Multi-mode signal acquisition circuit

Abstract

The utility model discloses a multi-mode signal acquisition circuit, which comprises a terminal connector used for being connected with an external acquisition electrode, a first voltage follower, a second voltage follower and a differential amplifier used for amplifying voltage difference between two input ends, the inertial sensing circuit is used for amplifying a skin electric signal, the inertial sensing circuit comprises an integrated sensor for simultaneously detecting acceleration and angular velocity, the pulse blood oxygen acquisition circuit comprises a photodiode and a chip, and the photodiode receives a reflected light signal emitted by an LED, generates a weak current signal and transmits the weak current signal to the chip; signals are transmitted to a differential input channel of the chip through the INP and the INN, an LED driving circuit is integrated in the chip, driving current is output through the LEDP and the LEDN, the infrared body temperature module comprises an integrated infrared sensor and a signal processing circuit, various physiological signals such as galvanic skin, body temperature, pulse and acceleration can be collected at the same time, and the requirement for comprehensive monitoring of individual health is met. The modularization idea is adopted, the integration level is high, the signal output mode is standard, the circuit adaptability is high, and the follow-up processing process of signals is simplified; and a certain voltage protection function is realized.

Description

Technical Field

[0001] This utility model belongs to the field of signal acquisition circuits, and specifically relates to a multi-mode signal acquisition circuit. Background Technology

[0002] With the development of health monitoring technology, an increasing number of multimodal physiological signal acquisition systems are being applied to personal health monitoring and medical diagnosis. Traditional single-signal acquisition devices can only monitor a limited number of physiological parameters, such as heart rate, blood oxygen saturation, and body temperature. However, with the increasing demand for accuracy and comprehensiveness in health monitoring, single-signal acquisition methods can no longer meet the needs of comprehensive analysis of multiple physiological signals. Therefore, designing a system capable of efficiently acquiring and fusing multimodal signals has become a pressing problem in the current technological field. This invention aims to provide a circuit solution that integrates the acquisition of multiple physiological signals. Employing a hybrid analog and digital circuit, it can simultaneously and efficiently acquire multiple parameters such as skin conductance, acceleration, pulse wave, blood oxygen, and body temperature, meeting the needs of real-time monitoring and data analysis of human health status. Utility Model Content

[0003] To achieve the above objectives, the technical solution of this utility model is as follows: A multi-mode signal acquisition circuit, comprising:

[0004] The skin conductance acquisition circuit includes a terminal connector for connecting external acquisition electrodes, a first voltage follower and a second voltage follower to pass the input to the subsequent circuit, and also includes a differential amplifier for amplifying the voltage difference between the two input terminals to amplify the skin conductance signal.

[0005] Inertial sensing circuits include integrated sensors that simultaneously detect acceleration and angular velocity;

[0006] The pulse oximetry acquisition circuit includes a photodiode and a chip AFE4400RHAT. The photodiode receives the reflected light signal emitted by the LED and generates a weak current signal. The signal is transmitted to the differential input channel of the chip AFE4400 through IN_P and IN_N. The AFE4400 integrates an LED driver circuit, which outputs the drive current through LED_P and LED_N.

[0007] The infrared body temperature module includes an integrated infrared sensor and signal processing circuitry.

[0008] As an improvement of this utility model, the skin conductance acquisition circuit includes a decoupling capacitor C401, a resistor R401, and a resistor R402. Resistors R401 and R402 form a voltage divider to provide a stable reference voltage for the input signal. Resistors R401 and R402 are connected together. One end of the decoupling capacitor C401 is connected to both ends of the resistor R402. Voltage followers U127.1 and U127.3 transmit the input to the subsequent circuit. Differential amplifier U127.2 is used to amplify the voltage difference between the two input terminals, thereby amplifying the skin conductance signal and generating the final output.

[0009] Based on the aforementioned technical features, this circuit is an analog circuit used to acquire electrical skin activity (EDA, also known as skin conductance). Skin conductance signals are typically used to measure changes in skin conductivity, which are related to physiological states such as emotions and stress. The following is a detailed description of the circuit: H2 is a terminal connector used to connect external acquisition electrodes. R401 (4.7kΩ) and R402 (4.7kΩ) form a voltage divider, providing a stable reference voltage for the input signal. C401 (100nF) is a decoupling capacitor used to filter out high-frequency noise and stabilize the input signal. U127 is an operational amplifier used to amplify the skin conductance signal. U127.1 and U127.3 are voltage followers that pass the input to subsequent circuits. U127.2 is a differential amplifier used to amplify the voltage difference between the two input terminals, amplifying the skin conductance signal to produce the final output.

[0010] As an improvement of this utility model, in the inertial sensing circuit sensor LSM6DS3TR-C, capacitor C24 is connected between VDDIO and ground, INT1 and INT2 are interrupt output pins, SDA and SCL are the data line and clock line of I2C communication, pull-up resistors R14 and R15 are connected on the SDA and SCL lines, and capacitor C23 is connected between the 3.3V power supply and ground.

[0011] Based on the above technical features, the LSM6DS3TR-C is a low-power inertial sensor that provides 3-axis accelerometer and 3-axis gyroscope functionality, supporting I²C and SPI communication. It features low power consumption and powerful motion detection capabilities. The sensor supports multiple operating modes and has a built-in FIFO buffer for batch processing and storage of sensor data. The circuit operates on a 3.3V power supply. IMU_INT1 is the interrupt pin, IMU_SDA is the data line, and IMU_SCL is the clock line. Pull-up resistors (R14 and R15) ensure the I²C bus is high when idle, preventing erroneous signals.

[0012] As an improvement of this utility model, the pulse oximetry signal acquisition circuit includes a positive input INP and a negative input INN connected to the pins of the chip AFE4400RHAT through resistors R7 and R5 respectively, a common-mode voltage VCM connected to the VCOM pin of the chip AFE4400RHAT through resistor R6, and a transmit reference TX_REF and transmit positive and negative TXP / TXN connected to the pins of the chip AFE4400RHAT through resistors R8 and R9.

[0013] Based on the aforementioned technical features, this circuit design utilizes the AFE4400 and a photoelectric sensor for pulse oximetry signal acquisition. The circuit achieves real-time detection of blood oxygen and heart rate through LED driving, optical signal reception, and SPI data transmission.

[0014] Signal acquisition steps:

[0015] 1. The photodiode receives the reflected light signal emitted by the LED and generates a weak current signal. The signal is transmitted to the differential input channels (Pin 1 and Pin 2) of the AFE4400 through IN_P and IN_N, where the AFE4400 amplifies and filters the signal.

[0016] 2. The AFE4400 integrates an LED driver circuit, which controls the brightness of the LEDs by outputting drive current through LED_P and LED_N.

[0017] External diodes (such as D2, D3, D4) are used to protect the circuit and prevent reverse current flow from damaging the circuit.

[0018] 3. The SPI interface is used to communicate with an external MCU and transmit the collected blood oxygen and heart rate data. Resistors R10 and R12 are used for current limiting and to protect the communication pins.

[0019] 4. AFE_RESET is an external reset pin used to initialize the AFE4400. AFE_PDNz is a power-saving mode control pin, which controls the AFE to be enabled or disabled via the MCU.

[0020] 5. The AFE4400 drives an LED to emit light of a specific wavelength (such as red and infrared light). This light is received by a photodiode after passing through tissue. The photodiode converts the optical signal into an electrical signal, which the AFE4400 amplifies, filters, and performs analog-to-digital conversion on. Finally, a digital signal is output via SPI. Blood oxygen saturation is calculated by analyzing the absorption characteristics of the reflected light.

[0021] As an improvement of this utility model, the infrared body temperature module includes an infrared temperature sensor, the SCL / VZ pin is the clock line for I2C communication, which is connected to a 3.3V power supply through resistor R504 and is connected to the SCL pin of an external microcontroller, and the SDA / PWM pin is the data line for I2C communication, which is connected to a 3.3V power supply through resistor R505 and is connected to the SDA pin of an external microcontroller.

[0022] Based on the aforementioned technical features, this section is an infrared temperature sensing circuit. The MLX90614 is a low-power temperature sensor that integrates an infrared sensor and signal processing circuitry, capable of measuring the temperature of objects or the human body in a non-contact manner. It features small size and low cost. The circuit communicates with the main controller via the I²C protocol, where T_SCL is the clock signal and T_SDA is the data signal. The circuit is simple, requiring only the sensor, pull-up resistors, and a power supply to achieve its function.

[0023] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0024] Through the improvements of this invention, multiple physiological signals such as skin conductance, body temperature, pulse, and acceleration can be collected simultaneously to meet the needs of comprehensive individual health monitoring; the modular design facilitates individual use and upgrades; the high integration reduces the size of the device; the standardized signal output method and strong circuit adaptability simplify the subsequent signal processing; it has a certain voltage protection function; and it has strong anti-noise capability and good signal acquisition effect.

[0025] For the skin conductance acquisition circuit, the key technical points of this solution are: the use of a front-end filter to effectively remove high-frequency noise in the input signal; the adoption of an instrumentation amplifier structure to improve the common-mode rejection capability of the circuit and reduce external noise interference; the multi-stage amplification and filtering design to adapt to the minute dynamic changes in skin conductance signal; the setting of a stable reference voltage to reduce acquisition noise; and the high-resistance resistor to ensure high sensitivity detection of minute voltage changes.

[0026] For the inertial sensing module, the key technical points of this solution are: the use of a low-power integrated sensor that can simultaneously detect acceleration and angular velocity; the design of a reasonable power supply decoupling capacitor to ensure stable system operation; the reduction of system power consumption and improvement of response speed through interrupt pins; and the combination of acceleration and angular velocity sensors to provide high-precision motion data in real time, which is convenient for use and experimentation in motion scenarios.

[0027] For the infrared body temperature module, the key technical point of this solution is the use of an integrated temperature sensor, which has the characteristics of small size and low cost, and can collect data in a non-contact manner.

[0028] For pulse detection, the key features of this solution lie in its highly integrated analog front-end, including amplification, filtering, and analog-to-digital conversion, which helps reduce equipment size and noise interference. The use of surround signal lines optimizes interference protection for the PPG signal, reducing noise coupling and improving acquisition accuracy. Decoupling capacitors effectively suppress high-frequency noise, ensuring power supply stability. The addition of fast diodes prevents surge voltage and reverse current damage to components, enhancing system reliability.

[0029] This solution enables simultaneous acquisition and data output of multiple physiological signals. Through the configuration and coordination of various circuits and the integration of multiple sensors, it can simultaneously acquire signals such as pulse, acceleration, and body temperature. The highly integrated design of the multimodal signal sensors includes comprehensive signal protection and power supply noise suppression to ensure long-term stable operation. It also features a simple circuit and small size; the signal conditioning circuit and digital interface (SPI / I) are integrated. 2 C) Combined, it enables the digitization and transmission of analog signals. Suitable for wearable health monitoring devices. Attached Figure Description

[0030] Figure 1 This is a circuit module connection diagram as described in this embodiment;

[0031] Figure 2 This is the circuit diagram for the skin conductance acquisition described in this embodiment;

[0032] Figure 3 This is a circuit diagram of the inertial sensing circuit described in this embodiment;

[0033] Figure 4 This is a circuit diagram of the pulse oximetry acquisition circuit described in this embodiment;

[0034] Figure 5 This is the circuit diagram of the infrared body temperature module described in this embodiment. Detailed Implementation

[0035] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0036] Example: Figure 1As shown, the circuit of this utility model consists of four signal acquisition circuits, and the MCU performs unified acquisition and data acquisition. The PPG signal acquisition module mainly includes an AFE4400 chip, which is used to acquire and process PPG signals. Its input terminal is connected to a photoelectric sensor to detect pulse wave information, and the data is connected to the main controller via SPI communication. The skin conductance signal acquisition module acquires signals in a differential manner, and the acquired analog signals are then converted into digital signals by an ADC and input to the MCU. The temperature signal acquisition module is an infrared temperature sensor used to detect the temperature signal of the human body surface or the environment, and transmits the temperature signal data to the MCU through an I²C communication interface. The inertial signal acquisition module includes an inertial sensor used to detect motion state, including acceleration, angular velocity, and other signals. It communicates with the MCU through an I²C communication interface and transmits the motion signal data to the MCU in real time.

[0037] like Figure 2 As shown, the circuit diagram is an amplification and processing circuit for electrodermal signals, used to convert bioelectrical signals into voltage signals that can be read by an analog-to-digital converter (ADC).

[0038] This section of the circuit is an analog circuit used to collect electrical skin activity (EDA, also known as skin conductance). Skin conductance signals are commonly used to measure changes in skin conductivity, which are related to physiological states such as emotions and stress. In this embodiment, the circuit structure includes:

[0039] H2 is a terminal connector used to connect external acquisition electrodes.

[0040] R401 (4.7kΩ) and R402 (4.7kΩ) form a voltage divider to provide a stable reference voltage for the input signal. C401 (100nF) is a decoupling capacitor used to filter out high-frequency noise and stabilize the input signal.

[0041] U127 is an operational amplifier used to amplify the ductal signal. U127.1 and U127.3 are voltage followers that pass the input to the subsequent circuitry. U127.2 is a differential amplifier used to amplify the voltage difference between the two input terminals, thereby amplifying the ductal signal and producing the final output.

[0042] like Figure 3 As shown in the diagram, the circuit diagram illustrates the circuit structure of an inertial sensor, specifically using the LSM6DS3TR-C model sensor.

[0043] The LSM6DS3TR-C is a low-power inertial sensor providing 3-axis accelerometer and 3-axis gyroscope functionality, supporting I²C and SPI communication. It features low power consumption and powerful motion detection capabilities. The sensor supports multiple operating modes and has a built-in FIFO buffer for batch processing and storage of sensor data. The circuit operates on a 3.3V power supply. IMU_INT1 is the interrupt pin, IMU_SDA is the data line, and IMU_SCL is the clock line. Pull-up resistors (R14 and R15) ensure the I²C bus is high when idle, preventing erroneous signals.

[0044] like Figure 4 As shown, the circuit diagram is a schematic diagram of the SPI serial peripheral interface connection of a blood oxygenation module, mainly involving the connection of the AFE4400RHAT chip U4 and the PM200-1-05-Z busbar U128.

[0045] This circuit design, based on the AFE4400 and a photoelectric sensor, is used for acquiring pulse oximetry signals. The circuit achieves real-time detection of blood oxygen and heart rate through LED driving, optical signal reception, and SPI data transmission.

[0046] Signal acquisition steps:

[0047] 1. The photodiode receives the reflected light signal emitted by the LED and generates a weak current signal. The signal is transmitted to the differential input channels (Pin 1 and Pin 2) of the AFE4400 through IN_P and IN_N, where the AFE4400 amplifies and filters the signal.

[0048] 2. The AFE4400 integrates an LED driver circuit, which controls the brightness of the LEDs by outputting drive current through LED_P and LED_N.

[0049] External diodes (such as D2, D3, D4) are used to protect the circuit and prevent reverse current flow from damaging the circuit.

[0050] 3. The SPI interface is used to communicate with an external MCU to transmit the collected blood oxygen and heart rate data. Resistors R10 and R12 are used for current limiting and to protect the communication pins.

[0051] 4. AFE_RESET is an external reset pin used to initialize the AFE4400. AFE_PDNz is a power-saving mode control pin, which controls the AFE to be enabled or disabled via the MCU.

[0052] 5. The AFE4400 drives an LED to emit light of a specific wavelength (such as red and infrared light), not shown in the diagram. The light is received by a photodiode after passing through tissue. The photodiode converts the optical signal into an electrical signal, which is then amplified, filtered, and converted from analog to digital by the AFE4400, ultimately outputting a digital signal via SPI. Blood oxygen saturation is calculated by analyzing the absorption characteristics of the reflected light.

[0053] like Figure 5 The diagram shows the circuit structure of the infrared body temperature module, which uses an infrared temperature sensor of model MLX90614ESF-BBA-000-TU.

[0054] This section is the infrared temperature sensing circuit. The MLX90614 is a low-power temperature sensor that integrates an infrared sensor and signal processing circuitry, enabling non-contact measurement of the temperature of objects or the human body. It features small size and low cost. The internal thermopile sensor receives infrared radiation and generates a voltage proportional to the radiation intensity, which is converted into a digital signal by the ADC. The circuit communicates with the host controller via the I²C protocol; T_SCL is the clock signal, and T_SDA is the data signal. R504 and R505 are 4.7KΩ resistors connected to the I²C clock line (SCL) and data line (SDA), respectively, to pull up to the 3.3V power supply. When the host controller needs to communicate with the MLX90614, it sends the I²C protocol clock signal and data via T_SCL and T_SDA. The MLX90614 receives data through the SDA / PWM pin and sends data back to the host controller via the same pin when needed. Data can be output in PWM form, with a duty cycle linearly related to the temperature.

[0055] It should be noted that the above content merely illustrates the technical concept of this utility model and cannot be used to limit the scope of protection of this utility model. For those skilled in the art, several improvements and modifications can be made without departing from the principle of this utility model, and all such improvements and modifications fall within the scope of protection of the claims of this utility model.

Claims

1. A multi-modal signal acquisition circuit, characterized by, include: The skin conductance acquisition circuit includes a terminal connector for connecting external acquisition electrodes, a first voltage follower and a second voltage follower to pass the input to the subsequent circuit, and also includes a differential amplifier for amplifying the voltage difference between the two input terminals to amplify the skin conductance signal. Inertial sensing circuitry, including integrated sensors that simultaneously detect acceleration and angular velocity; The pulse oximetry acquisition circuit includes a photodiode and a chip AFE4400RHAT. The photodiode receives the reflected light signal emitted by the LED and generates a weak current signal. The signal is transmitted to the differential input channel of the chip AFE4400 through IN_P and IN_N. The AFE4400 integrates an LED driver circuit, which outputs the drive current through LED_P and LED_N. The infrared body temperature module includes an integrated infrared sensor and signal processing circuitry.

2. The multi-modal signal acquisition circuit of claim 1, wherein, The skin conductance acquisition circuit includes a decoupling capacitor C401, resistors R401 and R402. Resistors R401 and R402 form a voltage divider to provide a stable reference voltage for the input signal. Resistors R401 and R402 are connected together. One end of the decoupling capacitor C401 is connected to both ends of resistor R402. Voltage followers U127.1 and U127.3 transmit the input to the subsequent circuit. Differential amplifier U127.2 amplifies the voltage difference between the two input terminals, thus amplifying the skin conductance signal and generating the final output.

3. The multi-modal signal acquisition circuit of claim 1, wherein, The inertial sensing circuit includes a sensor LSM6DS3TR-C, a capacitor C24 connected between VDDIO and ground, INT1 and INT2 as interrupt output pins, SDA and SCL as the data and clock lines for I2C communication, pull-up resistors R14 and R15 connected on the SDA and SCL lines, and a capacitor C23 connected between the 3.3V power supply and ground.

4. The multi-modal signal acquisition circuit of claim 1, wherein, In the pulse oximetry signal acquisition circuit, the positive input INP and negative input INN are connected to the pins of the chip AFE4400RHAT through resistors R7 and R5, respectively. The common-mode voltage VCM is connected to the VCOM pin of the chip AFE4400RHAT through resistor R6. The transmit reference voltage TX_REF and the transmit positive and negative signal lines TXP / TXN are connected to the pins of the chip AFE4400RHAT through resistors R8 and R9. The receive reference voltage RX_REF and the receive positive and negative signal lines RXP / RXN are connected through the pins of the chip AFE4400RHAT.

5. The multi-modal signal acquisition circuit of claim 1, wherein, The infrared body temperature module includes an infrared temperature sensor. The SCL / VZ pin is the clock line for I2C communication, which is connected to a 3.3V power supply through a resistor R504 and is also connected to the SCL pin of an external microcontroller. The SDA / PWM pin is the data line for I2C communication, which is connected to a 3.3V power supply through a resistor R505 and is also connected to the SDA pin of an external microcontroller.

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