Portable EIT data acquisition device

Abstract

The invention discloses a portable EIT data acquisition device. The portable EIT data acquisition device comprises a microcontroller module, a current source excitation module, m multi-way switch modules, m 32 electrode arrays and an analog-to-digital converter module. The microcontroller controls the switch module to select injection and measurement electrodes according to a measurement mode, the current source excitation module generates alternating current signals and injects the alternating current signals into a measured field domain, and the electrode array collects voltage signals. And the analog-to-digital converter module converts the voltage signal into a digital signal and transmits the digital signal to the microcontroller, so that field impedance information is obtained, multi-electrode configuration is supported, and different measurement requirements are met. According to the invention, the problems of large size, poor expansibility and the like of existing equipment can be solved, and the most appropriate gain setting is adaptively selected through an automatic calibration technology, so that the measurement precision is improved; meanwhile, the multi-electrode requirement is met, different measurement conditions are adapted, more accurate electrical impedance distribution detection is achieved, and finally the application requirements of wearable equipment and mobile monitoring can be met.

Description

Technical Field

[0001] The invention relates to the technical field of EIT (Electrical Impedance Tomography) data acquisition, in particular to a portable EIT data acquisition device. Background Art

[0002] EIT (Electrical Impedance Tomography) is a non-destructive functional imaging technology. Compared with traditional imaging technologies such as CT and MRI, EIT has the advantages of being non-invasive, radiation-free, low-cost and capable of long-term monitoring.

[0003] The EIT data acquisition device arranges a circle of electrodes on the surface of the object being measured, uses some electrodes to apply electrical excitation to the measured field, and measures the electrical response signals of the remaining electrodes at the same time. By performing inverse problem algorithm analysis on these measurement data, the conductivity distribution inside the measured field can be reconstructed.

[0004] In some application scenarios, such as real-time muscle monitoring, wearable and portable EIT data acquisition devices are required. However, existing commercial devices are usually large stand-alone devices used in hospitals, which are bulky and expensive, and most EIT data acquisition devices are only equipped with 8, 16 or 32 electrodes, among which 16-electrode configuration is the most common. When the measurement requirements require more electrodes, existing devices often have difficulty meeting this demand.

[0005] Therefore, it is particularly necessary to design a portable data acquisition device with multi-electrode expansion capabilities. Summary of the invention

[0006] The present invention aims to solve the deficiencies of the above-mentioned prior art and proposes a portable EIT data acquisition device, in order to solve the problems of large size and poor scalability of the existing equipment, and to adaptively select the most appropriate gain setting through automatic calibration technology, so as to improve the measurement accuracy; at the same time, it meets the multi-electrode requirements, adapts to different measurement conditions, and realizes more accurate electrical impedance distribution detection, and finally can meet the application requirements of wearable devices and mobile monitoring. To achieve the above purpose, the embodiment of the present invention provides the following technical solutions: A portable EIT data acquisition device of the present invention is characterized in that it includes: a microcontroller module, a current source excitation module, m multi-way switch modules, m 32-electrode arrays and an analog-to-digital converter module;

[0007] The microcontroller module, current source excitation module and analog-to-digital converter module are integrated on the main board;

[0008] Any multiplexer module and its corresponding 32-electrode array are mounted on a multiplexer board;

[0009] The main board is connected to any multiplexer board via a connector, and any two multiplexer boards are connected to each other via a connector;

[0010] The microcontroller module sends an excitation gating signal to the multi-way switch module according to the measurement mode, so that the multi-way switch module selects one pair of electrodes as the injection electrode according to the excitation gating signal;

[0011] The microcontroller controls the current source excitation module to generate an AC signal with a certain amplitude and frequency and provides the AC signal to the multi-way switch module;

[0012] The multi-way switch module injects the received alternating current signal into the measured field through the injection electrode;

[0013] The microcontroller module sends a measurement selection signal to the multi-way switch module according to the measurement mode, so that the multi-way switch module selects another pair of electrodes as measurement electrodes according to the measurement selection signal, and is used to collect the voltage of the measured field;

[0014] The analog-to-digital converter module collects and converts the voltage signal of the measuring electrode, obtains a digital signal and sends it to the microcontroller for processing, thereby obtaining the impedance information of the measured field.

[0015] The portable EIT data acquisition device described in the present invention is also characterized in that the current source excitation module includes: a waveform generator, a digital potentiometer, an instrument amplifier and a voltage-controlled current source;

[0016] The waveform generator generates a differential sine wave signal, which is amplified by the instrument amplifier to obtain an amplified signal, and the amplified signal is modulated by calibrating the gain of the digital potentiometer. The modulated signal is used to drive the voltage-controlled current source and generate a differential current centered at 0, which is an alternating current signal.

[0017] Further, the analog-to-digital converter module includes: two input buffers, an adjustable instrumentation amplifier, a digital potentiometer, a bandpass RC filter and an analog-to-digital converter ADC;

[0018] Each input buffer uses an operational amplifier configured for unity gain and connected to an RC high-pass filter;

[0019] After each input buffer feeds the voltage signal into the adjustable instrumentation amplifier, it is then modulated by a digital potentiometer to obtain a stepped-down signal, which is then processed by a bandpass RC filter to obtain a filtered signal;

[0020] The analog-to-digital converter ADC converts the filtered signal at a set sampling frequency and outputs a digital signal.

[0021] Furthermore, any multi-way switch module includes four multi-way switch chips, two of which are used to select the injection electrodes, and the other two multi-way switch chips are used to select the measurement electrodes.

[0022] Furthermore, the gain of the digital potentiometer is automatically calibrated according to the following steps:

[0023] Step 1: Define the current optimization number as i, and initialize i=0; let the gain value of the digital potentiometer under the i-th optimization be =0;

[0024] Step 2: Set the resistance of the digital potentiometer to ; and after a delay, the EIT data acquisition device reaches a stable state;

[0025] Step 3: Get the current gain value The amplitude measured by the lower analog-to-digital converter module at the jth time and error , thus obtaining the amplitude and error of the Jth measurement, and using equations (1) and (2) to calculate the amplitude accumulation parameter m under the i-th optimization i and the error accumulation parameter ;

[0026] (1)

[0027] (2)

[0028] Step 4: Use equations (3) and (4) to calculate the average amplitude under the i-th optimization: and the average error :

[0029] (3)

[0030] (4)

[0031] Step 5: If It is within the set valid range, and If the current gain value is less than the set threshold, Output as the optimal gain value, otherwise, execute step 6;

[0032] Step 6: +1 assigned to After; if >N, it means that no gain value that meets the conditions is found and the process ends. Otherwise, return to step 2 and execute sequentially.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention solves the measurement bias problem caused by fixed gain setting in the prior art by adaptively adjusting the driving gain and the measurement gain, ensures high-precision electrical impedance imaging, and significantly improves the accuracy and reliability of the device under different measurement conditions.

[0035] 2. The present invention adopts a stacked multiplexer design, which supports users to flexibly select 32 or 64 electrodes according to their needs, solves the problem that the number of electrodes of traditional equipment cannot be expanded, meets the needs of various application scenarios such as medicine, sports health, etc., and improves the applicability and scalability of the equipment.

[0036] 3. The present invention integrates components such as a microcontroller, a current source excitation module, and an analog-to-digital converter module on a mainboard through a compact integrated design, thereby reducing the size and weight of the device and improving portability, making it suitable for wearable devices and mobile monitoring scenarios.

[0037] 4. The present invention adopts a high-performance analog-to-digital converter and a current source excitation module, combined with a bandpass filter and gain control, to optimize signal quality and stability, reduce noise interference, and ensure the accuracy of data acquisition and the reliability of imaging results. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the structure of the portable EIT data acquisition device of the present invention;

[0039] Figure 2 It is a schematic diagram of the structure of the stacked multiplexer of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0041] The present invention provides a portable EIT data acquisition device comprising: a microcontroller module 10, a current source excitation module 11, a multi-way switch module 12, a 32-electrode array 3 and an analog-to-digital converter module 13.

[0042] The microcontroller module 10, the current source excitation module 11 and the analog-to-digital converter module 13 are integrated in the Figure 2 On the main board 4 of 6.2 cm × 6.2 cm shown;

[0043] like Figure 2 As shown, any multiplexer module 12 and its corresponding 32-electrode array 3 are mounted on a detachable and stackable multiplexer board, and each multiplexer board has four multiplexer chips built in. The sizes of the two multiplexer boards are 3.7 cm × 4.3 cm and 3.1 cm × 4.3 cm respectively;

[0044] The main board is connected to a multiplexer board with a size of 3.7 cm × 4.3 cm through a connector, and the multiplexer board is connected to a multiplexer board with a size of 3.1 cm × 4.3 cm through a connector;

[0045] like Figure 1 As shown, the microcontroller module 10 sends an excitation gating signal to the multi-way switch module 12 according to the measurement mode, so that the multi-way switch module 12 selects one pair of electrodes as the injection electrode according to the excitation gating signal;

[0046] The microcontroller module 10 controls the current source excitation module 11 to generate an AC signal with a certain amplitude and frequency and provides it to the multi-way switch module 12;

[0047] The multi-way switch module 12 injects the received AC signal into the measured field through the injection electrode;

[0048] The microcontroller module 10 sends a measurement selection signal to the multi-way switch module 12 according to the measurement mode, so that the multi-way switch module 12 selects another pair of electrodes as measurement electrodes according to the measurement selection signal, and is used to collect the voltage of the measured field;

[0049] Depending on the measurement requirements, you can choose 32-electrode measurement or 64-electrode measurement. When choosing 32-electrode measurement, you only need to insert the multiplexer board with a size of 3.7cm×4.3cm into the main board through the connector; if choosing 64-electrode measurement, you need to insert the multiplexer board with a size of 3.1cm×4.3cm into the multiplexer board with a size of 3.7cm×4.3cm through the connector;

[0050] The analog-to-digital converter module 13 collects and converts the voltage signal of the measuring electrode, obtains a digital signal and sends it to the microcontroller for processing, thereby obtaining the impedance information of the measured field. The microcontroller module 10 uses a teensy 4.1 chip.

[0051] In a specific implementation, the current source excitation module 11 includes: a waveform generator, a digital potentiometer, an instrument amplifier and a voltage-controlled current source VCCS;

[0052] In this embodiment, the waveform generator uses the AD9910 chip, the digital potentiometer uses the AD5260 chip, and the instrument amplifier uses the AD8421 chip;

[0053] The waveform generator generates a differential sine wave signal, which is amplified by the instrument amplifier to obtain an amplified signal. The amplified signal is modulated by calibrating the gain of the digital potentiometer. The modulated signal is used to drive the voltage-controlled current source and generate a differential current centered on 0, which is an AC signal.

[0054] In this embodiment, the analog-to-digital converter module 13 includes: two input buffers, an adjustable instrumentation amplifier, a digital potentiometer, a bandpass RC filter, and an analog-to-digital converter ADC;

[0055] In this embodiment, the adjustable instrument amplifier uses the AD8421 chip, and the analog-to-digital converter ADC uses the ADS901E chip.

[0056] Each input buffer uses an operational amplifier configured for unity gain and connected to an RC high-pass filter with a cutoff frequency of 350Hz;

[0057] After each input buffer feeds the voltage signal into the adjustable instrumentation amplifier, it is then stepped down by a digital potentiometer, and the output voltage is reduced from 5V to 3.3V. The resulting stepped-down signal is then passed through a bandpass RC filter with cutoff frequencies of 1kHz and 1MHz, and the filtered signal is obtained after processing.

[0058] The analog-to-digital converter ADC converts the filtered signal at a sampling frequency of 20 MHz and outputs a 10-bit digital signal.

[0059] Any multi-way switch module 12 includes four multi-way switch chips, two of which are used to gate the injection electrodes, and the other two multi-way switch chips are used to gate the measurement electrodes.

[0060] The automatic calibration method is to control the digital potentiometer in the current source excitation module 11 and the analog-to-digital converter module 13 during device initialization, increase the resistance of the digital potentiometer incrementally, and perform multiple measurements to obtain the average amplitude value and the average error value of the measured signal compared with the sine wave. When the above measurement parameters of the selected resistance value meet the set range conditions, the driving gain and measurement gain of the circuit can be determined. Up to 2048 selections can be made, and finally a combination that maximizes the voltage response within the ADC channel range is selected. This method can automatically calibrate the most suitable driving gain and measurement gain according to different objects under test.

[0061] In this embodiment, the gain of the digital potentiometer is automatically calibrated according to the following steps:

[0062] Step 1: Define the current optimization number as i, and initialize i=0; let the gain value of the digital potentiometer under the i-th optimization be =0;

[0063] Step 2: Set the resistance of the digital potentiometer to ; and after a delay, the EIT data acquisition device reaches a stable state;

[0064] Step 3: Get the current gain value The amplitude measured by the lower analog-to-digital converter module at the jth time and error , thus obtaining the amplitude and error of the Jth measurement, and using equations (1) and (2) to calculate the amplitude accumulation parameter m under the i-th optimization i and the error accumulation parameter ;

[0065] (1)

[0066] (2)

[0067] Step 4: Use equations (3) and (4) to calculate the average amplitude under the i-th optimization: and the average error :

[0068] (3)

[0069] (4)

[0070] Step 5: If It is within the set valid range, and If the current gain value is less than the set threshold, Output as the optimal gain value, otherwise, execute step 6;

[0071] Step 6: +1 assigned to After; if >N, it means that no gain value that meets the conditions is found and the process ends. Otherwise, return to step 2 and execute sequentially.

[0072] In this embodiment, an electronic device includes a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the above method, and the processor is configured to execute the program stored in the memory.

[0073] In this embodiment, a computer-readable storage medium stores a computer program on the computer-readable storage medium, and the computer program executes the steps of the above method when executed by a processor.

Claims

1. A portable EIT data acquisition device, characterized in that: include: a microcontroller module, a current source excitation module, m multiplexer modules, m 32-electrode arrays, and an analog-to-digital converter module; The microcontroller module, current source excitation module and analog-to-digital converter module are integrated on the main board; Any multiplexer module and its corresponding 32-electrode array are mounted on a multiplexer board; The main board is connected to any multiplexer board through a connector, and any two multiplexer boards are connected to each other through a connector; The microcontroller module sends an excitation gating signal to the multi-way switch module according to the measurement mode, so that the multi-way switch module selects one pair of electrodes as the injection electrode according to the excitation gating signal; The microcontroller controls the current source excitation module to generate an AC signal with a certain amplitude and frequency and provides the AC signal to the multi-way switch module; The multi-way switch module injects the received alternating current signal into the measured field through the injection electrode; The microcontroller module sends a measurement selection signal to the multi-way switch module according to the measurement mode, so that the multi-way switch module selects another pair of electrodes as measurement electrodes according to the measurement selection signal, and is used to collect the voltage of the measured field; The analog-to-digital converter module collects and converts the voltage signal of the measuring electrode, obtains a digital signal and sends it to the microcontroller for processing, thereby obtaining the impedance information of the measured field.

2. A portable EIT data acquisition device according to claim 1, characterized in that: The current source excitation module includes: a waveform generator, a digital potentiometer, an instrument amplifier and a voltage-controlled current source; The waveform generator generates a differential sine wave signal, which is amplified by the instrument amplifier to obtain an amplified signal, and the amplified signal is modulated by calibrating the gain of the digital potentiometer. The modulated signal is used to drive the voltage-controlled current source and generate a differential current centered at 0, which is an alternating current signal.

3. A portable EIT data acquisition device according to claim 1, characterized in that: The analog-to-digital converter module includes: two input buffers, an adjustable instrumentation amplifier, a digital potentiometer, a bandpass RC filter and an analog-to-digital converter ADC; Each input buffer uses an operational amplifier configured for unity gain and connected to an RC high-pass filter; After each input buffer feeds the voltage signal into the adjustable instrumentation amplifier, it is then modulated by a digital potentiometer to obtain a stepped-down signal, which is then processed by a bandpass RC filter to obtain a filtered signal; The analog-to-digital converter ADC converts the filtered signal at a set sampling frequency and outputs a digital signal.

4. A portable EIT data acquisition device according to claim 1, characterized in that: Any multi-way switch module includes four multi-way switch chips, two of which are used to select the injection electrodes, and the other two multi-way switch chips are used to select the measurement electrodes.

5. A portable EIT data acquisition device according to claim 3, characterized in that: The gain of the digital potentiometer is automatically calibrated as follows: Step 1: Define the current optimization number as i, and initialize i=0; let the gain value of the digital potentiometer under the i-th optimization be =0; Step 2: Set the resistance of the digital potentiometer to ; and after a delay, allowing the EIT data acquisition device to reach a stable state; Step 3: Get the current gain value The amplitude measured by the lower analog-to-digital converter module at the jth time and error , thus obtaining the amplitude and error of the Jth measurement, and using equations (1) and (2) to calculate the amplitude accumulation parameter m under the i-th optimization respectively i and the error accumulation parameter ; (1) (2) Step 4: Use equations (3) and (4) to calculate the average amplitude under the i-th optimization: and the average error : (3) (4) Step 5: If It is within the set valid range, and If the current gain value is less than the set threshold, Output as the optimal gain value, otherwise, execute step 6; Step 6: +1 assigned to After; if >N, it means that no gain value that meets the conditions is found and the process ends. Otherwise, return to step 2 and execute sequentially.

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