Wearable impedance measurement method and device based on alternating voltage excitation

Abstract

The present application relates to a wearable impedance measurement method and device based on alternating voltage excitation, the method comprising: in the case of determining that three electrode pieces are not worn, inputting a micro voltage excitation signal generated by a micro voltage excitation module to the in-phase input end of a preamplifier through a switching circuit, and determining the amplification multiple of the preamplifier based on the input end reference resistance of the preamplifier and the first output frequency component of the preamplifier; in the case of determining that the three electrode pieces are worn, inputting the micro voltage excitation signal to different input ends of the preamplifier through the switching circuit; and determining the wearable impedance of each electrode piece based on the amplification multiple of the preamplifier, the second output frequency component of the preamplifier, and the series-parallel connection relationship among the three electrode pieces. Based on this, the requirements for the limited value of the patient's leakage current can be met, and accurate impedance measurement among the three electrode pieces can be realized at low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of computer, in particular to a wearing impedance measurement method and device based on alternating voltage excitation. BACKGROUND

[0002] EEG signal has low frequency, small signal amplitude and large common-mode interference, and the size of the wearing impedance of the sensor electrode seriously affects the signal quality. Therefore, before the EEG signal acquisition program starts, it is necessary to ensure that the wearing impedance of each electrode is good, or in other words, to control it below a smaller limit; on the other hand, during the EEG signal acquisition process, due to the long wearing or shaking of the electrode, the wearing impedance may become larger, or even the electrode may fall off, resulting in poor signal quality and affecting the accuracy of the collected signal. Therefore, during the EEG signal acquisition process, it is necessary to monitor whether the wearing impedance of the electrode is good in real time.

[0003] In the prior art, the wearing impedance between two electrodes is usually measured by a direct current signal. However, due to the large polarization voltage of different EEG electrodes, especially the ECG electrode with conductive gel, using a direct current signal for testing will result in a large measurement error; on the other hand, the safety regulations 9706.1-2020 of medical electrical equipment limit the patient leakage current to a value, especially the DC patient leakage current as low as 10uA, so under the given direct current excitation level, a larger current limiting resistor must be used, but the larger the current limiting resistor, the smaller the voltage value collected by the excited electrode end ADC, and the lower the precision, which will further cause measurement error. At the same time, the hardware design of the electrode input end analog switch switching circuit is complex, which increases the additional cost.

[0004] Therefore, how to meet the patient leakage current limit value requirement and accurately measure the impedance between EEG electrodes with three electrode pads at low cost is a current research direction. SUMMARY

[0005] The present application provides a wearing impedance measurement method and device based on alternating voltage excitation, to solve the problem that the prior art cannot meet the patient leakage current limit value requirement and cannot accurately measure the impedance between EEG electrodes with three electrode pads at low cost, and to realize both meeting the patient leakage current limit value requirement and accurately measuring the impedance between EEG electrodes with three electrode pads at low cost.

[0006] The application discloses a wearable impedance measurement method based on alternating voltage excitation, which is applied to a wearable impedance measurement device, wherein a micro voltage excitation module, a current limiting resistor, an amplification factor measurement module, a switching circuit, three electrode pads, a preamplifier and a wearable impedance measurement module are arranged in the wearable impedance measurement device; the three electrode pads are connected with a non-inverting input end, an inverting input end of the preamplifier and a driving circuit respectively; the method comprises the following steps: determining whether the three electrode pads are worn; in the case that it is determined that the three electrode pads are not worn, inputting a micro voltage excitation signal generated by the micro voltage excitation module to the non-inverting input end of the preamplifier through the switching circuit, and determining an amplification factor of the preamplifier based on an input end reference resistor of the preamplifier and a first output frequency component of the preamplifier provided by the wearable impedance measurement module; or in the case that it is determined that the three electrode pads are worn, inputting the micro voltage excitation signal to different input ends of the preamplifier through the switching circuit to change a series-parallel connection relationship of the three electrode pads; and determining a wearable impedance corresponding to each electrode pad based on the amplification factor of the preamplifier, a second output frequency component of the preamplifier and the series-parallel connection relationship of the three electrode pads.

[0007] In one of the embodiments, the step of determining the wearable impedance corresponding to each electrode pad based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship of the three electrode pads comprises the following steps: determining three first impedance equations between two input ends of the preamplifier based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship of the three electrode pads, wherein the three first impedance equations are a set of three first impedance equations of star models corresponding to the three electrode pads; and determining the wearable impedance corresponding to each electrode pad in the three electrode pads based on the three first impedance equations.

[0008] In one of the embodiments, the step of determining the three first impedance equations between the two input ends of the preamplifier based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship of the three electrode pads comprises the following steps: determining three second impedance equation groups between the two input ends of the preamplifier based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship of the three electrode pads, wherein each second impedance equation group is a set of three second impedance equations of triangular models corresponding to the three electrode pads; and determining the three first impedance equations between the two input ends of the preamplifier based on the three second impedance equation groups and a conversion relationship between the triangular models corresponding to the three electrode pads and the star models.

[0009] In one of the embodiments, the inputting of the micro-voltage excitation signal to different input terminals of the preamplifier to change the series-parallel relationship of the three electrode pads comprises: inputting the micro-voltage excitation signal generated by the micro-voltage excitation module to the non-inverting input terminal or the inverting input terminal of the preamplifier through one electrode pad, and grounding at least one of the other electrode pads not excited by the micro-voltage excitation signal.

[0010] In one of the embodiments, the three electrode pads are a frontal electrode pad, an ear lobe electrode pad and a temporal electrode pad; in the case where the non-inverting input terminal of the preamplifier is connected to the frontal electrode pad and the inverting input terminal of the preamplifier is connected to the ear lobe electrode pad, the inputting of the micro-voltage excitation signal generated by the micro-voltage excitation module to the non-inverting input terminal or the inverting input terminal of the preamplifier, and grounding at least one of the other electrode pads not excited by the micro-voltage excitation signal comprises: inputting the micro-voltage excitation signal to the non-inverting input terminal of the preamplifier through the frontal electrode pad, and grounding the ear lobe electrode pad; or inputting the micro-voltage excitation signal to the non-inverting input terminal of the preamplifier through the frontal electrode pad, and grounding the ear lobe electrode pad and the temporal electrode pad; or inputting the micro-voltage excitation signal to the inverting input terminal of the preamplifier through the ear lobe electrode pad, and grounding the frontal electrode pad and the temporal electrode pad.

[0011] In one of the embodiments, the determination of the amplification factor of the preamplifier based on the input terminal reference resistance of the preamplifier provided by the wearing impedance measurement module and the first output frequency component of the preamplifier comprises:

[0012] The amplification factor of the preamplifier is determined based on the first output frequency component of the preamplifier, the input terminal reference resistance of the preamplifier, the current limiting resistance and the frequency component of the micro-voltage excitation signal; wherein the expression of the amplification factor of the preamplifier is: wherein, is the first output frequency component of the preamplifier, is the frequency component of the micro-voltage excitation signal, is the resistance value of the current limiting resistance, is the input terminal reference resistance of the preamplifier.

[0013] In one of the embodiments, in the case where the micro-voltage excitation signal is inputted to the non-inverting input terminal of the preamplifier through the frontal electrode pad and the ear lobe electrode pad is grounded, the expression of the second impedance equation between the two input terminals of the preamplifier is: wherein, The second output frequency component of the preamplifier in this case; respectively represent the resistance between the auricle electrode and the temporal electrode, the resistance between the frontal electrode and the temporal electrode, and the resistance between the frontal electrode and the auricle electrode in the triangular model. In the case of inputting the micro-voltage excitation signal through the frontal electrode to the non-inverting input terminal of the preamplifier and grounding the auricle electrode and the temporal electrode, the expression of the second impedance equation between the two input terminals of the preamplifier is: wherein, The second output frequency component of the preamplifier in this case; in the case of inputting the micro-voltage excitation signal through the auricle electrode to the inverting input terminal of the preamplifier and grounding the frontal electrode and the temporal electrode, the expression of the second impedance equation between the two input terminals of the preamplifier is: wherein, The second output frequency component of the preamplifier in this case.

[0014] In one of the embodiments, after determining the wearing impedance corresponding to each of the three electrode pieces, the method further comprises: in the case that the wearing impedance corresponding to any one of the three electrode pieces is greater than a preset target threshold, re-measuring the wearing impedance in response to the operation of the user; or, in the case that the wearing impedance corresponding to each of the three electrode pieces is less than or equal to the preset target threshold, re-measuring the wearing impedance after a preset time interval.

[0015] In one of the embodiments, the micro-voltage excitation signal is an alternating current signal with a frequency component of 110 Hz and a voltage peak-to-peak value of 20 mVpp.

[0016] The application discloses a wearable impedance measurement device based on alternating voltage excitation, which comprises a micro voltage excitation module, an amplification factor measurement module, a switching circuit, three electrode pads, a preamplifier and a wearable impedance measurement module; the micro voltage excitation module is used for generating a micro excitation voltage; the preamplifier is used for amplifying brain electrical signals measured by the three electrode pads and the micro voltage excitation signal generated by the micro voltage excitation module, and is used for providing data of the wearable impedance measurement for the wearable impedance measurement module; the three electrode pads comprise a frontal electrode pad, an ear electrode pad and a temporal electrode pad; the three electrode pads are connected with a non-inverting input end, an inverting input end of the preamplifier and a driving circuit respectively; the amplification factor measurement module determines an amplification factor of the preamplifier based on a reference resistance of an input end of the preamplifier and a first output frequency component of the preamplifier; the switching circuit is used for changing a connection relationship between the micro voltage excitation module and the non-inverting input end and the inverting input end of the preamplifier so as to change a series-parallel connection relationship of the three electrode pads; and the wearable impedance measurement module is used for determining respective wearable impedances of the three electrode pads based on the amplification factor of the preamplifier, a second output frequency component of the preamplifier and the series-parallel connection relationship of the three electrode pads.

[0017] The application discloses a computer device comprising a memory and a processor, wherein the memory stores computer readable instructions, and the computer readable instructions are executed by the processor to make the processor execute the steps of the wearable impedance measurement method based on alternating voltage excitation.

[0018] The application discloses a storage medium storing computer readable instructions, and the computer readable instructions are executed by one or more processors to make the one or more processors execute the steps of the wearable impedance measurement method based on alternating voltage excitation.

[0019] The wearable impedance measurement method and device based on alternating voltage excitation can generate an alternating signal with a small frequency component as an excitation signal by using the micro voltage excitation module, and the alternating signal is combined with the preamplifier, so that the alternating signal with the small frequency component is used as the excitation signal, even if a large current limiting resistor is used, the measurement of the resistance between the electrode pads is not affected, the leakage current is small, and the wearable impedance corresponding to each electrode pad is only determined by the size of the output frequency component of the preamplifier, so that the influence of the polarization voltage caused by different EEG electrodes on the measurement result is avoided, and the measured impedance value is more accurate. In addition, the preamplifier required in the EEG signal acquisition circuit is reused, and the hardware implementation cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1Fig. 1 is a schematic diagram of a wearable impedance measurement device based on AC voltage excitation according to an embodiment;

[0021] Figure 2 Fig. 2 is a schematic diagram of a flow of a method of wearable impedance measurement based on AC voltage excitation according to an embodiment;

[0022] Figure 3 Fig. 3 is a schematic diagram of another flow of a method of wearable impedance measurement based on AC voltage excitation according to an embodiment;

[0023] Figure 4 Fig. 4 is a schematic diagram of a triangle model and a star model corresponding to three electrode pads according to an embodiment. DETAILED DESCRIPTION

[0024] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0025] It should be noted that, unless otherwise defined, technical terms or scientific terms used in the present application should be understood as their common meanings to those skilled in the art to which the present application pertains. The terms "first", "second" and similar terms used in the present application do not indicate any order, number or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar terms mean that the components or objects before the terms encompass the components or objects listed after the terms and their equivalents, and do not exclude other components or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right" and the like are only used to indicate relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships can also be changed accordingly.

[0026] In the prior art, analog switches are used to switch the electrode input between the analog front end and the MCU. During EEG acquisition, the electrode input is to the analog front end; while during EEG electrode wearing impedance measurement, the electrode input is to the ADC or IO of the MCU. When measuring impedance, a direct current signal is excited to a certain electrode input through a current-limiting resistor, and then the states of the other two electrodes are set to high resistance and low, low and high resistance, and low respectively, and the voltage values of the excited electrode end in the three states are collected respectively, three three-element linear equations are obtained, and the wearing impedance of each electrode is calculated by solving the equation set. However, due to the existence of a large polarization voltage of different EEG electrodes, especially ECG electrodes with conductive gel, using a direct current signal for testing will cause a large measurement error; on the other hand, the safety regulations 9706.1-2020 of medical electrical equipment have a limited value requirement for patient leakage current, especially the DC patient leakage current is as low as 10uA, so under the given direct current excitation level, a larger current-limiting resistor must be used, but the larger the current-limiting resistor, the smaller the voltage value collected by the ADC at the excited electrode end, and the lower the precision, which will further cause measurement error. At the same time, the hardware design of the electrode input analog switch switching circuit is complex, which increases the additional cost. Therefore, in order to meet the limited value requirement of patient leakage current and accurately measure the impedance between EEG electrodes with three electrode pads at low cost, the present application provides an alternating current voltage excitation based wearing impedance measurement method and device.

[0027] The application will be described below in conjunction with Figures 1-4 The application provides an alternating current voltage excitation based wearing impedance measurement method and device.

[0028] Figure 1 The application provides an alternating current voltage excitation based wearing impedance measurement device. As shown in Figure 1As shown, the device comprises: the micro-voltage excitation module 110, the current-limiting resistor 120, the amplification factor measurement module 130, the switching circuit 140, the electrode sheet 150 comprising three electrode sheets, the preamplifier 160, the wearable impedance measurement module 170, and the analog-to-digital conversion module 180. Among them, the micro-voltage excitation module 110 is used to generate a micro excitation voltage; the preamplifier 160 is used to amplify the brain electrical signal measured by the electrode sheet 150 and the micro-voltage excitation signal generated by the micro-voltage excitation module, and to provide the wearable impedance measurement module 170 with the data of the wearable impedance measurement; the electrode sheet 150 comprises a frontal electrode sheet 1501, an ear lobe electrode sheet 1502, and a temporal electrode sheet 1503; the electrode sheet 150 is connected with the non-inverting input terminal, the inverting input terminal of the preamplifier, and the driving circuit, respectively; the amplification factor measurement module 130 is used to determine the amplification factor of the preamplifier 160 based on the input terminal reference resistor of the preamplifier provided by the wearable impedance measurement module and the first output frequency component of the preamplifier; the switching circuit 140 is used to change the connection relationship between the micro-voltage excitation module 110 and the non-inverting input terminal and the inverting input terminal of the preamplifier 160 to change the series-parallel relationship of the three electrode sheets; the wearable impedance measurement module 170 is used to determine the respective wearable impedance of the three electrode sheets 150 based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier, and the series-parallel relationship between the three electrode sheets.

[0029] As shown in the device, the device can further comprise a confirmation module 190 for confirming whether the electrode sheet is worn or not, which is used to make the amplification factor measurement module 130 and the wearable impedance measurement module 170 in the working state in the case of determining that the three electrode sheets are not worn; and is used to make the wearable impedance measurement module 170 in the working state in the case of determining that the three electrode sheets are worn. Figure 1

[0030] Among them, the micro-voltage excitation module 110 can comprise an MCU-PWM port and a direct-current filtering voltage dividing circuit, for example, wherein the MCU-PWM port is used to generate a 110hz, 3V single positive square wave, and the direct-current filtering voltage dividing circuit is used to filter the direct current component in the 110hz, 3V single positive square wave to obtain a square wave with a frequency component of 110hz and a voltage peak-to-peak value of 20mVpp. The square wave with a frequency component of 110hz and a voltage peak-to-peak value of 20mVpp is input to the current-limiting resistor and the switching circuit as a micro-voltage excitation signal, and is input to the preamplifier through one of the three electrode sheets. Specifically, the switching circuit can determine the excitation relationship between the micro-voltage excitation signal generated by the micro-voltage excitation module and the input terminal of the preamplifier based on the configuration of the MCU-IO.

[0031] ​The current-limiting resistor is used to limit the current flowing to the three electrode pads. Specifically, in the present application, the current-limiting resistor is an M-ohm resistor. For example, it can be 1 M-ohm.

[0032] It can be understood that by using a micro-voltage excitation module to generate an alternating current signal with a small frequency component as an excitation signal, and combining it with a preamplifier, an alternating current signal with a small frequency component can be used as an excitation signal. Even if a larger current-limiting resistor is used, it will not affect the measurement of the resistance between the subsequent electrode pads. While ensuring that the leakage current is small, the measured impedance of each electrode pad only depends on the size of the preamplifier output frequency component, avoiding the influence of the polarization voltage caused by different EEG electrodes on the measurement results, making the measured impedance value more accurate. In addition, since the preamplifier required in the EEG signal acquisition circuit is reused, the hardware implementation cost is low. At the same time, the 110hz alternating current excitation signal is used during measurement, avoiding the EEG signal frequency range, and having no effect on the normal EEG signal. At the same time, it can be understood that since the present application uses a micro-voltage excitation, the signal is amplified through the preamplifier during acquisition, so the excitation signal source is small, the leakage current during measurement is as low as nA level, and the impedance is only considered when calculating the resistance, ignoring the reactance.

[0033] Figure 2 For an embodiment of the present application, a schematic flow chart of the alternating current voltage excitation-based wearable impedance measurement method is provided. The alternating current voltage excitation-based wearable impedance measurement method can be performed by an alternating current voltage excitation-based wearable impedance measurement device. Specifically, as shown in Figure 2 The alternating current voltage excitation-based wearable impedance measurement method provided by the present application can include the following steps:

[0034] Step 210, determining whether the three electrode pads are worn.

[0035] Specifically, whether the three electrode pads are worn can be determined based on the resistance between the three electrode pads two by two.

[0036] It can be understood that when the three electrode pads are not worn, the resistance between the two electrode pads is infinite, and when the three electrode pads are worn, the resistance between the two electrode pads is significantly smaller than the resistance between the two electrode pads when the three electrode pads are not worn. Therefore, if the resistance between the three electrode pads two by two is less than or equal to a preset threshold, it is determined that the three electrode pads are worn; if the resistance between the three electrode pads two by two is greater than the preset threshold, it is determined that the three electrode pads are not worn.

[0037] It can also be understood that by distinguishing whether the three electrode pieces are worn, the micro-voltage excitation signal generated by the micro-voltage excitation module can be input to different input terminals of the preamplifier, and different input terminals can use different grounding methods to prepare for subsequent measurement of the impedance corresponding to the three electrode pieces. Specifically, when the three electrode pieces are not worn, step 220 can be performed to determine the amplification factor of the preamplifier; when the three electrode pieces are worn, step 230 can be performed to determine the impedance corresponding to the three electrode pieces.

[0038] In step 220, when it is determined that the three electrode pieces are not worn, the micro-voltage excitation signal generated by the micro-voltage excitation module is input to the in-phase input terminal of the preamplifier through the switching circuit, and the amplification factor measurement module determines the amplification factor of the preamplifier based on the input terminal reference resistance of the preamplifier provided by the wearing impedance measurement module and the first output frequency component of the preamplifier.

[0039] It can be understood that when it is determined that the three electrode pieces are not worn, the wearing impedance measurement module and the amplification factor measurement module are in working state.

[0040] It can also be understood that since the resistance corresponding to each two electrode pieces of the three electrode pieces is infinite when the three electrode pieces are not worn, that is, the input resistance of the corresponding preamplifier is an uncertain value, therefore, in order to facilitate the determination of the amplification factor of the preamplifier, the amplification factor measurement module can first calculate the amplification factor of the corresponding preamplifier based on the input terminal reference resistance of the preamplifier provided by the wearing impedance measurement module as the corresponding input resistance of the preamplifier. In the subsequent actual wearing impedance measurement process, the wearing impedance measurement module determines the actual impedance between the two input terminals of the preamplifier according to the amplification factor of the amplifier determined by the amplification factor measurement module, and further determines the wearing impedance corresponding to each electrode piece.

[0041] As mentioned earlier, the amplification factor of the preamplifier can be determined based on the input terminal reference resistance of the preamplifier provided by the wearing impedance measurement module and the first output frequency component of the preamplifier. Further, the wearing impedance corresponding to each electrode piece is determined based on the amplification factor of the preamplifier, that is, the measured wearing impedance corresponding to each electrode piece only depends on the size of the output frequency component of the preamplifier, avoiding the influence of the polarization voltage caused by different EEG electrodes on the measurement results, so that the measured impedance value is more accurate.

[0042] The switching circuit can determine the excitation relationship between the micro-voltage excitation signal generated by the micro-voltage excitation module and the input terminal of the preamplifier based on the configuration of the MCU-IO.

[0043] Step 230, in the case of determining that the three electrode pieces are worn, inputting a micro-voltage excitation signal into different input terminals of the preamplifier through the switching circuit to change the series-parallel relationship of the three electrode pieces; the wearing impedance measurement module determines the wearing impedance corresponding to each electrode piece based on the amplification multiple of the preamplifier, the second output frequency component of the preamplifier and the series-parallel relationship between the three electrode pieces.

[0044] It can be understood that in the case of determining that the three electrode pieces are worn, the wearing impedance measurement module can be in a working state.

[0045] Among them, the wearing impedance corresponding to each electrode piece is the wearing impedance corresponding to each electrode piece in the star model corresponding to the three electrode pieces.

[0046] Among them, the star model is also called Y star model, which can be understood as the resistance corresponding to the three electrode pieces respectively. Corresponding to the triangle model, the triangle model is the resistance between the three electrode pieces. It can be understood that in general, the resistance between the three electrode pieces corresponding to the triangle model can be measured, but since it reflects the resistance between two electrode pieces, it cannot directly reflect which electrode piece is not worn well. Therefore, in the present application, by calculating the wearing impedance of each electrode piece corresponding to the star model, it can be directly reflected which electrode piece is not worn well. The star model and the triangle model are described in detail in Figure 4 .

[0047] It can also be understood that since the three electrode pieces are connected to the non-inverting input terminal or the inverting input terminal of the preamplifier and the driving circuit respectively, inputting the micro-voltage excitation signal into different input terminals of the preamplifier can change the series-parallel relationship of the three electrode pieces, and the series-parallel relationship of the three electrode pieces can reflect the size of the resistance of the input terminal of the preamplifier.

[0048] As described above, in the present embodiment, the wearing impedance corresponding to each electrode piece is determined based on the amplification multiple of the preamplifier, the second output frequency component of the preamplifier and the series-parallel relationship between the three electrode pieces, and the amplification multiple of the preamplifier is determined based on the input terminal reference resistance of the preamplifier provided by the wearing impedance measurement module and the first output frequency component of the preamplifier. That is, the measured wearing impedance corresponding to each electrode piece only depends on the size of the output frequency component of the preamplifier, and does not use the voltage corresponding to the EEG electrode, so as to avoid the influence of the polarization voltage of different EEG electrodes on the measurement result, so that the measured impedance value is more accurate.

[0049] The application provides a wearable impedance measurement method based on alternating voltage excitation. A small alternating signal with a small frequency component is generated by a small voltage excitation module as an excitation signal, and is combined with a preamplifier. The small alternating signal with a small frequency component is used as an excitation signal, and even if a large current-limiting resistor is used, the measurement of the resistance between subsequent electrode pads is not affected. The leakage current is small, and the measured impedance of each electrode pad only depends on the frequency component of the preamplifier output, thereby avoiding the influence of polarization voltage caused by different EEG electrodes on the measurement result, and the measured impedance value is more accurate. In addition, the preamplifier required in the EEG signal acquisition circuit is reused, and the hardware implementation cost is low. In addition, by calculating the wearable impedance of each electrode pad corresponding to the star model, it can be directly reflected which electrode pad is not worn well.

[0050] In one embodiment, the input end reference resistance of the preamplifier provided by the wearable impedance measurement module and the first output frequency component of the preamplifier determine the amplification factor of the preamplifier, including:

[0051] The amplification factor of the preamplifier is determined based on the first output frequency component of the preamplifier, the input end reference resistance of the preamplifier, the current-limiting resistor, and the frequency component of the small voltage excitation signal.

[0052] Specifically, the expression of the amplification factor of the preamplifier is: , wherein, is the first output frequency component of the preamplifier, is the frequency component of the small voltage excitation signal, is the resistance value of the current-limiting resistor, is the input end reference resistance corresponding to the preamplifier.

[0053] For example, the input end reference resistance corresponding to the preamplifier can be 2k ohms.

[0054] As can be known from the foregoing description, the first output frequency component of the preamplifier is the small voltage excitation signal after removing the frequency component corresponding to the current-limiting resistor.

[0055] In one embodiment, the small voltage excitation signal is input to different input ends of the preamplifier to change the series-parallel connection relationship of the three electrode pads, including:

[0056] The small voltage excitation signal generated by the small voltage excitation module is input to the non-inverting input end or the inverting input end of the preamplifier through one electrode pad, and at least one of the other electrode pads not excited by the small voltage excitation signal is grounded.

[0057] In one of the embodiments, the three electrode pads are a frontal electrode pad, an ear protrusion electrode pad and a temporal electrode pad; in the case that the non-inverting input terminal of the preamplifier is connected with the frontal electrode pad and the inverting input terminal of the preamplifier is connected with the ear protrusion electrode pad, correspondingly, the micro-voltage excitation signal generated by the micro-voltage excitation module is input to the non-inverting input terminal or the inverting input terminal of the preamplifier through one electrode pad, and at least one of the other electrode pads not excited by the micro-voltage excitation signal is grounded, including:

[0058] the micro-voltage excitation signal is input to the non-inverting input terminal of the preamplifier through the frontal electrode pad, and the ear protrusion electrode pad is grounded, or

[0059] the micro-voltage excitation signal is input to the non-inverting input terminal of the preamplifier through the frontal electrode pad, and the ear protrusion electrode pad and the temporal electrode pad are grounded, or

[0060] the micro-voltage excitation signal is input to the inverting input terminal of the preamplifier through the ear protrusion electrode pad, and the frontal electrode pad and the temporal electrode pad are grounded.

[0061] It can be understood that in this embodiment, only one possible connection relationship of three electrode pads with the preamplifier is provided, and in actual application, a connection relationship different from this embodiment can be adopted to achieve, and correspondingly, the input relationship of the three electrode pads with the preamplifier and the input resistance between the two input terminals of the preamplifier can change.

[0062] In one of the embodiments, as shown in Figure 3 based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship among the three electrode pads, the corresponding wearing impedance of each electrode pad is determined, including:

[0063] Step 310, based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship among the three electrode pads, three first impedance equations between the two input terminals of the preamplifier are determined, and the three first impedance equations are a set of three first impedance equations of the star model corresponding to the three electrode pads.

[0064] Specifically, this step 310 can be divided into step 3101 and step 3102.

[0065] Step 3101, based on the amplification of the preamplifier, the second output frequency component of the preamplifier and the series-parallel relationship between the three electrode pieces, determine the three second impedance equation groups between the two input terminals of the preamplifier, each second impedance equation group is a three second impedance of the three electrode pieces corresponding to the triangular model.

[0066] In one embodiment, in combination Figure 4 The three electrode pieces corresponding to the triangular model and the star model are given, and in the case of inputting the micro-voltage excitation signal through the frontal electrode piece to the non-inverting input terminal of the preamplifier and grounding the ear lobe electrode piece, the expression of the second impedance equation between the two input terminals of the preamplifier is:

[0067] , wherein, is the second output frequency component of the preamplifier in this case; respectively represent the resistance between the ear lobe electrode piece and the temporal electrode piece, the resistance between the frontal electrode piece and the temporal electrode piece, and the resistance between the frontal electrode piece and the ear lobe electrode piece in the triangular model;

[0068] In the case of inputting the micro-voltage excitation signal through the frontal electrode piece to the non-inverting input terminal of the preamplifier and grounding the ear lobe electrode piece and the temporal electrode piece, the expression of the second impedance equation between the two input terminals of the preamplifier is:

[0069] , wherein, is the second output frequency component of the preamplifier in this case;

[0070] In the case of inputting the micro-voltage excitation signal through the ear lobe electrode piece to the inverting input terminal of the preamplifier and grounding the frontal electrode piece and the temporal electrode piece, the expression of the second impedance equation between the two input terminals of the preamplifier is:

[0071] , wherein, is the second output frequency component of the preamplifier in this case.

[0072] It can be understood that in order to facilitate representation, the above three second impedance corresponding equations can be converted according to the conversion formula between conductance and impedance: ; ; The simultaneous solution of the above three second impedance equations can be obtained , , .

[0073] In step 3102, based on the three second impedance equations and the conversion relationship between the triangular model and the star model corresponding to the three electrode pads, three first impedance equations between the two input ends of the preamplifier are determined.

[0074] In combination Figure 4 The conversion relationship between the triangular model and the star model is given as follows:

[0075] , , .

[0076] wherein, Rfront, Rtemp and Rtemp represent the resistances corresponding to the frontal electrode pad, the ear electrode pad and the temporal electrode pad in the star model respectively.

[0077] In combination with the conversion relationship between the triangular model and the star model, the three second impedance equations corresponding to are converted into the three first impedance equations of .

[0078] In step 320, based on the three first impedance equations, the wearing impedance corresponding to each of the three electrode pads is determined.

[0079] It can be understood that, in combination with the above-mentioned corresponding formula, the specific value of can be obtained, that is, the wearing impedance corresponding to each of the three electrode pads is determined.

[0080] In one embodiment, after the wearing impedance corresponding to each of the three electrode pads is determined, the method further comprises:

[0081] In the case where the wearing impedance corresponding to any one of the three electrode pads is greater than a preset target threshold, the measurement of the wearing impedance is re-performed in response to the operation of the user; or,

[0082] In the case where the wearing impedance corresponding to each of the three electrode pads is less than or equal to the preset target threshold, the measurement of the wearing impedance is re-performed after a preset time interval.

[0083] For example, the operation of the user can be the operation of restarting the wearing impedance measurement device.

[0084] ​It can be understood that if the wearing impedance corresponding to any one of the three electrode pieces is greater than the preset target threshold, it indicates that the corresponding electrode piece in the three electrode pieces has a poor connection state, so the user further processes to wear the electrode piece well, and then restarts the measurement of the wearing impedance. In addition, in the case where the wearing impedance corresponding to each of the three electrode pieces is less than or equal to the preset target threshold, it indicates that the three electrode pieces are normally worn, but in order to prevent the electrode pieces from being poorly connected after a period of time, the wearing impedance measurement can be performed again after a preset time interval. The preset time interval may be, for example, 1 minute.

[0085] In one embodiment, the micro-voltage excitation signal is an alternating current signal with a frequency component of 110 Hz and a voltage peak-to-peak value of 20 mVpp.

[0086] It can be understood that the use of a 110 Hz alternating current excitation signal during measurement avoids the EEG signal frequency range and has no effect on normal EEG signals.

[0087] Figure 4 The three electrode pieces provided by the present application correspond to a triangular model and a star model.

[0088] As shown in Figure 4 , the triangular model and the star model corresponding to the three electrode pieces are shown respectively. As shown in Figure 4 , for the triangular model, R1, R2 and R3 respectively represent the resistance between the ear electrode piece and the temporal electrode piece, the resistance between the frontal electrode piece and the temporal electrode piece, and the resistance between the frontal electrode piece and the ear electrode piece in the triangular model. For the star model, R1, R2 and R3 respectively represent the resistance corresponding to the frontal electrode piece, the ear electrode piece and the temporal electrode piece in the star model.

[0089] In one embodiment, a computer device is provided, which comprises a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the following steps of the method for measuring wearing impedance based on alternating voltage excitation: determining whether the three electrode pads are worn; in the case that it is determined that the three electrode pads are not worn, inputting a micro-voltage excitation signal generated by the micro-voltage excitation module to the in-phase input end of the preamplifier through the switching circuit, and determining the amplification factor of the preamplifier based on the input end reference resistance of the preamplifier and the first output frequency component of the preamplifier provided by the wearing impedance measurement module; or in the case that it is determined that the three electrode pads are worn, inputting the micro-voltage excitation signal to different input ends of the preamplifier through the switching circuit to change the series-parallel connection relationship of the three electrode pads; and determining the wearing impedance corresponding to each electrode pad based on the amplification factor and the series-parallel connection relationship between the three electrode pads by the wearing impedance measurement module.

[0090] In another aspect, the present application also provides a computer program product, which comprises a computer program stored on a non-transitory computer readable storage medium, wherein the computer program comprises program instructions, and when the program instructions are executed by a computer, the computer can execute the method for measuring wearing impedance based on alternating voltage excitation provided by the present application, wherein the method for measuring wearing impedance based on alternating voltage excitation comprises: determining whether the three electrode pads are worn; in the case that it is determined that the three electrode pads are not worn, inputting a micro-voltage excitation signal generated by the micro-voltage excitation module to the in-phase input end of the preamplifier through the switching circuit, and determining the amplification factor of the preamplifier based on the input end reference resistance of the preamplifier and the first output frequency component of the preamplifier provided by the wearing impedance measurement module; or in the case that it is determined that the three electrode pads are worn, inputting the micro-voltage excitation signal to different input ends of the preamplifier through the switching circuit to change the series-parallel connection relationship of the three electrode pads; and determining the wearing impedance corresponding to each electrode pad based on the amplification factor and the series-parallel connection relationship between the three electrode pads by the wearing impedance measurement module.

[0091] In another aspect, the application also provides a non-transitory computer readable storage medium having stored thereon a computer program, which, when executed by a processor, implements an AC voltage excitation based wearable impedance measurement method provided by the application, wherein the AC voltage excitation based wearable impedance measurement method comprises: determining whether the three electrode pads are worn; in a case where it is determined that the three electrode pads are not worn, inputting a micro voltage excitation signal generated by the micro voltage excitation module to the non-inverting input terminal of the preamplifier through the switching circuit, and determining the amplification factor of the preamplifier based on the input terminal reference resistor of the preamplifier and the first output frequency component of the preamplifier provided by the wearable impedance measurement module; or in a case where it is determined that the three electrode pads are worn, inputting the micro voltage excitation signal to different input terminals of the preamplifier through the switching circuit to change the series-parallel connection relationship of the three electrode pads; and determining the wearable impedance corresponding to each electrode pad based on the amplification factor and the series-parallel connection relationship between the three electrode pads by the wearable impedance measurement module.

[0092] The system embodiments described above are merely illustrative, wherein the units described as separate components can or can not be physically separate, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0093] From the above description of the embodiments, those skilled in the art can clearly understand that the embodiments can be implemented by means of software plus necessary general hardware platforms, and of course can also be implemented by hardware. Based on such understanding, the above technical solutions, essentially or in terms of contribution to the prior art, can be embodied in the form of a software product. The computer software product can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, etc., and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0094] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, rather than limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application.

Claims

1. A method of wearable impedance measurement based on alternating voltage excitation, characterized in that, The application is applied to a wearable impedance measurement device, which comprises a micro-voltage excitation module, a current-limiting resistor, an amplification factor measurement module, a switching circuit, three electrode pads, a preamplifier and a wearable impedance measurement module; the three electrode pads are connected with the non-inverting input terminal, the inverting input terminal of the preamplifier and the driving circuit respectively; the method comprises: determining whether the three electrode pads are worn; in the case that it is determined that the three electrode pads are not worn, inputting a micro-voltage excitation signal generated by the micro-voltage excitation module into the non-inverting input terminal of the preamplifier through the switching circuit, and determining the amplification factor of the preamplifier based on the input terminal reference resistor of the preamplifier provided by the wearable impedance measurement module and the first output frequency component of the preamplifier; the micro-voltage excitation signal is a signal with a preset frequency component and a preset voltage peak-to-peak value; in the case that it is determined that the three electrode pads are worn, inputting the micro-voltage excitation signal into different input terminals of the preamplifier through the switching circuit to change the series-parallel connection relationship of the three electrode pads; the wearable impedance measurement module determines the wearable impedance corresponding to each electrode pad based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship between the three electrode pads.

2. The AC voltage excitation based wearable impedance measurement method of claim 1, wherein, The determination of the wearable impedance corresponding to each electrode pad based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship between the three electrode pads comprises: determining three first impedance equations between the two input terminals of the preamplifier based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship between the three electrode pads, the three first impedance equations being a set of equations of three first impedances of star models corresponding to the three electrode pads; determining the wearable impedance corresponding to each electrode pad in the three electrode pads based on the three first impedance equations.

3. The AC voltage excitation based wearable impedance measurement method of claim 2, wherein, The determination of the three first impedance equations between the two input terminals of the preamplifier based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship between the three electrode pads comprises: determining three second impedance equation groups between the two input terminals of the preamplifier based on the amplification factor of the preamplifier, the second output frequency component of the preamplifier and the series-parallel connection relationship between the three electrode pads, each second impedance equation group being a set of three second impedances of triangular models corresponding to the three electrode pads; determining the three first impedance equations between the two input terminals of the preamplifier based on the three second impedance equation groups and the conversion relationship between the triangular models and the star models corresponding to the three electrode pads.

4. The AC voltage excitation based wearable impedance measurement method of claim 3, wherein, The inputting of the micro-voltage excitation signal into different input terminals of the preamplifier to change the series-parallel connection relationship of the three electrode pads comprises: The micro-voltage excitation signal generated by the micro-voltage excitation module is input to the non-inverting input terminal or the inverting input terminal of the preamplifier through one electrode piece, and at least one of the other electrode pieces not excited by the micro-voltage excitation signal is grounded.

5. The AC voltage excitation based wearable impedance measurement method of claim 4, wherein, The three electrode pieces are a frontal electrode piece, an ear lobe electrode piece, and a temporal electrode piece; in the case that the non-inverting input terminal of the preamplifier is connected to the frontal electrode piece and the inverting input terminal of the preamplifier is connected to the ear lobe electrode piece, the micro-voltage excitation signal generated by the micro-voltage excitation module is input to the non-inverting input terminal or the inverting input terminal of the preamplifier through one electrode piece, and at least one of the other electrode pieces not excited by the micro-voltage excitation signal is grounded, which comprises: inputting the micro-voltage excitation signal to the non-inverting input terminal of the preamplifier through the frontal electrode piece and grounding the ear lobe electrode piece, or inputting the micro-voltage excitation signal to the non-inverting input terminal of the preamplifier through the frontal electrode piece and grounding the ear lobe electrode piece and the temporal electrode piece, or inputting the micro-voltage excitation signal to the inverting input terminal of the preamplifier through the ear lobe electrode piece and grounding the frontal electrode piece and the temporal electrode piece.

6. The AC voltage excitation based wearable impedance measurement method of claim 5, wherein, The input terminal reference resistance of the preamplifier provided by the wearing impedance measurement module and the first output frequency component of the preamplifier determine the amplification factor of the preamplifier, which comprises: The amplification multiple of the pre-amplifier is determined based on the first output frequency component of the pre-amplifier, an input terminal reference resistance of the pre-amplifier, a current limiting resistance and a frequency component of the micro-voltage excitation signal; wherein the expression of the amplification multiple of the pre-amplifier is: wherein, is the first output frequency component of the pre-amplifier, is the frequency component of the micro-voltage excitation signal, is the resistance value of the current limiting resistance, is the input terminal reference resistance of the pre-amplifier.

7. The AC voltage excitation based wearable impedance measurement method of claim 6, wherein, in the case that the micro-voltage excitation signal is input to the non-inverting input terminal of the preamplifier through the frontal electrode piece and the ear lobe electrode piece is grounded, the expression of the second impedance equation between the two input terminals of the preamplifier is: wherein is a second output frequency component of the preamplifier in this case; respectively represent the resistance between the mastoid electrode and the temporal electrode, the resistance between the frontal electrode and the temporal electrode, and the resistance between the frontal electrode and the mastoid electrode in the triangular model. in the case that the micro-voltage excitation signal is input to the non-inverting input terminal of the preamplifier through the frontal electrode piece and the ear lobe electrode piece and the temporal electrode piece are grounded, the expression of the second impedance equation between the two input terminals of the preamplifier is: wherein is a second output frequency component of the preamplifier in this case; in the case that the micro-voltage excitation signal is input to the inverting input terminal of the preamplifier through the ear lobe electrode piece and the frontal electrode piece and the temporal electrode piece are grounded, the expression of the second impedance equation between the two input terminals of the preamplifier is: wherein is the second output frequency component of the preamplifier in this case.

8. The AC voltage excitation-based wearable impedance measurement method of claim 1, wherein, after determining the wearing impedance corresponding to each of the three electrode pieces, the method further comprises: in the case that the wearing impedance corresponding to any one of the three electrode pieces is greater than a preset target threshold, re-measuring the wearing impedance in response to the user's operation; or, in the case that the wearing impedance corresponding to each of the three electrode pieces is less than or equal to the preset target threshold, re-measuring the wearing impedance after a preset time interval.

9. The AC voltage excitation-based wearable impedance measurement method of claim 1, wherein, The micro-voltage excitation signal is an alternating current signal with a frequency component of 110 Hz and a voltage peak-to-peak value of 20 mVpp.

10. A wearable impedance measuring device based on alternating voltage excitation, characterized in that, The device comprises a micro-voltage excitation module, an amplification factor measurement module, a switching circuit, three electrode pieces, a preamplifier, and a wearing impedance measurement module. The micro-voltage excitation module is configured to generate a micro-voltage excitation signal, which is a signal with a preset frequency component and a preset voltage peak-to-peak value. The pre-amplifier is configured to amplify the EEG signals measured by the three electrode pads and the micro-voltage excitation signal generated by the micro-voltage excitation module, and to provide data for the wearable impedance measurement module to measure the wearable impedance. The three electrode pads include a frontal electrode pad, an ear electrode pad, and a temporal electrode pad, and are respectively connected to the non-inverting input terminal, the inverting input terminal, and the driving circuit of the pre-amplifier. The amplification factor measurement module is configured to determine the amplification factor of the pre-amplifier based on the input terminal reference resistance of the pre-amplifier and the first output frequency component of the pre-amplifier. The switching circuit is configured to change the connection relationship between the micro-voltage excitation module and the non-inverting input terminal and the inverting input terminal of the pre-amplifier to change the series-parallel connection relationship of the three electrode pads. The wearable impedance measurement module is configured to determine the respective wearable impedance of the three electrode pads based on the amplification factor of the pre-amplifier, the second output frequency component of the pre-amplifier, and the series-parallel connection relationship of the three electrode pads.

11. A computer device comprising a memory and a processor, the memory having stored therein computer readable instructions, characterized in that, The computer readable instructions, when executed by the processor, cause the processor to perform the steps of the method for measuring the wearable impedance based on the AC voltage excitation according to any one of claims 1 to 9.

12. A storage medium storing computer readable instructions, wherein, The computer readable instructions, when executed by the one or more processors, cause the one or more processors to perform the steps of the method for measuring the wearable impedance based on the AC voltage excitation according to any one of claims 1 to 9.

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