CN104825152A - Single-path acquisition device for multiple paths of signals modulated by bioelectricity and square waves and method for single-path acquisition device - Google Patents

Abstract

The invention discloses a single-channel acquisition device and method for multi-channel signals modulated by bioelectricity and square waves. The acquisition device collects N-channel biomedical signals through an analog-to-digital converter, including high-frequency square waves loaded with PPG signals. and low-frequency bioelectrical signals. The current signal is converted into a preset amplitude voltage signal by the current/voltage conversion amplifier, and the preset amplitude bioelectric signal is obtained by the bioelectric signal detection circuit, and the preset amplitude voltage signal and the preset amplitude bioelectric signal are passed through the addition circuit After the addition, the mixed signal is obtained, and the mixed signal is converted into a digital signal by a single-channel analog-to-digital converter. The microprocessor processes the digital signal, separates the modulated square wave signal and the low-frequency bioelectrical signal, and decomposes Call out multiple PPG signals. The invention realizes synchronous collection of multiple biomedical signals via a single analog-to-digital converter, and has the characteristics of simple circuit, low cost and accurate measurement.

Description

Single-channel acquisition device and method for multi-channel signal modulated by bioelectricity and square wave

technical field

The invention relates to the field of biomedical signal acquisition, in particular to a single-channel acquisition device and method for multi-channel signals modulated by bioelectricity and square waves.

Background technique

The amount of information-carrying changes such as voltage signals is expressed in analog form in its natural state. However, in order to facilitate computer processing, transmission and storage, it is usually converted into a digital signal through an analog-to-digital converter. Therefore, in biological In medical signal processing, analog-to-digital conversion is essential.

The inventor found in the process of realizing the present invention that in the existing multi-channel biomedical signal acquisition, it is usually necessary to use a multi-chip ADC or a multi-channel analog switch with a single-chip ADC. The former has complex circuits, high system power consumption and low The disadvantage of large circuit size; and the latter will introduce switching noise due to the switching of multiple switches during the acquisition process, and due to the setup time of multiple switches, it will cause mutual interference between adjacent channel signals.

Contents of the invention

The present invention provides a single-channel acquisition device and method for multi-channel signals modulated by bioelectricity and square waves. The present invention realizes analog-to-digital conversion of multiple-channel biomedical signals through a single-channel analog-to-digital converter. See the following description for details:

A single-channel acquisition device for bioelectricity and square wave modulation multi-channel signals, the single-channel acquisition device includes: a microprocessor, the microprocessor outputs square waves with different frequencies and a ratio of 2 times, and the square wave drives At least two types of light-emitting diodes, the light emitted by the light-emitting diodes is received by the photosensitive device after passing through the finger under test, and the photosensitive device is converted into a current signal, and the current signal is converted into a preset amplitude voltage signal by a current/voltage conversion amplifier;

The single-channel acquisition device also includes: a low-frequency bioelectrical signal detection circuit, an addition circuit, and a single-channel analog-to-digital converter;

The low-frequency bioelectric signal detection circuit acquires a preset amplitude bioelectric signal, and the preset amplitude voltage signal and the preset amplitude bioelectric signal are added to obtain a mixed signal by the addition operation circuit, and the The mixed signal is converted into a digital signal by the single analog-to-digital converter;

The microprocessor processes the digital signal, separates the modulated square wave signal and the low-frequency bioelectrical signal, and demodulates the PPG signal from the modulated square wave signal.

Wherein, the low-frequency bioelectric signal is specifically any one of ECG, EEG, EMG, EGG and EOG.

Wherein, the addition operation circuit includes: a first resistor and a second resistor, one end of the first resistor is connected to the first signal source, one end of the second resistor is connected to the second signal source, and the first resistor The other end of the second resistor and the other end of the second resistor are connected to the negative input terminal of the operational amplifier; the positive input terminal of the operational amplifier is connected to one end of the fourth resistor, and the other end of the fourth resistor is grounded; The negative polarity input terminal is also connected to one terminal of the third resistor at the same time, and the other terminal of the third resistor is connected to the output terminal of the operational amplifier to output the signal voltage.

In another embodiment, the adding operation circuit includes: a first resistor and a second resistor, one end of the first resistor is connected to the first signal source, one end of the second resistor is connected to the second signal source, and the The other end of the first resistor and the other end of the second resistor are connected to the positive input terminal of the operational amplifier; the negative input terminal of the operational amplifier is connected to one end of the third resistor and the fourth resistor at the same time; the fourth resistor The other end of the third resistor is connected to the ground; the other end of the third resistor is connected to the output end of the operational amplifier to output the signal voltage.

An acquisition method for a single-channel acquisition device for bioelectricity and square wave modulation multi-channel signals, the method includes the following steps:

The mixed signal is converted into a digital signal by a single analog-to-digital converter and sent to the microprocessor;

The microprocessor performs low-pass filtering on the digital signal to restore the low-frequency bioelectrical signal; the microprocessor separates the digital signal to obtain the PPG signal and the bioelectrical signal, and the background light interference in the PPG signal is eliminated;

Calculate the valley value and peak value of the PPG signal respectively; then calculate the absorbance difference ΔA corresponding to each wavelength from the valley value and peak value of the PPG signal, and obtain the spectral value composed of the absorbance difference ΔA.

Wherein, the microprocessor separates and processes the digital signal to obtain the PPG signal and the bioelectric signal, and the steps of eliminating background light interference in the PPG signal are specifically:

Assuming that the frequency of the square wave signal output by the microprocessor to drive the LED 2 is 8f, 4f, 2f, 1f respectively, the sampling frequency of the single-channel analog-to-digital converter is f _s , and f _s = 16f, and it is guaranteed to drive at the highest frequency High and low intermediate sampling of the signal;

The number of high-level and low-level sampling points of the square wave signal is n, and it is the entire period of the lowest frequency signal; the sum of the voltage amplitudes of n high-level sampling points and the voltage amplitude of n low-level sampling points are respectively calculated The difference between the sum of the two voltage amplitudes is obtained; the difference is n times the PPG signal; the interference of background light and low-frequency bioelectrical signals is eliminated to obtain the PPG signal.

The beneficial effects of the technical solution provided by the present invention are: the present invention realizes analog-to-digital conversion of multiple biomedical signals through a single-channel analog-to-digital converter, and has the advantages of simple circuit, low cost and accurate measurement; and when the addition operation circuit adopts The circuit designed by the invention can conveniently obtain a stable and high-precision mixed frequency signal, is easy to integrate, reduces the circuit cost, expands the dynamic range of the signal, and satisfies various needs in practical applications.

Description of drawings

Fig. 1 is a structural schematic diagram of a single-channel acquisition device for bioelectricity and square wave modulation multi-channel signals;

Fig. 2 is the structural representation of addition operation circuit;

Fig. 3 is another structural representation of the addition operation circuit;

Fig. 4 is the schematic diagram that separates PPG signals of different wavelengths provided by the present invention;

Fig. 5 is a flow chart of a single-channel acquisition method of bioelectricity and square wave modulation multi-channel signals.

In the accompanying drawings, the list of parts represented by each label is as follows:

1: Microprocessor; 2: LED;

3: Photosensitive device; 4: Current/voltage conversion amplifier;

5: Low-frequency bioelectrical signal detection circuit; 6: Addition circuit;

7: Single channel analog-to-digital converter.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the implementation manners of the present invention will be further described in detail below.

Example 1

A single-channel acquisition device for multi-channel signals modulated by bioelectricity and square wave, as shown in Figure 1, the single-channel acquisition device includes: a microprocessor 1, at least two kinds of light-emitting diodes 2, a photosensitive device 3, and a current/voltage conversion amplifier 4 , a low-frequency bioelectrical signal detection circuit 5, an addition operation circuit 6 and a single-channel analog-to-digital converter 7,

The microprocessor 1 outputs square waves with different frequencies and a ratio of 2 times. The square waves drive at least two kinds of light-emitting diodes 2. The light emitted by the light-emitting diodes 2 is received by the photosensitive device 3 after passing through the finger under test, and the photosensitive device 3 is converted into a current. signal, the current signal is converted into a preset amplitude voltage signal by the current/voltage conversion amplifier 4.

The low-frequency bioelectrical signal detection circuit 5 obtains the preset amplitude bioelectric signal, and the preset amplitude voltage signal and the preset amplitude bioelectric signal are added by the addition operation circuit 6 to obtain a mixed signal, and the mixed signal is converted by a single channel analog to digital Converter 7 into a digital signal, the microprocessor 1 processes the digital signal, separates the modulated square wave signal and the low-frequency bioelectrical signal, and demodulates the PPG signal from the modulated square wave signal.

Wherein, the number of light emitting diodes 2 is greater than or equal to two. During specific implementation, the number of light-emitting diodes 2 is set according to the needs in practical applications; the amplitude of the preset amplitude voltage signal and the preset amplitude bioelectric signal is set according to the needs of practical applications. During specific implementation, This embodiment of the present invention does not limit this.

Wherein, the low-frequency bioelectric signal includes: any one of ECG, EEG, EMG, EGG, EOG and other bioelectric signals. The microprocessor 1 can be any one of MCU, ARM, DSP or FPGA. The addition operation circuit 6 adopts conventional addition devices on the market.

Wherein, the gain and bandwidth of the bioelectrical signal detection circuit 5 are determined by the amplitude and frequency range of the detected bioelectrical signal.

Example 2

A single-channel acquisition device for multi-channel signals modulated by bioelectricity and square wave, as shown in Figure 1, the single-channel acquisition device includes: a microprocessor 1, at least two kinds of light-emitting diodes 2, a photosensitive device 3, and a current/voltage conversion amplifier 4 , a low-frequency bioelectrical signal detection circuit 5, an addition circuit 6 and a single analog-to-digital converter 7. This embodiment is different from Embodiment 1 in that the addition operation circuit 6 is realized by the addition operation circuit 6 designed in the embodiment of the present invention, referring to Fig. 2, the addition operation circuit 6 includes: _{a first} resistor R1 and a second resistor R ₂ ,

One end of the first resistor R ₁ is connected to the first signal source V ₁ , one end of the second resistor R ₂ is connected to the second signal source V ₂ , the other end of the first resistor R ₁ is connected to the other end of the second resistor R ₂ The negative polarity input terminal of the operational amplifier A; the positive polarity input terminal of the operational amplifier A is connected to one end of the _fourth resistor R4, and the other end of the _fourth resistor R4 is grounded; the negative polarity input terminal of the operational amplifier A is also connected to the third One end of the resistor R ₃ and the other end of the third resistor R ₃ are connected to the output end of the operational amplifier A to output the signal voltage V _o .

The first signal source V ₁ and the second signal source V ₂ are respectively preset amplitude voltage signals and preset amplitude bioelectric signals; or, the first signal source V ₁ and the second signal source V ₂ are respectively preset amplitude The value bioelectrical signal and the preset amplitude voltage signal; the signal voltage V _o is a mixed signal.

Example 3

A single-channel acquisition device for multi-channel signals modulated by bioelectricity and square wave, as shown in Figure 1, the single-channel acquisition device includes: a microprocessor 1, at least two kinds of light-emitting diodes 2, a photosensitive device 3, and a current/voltage conversion amplifier 4 , a low-frequency bioelectrical signal detection circuit 5, an addition circuit 6 and a single analog-to-digital converter 7. This embodiment is different from Embodiment 1 in that the addition operation circuit 6 can be realized by using the addition operation circuit 6 designed in the embodiment of the present invention. Referring to FIG. 3, the addition operation circuit 6 includes: _{a first} resistor R1 and a second resistor R1 Resistor _R2 ,

One end of the first resistor R ₁ is connected to the first signal source V ₁ , one end of the second resistor R ₂ is connected to the second signal source V ₂ , the other end of the first resistor R ₁ is connected to the other end of the second resistor R ₂ The positive polarity input terminal of the operational amplifier A; the negative polarity input terminal of the operational amplifier A is connected to one end of the third resistor _R3 and the _fourth resistor R4 at the same time; the other end of the _fourth resistor R4 is grounded; the other end of the third resistor _R3 One end is connected to the output end of the operational amplifier A to output the signal voltage V _o .

The first signal source V ₁ and the second signal source V ₂ are respectively preset amplitude voltage signals and preset amplitude bioelectric signals; or, the first signal source V ₁ and the second signal source V ₂ are respectively preset amplitude The value bioelectrical signal and the preset amplitude voltage signal; the signal voltage V _o is a mixed signal.

Example 4

A single-channel acquisition method of bioelectricity and square wave modulation multi-channel signals, see Figure 4 and Figure 5, the method comprises the following steps:

101: the mixed signal is converted into a digital signal by the single-channel analog-to-digital converter 7 and sent to the microprocessor 1;

102: Microprocessor 1 performs low-pass filtering on digital signals to recover low-frequency bioelectric signals; microprocessor 1 separates and processes digital signals to obtain PPG signals and bioelectric signals, and background light and other interference in PPG signals are eliminated .

Among them, this step is specifically:

1) Assuming that the microprocessor 1 outputs the square wave signal frequencies for driving the light-emitting diode 2 to be 8f, 4f, 2f, 1f respectively, the sampling frequency of the single-channel analog-to-digital converter 7 is _fs , and _fs =16f, and it is guaranteed to be at High and low level intermediate sampling of the highest frequency (8f) drive signal;

2) The number of high and low level sampling points of the square wave signal is n, and it is the entire period of the lowest frequency (1f) signal, and the sum of the voltage amplitudes of n high level sampling points and n low level The sum of the voltage amplitudes of the sampling points, and obtain the difference between the sum of the two voltage amplitudes; the difference is n times the PPG signal (corresponding to the wavelength of the square wave); eliminate the interference of background light and low-frequency bioelectrical signals , to obtain the PPG signal.

For the sake of simplicity, the light-emitting diodes 2 with four wavelengths are taken as an example. It is assumed that the driving square-wave frequencies of the light-emitting diodes with λ1, λ2, λ3 and λ4 wavelengths are 8f, 4f, 2f and f respectively.

Assume that the sampling frequency of the single-channel analog converter 7 is f _S , and f _S =2f, and it is guaranteed to sample between the high and low levels of the λ1 driving signal.

digital signal sequence It can be expressed as:

${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

in, and are the PPG signals of wavelengths λ1, λ2, λ3 and λ4, respectively, It is a low-frequency signal, including: low-frequency bioelectrical signal, background light, dark current of the photosensitive device 3 , and offset voltage of the current/voltage conversion amplifier 4 .

Assuming that the sampling frequency f _S is much higher than the changing frequency of the modulated square wave signal and low-frequency signal, it can be approximately considered that the amplitude of each square wave signal and the amplitude of the low-frequency signal remain unchanged in one cycle of the lowest driving signal frequency. Take the first 16 sampling data as an example:

in, and are the amplitudes of the PPG signal and the background signal at wavelengths λ1, λ2, λ3, and λ4, respectively.

In other words, operations are performed in groups of 16 digital signals in sequence:

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>\\ {\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 13</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 15</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 16</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; An</span>}}^{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1,2</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

That is, the PPG signal with 8 times the wavelength λ1 is obtained and completely eliminates low frequency signals Impact.

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; -</span>\\ {\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 13</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 15</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 16</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; An</span>}}^{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1,2</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

That is, the PPG signal with 8 times the wavelength λ2 is obtained and completely eliminates low frequency signals Impact.

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; +</span>\\ {\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 13</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 15</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 16</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; An</span>}}^{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1,2</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

That is, the PPG signal with 8 times the wavelength λ3 is obtained and completely eliminates low frequency signals Impact.

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 6</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 8</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 9</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; -</span>\\ {\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 11</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 12</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 13</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 14</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 15</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; 16</span>}\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 16</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; 8</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; An</span>}}^{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1,2</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

That is, the PPG signal with 8 times the wavelength λ4 is obtained and completely eliminates low frequency signals Impact.

103: Calculate the valley value and peak value of the PPG signal respectively; then calculate the absorbance difference ΔA corresponding to each wavelength from the valley value and peak value of the PPG signal, and obtain the spectral value composed of ΔA _λ1 , ΔA _λ2 ... ΔA _λn .

Due to the pulsation phenomenon of the artery, the blood flow in the blood vessel changes periodically, and the blood is a highly opaque liquid, so the change of the pulsation will inevitably cause the change of the absorbance.

Considering the state of the lowest arterial vessel filling degree, the incident light from the light source is not absorbed by the pulsating arterial blood, and the outgoing light intensity I _max is the strongest at this time, which can be regarded as the incident light I of the pulsating arterial blood; while the state of the highest arterial vessel filling degree corresponds to The valley point of the photoelectric pulse wave is the moment when the pulsating arterial blood has the greatest effect, and the outgoing light intensity I _min at this time is the weakest, which is the minimum outgoing light intensity I of the pulsating arterial blood. Therefore, by recording the absorbance value when the artery is filled to the maximum and the artery is contracted to the minimum, the influence of all body components with constant absorption characteristics such as skin tissue and subcutaneous tissue on the absorbance can be eliminated.

Assuming that the incident light intensity is I ₀ , and the detection light intensity during arterial filling and arterial contraction are respectively I _min and I _max , then the difference between the absorbance during arterial filling and the absorbance during arterial contraction is:

$\mathrm{<span\; class="notranslate">\; \&Delta;A</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; lg</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; lg</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; lg</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

The absorbance difference ΔA corresponding to the photoplethysmogram can be obtained by measuring the valley value I _min and peak value I _max of each photoplethysmography wave, and the spectral value composed of ΔA _λ1 , ΔA _λ2 ... ΔA _λn can be obtained.

That is, the valleys and peaks of the PPG signal at wavelengths λ1, λ2, λ3, and λ4 are calculated: I _minλ1 , I _maxλ1 , I _minλ2 , I _maxλ2 , I _minλ3 , I _maxλ3 , I _minλ4 , and I _maxλ4 .

In the embodiments of the present invention, unless otherwise specified, the models of the devices are not limited, as long as they can complete the above functions.

Those skilled in the art can understand that the accompanying drawing is only a schematic diagram of a preferred embodiment, and the serial numbers of the above-mentioned embodiments of the present invention are for description only, and do not represent the advantages and disadvantages of the embodiments.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (6)

1. A single-channel collection device for modulating multiple signals with bioelectricity and square waves, the single-channel collection device comprising: the microprocessor outputs square waves with different frequencies and a 2-time ratio relation, the square waves drive at least 2 light emitting diodes, light emitted by the light emitting diodes is received by a photosensitive device after passing through a detected finger, the photosensitive device converts the light into a current signal, and the current signal is converted into a preset amplitude voltage signal through a current/voltage conversion amplifier; it is characterized in that the preparation method is characterized in that,

the single-channel collection device further comprises: the low-frequency bioelectricity signal detection circuit comprises a low-frequency bioelectricity signal detection circuit, an addition operation circuit and a single-path analog-to-digital converter;

the low-frequency bioelectricity signal detection circuit acquires a preset amplitude bioelectricity signal, the preset amplitude voltage signal and the preset amplitude bioelectricity signal are added by the addition operation circuit to obtain a mixed signal, and the mixed signal is converted into a digital signal by the single-path analog-to-digital converter;

and the microprocessor processes the digital signal, separates out a modulation square wave signal and a low-frequency bioelectricity signal, and demodulates a PPG signal from the modulation square wave signal.

2. The single-path acquisition device for the bioelectricity and square-wave modulated multi-path signals according to claim 1, wherein the low-frequency bioelectricity signal is specifically: any one of ECG, EEG, EMG, EGG and EOG.

3. The single-channel signal acquisition device for bioelectricity and square wave modulation of multiple signals according to claim 1, wherein the addition operation circuit comprises: a first resistance and a second resistance, wherein the first resistance and the second resistance are connected,

one end of the first resistor is connected to a first signal source, one end of the second resistor is connected to a second signal source, and the other end of the first resistor and the other end of the second resistor are connected to a negative-polarity input end of the operational amplifier; the positive polarity input end of the operational amplifier is connected with one end of a fourth resistor, and the other end of the fourth resistor is grounded; the negative polarity input end of the operational amplifier is also connected to one end of a third resistor, and the other end of the third resistor is connected to the output end of the operational amplifier to output signal voltage.

4. The single-channel signal acquisition device for bioelectricity and square wave modulation of multiple signals according to claim 1, wherein the addition operation circuit comprises: a first resistance and a second resistance, wherein the first resistance and the second resistance are connected,

one end of the first resistor is connected to a first signal source, one end of the second resistor is connected to a second signal source, and the other ends of the first resistor and the second resistor are connected to a positive-polarity input end of an operational amplifier; the negative polarity input end of the operational amplifier is simultaneously connected with one end of the third resistor and one end of the fourth resistor; the other end of the fourth resistor is grounded; the other end of the third resistor is connected with the output end of the operational amplifier to output signal voltage.

5. A method for acquiring a single-channel acquisition device of bioelectrical and square-wave modulated multiplex signals according to any of claims 1 to 4, characterized in that it comprises the following steps:

the mixed signal is converted into a digital signal by a single-path analog-to-digital converter and sent to a microprocessor;

the microprocessor carries out low-pass filtering processing on the digital signal to recover a low-frequency bioelectricity signal; the microprocessor separates and processes the digital signal to obtain a PPG signal and a bioelectricity signal, and background light interference in the PPG signal is eliminated;

respectively calculating a valley value and a peak value of the PPG signal; and then calculating the absorbance difference delta A corresponding to each wavelength according to the valley value and the peak value of the PPG signal, and obtaining a spectral value consisting of the absorbance difference delta A.

6. The acquisition method according to claim 5, wherein the microprocessor performs separation processing on the digital signal to obtain a PPG signal and a bioelectric signal, and the step of eliminating the background light interference in the PPG signal specifically comprises:

assuming that the frequencies of the square wave signals output by the microprocessor to drive the light emitting diode 2 are respectively 8f, 4f, 2f and 1f, and the sampling frequency of the one-way analog-to-digital converter is f_sAnd f is_s16f and ensures intermediate sampling at the high and low levels of the highest frequency drive signal;

the number of the high and low level sampling points of the square wave signal is n, and the sampling points are the whole period of the lowest frequency signal; respectively solving the sum of the voltage amplitudes of n high-level sampling points and the sum of the voltage amplitudes of n low-level sampling points to obtain the difference value of the two voltage amplitude sums; the difference is n times the PPG signal; and eliminating the interference of background light and low-frequency bioelectricity signals to obtain a PPG signal.