阅读说明：本技术 一种用于经颅电刺激和迷走神经刺激的脑电采集系统 (Electroencephalogram acquisition system for transcranial electrical stimulation and vagus nerve stimulation ) 是由 秦伟 杨群 郑斌 于 2019-08-22 设计创作，主要内容包括：本发明公开了用于经颅电刺激和迷走神经刺激的脑电采集系统,由脑电帽、转接电路、预处理电路、模数转换芯片ADS1299和微控制单元MCU组成,预处理电路包括低通滤波电路、高通滤波电路和工频陷波电路,脑电帽获得的脑电信号经过滤波放大预处理后,进入ADS1299完成信号的模数转换,得到高分辨率的数字信号,然后数字信号通过ADS1299的SPI接口传送到微控制单元MCU,微控制单元MCU将数据通过USB传送至上位机。本发明的脑电采集系统有较强的抗干扰能力,能够保证纯净的脑电信号,采用模数转换芯片ADS1299,能高输入阻抗、高共模抑制比、降低低功耗、缩小设备的体积。(The invention discloses an electroencephalogram acquisition system for transcranial electrical stimulation and vagus nerve stimulation, which comprises an electroencephalogram cap, a switching circuit, a preprocessing circuit, an analog-to-digital conversion chip ADS1299 and a micro control unit MCU, wherein the preprocessing circuit comprises a low-pass filter circuit, a high-pass filter circuit and a power frequency trap circuit, electroencephalogram signals obtained by the electroencephalogram cap enter the ADS1299 to complete analog-to-digital conversion of the signals after being subjected to filtering, amplifying and preprocessing, so as to obtain high-resolution digital signals, then the digital signals are transmitted to the micro control unit MCU through an SPI interface of the ADS1299, and the micro control unit MCU transmits data to an upper computer through a USB. The electroencephalogram acquisition system has strong anti-interference capability, can ensure pure electroencephalogram signals, and can have high input impedance, high common-mode rejection ratio, low power consumption and small equipment volume by adopting the analog-to-digital conversion chip ADS 1299.)

1. An electroencephalogram acquisition system for transcranial electrical stimulation and vagus nerve stimulation, characterized by: the electroencephalogram signal processing device comprises an electroencephalogram cap, a switching circuit, a preprocessing circuit, an analog-to-digital conversion chip ADS1299 and a micro control unit MCU, wherein the preprocessing circuit comprises a low-pass filter circuit, a high-pass filter circuit and a power frequency trap circuit, the electroencephalogram signal obtained by the electroencephalogram cap enters the ADS1299 to complete analog-to-digital conversion of the signal after being subjected to filtering, amplifying and preprocessing, a digital signal with high resolution is obtained, then the digital signal is transmitted to the micro control unit MCU through an SPI interface of the ADS1299, and the micro control unit MCU transmits data to an upper computer through a USB.

2. The brain electrical acquisition system of claim 1, wherein: the Brain cap is compatible with Brain Products, and the Brain cap connector adopts a Pak-50-P50E series rectangular connector produced by 3M company.

3. The brain electrical acquisition system of claim 1, wherein: the switching circuit is arranged between the electroencephalogram cap and the preprocessing circuit and used for connecting the electroencephalogram cap and the preprocessing circuit, and each switching circuit is provided with a 5K resistor.

4. The brain electrical acquisition system of claim 1, wherein: the high-pass filter circuit is a second-order active high-pass filter with an amplification function and consists of a passive device resistor, a capacitor and an active device operational amplifier TLC 2252.

5. The brain electrical acquisition system of claim 1, wherein: the low-pass filter circuit is a second-order active low-pass filter and is used for filtering high-frequency interference in the collected signals.

6. The brain electrical acquisition system of claim 1, wherein: the trap circuit is used for eliminating 50Hz power frequency interference.

The technical field is as follows:

the invention belongs to the technical field of medical instruments, and particularly relates to an electroencephalogram acquisition system for transcranial electrical stimulation and vagus nerve stimulation.

Background art:

the EEG signal frequency is low, generally in the range of 1 Hz-100 Hz, most of the EEG signals are concentrated below 30Hz, and the EEG signals are extremely easily interfered by high-frequency noise and power frequency noise in the acquisition process, so the acquired EEG signals are required to be filtered by a preprocessing circuit firstly.

The electroencephalogram signal is very weak, the amplitude value is generally between 10 muV and 100 muV, so the acquisition system is required to have better amplification performance, generally, the electroencephalogram acquisition module needs to amplify the electroencephalogram signal by about twenty thousand times, meanwhile, the electroencephalogram acquisition module needs to have higher Common Mode Rejection Ratio (CMRR), and generally, the common mode rejection ratio is more than 100 dB.

The electroencephalogram signal has small amplitude and low frequency, and the acquired electroencephalogram signal is usually mixed with various interference signals such as baseline drift, electro-oculogram interference, electromyogram interference and the like, so that the system is required to have strong anti-interference capability to ensure the purity of the electroencephalogram signal.

In the process of acquiring the electroencephalogram signals, because the human impedance is large, in order to acquire the electroencephalogram signals better, an acquisition system is generally required to have high input impedance, and the general condition is larger than 10M omega. The traditional electroencephalogram acquisition method is used for independently amplifying, filtering and performing analog-to-digital conversion on each channel, and is suitable for the condition that the number of acquisition channels is small, and if the number of the acquisition channels is large, the equipment is large in size and high in power consumption.

The invention content is as follows:

the invention aims to overcome the defects of the prior art and provides an electroencephalogram acquisition system for transcranial electrical stimulation and vagus nerve stimulation, which has the advantages of higher common mode rejection ratio, strong anti-interference capability, pure acquired electroencephalogram signals, safety and harmlessness.

The purpose of the invention is solved by the following technical scheme:

an electroencephalogram acquisition system for transcranial electrical stimulation and vagus nerve stimulation is composed of an electroencephalogram cap, a switching circuit, a preprocessing circuit, an analog-to-digital conversion chip ADS1299 and a micro control unit MCU, wherein the preprocessing circuit comprises a low-pass filter circuit, a high-pass filter circuit and a power frequency notch circuit, electroencephalogram signals obtained by the electroencephalogram cap enter the ADS1299 to complete analog-to-digital conversion of the signals after being subjected to filtering amplification preprocessing, high-resolution digital signals are obtained, then the digital signals are transmitted to the micro control unit MCU through an SPI interface of the ADS1299, and the micro control unit MCU transmits the data to an upper computer through a USB.

The electroencephalogram cap is compatible with brain devices of brain products, and the connector of the electroencephalogram cap adopts a Pak-50-P50E series rectangular connector produced by 3M company.

The switching circuit is arranged between the electroencephalogram cap and the preprocessing circuit and used for connecting the electroencephalogram cap and the preprocessing circuit, and each switching circuit is provided with a 5K resistor.

The high-pass filter circuit is a second-order active high-pass filter with an amplification function and consists of a passive device resistor, a capacitor and an active device operational amplifier TLC 2252.

The low-pass filter circuit is a second-order active low-pass filter and is used for filtering high-frequency interference in the collected signals.

The trap circuit is used for eliminating 50Hz power frequency interference.

The invention has the beneficial effects that:

the electroencephalogram acquisition system has strong anti-interference capability and can ensure pure electroencephalogram signals, the electrode material used for the electroencephalogram cap adopts powder electrodes, the electroencephalogram cap is safe and harmless, no stimulation is generated to a human body, and the electroencephalogram signals with higher precision can be acquired by matching with the conductive paste when the electroencephalogram acquisition system is used; the analog-digital conversion chip ADS1299 is adopted, so that the input impedance and the common-mode rejection ratio can be high, the power consumption can be reduced, and the volume of equipment can be reduced.

Description of the drawings:

FIG. 1 is a diagram of a brain electrical acquisition system;

FIG. 2 is a diagram of a topology of a patching circuit;

FIG. 3 is a high pass filter circuit diagram;

FIG. 4 is a circuit diagram of a low pass filter;

FIG. 5 is a diagram of a power frequency notch circuit.

The specific implementation mode is as follows:

the invention is described in further detail below with reference to the accompanying drawings:

as shown in fig. 1 and fig. 2, because the electroencephalogram signal frequency is low, generally in the range of 1Hz to 100Hz, most of the electroencephalogram signals are concentrated below 30Hz, and the electroencephalogram signals are extremely susceptible to interference of high-frequency noise and power-frequency noise in the acquisition process, the acquired electroencephalogram signals are required to be filtered by a preprocessing circuit first.

The electroencephalogram signal is very weak, the amplitude value is generally between 10 muV and 100 muV, so the acquisition system is required to have better amplification performance, generally, the electroencephalogram acquisition module needs to amplify the electroencephalogram signal by about twenty thousand times, meanwhile, the electroencephalogram acquisition module needs to have higher Common Mode Rejection Ratio (CMRR), and generally, the common mode rejection ratio is more than 100 dB.

The electroencephalogram signal has small amplitude and low frequency, and the acquired electroencephalogram signal is usually mixed with various interference signals such as baseline drift, electro-oculogram interference, electromyogram interference and the like, so that the system is required to have strong anti-interference capability to ensure the purity of the electroencephalogram signal.

In the process of acquiring the electroencephalogram signals, because the human impedance is large, in order to acquire the electroencephalogram signals better, an acquisition system is generally required to have high input impedance, and the general condition is larger than 10M omega.

This patent adopts the 32 of wuhan green tach limited company production to lead the electroencephalogram cap, chooses eight passageways for use as the passageway of this patent electroencephalogram collection module, and this kind of electroencephalogram cap fixes the electrode on the cap that has elasticity according to international 10-20 brain electrode positioning method, and electrode material adopts the powder electrode, and is safe harmless, does not have any stimulation to the human body, and the higher brain electricity signal of precision can be gathered to the cooperation conductive paste during the use.

The traditional electroencephalogram acquisition method is used for independently amplifying, filtering and performing analog-to-digital conversion on each channel, and is suitable for the condition that the number of acquisition channels is small, and if the number of the acquisition channels is large, the equipment is large in size and high in power consumption.

The analog-digital conversion chip ADS1299 special for biopotential measurement, which is introduced by American TI company, is a synchronous sampling and analog-digital conversion chip with low noise, 8 channels, 24 bits, high precision, high input impedance, high common mode rejection ratio and low power consumption, and is mainly characterized in that:

1) having 8 low noise programmable gain amplifiers and 8 high resolution synchronous sampling analog to digital converters;

2) inputting reference noise: 1 μ VPP;

3) inputting a bias current: 300 pA;

4) data rate: between 250SPS and 16 kSPS;

5) common Mode Rejection Ratio (CMRR): -110 dB;

6) programmable gain, which is selectable by 1, 2, 4, 6, 8, 12 and 24 times;

7) a unipolar or bipolar power supply, an analog power supply is 4.75V to 5.25V, and a digital power supply is 1.8V to 3.6V;

8) built-in bias drive amplifier, lead detection, test signal;

9) flexible power down, standby mode;

10) the pin is compatible with the ADS129x, so that the expansion is convenient;

11) SPI compatible serial interface.

What this patent adopted is compatible brain electricity cap of brain electrical equipment of brain products, what its connector adopted is the Pak-50-P50E series rectangular connector of 3M company production, so need design circuit board to draw forth the contact pin that the electrode corresponds on this plug and the brain electricity cap to the terminal, conveniently couple together brain electricity cap and preprocessing circuit, the messenger can gather brain electrical signal better, use the different passageway of selection that the terminal can be more convenient simultaneously, be favorable to the development of follow-up equipment and going on of experiment. In addition, in the electroencephalogram signal acquisition process, as the human body impedance is larger, in order to acquire electroencephalogram signals better, the acquisition system is generally required to have higher input impedance, so that a 5K resistor is added on a switching circuit of each channel, the input impedance is increased, and the electroencephalogram signals are easier to acquire.

As mentioned above, the electroencephalogram signal is very susceptible to various low-frequency interference signals such as baseline drift, electro-ocular noise, myoelectric noise, and the like, so a high-pass filter is designed to remove these interferences, and meanwhile, because the electroencephalogram signal is very weak, has a small amplitude and needs a high amplification factor, a second-order active high-pass filter with an amplification function is selected, and the second-order active high-pass filter consists of a passive device resistor, a capacitor and an active device operational amplifier TLC2252, as shown in fig. 3.

The useful EEG signal frequency is mainly concentrated below 30Hz, such as EEG alpha wave, beta wave, theta wave and delta wave mentioned in the second chapter, so a low-pass filter is needed to be designed to filter out high-frequency interference in the collected signals, and a second-order active low-pass filter is selected in the patent, as shown in fig. 4.

50Hz power frequency interference generally comes from mains voltage, and its influence is great to electronic equipment, can design smoothing filter, trapper and band elimination filter to power frequency interference generally and eliminate, and this patent has designed the trap circuit and has eliminated 50Hz power frequency interference, as figure 5.