CN201085618Y - Volume pulsation wave signal capture apparatus based on USB interface - Google Patents

Abstract

Disclosed is a volume pulse wave signal acquisition device based on a USB interface, which belongs to the human parameters detection field and is used for the biomedical engineering, and comprises a photoelectric sensor, a CPU central processing unit, a signal filter circuit, a signal amplifying circuit, a numerical control gain circuit, a pulse power supply circuit, a power switch control circuit, a USB universal serial bus interface circuit and a personal computer. The pulse power supply circuit supplies pulse voltage for the photoelectric sensor; the power switch control circuit is used for controlling the start-up or stop of the sensor; the electrical signal acquired by the photoelectric sensor is processed by the signal filter circuit and the signal amplifying circuit and is inputted to the CPU after the amplitude regulation of the numerical control gain circuit, and then is processed with analog-to-digital convert in an A/D converter in the CUP and the data is stored in the CPU; the acquired data is transmitted to the personal computer through real-time transmission by the USB universal serial bus interface circuit; the personal computer supplies power for the whole system; the device has small volume, convenient carrying and is applicable to the detection and analysis of the cardiovascular function.

Description

A Volume Pulse Wave Signal Collector Based on USB Interface

technical field

The utility model belongs to the field of human body parameter detection of biomedical engineering. It is a volumetric pulse wave signal collector based on USB interface, which can collect fingertip volumetric pulse wave signal and send the signal to PC through USB universal serial bus interface, which can be widely used in cardiovascular function detection and analysis.

Background technique

At present, the non-invasive detection of cardiovascular hemodynamic parameters at home and abroad mainly includes: echocardiography, cardiac impedance method, spiral CT, cardiac nuclear medicine method, magnetic resonance method, etc., but these methods are bulky and complicated to operate. , expensive, strict testing environment and other shortcomings. In 1938, Hertzman first proposed photoplethysmography, which is a non-invasive detection method for detecting changes in blood volume in living tissue by means of photoelectric means. At present, this method is generally used to detect blood oxygen, brain oxygen, muscle oxygen, respiratory rate and respiratory volume. Around the 1990s, researchers at home and abroad began to combine the mechanism research of the volume pulse wave with the pressure pulse wave theory, and believed that it would be more intuitive and effective to derive and analyze the blood flow characteristics of the volume pulse wave from the characteristics of the pressure pulse wave. The relationship between them will constitute the key cardiovascular blood flow parameters such as peripheral resistance and vascular compliance of the cardiovascular system.

Under this premise, using volume pulse wave to detect and calculate cardiovascular hemodynamic parameters can become a very feasible non-invasive detection method. The acquisition equipment for the volume pulse wave signal is mainly a monitor for clinical application, but most of these equipment are expensive and not suitable for carrying. Part of the pulse wave signal acquisition system also has RS232 standard serial communication interface circuit to connect with PC.

However, these large and expensive equipment used in fixed places cannot meet the current requirements for real-time and convenient detection of cardiovascular hemodynamic parameters, thus missing the evaluation of many key physiological states and physiological processes. In addition, RS232 standard serial communication is a low-speed data transmission technology, and the transmission rate is generally between 9600bps-38400bps. It takes a long time to transmit a large amount of detection data, and it does not support plug and play and hot swap, so it is very inconvenient to use as a pulse wave signal collector.

Utility model content

The purpose of the utility model is to overcome the shortcomings of the existing volumetric pulse wave signal acquisition system, which are relatively large in size and inconvenient to carry, as well as the inconvenience caused by using the RS232 communication interface.

The technical scheme of the utility model is shown in Figure 1 and Figure 2, a volumetric pulse wave signal collector based on the USB interface, including a photoelectric sensor, CPU central processing unit, signal filter circuit, signal amplification circuit, numerical control gain circuit, pulse Power supply circuit, power supply switch control circuit, USB universal serial bus interface circuit, PC. The pulse power supply circuit is used to provide pulse voltage for the photoelectric sensor; the PC sends instructions to the CPU through the USB universal serial bus interface circuit, and the CPU controls the power supply switch control circuit, thereby controlling the photoelectric sensor to start or stop working; collected by the photoelectric sensor The electrical signal first passes through the signal filter circuit and signal amplification circuit for signal processing; the numerical control gain circuit is composed of numerical control potentiometer, operational amplifier and CPU connection, and the increase or decrease of its magnification is controlled by the CPU; the signal is finally output to the CPU, in the CPU A/D conversion is completed in the A/D converter, and the digital signal is stored in the CPU; the USB universal serial bus interface circuit is composed of a USB interface connected to the CPU, which is used to convert the volume pulse after the A/D conversion in the CPU The waveform data is uploaded to the PC in real time through the USB cable, or receives instructions from the PC, and the data sending and receiving process is controlled by the CPU; the PC supplies power to the system through the USB interface.

Described CPU central processing unit is the 51 series single-chip microcomputers of Siliconlabs Company, and it has integrated 10 A/D converters and USB controller etc.; Control other each circuit work by the input and output signals of its each port.

The signal filtering circuit is composed of a high-pass filter and a first-order low-pass filter. A high-pass filter consists of an RC circuit, and a first-order low-pass filter consists of an operational amplifier and an RC feedback network.

The signal amplifying circuit includes a preamplifier and a secondary amplifier. The preamplifier consists of an instrumentation amplifier and peripheral resistors, and the secondary amplifier consists of an operational amplifier and feedback resistors.

The pulse power supply circuit is composed of a multivibrator composed of a 555 timer and peripheral circuits and a triode. The pulse width is adjusted by the resistance of resistors RA and RB, and IRED+ is the output pulse voltage.

The power supply switch control circuit is composed of a PNP transistor and its external resistor. The base of the transistor is connected to the P0.0 port of the CPU through the resistor Rk-1 to control the conduction of the transistor.

The USB universal serial bus interface circuit is composed of CPU, USB interface and filter capacitor. Five filter capacitors with different capacities are used to shield various high-frequency interferences of the USB interface. The four wires of the USB universal serial bus interface are respectively connected to VBUS, D+, D- and GND of the CPU. VBUS is +5V voltage input, D+ and D- are positive and negative signal inputs, and GND is the ground wire. The data in the CPU can be transmitted to the PC through the USB universal serial bus, and the PC also sends instructions to the CPU through the USB interface.

The numerically controlled gain circuit is composed of a numerically controlled potentiometer and an operational amplifier connected to the CPU, and the I/O ports of the CPU are respectively connected to each control terminal of the numerically controlled potentiometer, including chip selection, sending pulses, and amplitude change direction control. The potentiometer and operational amplifier form the feedback circuit. The final output of the signal is connected to the analog signal input port of the CPU through a diode, and the A/D conversion is performed inside the CPU.

The whole system of the utility model utilizes the USB universal serial bus interface to supply power, and supplies power to each amplifier after being stepped down by a voltage conversion circuit. The CPU controls the opening and closing of the photoelectric sensor pulse power supply circuit. When it is turned on, the electrical signal will pass through a high-pass filter, a preamplifier circuit, a low-pass filter and a digitally controlled gain adjustment circuit, and after baseline adjustment, it will be sent to the 10-bit A/D converter in the CPU. The PC sends instructions to the CPU through the universal serial bus interface, turns on the pulse power supply circuit and controls the change of the resistance value of the numerical control gain resistor. The collected data is uploaded to the PC in real time through the USB universal serial bus interface.

The utility model is characterized in that:

The utility model selects a high-integration CPU, which integrates an A/D converter and a USB controller, thereby reducing some cumbersome external circuits, making the entire signal collector realize a miniaturized design and being easy to carry.

The opening and closing of the sensor can be controlled on the PC side, the sensor is turned on when detecting, and it is turned off when not detecting, which can protect the sensor and reduce power consumption. At the same time, the amplitude of the collected signal can also be adjusted by sending instructions from the PC, so as to adapt to the characteristics of large gaps in the signal amplitude of different groups of people.

In view of the shortcomings of the RS232 standard serial communication interface used by some existing signal collectors at present with low transmission rate, no support for plug and play, and no support for hot swap, the utility model uses a USB universal serial bus interface to communicate with a PC . This interface has the characteristics of fast, plug and play, and supports hot plugging, so that the connection between the collector and the computer is more efficient, convenient, and easy to operate. At the same time, the utility model can transmit the collected signal to the PC in real time, so that the detection and analysis of the cardiovascular function is more rapid and convenient.

Description of drawings

The schematic block diagram of Fig. 1 utility model;

Fig. 2 is the schematic circuit diagram of the utility model;

Detailed ways

The utility model is described further in conjunction with Fig. 1, Fig. 2:

A volume pulse wave signal collector based on a USB interface, composed of a photoelectric sensor, a CPU central processing unit, a signal filter circuit, a signal amplification circuit, a numerical control gain circuit, a pulse power supply circuit, a power supply switch control circuit, and a USB universal serial bus interface circuit, power conversion circuit, baseline adjustment circuit, JTAG interface circuit.

The CPU central processing unit U4 is the 51 series single-chip microcomputer of Siliconlabs Company, the model is C8051F320. It integrates 10-bit A/D converter, USB controller, and supports online debugging. The VDD port of the CPU is the output of its internal regulator that converts +5V voltage to +3.3V, which can provide voltage for external circuits. The light-emitting diode is connected with the protection resistor R4-3, and when the light is on, it indicates that the USB universal serial bus interface circuit has been connected.

The pulse power supply switch control circuit is composed of Q1 connected with CPU. Pin 4 of the photoelectric sensor interface J1 is the power supply port of the photoelectric sensor, which is connected to the collector of Q1 with Rin; Q1 is a PNP transistor with a model number of 9015. The base of Q1 is connected to the P0.0 pin of the CPU through the protection resistor Rk-1, and the voltage of this port is controlled by the CPU, thereby controlling the conduction and disconnection of the triode. When it is turned on, it supplies power to the photoelectric sensor, and when it is turned off, it stops supplying power.

The pulse power supply circuit consists of a UR model 555 timer, external resistors, capacitors, and diodes to form a multivibrator circuit. The duty ratio of the pulse voltage is controlled by the resistance of RA and RB, and the Q pin of UR is the output of the pulse voltage. The Q foot is connected to the base of Q2 through the protection resistor RIRI; Q2 is an NPN transistor with a model number of 9013. The Q pin voltage output of UR controls the conduction and closure of Q2. When it is turned on, the IRED+ output is VDD (+3.3V), and when it is turned off, the IRED+ output is 0V.

The volumetric pulse wave electrical signal is input from pins 1 and 3 of the interface J1. After passing through the high-pass filter circuits of C1-1, R1-1 and C1-2, R1-2 respectively, it is input to the preamplifier U1 of the system, and the model of U1 is the instrumentation amplifier AD620 of ADI Company. Rg is the feedback resistor, which is connected between pin 1 and pin 8 of U1, and its resistance determines the preamplification factor. Pins 7 and 4 of U1 provide voltages of +5V and -5V for the chip respectively, and C1-3 and C1-4 are filter resistors, which are used to filter out high-frequency interference on the power line. The secondary amplifier circuit consists of U2A, R2-1, R1-3, and U2 is one of the operational amplifiers of model NE5532. The secondary magnification is the ratio of R2-1 to R1-3. The RC network formed by R2-1 and C2-1 forms a first-order low-pass filter with U2A. The pins 4 and 8 of the chip provide voltages of -5V and +5V respectively, and C2-2 and C2-3 are filter capacitors.

The signal is output from pin 1 of U2A, and then the magnification is adjusted through the digital control gain circuit. U3 is connected with U2B and CPU to form a numerical control gain circuit. U3 is a digitally controlled gain potentiometer, model X9C103; U2B is another operational amplifier model NE5532. The CS pin of U3 is connected with P0.1 of the CPU for chip selection. The INC pin is connected to the P1.2 pin of the CPU, and is used to send pulses to the chip, and the resistance adjustment will be triggered when the pulse arrives. The U/D pin is connected to P1.3 of the CPU to control the increase or decrease of the resistance value of the digital potentiometer. VL, VH, and VW are respectively connected to pin 6 and pin 7 of U2B to form a feedback network and form an amplification circuit, and its amplification factor is the ratio of the resistance value of X9C103 to R2-3. The potentiometer RBase and the resistors RBase1-1, RBase1-2 and U2B form a baseline adjustment circuit. By adjusting the resistance value of the potentiometer RBase, the reference voltage to U2B is adjusted so that the effective output signal is within the range allowed by the A/D converter. Inside. The signal output of pin 7 of U2B passes through the diode D2, and after filtering out the negative signal, it is connected to P1.4 of the CPU, and P1.4 is used as the analog signal input port of the A/D converter in the CPU.

USB universal serial bus interface circuit is composed of USB interface and CPU connection. J2 is a USB universal serial bus interface with 4 wires in total. Pin 4 is grounded, and pins 3 and 2 are respectively connected to D+ and D- of the CPU, which are the positive and negative input terminals of the signal. Pin 1 provides +5V voltage for the entire system, which is the VCC of the system, and is connected to the VBUS and REGIN of the CPU to make it supply power to the CPU. C4-4, C4-5, C4-6, C4-7, and C4-8 are connected to VBUS, and the other end is grounded. They are filter capacitors, which are used to filter out high-frequency noise interference on the power supply.

The voltage conversion circuit consists of U5 and its external resistors, capacitors, inductors and diodes. The model of U5 is MAX735, and the V+ pin provides +5V voltage, which is provided by the PC through the USB interface. The VOUT pin is the -5V output after voltage conversion, which supplies power for each amplifier of the system.

The external reset circuit of the CPU is composed of a RESET switch, a capacitor connected to the CPU. One end of the RESET switch is connected to the VDD of the CPU through the resistor R4-2, and the other end is grounded. When the switch is pressed, the system resets.

The JTAG interface circuit is composed of J4 connected with the CPU. Since the CPU has the function of online debugging, the JTAG interface can be set in the circuit, and the CPU program can be written and downloaded flexibly.

When the utility model detects, first insert the device into the USB interface of the PC, and at the same time, only need to put the index finger or middle finger of the human body into the photoelectric sensor; after the PC starts to collect, the volumetric pulse wave signal can be collected in real time, and the The data is uploaded to a PC for further analysis. The utility model has small volume (about 4.5cm*1.7cm), is similar in size to an ordinary U disk, is convenient to carry, simple to operate and strong in practicability.

Claims (4)

1. USB interface-based volume pulsation wave signal picker, comprise photoelectric sensor, cpu central processing unit, signal filter circuit, signal amplification circuit, numerical control gain circuit, pulse power supply circuit, power switch control circuit, USB USB circuit, PC; The pulse power supply circuit is used for providing pulse voltage for photoelectric sensor; PC sends to CPU by USB USB circuit with instruction, CPU control power switch control circuit, thus the control photoelectric sensor begins or quits work; The signal of telecommunication that is collected by photoelectric sensor at first carries out signal processing through signal filter circuit, signal amplification circuit; The numerical control gain circuit is connected to form by digital potentiometer, operational amplifier and CPU, is controlled the increase or the minimizing of its amplification by CPU; Signal exports CPU at last to, finishes the A/D conversion in the A/D converter of CPU, and digital signal is stored among the CPU; USB USB circuit is connected to form by USB interface and CPU, be used for the volume pulsation wave Wave data after the CPU A/D conversion is uploaded to PC in real time by USB cable, or from PC reception instruction, the transmission of its data and receiving course are controlled by CPU; PC is system's power supply by USB interface.

2. a kind of USB interface-based volume pulsation wave signal picker according to claim 1, it is characterized in that: cpu central processing unit is 51 series monolithics.

3. a kind of USB interface-based volume pulsation wave signal picker according to claim 1, it is characterized in that: multivibrator and audion that the pulse power supply circuit is made up of 555 intervalometers and peripheral circuit are formed.

4. a kind of USB interface-based volume pulsation wave signal picker according to claim 1, it is characterized in that: the power switch control circuit is made up of PNP audion and non-essential resistance thereof.

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