequence to the AC amplification unit and the DC amplification unit.

[0024] Preferably, the signal processing circuit includes:

[0025] The analog signal processing module is connected to the first single-pole double-throw switch and the analog-to-digital and digital-to-analog converter module, respectively, and is used to process the measured current and voltage analog signals.

[0026] The analog-to-digital (ADC) and digital-to-analog (DAC) conversion module is used for the mutual conversion between analog and digital signals; it includes an ADC and a DAC. The ADC is connected to the analog signal processing module to convert the analog signals amplified by the amplifier into digital signals, and the DAC is used to convert the digital signals of the control module FPGA into analog signals.

[0027] The FPGA control module is used to receive signals from the ARM microprocessor and control the front-end signal acquisition.

[0028] The digital signal processing module (DSP) is used to process digital signals converted by the analog-to-digital converter and upload the processed digital signals to the computer via Ethernet through the microprocessor (ARM).

[0029] The ARM microprocessor receives instructions from the computer and sends them to the FPGA control module, and uploads the digital signals processed by the DSP digital signal processing module to the computer via Ethernet.

[0030] As a further preferred embodiment, the analog signal processing module includes a switch, a voltage acquisition module, a current acquisition module, a subtraction circuit, a DC amplifier unit, and a bandpass filter. The switch controls the switching state of the entire analog signal processing module circuit, allowing the circuit's switching state to be remotely or automatically controlled. The voltage acquisition module and the current acquisition module are used to acquire voltage and current signals from the circuit, respectively, for further processing. The subtraction circuit subtracts one signal from two input signals. In this invention, the subtraction circuit subtracts the voltage and current signals to generate a signal representing resistance. The DC amplifier unit amplifies the signal magnitude. In this invention, it amplifies the output signal of the subtraction circuit so that it can be further processed by the bandpass filter. The bandpass filter removes unwanted frequency components from the input signal. In this invention, it filters out high-frequency and low-frequency noise from the output signal of the DC amplifier unit, ensuring that the output signal contains only signals within the desired frequency range. As a further preferred embodiment, the analog-to-digital converter (ADC) is an ADI LTC2440 high-speed 24-bit delay-free low-noise ADC; the digital-to-analog converter (DAC) is a TI DAC81001 high-performance, low-noise 12-bit DAC; the digital signal processing module (DSP) is an AD ADSP-BF707 chip; the microprocessor (ARM) is an STMicroelectronics STM32F769 microprocessor; the control module (FPGA) is a Xilinx Spartan-6 LX9 FPGA chip; and a power control switch is connected to the control module (FPGA) to control the operation and shutdown of the entire system.

[0031] Secondly, the present invention provides a method for testing marine electric field electrodes using the above-described testing system, comprising the following steps:

[0032] Step 1: Immerse the electrodes: Immerse the first and second electrodes under test in simulated seawater in the test tank to stabilize them in the test environment.

[0033] Step 2: Electrode source impedance test: The computer provides a signal, and the FPGA control module controls the circuit connection between the first single-pole double-throw switch and the direct-connected three-electrode system; a sinusoidal signal is applied to the three-electrode system using an external power supply, and the AC voltage U between the two electrodes under test is measured by the voltage acquisition module in the analog signal processing module, and the AC current I between the two electrodes under test is measured by the current acquisition module in the analog signal processing module. The impedance R of the electrode under test is calculated as R = U / I.

[0034] Step 3: Electrode Pole Potential Difference Test: A signal is provided by the computer, and the FPGA control module connects the first and second single-pole double-throw switches, and connects the second single-pole double-throw switch to the second amplifier; the analog signal processing module is used to test the response voltage difference U between the two electrodes under test. 差 This is the range potential of the electrode to be measured.

[0035] Step 4: Noise Test: The computer provides a signal, and the FPGA control module controls the connection between the first single-pole double-throw switch and the second single-pole double-throw switch, and controls the connection between the second single-pole double-throw switch and the second amplifier. At the same time, by controlling the sampling frequency of the analog circuit, the voltage acquisition module in the analog signal processing module measures the time-domain noise signal of the electrode under test, and then the computer software uses the Fourier transform method to convert the time-domain noise signal into a frequency-domain noise signal.

[0036] Step 5: Potential Drift Test: A signal is provided by the computer, and the FPGA control module connects the first and second single-pole double-throw switches, and connects the second single-pole double-throw switch to the second amplifier; the voltage acquisition module in the analog signal processing module is used to test the response voltage difference U between the two electrodes under test. 差 The maximum potential signal measured during the acquisition period is U. 差max The minimum potential signal is U 差min The drift potential U measured during the acquisition period 漂 =U 差max -U 差min .

[0037] Step 6: Electric Field Response Performance Test: A signal is provided by the computer, and the FPGA control module connects the first and second single-pole double-throw switches. The reference electrode is retracted, and a sinusoidal signal excitation is applied to the two electrodes under test through two plate-shaped electrodes using a signal generator. The response signal U between the electrodes under test is measured by the voltage acquisition module in the analog signal processing module. * By analyzing and comparing the collected response signal with the sinusoidal excitation signal, the electric field response performance of the electrode under test can be determined.

[0038] Step 7: Calibration test of the electrode under test: The computer provides a signal, and the FPGA control module controls the connection of the first single-pole double-throw switch and the second single-pole double-throw switch, controls the connection of the second single-pole double-throw switch to the first amplifier, and the third single-pole double-throw switch is connected to the first electrode under test and the second electrode under test in sequence; the voltage differences U1 and U2 between the reference electrode and the two electrodes under test are measured respectively; the data are uploaded to the computer and calibrated by the software, and the performance of the electrode pair under test is comprehensively judged by combining the test data from steps 2-6.

[0039] Preferably, in step 1, the simulated seawater is a 3.0-4.0 wt% sodium chloride solution, the temperature is maintained at 5-10℃, and the soaking time is not less than 24 hours.

[0040] Preferably, in step 1, the method for judging whether the electrode under test has reached stability in the simulated seawater environment is to use the test method in step 3 to test the response voltage difference between the two electrodes under test. When the response voltage difference is within 1mV and the change within 24 hours does not exceed 0.01mV, the electrode under test has reached stability in the test environment.

[0041] Preferably, in step 2, the frequency of the sinusoidal signal is 0.01-220Hz and the amplitude is 50-200mV.

[0042] Preferably, in step 4, the sampling frequency of the analog circuit is set to 900-1100Hz.

[0043] Preferably, in step 6, the frequency of the sinusoidal excitation signal is 0.001-100Hz and the amplitude is 0.01-1mV.

[0044] Preferably, in step 7, the performance determination involves first establishing an evaluation model, and then using this evaluation model to calibrate different electrodes under test: using a multiple linear regression equation, the potential difference between the reference electrode and different electrodes under test is taken as an independent variable, and the range potential, noise, potential drift, and electric field response between the electrodes under test are taken as dependent variables. After fitting multiple multiple linear regression equations, an evaluation model is obtained. This evaluation model is then used to calibrate other electrodes under test and evaluate their performance.

[0045] Further preferred, in step 7, the method for constructing the evaluation model specifically includes: to establish the relationship between any two electrodes under test, a multiple linear regression equation is used to predict the response of the two electrodes under test, with the range potential, noise, potential drift, and electric field response between the electrodes under test as dependent variables Y; taking the range potential as the dependent variable as an example, the potential difference between the reference electrode and one of the electrodes under test are respectively used as independent variables V1 and V2; assuming there are N electrodes under test, the relationship between all possible pairs of electrodes under test is fitted by N linear regression equations; assuming the range potential between the i-th pair of electrodes under test is Y i The potential difference between the first electrode under test and the reference electrode is V. 1i The potential difference between the second electrode under test and the reference electrode is V. 2i Then the following multiple linear regression equation can be obtained:

[0046] Y1 = β0 + β1V 11 +β2V 21 +ε1,

[0047] Y2 = β0 + β1V 12 +β2V 22 +ε2,

[0048] ...

[0049] Y N = β0+β1V 1N + β2V 2N + ε N ;

[0050] Where β0 is the intercept, β1 and β2 are regression coefficients, and ε1, ε2, ..., ε N This is the error term; the LinearRegression class from the Scikit-learn library is used to fit the above linear regression equation, thus obtaining an evaluation model.

[0051] Compared with the prior art, the beneficial effects of the present invention are:

[0052] (1) This invention can perform automated testing of source impedance, range potential, noise, potential drift and electric field response of marine electric field electrodes in a unified manner, and use a reference electrode as a scale to calibrate and construct a set of marine electric field electrode performance evaluation models, which greatly improves the efficiency and accuracy of marine electric field electrode testing and establishes a unified and standardized testing system for research in the field of marine electric field electrodes.

[0053] (2) The test system of the present invention can be automated and electromagnetic shielding is applied to the test system, which is conducive to maintaining the standardization and uniformity of the test environment. Attached Figure Description

[0054] Figure 1 This is a connection diagram of the test system of the present invention.

[0055] Figure 2 This is a schematic diagram of the circuit connection of the low-noise chopper amplifier in the test system of this invention.

[0056] Figure 3 This is a schematic diagram of the connection of the analog signal processing module in the test system of the present invention.

[0057] Figure 4 This is a flowchart illustrating the testing method of the present invention.

[0058] Figure 5 The graph shows the source impedance test results of two types of marine electric field electrodes in this embodiment of the invention: a carbon fiber-loaded silver silver chloride electrode and a filamentous silver silver chloride electrode.

[0059] Figure 6 The figure shows the potential drift test results of two types of marine electric field electrodes in this embodiment of the invention: a carbon fiber-loaded silver chloride electrode and a filamentous silver chloride electrode.

[0060] Figure 7 The figure shows the noise test results of two types of marine electric field electrodes in this embodiment of the invention: carbon fiber-loaded silver chloride electrode and filamentous silver chloride electrode.

[0061] The attached figures are labeled as follows: 1. Three-electrode system; 11. First electrode under test; 12. Second electrode under test; 13. Reference electrode; 2. Water tank assembly; 21. Plate electrode; 22. Simulated seawater; 23. Test water tank; 24. Water bath liquid; 25. Water bath tank; 3. Pre-amplifier signal acquisition circuit; 31. First single-pole double-throw switch; 311. Terminal 1 of first single-pole double-throw switch; 312. Second single-pole double-throw switch; 32. Terminal 1 of second single-pole double-throw switch; 322. Terminal 2 of second single-pole double-throw switch; 33. Third single-pole double-throw switch; 331. 332, terminal 2 of the three-pole double-throw switch; 34, first amplifier; 341, chopper; 342, AC amplifier unit; 343, demodulator; 344, low-pass filter; 345, DC amplifier unit; 346, power supply; 35, second amplifier; 4, electromagnetic shielding box; 5, signal generator; 6, signal processing circuit; 61, analog signal processing module; 611, switch; 612, voltage acquisition unit; 613, current acquisition unit; 614, subtraction circuit; 615, DC amplifier unit; 616, bandpass filter; 62, analog-to-digital and digital-to-analog converter module; 621, analog-to-digital converter; 622, digital-to-analog converter; 63, digital signal processing module DSP; 64, control module FPGA; 65, microprocessor ARM; 7, computer. Detailed Implementation

[0062] The present invention will be further described below with reference to embodiments.

[0063] General Implementation Examples

[0064] An automated testing system for standardized marine electric field electrodes includes:

[0065] Three-electrode systems include:

[0066] First electrode to be tested;

[0067] The second electrode to be tested;

[0068] The reference electrode has a fixed potential. Preferably, the reference electrode is a quartz tube with an internal Ag / AgCl electrode wire, containing a potassium chloride solution, and has a porous ceramic seal at the bottom.

[0069] Water tank assembly, including:

[0070] A water bath tank containing bath liquid;

[0071] The test tank is equipped with simulated seawater and is placed inside a water bath. Two opposing plate-shaped electrodes are placed in the simulated seawater. The plate-shaped electrodes are connected to the signal generator respectively. The area between the two plate-shaped electrodes is the placement area for the reference electrode and the electrode to be tested.

[0072] A pre-amplifier signal acquisition circuit is connected to the three-electrode system. The pre-amplifier signal acquisition circuit includes: a first single-pole double-throw switch, a second single-pole double-throw switch, a third single-pole double-throw switch, a first amplifier, and a second amplifier. The first input terminal of the first amplifier is connected to the third single-pole double-throw switch; the two terminals of the third single-pole double-throw switch are connected to the first electrode under test (DUT) and the second electrode under test, respectively. The second input terminal of the first amplifier is connected to a reference electrode. The two terminals of the first single-pole double-throw switch are connected to the second single-pole double-throw switch and the circuit directly connected to the three-electrode system, respectively. The first and second input terminals of the second amplifier are connected to the second electrode under test and the first electrode under test, respectively. The two terminals of the second single-pole double-throw switch are connected to the first amplifier and the second amplifier, respectively. The third single-pole double-throw switch is directly connected to the first amplifier; its two terminals are connected to the first electrode under test and the second electrode under test, respectively. When the first single-pole double-throw switch is connected to the circuit directly connected to the three-electrode system, source impedance testing is performed; when connected to the second single-pole double-throw switch, range potential, noise, potential drift, and electric field response testing are performed. As a further preferred embodiment, both the first amplifier and the second amplifier are low-noise chopper amplifiers, including a chopper, an AC amplification unit, a demodulator, a low-pass filter, a DC amplification unit, and a power supply connected in sequence to the AC amplification unit and the DC amplification unit.

[0073] The electromagnetic shielding box, the three-electrode system, and the water tank assembly are housed inside the electromagnetic shielding box.

[0074] The signal generator is connected to two plate-shaped electrodes in the test tank.

[0075] The signal processing circuit is connected to the pre-amplifier signal acquisition circuit; the signal processing circuit includes:

[0076] The analog signal processing module, connected to the first single-pole double-throw switch and the analog-to-digital (ADC) to digital-to-analog (DAC) module, processes the measured analog current and voltage signals. The module includes a switch, a voltage acquisition module, a current acquisition module, a subtraction circuit, a DC amplifier unit, and a bandpass filter. The switch controls the circuit's on / off state, allowing for remote or automatic control. The voltage and current acquisition modules acquire the voltage and current signals from the circuit, respectively, for further processing. The subtraction circuit subtracts one signal from two input signals. In this example, the subtraction circuit subtracts the voltage and current signals to produce a signal representing resistance. The DC amplifier unit amplifies the signal magnitude. In this example, it amplifies the output signal of the subtraction circuit, enabling further processing by the bandpass filter. The bandpass filter removes unwanted frequency components from the input signal. In this example, it filters out high-frequency and low-frequency noise from the output signal of the DC amplifier unit, ensuring the output signal contains only signals within the desired frequency range.

[0077] The analog-to-digital (ADC) and digital-to-analog (DAC) conversion module is used for the mutual conversion between analog and digital signals; it includes an ADC and a DAC. The ADC is connected to the analog signal processing module to convert the analog signals amplified by the amplifier into digital signals, and the DAC is used to convert the digital signals of the control module FPGA into analog signals.

[0078] The FPGA control module is used to receive signals from the ARM microprocessor and control the front-end signal acquisition.

[0079] The digital signal processing module (DSP) is used to process digital signals converted by the analog-to-digital converter and upload the processed digital signals to the computer via Ethernet through the microprocessor (ARM).

[0080] The ARM microprocessor receives instructions from the computer and sends them to the FPGA control module, and uploads the digital signals processed by the DSP digital signal processing module to the computer via Ethernet.

[0081] The computer is connected to the signal processing circuitry.

[0082] Preferably, the analog-to-digital converter (ADC) is an ADI LTC2440 high-speed 24-bit delay-free low-noise ADC; the digital-to-analog converter (DAC) is a TI DAC81001 high-performance, low-noise 12-bit DAC; the digital signal processing module (DSP) is an AD ADSP-BF707 chip; the microprocessor (ARM) is an STMicroelectronics STM32F769 microprocessor; the control module (FPGA) is a Xilinx Spartan-6 LX9 FPGA chip; and a power control switch is connected to the control module (FPGA) to control the operation and shutdown of the entire system.

[0083] A method for testing marine electric field electrodes using the above-mentioned testing system includes the following steps:

[0084] Step 1: Electrode Immersion: Immerse the first and second test electrodes in simulated seawater in a test tank to allow them to stabilize in the test environment. The simulated seawater is a 3.0-4.0 wt% sodium chloride solution, maintained at 5-10℃, and the immersion time is no less than 24 hours. The method to determine whether the test electrodes have reached stability in the simulated seawater environment is to test the response voltage difference between the two test electrodes using the test method in Step 3. If the response voltage difference is within 1 mV and the change within 24 hours does not exceed 0.01 mV, then the test electrodes have reached stability in the test environment.

[0085] Step 2: Electrode Source Impedance Test: A signal is provided by the computer, and the FPGA control module controls the circuit connection between the first single-pole double-throw switch and the directly connected three-electrode system. A sinusoidal signal (frequency 0.01-220Hz, amplitude 50-200mV) is applied to the three-electrode system using an external power supply. The AC voltage U between the two electrodes under test is measured by the voltage acquisition module in the analog signal processing module, and the AC current I between the two electrodes under test is measured by the current acquisition module in the analog signal processing module. The impedance R of the electrode under test is calculated as R = U / I. Figure 5 As can be seen, at an excitation electric field signal of 1 Hz, the impedance of the CC / Ag / AgCl electrode under test is 5.6 Ω, and the impedance of the Ag / AgCl wire electrode under test is 167.8 Ω. This step achieves the test of the electrode source impedance of the marine electric field sensor.

[0086] Step 3: Electrode Pole Potential Difference Test: A signal is provided by the computer, and the FPGA control module connects the first and second single-pole double-throw switches, and connects the second single-pole double-throw switch to the second amplifier; the analog signal processing module is used to test the response voltage difference U between the two electrodes under test. 差 This is the range potential of the electrode under test. Figure 6 It can be seen that after the range potential of the CC / Ag / AgCl electrode pair reaches a stable value, U 差 =1.25mV, the range potential of the Ag / AgCl wire electrode pair reaches a stable value after U 差 =-0.75mV, this step enables the testing of the electrode range potential of the marine electric field sensor.

[0087] Step 4: Noise Test: A signal is provided by the computer, and the FPGA control module connects the first and second single-pole double-throw switches, and connects the second single-pole double-throw switch to the second amplifier. Simultaneously, by controlling the sampling frequency (900-1100Hz) of the analog circuit, the voltage acquisition module in the analog signal processing module measures the time-domain noise signal of the electrode under test. Then, the computer software uses Fourier transform to convert the time-domain noise signal into a frequency-domain noise signal. Figure 7 As can be seen, the self-noise of the CC / Ag / AgCl electrode pair under test is 4.26 nV / √Hz@1Hz, and the self-noise of the Ag / AgCl wire electrode pair under test is 7.63 nV / √Hz@1Hz. This step has enabled the testing of the self-noise of the marine electric field sensor electrodes.

[0088] Step 5: Potential Drift Test: A signal is provided by the computer, and the FPGA control module connects the first and second single-pole double-throw switches, and connects the second single-pole double-throw switch to the second amplifier; the voltage acquisition module in the analog signal processing module is used to test the response voltage difference U between the two electrodes under test. 差 The maximum potential signal measured during the acquisition period is U. 差max The minimum potential signal is U 差min The drift potential U measured during the acquisition period 漂 =U 差max -U 差min .Depend on Figure 6 As can be seen, after the range potential stabilizes, the range drift of the CC / Ag / AgCl electrode pair is 57.78 μV / 24h, and the range drift of the Ag / AgClwire electrode pair is 355.41 μV / 24h. This step achieves the test of the electrode potential drift of the marine electric field sensor.

[0089] Step 6: Electric Field Response Performance Test: A signal is provided by the computer, and the FPGA control module connects the first and second single-pole double-throw switches. The reference electrode is retracted, and a sinusoidal signal (frequency 0.001-100Hz, amplitude 0.01-1mV) is applied to the two electrodes under test through two plate-shaped electrodes using a signal generator. The response signal U between the electrodes under test is measured by the voltage acquisition module in the analog signal processing module. *By analyzing and comparing the collected response signal with the sinusoidal excitation signal, the electric field response performance of the electrode under test can be determined.

[0090] Step 7: Calibration test of the electrode under test: The computer provides a signal, and the FPGA control module controls the connection of the first single-pole double-throw switch and the second single-pole double-throw switch, controls the connection of the second single-pole double-throw switch to the first amplifier, and the third single-pole double-throw switch is connected to the first electrode under test and the second electrode under test in sequence; the voltage differences U1 and U2 between the reference electrode and the two electrodes under test are measured respectively; the data are uploaded to the computer and calibrated by the software, and the performance of the electrode pair under test is comprehensively judged by combining the test data from steps 2-6.

[0091] The performance determination involves first establishing an evaluation model, and then using this model to calibrate different electrodes under test. A multiple linear regression equation is used, with the potential difference between the reference electrode and different electrodes under test as independent variables, and the range potential, noise, potential drift, and electric field response between the electrodes under test as dependent variables. After fitting multiple multiple linear regression equations, an evaluation model is obtained. This evaluation model is then used to calibrate other electrodes under test and evaluate their performance.

[0092] The method for constructing the evaluation model specifically includes: to establish the relationship between any two electrodes under test, a multiple linear regression equation is used to predict the response of the two electrodes under test, with the range potential, noise, potential drift, and electric field response between the electrodes under test as dependent variables Y; taking the range potential as the dependent variable as an example, the potential difference between the reference electrode and one of the electrodes under test are respectively taken as independent variables V1 and V2; assuming there are N electrodes under test, the relationship between all possible pairs of electrodes under test is fitted by N linear regression equations; assuming the range potential between the i-th pair of electrodes under test is Y i The potential difference between the first electrode under test and the reference electrode is V. 1i The potential difference between the second electrode under test and the reference electrode is V. 2i Then the following multiple linear regression equation can be obtained:

[0093] Y1 = β0 + β1V 11 +β2V 21 +ε1,

[0094] Y2 = β0 + β1V 12 +β2V 22 +ε2,

[0095] ...

[0096] Y N = β0+β1V 1N + β2V 2N + ε N ;

[0097] Where β0 is the intercept, β1 and β2 are regression coefficients, and ε1, ε2, ..., ε N This is the error term; the LinearRegression class from the Scikit-learn library is used to fit the above linear regression equation, thus obtaining an evaluation model.

[0098] Example 1

[0099] like Figure 1 The figure shown is a preferred embodiment of the present invention, which provides an integrated automatic testing system for marine electric field electrode specifications, including a three-electrode system 1, a water tank group 2, a pre-signal acquisition circuit 3, an electromagnetic shielding box 4, a signal generator 5, a signal processing circuit 6, and a computer 7.

[0100] The three-electrode system 1 includes two electrodes to be tested (first electrode 11 and second electrode 12) and a reference electrode 13. The potential of the reference electrode 13 is a fixed value, used for potential reference of the electrodes to be tested and for calibration of test data for different electrodes to be tested, ensuring the standard universality of the system. Its main body is a quartz tube with an internal Ag / AgCl electrode wire containing potassium chloride solution, and a porous ceramic seal at the bottom.

[0101] The water tank assembly 2 includes two plate electrodes 21 (specifically platinum plate electrodes), simulated seawater 22 (3.5wt% sodium chloride solution), a test water tank 23, a water bath solution 24, and a water bath tank 25. The plate electrodes 21 are connected to a signal generator to apply an electric field signal to the test water tank 23. The area between the two plate electrodes 21 is the placement area for the reference electrode 13 and the electrode under test. The simulated seawater 22 simulates the underwater marine environment. The test water tank 23 is located inside the water bath tank 25, and the water bath tank 25 maintains the temperature of the test water tank 23 within a constant range using the water bath solution 24.

[0102] The preamplifier signal acquisition circuit 3 includes a first single-pole double-throw switch 31, a second single-pole double-throw switch 32, a third single-pole double-throw switch 33, a first amplifier 34, and a second amplifier 35. The first input terminal of the first amplifier 34 is connected to the third single-pole double-throw switch 33, and the two terminals of the third single-pole double-throw switch 33 are respectively connected to the first electrode under test 11 and the second electrode under test 12. The second input terminal of the first amplifier 34 is connected to the reference electrode 13. The two terminals of the first single-pole double-throw switch 31 (terminal 311 of the first single-pole double-throw switch 1 and terminal 312 of the first single-pole double-throw switch 2) are respectively connected to the second single-pole double-throw switch 32 and the circuit directly connected to the three-electrode system. The first and second input terminals of the second amplifier 35 are respectively connected to the second electrode under test 12 and the first electrode under test 11. The two terminals of the second single-pole double-throw switch 32 (terminal 321 of the second single-pole double-throw switch 1 and terminal 322 of the second single-pole double-throw switch 2) are respectively connected to the first amplifier 34 and the second amplifier 35. The third single-pole double-throw switch 33 is directly connected to the first amplifier 34. Its two terminals (terminal 331 of the third single-pole double-throw switch 1 and terminal 332 of the third single-pole double-throw switch 2) are connected to the first electrode under test 11 and the second electrode under test 12, respectively. When the first single-pole double-throw switch 31 is switched to terminal 312 of the first single-pole double-throw switch 2, source impedance testing can be performed. When switched to terminal 311 of the first single-pole double-throw switch 1, range potential, noise, potential drift, and electric field response testing can be performed.

[0103] Among them, the first amplifier 34 and the second amplifier 35 are both low-noise chopper amplifiers. Figure 2 As shown, the low-noise chopper amplifier mainly includes a chopper 341, an AC amplifier unit 342, a demodulator 343, a low-pass filter 344, a DC amplifier unit 345, and a power supply 346 connected in sequence to the AC amplifier unit and the DC amplifier unit.

[0104] Among them, the electromagnetic shielding box 4 is a fully enclosed box made of mu alloy, which is used to shield external power frequency and other electromagnetic noise to prevent interference with the test.

[0105] Among them, signal generator 5 is a waveform generator used to generate low-frequency sine wave signals, providing a signal source during electric field response testing.

[0106] The signal processing circuit 6 includes an analog signal processing module 61, an analog-to-digital (ADC) to digital-to-analog (DAC) conversion module 62, a digital signal processing module (DSP) 63, a control module (FPGA) 64, and a microprocessor (ARM) 65. The analog signal processing module 61, as shown in the diagram... Figure 3The circuit includes a switch 611, a voltage acquisition unit 612, a current acquisition unit 613, a subtraction circuit 614, a DC amplifier unit 615, and a bandpass filter 616. These components are used to process measured analog signals such as current and voltage. The switch controls the circuit's on / off state, allowing for remote or automatic control. The voltage and current acquisition modules acquire voltage and current signals from the circuit, respectively, for further processing. The subtraction circuit subtracts one signal from two input signals. In this example, the subtraction circuit subtracts the voltage and current signals to produce a signal representing resistance. The DC amplifier unit amplifies the signal magnitude. In this example, it amplifies the output signal of the subtraction circuit so that it can be further processed by the bandpass filter. The bandpass filter removes unwanted frequency components from the input signal. In this example, it filters out high-frequency and low-frequency noise from the output signal of the DC amplifier unit, ensuring the output signal contains only signals within the desired frequency range. The analog signal processing module is connected to the first single-pole double-throw switch 31 and the analog-to-digital (ADC) to digital-to-analog (DAC) module 62. The analog-to-digital (ADC) and digital-to-analog (DAC) module 62 is used for mutual conversion between analog and digital signals. Specifically, the ADC converter 621 converts the amplified analog signal into a digital signal, and the DAC 622 converts the digital signal from the control module into an analog signal. The digital signal processing module DSP 63 processes the digital signal converted by the ADC converter 621 and uploads the processed digital signal to the computer via Ethernet through the microprocessor ARM65. The control module FPGA 64 receives signals from the microprocessor ARM65 and controls the front-end signal acquisition. The microprocessor ARM65 receives instructions from the computer and sends them to the control module FPGA 64, and uploads the digital signal processed by the digital signal processing module DSP 63 to the computer via Ethernet.

[0107] The system comprises several key components: an analog-to-digital converter (ADC) 621 using Analog Devices' (ADI) LTC2440 high-speed 24-bit delay-free, low-noise ADC; and a digital-to-analog converter (DAC) 622 using TI's DAC81001 high-performance, low-noise 12-bit DAC. The digital signal processing module (DSP) 63 uses Analog Devices' (ADI) ADSP-BF707 chip, with a core power consumption of less than 95mW, providing a maximum processing capacity of 400 MHz and supporting single-cycle dual 16-bit and single 32-bit complex number fixed-point mathematical operations. The control module (FPGA) 64 uses Xilinx's Xilinx Spartan-6 LX9 FPGA chip, offering advantages such as high performance, low power consumption, and programmability. A power control switch is connected to the FPGA 64 to control the operation and shutdown of the entire system. The microprocessor (ARM65) uses STMicroelectronics' STM32F769 microprocessor, a high-performance 32-bit microcontroller.

[0108] The aforementioned testing system can perform automated testing of the source impedance, range potential, noise, potential drift, and electric field response of marine electric field electrodes in a unified manner. It can also use a reference electrode as a benchmark to calibrate and construct a performance evaluation model for marine electric field electrodes, which can greatly improve the efficiency and accuracy of marine electric field electrode testing and establish a unified and standardized testing system for research in the field of marine electric field electrodes.

[0109] Example 2

[0110] An integrated automated testing method for marine electric field electrode specifications is provided, using the testing system of Example 1. The flowchart is shown below. Figure 4 As shown, it includes the following steps:

[0111] S1 Immersion Electrode: Place the two measuring electrodes in the test water tank and immerse them for 24 hours to allow them to initially stabilize in the test environment.

[0112] In S1, the temperature of the simulated seawater is maintained within the range of 5-10℃, and the immersion time is no less than 24 hours. The method for judging whether the electrode under test has reached stability in the test environment is to use the test method in S3: the computer provides a signal, the control module FPGA controls the first single-pole double-throw switch to switch to terminal 1 of the first single-pole double-throw switch, and controls the second single-pole double-throw switch to switch to terminal 2 of the second single-pole double-throw switch; the analog signal processing module tests the response voltage difference between the two electrodes under test. When the response voltage difference is within 1mV and the change within 24 hours does not exceed 0.01mV, the electrode under test has reached stability in the test environment.

[0113] S2 Electrode Source Impedance Test: Once the electrode under test reaches stability, a signal is given by the computer, and the FPGA control module controls the first single-pole double-throw switch to switch terminal 2. A sinusoidal signal is applied to the three-electrode system using the external power supply in the analog signal processing module. The AC voltage U between the electrodes under test is measured by the voltmeter in the analog signal processing module, and the AC current I of the electrode under test is measured by the ammeter in the analog signal processing module. The impedance R of the electrode under test can be calculated as R = U / I.

[0114] In S2, the frequency of the sinusoidal signal is 0.01-220Hz, and the amplitude is 50-200mV.

[0115] S3 Electrode Range Potential Test: After the electrode under test reaches stability, a signal is sent via computer, and the FPGA control module controls the first single-pole double-throw switch to its terminal 1, and controls the second single-pole double-throw switch to its terminal 2. The analog signal processing module is used to test the response voltage difference U between the two electrodes under test. 差 This is the range potential of the electrode to be measured.

[0116] S4 Noise Test: Once the electrode under test (DUT) reaches stability, a signal is sent via the computer. The FPGA control module controls the first single-pole double-throw switch to its terminal 1 and the second single-pole double-throw switch to its terminal 2. Simultaneously, by controlling the sampling frequency of the analog circuit, the voltmeter in the analog signal processing module measures the time-domain noise signal of the DUT. The computer software then uses Fourier transform to convert the time-domain noise signal into a frequency-domain noise signal.

[0117] In S4, the sampling frequency of the analog circuit is set to 1000Hz.

[0118] S5 Potential Drift Test: Once the electrode under test reaches stability, a signal is sent via the computer, and the FPGA control module controls the first single-pole double-throw switch to its terminal 1, and controls the second single-pole double-throw switch to its terminal 2. The voltmeter in the analog signal processing module is used to measure the response voltage difference U between the two electrodes under test. 差 The maximum potential signal measured during the acquisition period is U. 差max The minimum potential signal is U 差min Therefore, the drift potential U measured during the acquisition period 漂 =U 差max -U 差min .

[0119] S6 Electric Field Response Performance Test: Once the electrode under test reaches stability, a signal is sent via computer, and the FPGA control module controls the first single-pole double-throw switch to switch to terminal 2. The reference electrode is retracted, and a sinusoidal excitation signal is applied to the two electrodes under test via two plate-shaped electrodes using a signal generator. The response signal U between the electrodes under test is measured by the voltmeter in the analog signal processing module. * By analyzing and comparing the collected response signal with the sinusoidal excitation signal, the electric field response performance of the electrode under test can be determined.

[0120] In S6, the frequency of the sinusoidal excitation signal is 0.001-100Hz, and the amplitude is 0.01-1mV.

[0121] S7 Electrode under Test (DUT) Calibration Test: Once the DUT reaches stability, a signal is sent from the computer, and the FPGA control module controls the first single-pole double-throw switch to its terminal 1, the second single-pole double-throw switch to its terminal 1, and the third single-pole double-throw switch to its terminals 1 and 2 respectively. The voltage differences U1 and U2 between the standard electrode and the first and second DUTs are measured. These values ​​are uploaded to the computer for calibration using software. The performance of the DUTs is then comprehensively evaluated based on the test data from the previous steps. The performance evaluation involves first establishing an evaluation model, which is then used to calibrate different DUTs. A multiple linear regression equation is used, with the potential difference between the reference electrode and different DUTs as independent variables, and the range potential, noise, potential drift, and electric field response between the DUTs as dependent variables. Multiple multiple linear regression equations are fitted to obtain an evaluation model, which is then used to calibrate other DUTs and evaluate their performance.

[0122] The construction of the evaluation model specifically includes: to establish the relationship between any two electrodes under test, a multiple linear regression equation is used to predict the response of the two electrodes under test, with the range potential, noise, potential drift, and electric field response between the electrodes under test as dependent variables Y; taking the range potential as the dependent variable as an example, the potential difference between the reference electrode and one of the electrodes under test are respectively used as independent variables V1 and V2; assuming there are N electrodes under test, the relationship between all possible pairs of electrodes under test is fitted through N linear regression equations; assuming the range potential between the i-th pair of electrodes under test is Y i The potential difference between the first electrode under test and the reference electrode is V. 1i The potential difference between the second electrode under test and the reference electrode is V. 2i Then the following multiple linear regression equation can be obtained:

[0123] Y1 = β0 + β1V 11 +β2V 21 +ε1,

[0124] Y2 = β0 + β1V 12 +β2V 22 +ε2,

[0125] ...

[0126] Y N = β0+β1V 1N + β2V 2N + ε N ;

[0127] Where β0 is the intercept, β1 and β2 are regression coefficients, and ε1, ε2, ..., εN This is the error term; the LinearRegression class from the Scikit-learn library is used to fit the above linear regression equation, thus obtaining an evaluation model.

[0128] The above-mentioned testing methods can uniformly and automatically test the source impedance, range potential, noise, potential drift, and electric field response of marine electric field electrodes. Furthermore, by using a reference electrode as a benchmark, a set of performance evaluation models for marine electric field electrodes can be calibrated and constructed, which greatly improves the efficiency and accuracy of marine electric field electrode testing and establishes a unified and standardized testing system for research in the field of marine electric field electrodes.

[0129] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. An automated testing system for standardized marine electric field electrodes, comprising: Three-electrode systems include: First and second electrodes to be tested; reference electrode, with a fixed potential; Water tank assembly, including: A water bath tank containing bath liquid; The test tank is placed in a water bath and contains simulated seawater. Two opposing plate-shaped electrodes are placed in the simulated seawater. The plate-shaped electrodes are connected to the signal generator. The area between the plate-shaped electrodes is the placement area for the reference electrode and the electrode to be tested. The pre-amplifier signal acquisition circuit is connected to the three-electrode system. The electromagnetic shielding box, the three-electrode system, and the water tank assembly are housed inside the electromagnetic shielding box. The signal generator, connected to two plate-shaped electrodes, is used to generate low-frequency sinusoidal signals. The signal processing circuit is connected to the pre-amplifier signal acquisition circuit. The computer is connected to the signal processing circuitry. The preamplifier signal acquisition circuit includes: first, second, and third single-pole double-throw switches, and first and second amplifiers; the first and second input terminals of the first amplifier are respectively connected to the third single-pole double-throw switch and the reference electrode; the two terminals of the third single-pole double-throw switch are respectively connected to the first and second electrodes under test; the two terminals of the first single-pole double-throw switch are respectively connected to the second single-pole double-throw switch and the three-electrode system circuit; the first and second input terminals of the second amplifier are respectively connected to the second and first electrodes under test; the two terminals of the second single-pole double-throw switch are respectively connected to the first and second amplifiers. When the first single-pole double-throw switch is connected to the circuit of the three-electrode system, source impedance is tested; when it is connected to the second single-pole double-throw switch, range potential, noise, potential drift, and electric field response are tested.

2. The testing system as described in claim 1, characterized in that: Both the first and second amplifiers are low-noise chopper amplifiers, including a chopper, an AC amplifier unit, a demodulator, a low-pass filter, a DC amplifier unit, and a power supply connected in sequence to the AC amplifier unit and the DC amplifier unit.

3. The testing system as described in claim 1 or 2, characterized in that: The signal processing circuit includes: The analog signal processing module is connected to the first single-pole double-throw switch and the analog-to-digital and digital-to-analog converter module, respectively, and is used to process the measured current and voltage analog signals. The analog-to-digital (ADC) and digital-to-analog (DAC) conversion module is used for the mutual conversion between analog and digital signals. It includes an ADC and a DAC. The ADC is connected to the analog signal processing module and is used to convert the analog signals amplified by the first and second amplifiers into digital signals. The DAC is used to convert the digital signals of the control module FPGA into analog signals. The FPGA control module is used to receive signals from the ARM microprocessor and control the front-end signals. The digital signal processing module (DSP) is used to process the digital signals converted by the analog-to-digital converter and upload the processed digital signals to the computer via Ethernet through the microprocessor (ARM). The ARM microprocessor receives instructions from the computer and sends them to the FPGA control module, and uploads the digital signals processed by the DSP digital signal processing module to the computer via Ethernet.

4. The testing system as described in claim 3, characterized in that: The analog signal processing module includes a switch, a voltage acquisition module, a current acquisition module, a subtraction circuit, a DC amplifier unit, and a bandpass filter. The switch is used to control the circuit switching state of the entire analog signal processing module. The voltage acquisition module and the current acquisition module are used to acquire voltage signals and current signals in the circuit, respectively. The DC amplifier unit is used to amplify the resistance signal. The bandpass filter is used to filter out high-frequency and low-frequency noise in the output signal of the DC amplifier unit, so that the output signal only contains signals within the required frequency range.

5. A standardized and automated testing method for marine electric field electrodes, characterized in that: The automated testing system for standardized marine electric field electrodes as described in claim 3 or 4 includes the following steps: Step 1: Immerse the electrodes: Immerse the first and second electrodes under test in simulated seawater in the test tank to stabilize them in the test environment; Step 2: Electrode source impedance test: The FPGA control module controls the circuit connection between the first single-pole double-throw switch and the three-electrode system; a sinusoidal signal is applied to the three-electrode system using an external power supply; the AC voltage U between the two electrodes under test is measured by the voltage acquisition module in the analog signal processing module; the AC current I between the two electrodes under test is measured by the current acquisition module in the analog signal processing module; and the impedance R of the electrode under test is calculated as R = U / I. Step 3: Electrode Range Potential Test: The FPGA control module connects the first single-pole double-throw (SPD) switch to the second SPD switch, and connects the second SPD switch to the second amplifier; the analog signal processing module is used to test the response voltage difference U between the two electrodes under test. 差 , which is the range potential of the electrode to be measured; Step 4: Noise Test: The FPGA control module controls the connection between the first single-pole double-throw switch and the second single-pole double-throw switch, and controls the connection between the second single-pole double-throw switch and the second amplifier; at the same time, by controlling the sampling frequency of the analog signal processing module, the voltage acquisition module in the analog signal processing module measures the time-domain noise signal of the electrode under test, and then the computer software uses the Fourier transform method to convert the time-domain noise signal into a frequency-domain noise signal. Step 5: Potential Drift Test: The FPGA control module connects the first single-pole double-throw (SPDT) switch to the second SPDT switch, and connects the second SPDT switch to the second amplifier; the voltage acquisition module in the analog signal processing module is used to test the response voltage difference U between the two electrodes under test. 差 The maximum potential signal measured during the acquisition period is U. 差max The minimum potential signal is U 差min The drift potential U measured during the acquisition period 漂 =U 差max -U 差min ; Step 6: Electric field response performance test: The control module FPGA controls the connection between the first single-pole double-throw switch and the second single-pole double-throw switch; The reference electrode is retracted, and a sinusoidal signal is applied to the two electrodes under test through two plate-shaped electrodes using a signal generator. The response signal U between the electrodes under test is measured by the voltage acquisition module in the analog signal processing module. * By analyzing and comparing the collected response signal with the sinusoidal excitation signal, the electric field response performance of the electrode under test can be determined. Step 7: Calibration test of the electrode under test: The FPGA control module controls the connection of the first single-pole double-throw switch and the second single-pole double-throw switch, controls the connection of the second single-pole double-throw switch to the first amplifier, and the third single-pole double-throw switch is connected to the first electrode under test and the second electrode under test in sequence; the voltage difference between the reference electrode and the two electrodes under test is measured as U1 and U2 respectively; the data is uploaded to the computer and calibrated by the software, and the performance of the electrode pair under test is comprehensively judged by combining the test data from steps 2-6.

6. The test method as described in claim 5, characterized in that: In step 1, The simulated seawater is a 3.0-4.0 wt% sodium chloride solution, the temperature is maintained at 5-10℃, and the soaking time is not less than 24 hours; The method to determine whether the electrode under test has reached stability in the simulated seawater environment is to test the response voltage difference between the two electrodes under test using the test method in step 3. When the response voltage difference is within 1mV and the change within 24 hours does not exceed 0.01mV, the electrode under test has reached stability in the test environment.

7. The test method as described in claim 5, characterized in that: In step 2, the frequency of the sinusoidal signal is 0.01-220Hz, and the amplitude is 50-200mV; In step 4, the sampling frequency of the analog signal processing module is set to 900-1100Hz; In step 6, the frequency of the sinusoidal excitation signal is 0.001-100Hz and the amplitude is 0.01-1mV.

8. The test method as described in claim 5, characterized in that: In step 7, the performance determination involves first establishing an evaluation model, and then using this evaluation model to calibrate different electrodes under test: using a multiple linear regression equation, the potential difference between the reference electrode and different electrodes under test is taken as an independent variable, and the range potential, noise, potential drift, and electric field response between the electrodes under test are taken as dependent variables. After fitting multiple multiple linear regression equations, an evaluation model is obtained. This evaluation model is then used to calibrate other electrodes under test and evaluate their performance.

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