Bracelet-type pulse sensor and bracelet-type heart rate measuring instrument

Abstract

The present invention discloses a bracelet-type heart rate measuring instrument, comprising a bracelet-type pulse sensor and a signal acquisition and processing circuit; the signal acquisition and processing circuit comprises a first voltage amplifying unit, a rectifier unit, a second voltage amplifying unit, a transistor switch unit, and a data processing and display unit; the output end of the bracelet-type pulse sensor is connected to the input end of the first voltage amplifying unit, the output end of the first voltage amplifying unit is connected to the input end of the rectifier unit, the output end of the rectifier unit is connected to the input end of the second voltage amplifying unit, the output end of the second voltage amplifying unit is connected to the input end of the transistor switch unit, and the output end of the transistor switch unit is connected to the input end of the data processing and display unit. The present invention can solve the problems of existing heart rate measuring instruments such as high cost, complex structure, difficulty in portability, and poor accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of heart rate measurement, and in particular relates to a bracelet-type pulse sensor and a bracelet-type heart rate measuring instrument. Background Art

[0002] Commonly used heart rate measuring instruments include hospital heart rate monitors, heart rate monitors, and traditional stethoscopes. Hospital heart rate monitors are comprehensive and highly accurate. However, they require specialized operator skills and are both expensive to purchase and operate. Heart rate monitors, such as heart rate monitors, use a light sensor that calculates heart rate based on changes in light caused by blood flowing through blood vessels. Therefore, their accuracy is significantly affected by environmental factors (such as temperature, humidity, and light), often resulting in higher-than-real-world readings. Traditional stethoscopes calculate heart rate by counting. This method is time-consuming and manually dependent, typically requiring more than half a minute of time. Chinese Utility Model Patent Publication No. CN208837931U discloses a portable heart rate monitor. While compact and low-cost, its pulse sensor uses a photoelectric reflective analog sensor, making its accuracy susceptible to environmental conditions such as temperature, humidity, and light. Therefore, it is necessary to develop a heart rate measurement device that is highly accurate, portable and low-cost. Summary of the Invention

[0003] The technical problem solved by the present invention is to provide a bracelet-type pulse sensor and a bracelet-type heart rate measuring instrument, thereby solving the problems of existing heart rate measuring instruments such as high cost, difficulty in portability and poor accuracy.

[0004] The technical solutions of the present invention are as follows:

[0005] The present invention discloses a bracelet-type pulse sensor, comprising an adhesive device, a first insulating material layer, a second insulating material layer, a first conductive material layer, a second conductive material layer, and a flexible piezoelectric film layer, wherein the lower surface of the first insulating material layer is bonded to the upper surface of the first conductive material layer, the lower surface of the first conductive material layer is bonded to the upper surface of the flexible piezoelectric film layer, the lower surface of the flexible piezoelectric film layer is bonded to the upper surface of the second conductive material layer, and the lower surface of the second conductive material layer is bonded to the upper surface of the second insulating material layer; a buckling device is provided at corresponding positions on the upper surface of the first insulating material layer and the lower surface of the second insulating material layer, so as to buckle the edge positions of the upper surface of the first insulating material layer and the lower surface of the second insulating material layer together, thereby wearing the bracelet-type pulse sensor on the wrist; drainage wires are respectively provided on the first conductive material layer and the second conductive material layer.

[0006] Furthermore, the first insulating material layer and the second insulating material layer are both made of elastic insulating material, and the first conductive material layer and the second conductive material layer are copper powder layers.

[0007] Furthermore, the flexible piezoelectric film layer is prepared by adding nano-carbon powder, nano-ZnO and tetraethoxysilane into PVDF powder and adopting an electrostatic spinning method.

[0008] Furthermore, the method for preparing the flexible piezoelectric film specifically includes the following steps:

[0009] (1) Nano-carbon powder, nano-ZnO, and tetraethoxysilane were added simultaneously to a solution of dimethylformamide and acetone in a certain mass ratio and stirred at 60°C for 3 h to obtain a uniform black spinning solution;

[0010] (2) After cooling the above solution to room temperature, ultrasonically disperse it for more than 30 minutes, then add 3 to 5 drops of ammonia water and stir the reaction at 30°C for 5 to 6 hours until it is completely dissolved to obtain a spinning solution;

[0011] (3) The spinning solution was transferred to a syringe to start the electrospinning process. During this process, the solution feed rate was controlled at 1.5 mL / h, the metal electrode tip was 15 cm away from the grounded aluminum foil plate, and the applied electric field voltage was 15 kV;

[0012] (4) The collected nanofibers and aluminum foil were placed in an oven for drying and finally cooled to room temperature.

[0013] The present invention also discloses a bracelet-type heart rate measuring instrument, comprising a bracelet-type pulse sensor and a signal acquisition and processing circuit; the signal acquisition and processing circuit comprises a first voltage amplifying unit for amplifying the current generated by the bracelet-type pulse sensor, a rectifier unit, a second voltage amplifying unit for amplifying the direct current output by the rectifier unit, a transistor switch unit, and a data processing and display unit for calculating and displaying the heart rate based on the number of current pulses generated by the bracelet-type pulse sensor and the elapsed time, wherein the output end of the bracelet-type pulse sensor is connected to the input end of the first voltage amplifying unit, the output end of the first voltage amplifying unit is connected to the input end of the rectifier unit, the output end of the rectifier unit is connected to the input end of the second voltage amplifying unit, the output end of the second voltage amplifying unit is connected to the input end of the transistor switch unit, and the output end of the transistor switch unit is connected to the input end of the data processing and display unit.

[0014] Furthermore, the first voltage amplification unit includes a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor, wherein the first end of the first resistor is connected to the first end of the second resistor, the second end of the first resistor is connected to the inverting input terminal of the first operational amplifier, the non-inverting input terminal of the first operational amplifier is grounded, and the second end of the second resistor is connected to the output terminal of the first operational amplifier; the first end of the third resistor is connected to the first end of the fourth resistor, the second end of the third resistor is connected to the inverting input terminal of the second operational amplifier, the non-inverting input terminal of the second operational amplifier is grounded, and the second end of the fourth resistor is connected to the output terminal of the second operational amplifier; the power supply terminals of the first operational amplifier and the second operational amplifier are both connected to a DC voltage source, the output terminal of the first operational amplifier and the output terminal of the second operational amplifier are two output terminals of the first voltage amplification unit, and the first end of the first resistor is connected to the output terminal of the first operational amplifier. One end and the first end of the third resistor are two input ends of the first voltage amplifying unit; the second voltage amplifying unit includes a third operational amplifier, a fourth operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor, wherein the first end of the fifth resistor is connected to the first end of the sixth resistor, the second end of the fifth resistor is connected to the inverting input end of the third operational amplifier, the output end of the third operational amplifier is respectively connected to the second end of the sixth resistor, the first end of the seventh resistor and the first end of the eighth resistor, the second end of the seventh resistor is connected to the inverting input end of the fourth operational amplifier, the output end of the fourth operational amplifier is connected to the second end of the eighth resistor, the non-inverting input ends of the third operational amplifier and the fourth operational amplifier are both grounded, and the power supply ends are both connected to a DC voltage source; the first end of the fifth resistor is the input end of the second voltage amplifying unit, and the output end of the fourth operational amplifier is the output end of the second voltage amplifying unit.

[0015] Furthermore, the transistor switch unit includes a transistor, a ninth resistor, a first capacitor and a second capacitor, wherein the first capacitor is a polarized capacitor and the second capacitor is a non-polarized capacitor, the base of the transistor is respectively connected to the first end of the first capacitor and the first end of the second capacitor, the collector of the transistor is connected to the first end of the ninth resistor, the second end of the ninth resistor is connected to a DC voltage source, the second end of the first capacitor, the second end of the second capacitor and the emitter of the transistor are all grounded, the base of the transistor is the input end of the transistor switch unit, and the second end of the ninth resistor is the output end of the transistor switch unit.

[0016] Furthermore, the data processing and display unit includes a first button switch, a second button switch, a single-chip microcomputer, a clock chip, a crystal oscillator and a character liquid crystal display, wherein the first end of the first button switch, the first end of the second button switch, the reset end of the clock chip, the clock input end of the clock chip, the I / O port of the clock chip and the input end of the display are all connected to the I / O port of the single-chip microcomputer; the second end of the first button switch, the second end of the second button switch and the ground end of the display are all grounded, the power end of the clock chip is connected to a DC voltage source, the two oscillation source interfaces of the clock chip are respectively connected to the two ends of the crystal oscillator, and the power end of the display is connected to the DC voltage source.

[0017] Furthermore, the single chip microcomputer model is AT89C51, the character liquid crystal display model is LCD1602, the first operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier model are LM324; the rectifier circuit adopts a diode bridge rectifier circuit.

[0018] The beneficial effects of the present invention are:

[0019] The pulse sensor is made into a bracelet type and provided with a buckling device, making it easy to carry. Due to the provision of a drainage wire, a first conductive material layer, a second conductive material layer, and a flexible piezoelectric film layer, when the pulse beats, the flexible piezoelectric film layer generates a weak current and draws the current out through the conductive material layer and the drainage wire.

[0020] By adding nano-carbon powder, nano-ZnO and tetraethoxysilane to PVDF powder and using electrospinning technology to prepare a flexible piezoelectric film layer, the elasticity, flexibility, toughness and piezoelectric properties of the flexible piezoelectric film layer are greatly enhanced.

[0021] The bracelet-type heart rate monitor disclosed in the present invention only includes a bracelet-type pulse sensor and a signal acquisition and processing circuit, and has a simple structure. Using the bracelet-type heart rate monitor disclosed in the present invention reduces the cost of the heart rate monitor and increases portability while ensuring the accuracy of heart rate measurement.

[0022] Since the microcontroller recognition voltage needs to reach above 3.3V, by setting up a transistor switch circuit, no matter how large the current generated by the bracelet pulse sensor is, it can be guaranteed that the microcontroller can recognize it, thereby greatly improving the accuracy of heart rate measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of a bracelet-type pulse sensor;

[0024] Figure 2 A circuit schematic diagram of a first voltage amplifying unit and a rectifying unit;

[0025] Figure 3 is a circuit schematic diagram of the second voltage amplifying unit;

[0026] Figure 4 This is the circuit schematic diagram of the triode switch circuit;

[0027] Figure 5 This is the circuit schematic diagram of the data processing and display unit. DETAILED DESCRIPTION

[0028] like Figure 1 As shown, the bracelet-type pulse sensor includes a fastening device, a first elastic insulating material layer 2, a second elastic insulating material layer 6, a first conductive material layer 3, a second conductive material layer 5, and a flexible piezoelectric film layer 4, wherein the lower surface of the first elastic insulating material layer 2 is bonded to the upper surface of the first conductive material layer 3, the lower surface of the first conductive material layer 3 is bonded to the upper surface of the flexible piezoelectric film layer 4, the lower surface of the flexible piezoelectric film layer 4 is bonded to the upper surface of the second conductive material layer 5, and the lower surface of the second conductive material layer 5 is bonded to the upper surface of the second elastic insulating material layer 6. A fastening device is provided at the edge of the upper surface of the first elastic insulating material layer 2 and the lower surface of the second elastic insulating material layer 6 to fasten the edge of the upper surface of the first elastic insulating material layer 2 and the lower surface of the second elastic insulating material layer together, thereby wearing the bracelet-type pulse sensor on the wrist; the first elastic insulating material layer 2 and the second elastic insulating material layer 6 can be made of fabric with good elasticity, and the fastening device can be made of Velcro, snap fasteners, or other devices that can perform a fastening function. The Velcro system includes bristles 1 and burrs 7. When using Velcro, the burrs 7 are sewn to the upper edge of the first elastic insulating material layer 2, and the bristles 1 are sewn to the lower edge of the second elastic insulating material layer 6. The first and second conductive material layers are copper powder layers, which are simply sprayed onto the upper and lower surfaces of the flexible piezoelectric film layer 4. Drainage points 9 are provided on each of the first and second conductive material layers 3 and 5, with one end of a drainage wire 8 connected to each of these points.

[0029] The flexible piezoelectric film layer is prepared by adding nano-carbon powder, nano-ZnO and tetraethoxysilane to PVDF powder using an electrospinning method. The preparation method of the flexible piezoelectric film specifically includes the following steps:

[0030] (1) Nano-carbon powder, nano-ZnO, and tetraethoxysilane were added simultaneously to a solution of dimethylformamide and acetone in a certain mass ratio and stirred at 60°C for 3 h to obtain a uniform black spinning solution;

[0031] (2) After cooling the above solution to room temperature, ultrasonically disperse it for more than 30 minutes, then add 3 to 5 drops of ammonia water and stir the reaction at 30°C for 5 to 6 hours until it is completely dissolved to obtain a spinning solution;

[0032] (3) The spinning solution was transferred to a syringe to start the electrospinning process. During this process, the solution feed rate was controlled at 1.5 mL / h, the metal electrode tip was 15 cm away from the grounded aluminum foil plate, and the applied electric field voltage was 15 kV;

[0033] (4) The collected nanofibers and aluminum foil were placed in an oven for drying and finally cooled to room temperature.

[0034] A bracelet-type heart rate meter includes a bracelet-type pulse sensor and a signal acquisition and processing circuit; the signal acquisition and processing circuit includes a first voltage amplifying unit for amplifying the current generated by the bracelet-type pulse sensor, a rectifier unit, a second voltage amplifying unit for amplifying the direct current output by the rectifier unit, a transistor switch unit, and a data processing and display unit for calculating and displaying the heart rate based on the number and duration of current pulses generated by the bracelet-type pulse sensor. The output end of the bracelet-type pulse sensor is connected to the input end of the first voltage amplifying unit, the output end of the first voltage amplifying unit is connected to the input end of the rectifier unit, the output end of the rectifier unit is connected to the input end of the second voltage amplifying unit, the output end of the second voltage amplifying unit is connected to the input end of the transistor switch unit, and the output end of the transistor switch unit is connected to the input end of the data processing and display unit.

[0035] like Figure 2As shown, the first voltage amplification unit includes a first operational amplifier OP1, a second operational amplifier OP2, a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4, wherein the first end of the first resistor R1 is connected to the first end of the second resistor R2, the second end of the first resistor R1 is connected to the inverting input terminal of the first operational amplifier OP1, the non-inverting input terminal of the first operational amplifier OP1 is grounded, and the second end of the second resistor R2 is connected to the output terminal of the first operational amplifier OP1; the first end of the third resistor R3 is connected to the first end of the fourth resistor R4, the second end of the third resistor R3 is connected to the inverting input terminal of the second operational amplifier OP2, the non-inverting input terminal of the second operational amplifier OP2 is grounded, and the second end of the fourth resistor R4 is connected to the output terminal of the second operational amplifier OP2; the power supply terminals of the first operational amplifier OP1 and the second operational amplifier OP2 are both connected to a 5V DC voltage source, and the first operational amplifier OP1 is connected to the first end of the fourth resistor R3. The output of amplifier OP1 and the output of the second operational amplifier OP2 serve as the two output terminals of the first voltage amplification unit. The first end of the first resistor R1 and the first end of the third resistor R3 serve as the two input terminals of the first voltage amplification unit, respectively connected to the output terminals of the two current-drawing wires of the bracelet-type pulse sensor. The rectifier circuit employs a diode bridge rectifier circuit, comprising a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The anode of the first diode D1 is connected to the ground wire and the anode of the third diode D3, respectively. The cathode of the first diode D1 is connected to the output of the first operational amplifier OP1 and the anode of the second diode D2, respectively. The cathode of the second diode D2 is connected to the cathode of the fourth diode D4, and the cathode of the third diode D3 is connected to the output of the second operational amplifier OP2 and the anode of the fourth diode D4, respectively. The cathode of the second diode D2 serves as the output terminal of the rectifier circuit. The amplification factor of the first and second operational amplifiers OP1 and OP2 is 100 times, and both utilize LM324 operational amplifiers.

[0036] like Figure 3As shown, the second voltage amplification unit includes a third operational amplifier OP3, a fourth operational amplifier OP4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7 and an eighth resistor R8, wherein the first end of the fifth resistor R5 is connected to the first end of the sixth resistor R6, the second end of the fifth resistor R5 is connected to the inverting input end of the third operational amplifier OP3, the output end of the third operational amplifier OP3 is respectively connected to the second end of the sixth resistor R6, the first end of the seventh resistor R7 and the first end of the eighth resistor R8, the second end of the seventh resistor R7 is connected to the inverting input end of the fourth operational amplifier OP4, the output end of the fourth operational amplifier OP4 is connected to the second end of the eighth resistor R8, the non-inverting input ends of the third operational amplifier OP3 and the fourth operational amplifier OP4 are both grounded, and the power supply ends are both connected to a 5V DC voltage source; the first end of the fifth resistor R5 is the input end of the second voltage amplification unit, connecting the input end of the second voltage amplification unit to the output end of the rectifier unit, and the output end of the fourth operational amplifier OP4 is the output end of the second voltage amplification unit. The third operational amplifier OP3 and the fourth operational amplifier OP4 both adopt an operational amplifier of model LM324, with an amplification factor of 10,000 times.

[0037] like Figure 4 As shown, the transistor switch unit includes a transistor BJT1, a ninth resistor R9, a first capacitor C1, and a second capacitor C2. The first capacitor C1 is a polarized capacitor, and the second capacitor C2 is a non-polarized capacitor. The base of the transistor BJT1 is connected to the first end of the first capacitor C1 and the first end of the second capacitor C2, respectively. The collector of the transistor BJT1 is connected to the first end of the ninth resistor R9. The second end of the ninth resistor R9 is connected to a 5V DC voltage source. The second end of the first capacitor C1, the second end of the second capacitor C2, and the emitter of the transistor BJT1 are all grounded. The base of the transistor BJT1 serves as the input of the transistor switch unit and is connected to the output of the second voltage amplification unit. The second end of the ninth resistor R9 serves as the output E of the transistor switch unit. The first capacitor C1 is used to filter high-frequency current, and the second capacitor C2 is used to filter low-frequency current, thereby ensuring more stable operation of the bracelet-type heart rate monitor. Because transistor BJT1 is provided, the output terminal E of the transistor switch unit is connected to a 5V DC voltage source and an I / O port of the microcontroller, respectively. When the bracelet-type pulse sensor generates current, the current passes through the first voltage amplification unit, the rectifier unit, and the second voltage amplification unit, becoming a pulse current greater than 1V. This current acts on the base of transistor BJT1, causing the collector and emitter of transistor BJT1 to momentarily saturate and conduct, and the 5V DC voltage source to be instantly grounded. Transistor BJT1 can be an NPN transistor with a conduction voltage of 1V.

[0038] like Figure 5As shown, the data processing and display unit includes a first push button switch 13, a second push button switch 14, a single-chip microcomputer 10, a clock chip 17, a crystal oscillator 18, and a character liquid crystal display 12. The first end of the first push button switch 13, the first end of the second push button switch 14, the reset terminal RST of the clock chip 17, the clock input terminal SCLK of the clock chip, the I / O port of the clock chip, and the input terminal of the display 12 are all connected to the I / O port of the single-chip microcomputer 10. The second end of the first push button switch 13, the second end of the second push button switch 14, and the ground terminal of the display are all grounded. The power supply terminal VCC2 of the clock chip is connected to a 5V DC voltage source, and the two oscillation source interfaces X1 and X2 of the clock chip are respectively connected to the two ends of the crystal oscillator 18. The power supply terminal of the character liquid crystal display is connected to a 5V DC voltage source. The crystal oscillator frequency of the crystal oscillator 18 is 32768 Hz. The single-chip microcomputer 10 can be an AT89C51 single-chip microcomputer. The model of the character type liquid crystal display is LCD1602, and the model of the clock chip 17 is ds1302. By arranging the clock chip 17 and the crystal oscillator 18, the time can be displayed on the character type liquid crystal display 12.

[0039] The signal acquisition and processing circuit can be integrated on a circuit board and encapsulated inside a shell. The character liquid crystal display screen is set on the outer surface of the shell. The entire shell is fixed on the bracelet-type pulse sensor, making the bracelet-type heart rate monitor easy to carry.

[0040] Set the microcontroller's internal timer to interrupt every T seconds. Error is minimized when T is an even number of seconds. Considering the actual heart rate, set T to 8 seconds. The initial count value, N, is 0. Each time a pulse is detected, N is incremented by 1. When the interrupt occurs after T seconds, multiply the count value, N, by 7.5 to obtain the heart rate per minute.

[0041] The operating principle of the bracelet-type heart rate monitor is as follows: First, the beating of the pulse causes the bracelet pulse sensor, which is placed against the pulse site, to deform. This in turn generates equal, oppositely shaped weak pulse voltages on both sides of the flexible piezoelectric film. This weak voltage is then directed via a lead wire to a first voltage amplification unit, where it is amplified 100 times and fed into the input of a rectifier circuit for rectification. This combined, equal, oppositely shaped weak pulse voltages are then combined into a positive voltage. This positive voltage is then further amplified by a second voltage amplification unit, reaching a voltage exceeding 1V, exceeding the transistor's turn-on voltage. This voltage acts on the transistor's base, causing it to conduct instantaneously. The 5V DC voltage source output is grounded, temporarily interrupting the current flowing into the microcontroller (MCU), and the internal counter of the MCU increments by one. After T seconds, the MCU's internal timer is interrupted, and the count value N is multiplied by 7.5 to obtain the heart rate per minute, which is then displayed on the character LCD.

Claims

1. A bracelet-type pulse sensor, characterized in that: The bracelet-type pulse sensor comprises a fastening device, a first insulating material layer, a second insulating material layer, a first conductive material layer, a second conductive material layer and a flexible piezoelectric film layer, wherein the lower surface of the first insulating material layer is bonded to the upper surface of the first conductive material layer, the lower surface of the first conductive material layer is bonded to the upper surface of the flexible piezoelectric film layer, the lower surface of the flexible piezoelectric film layer is bonded to the upper surface of the second conductive material layer, and the lower surface of the second conductive material layer is bonded to the upper surface of the second insulating material layer. A fastening device is provided at corresponding positions on the upper surface of the first insulating material layer and the lower surface of the second insulating material layer so as to fasten the edge positions of the upper surface of the first elastic material layer and the lower surface of the second elastic material layer together, thereby wearing the bracelet-type pulse sensor on the wrist; drainage wires are respectively provided on the first conductive material layer and the second conductive material layer; the flexible piezoelectric film layer is prepared by adding nano-carbon powder, nano-ZnO and tetraethoxysilane to PVDF powder using an electrospinning method; the preparation method of the flexible piezoelectric film specifically comprises the following steps: (1) Nano-carbon powder, nano-ZnO, and tetraethoxysilane were added simultaneously to a solution of dimethylformamide and acetone in a certain mass ratio and stirred at 60°C for 3 h to obtain a uniform black spinning solution; (2) After cooling the above solution to room temperature, ultrasonically disperse it for more than 30 minutes, then add 3 to 5 drops of ammonia water and stir the reaction at 30°C for 5 to 6 hours until it is completely dissolved to obtain a spinning solution; (3) The spinning solution was transferred to a syringe to start the electrospinning process. During this process, the solution feed rate was controlled at 1.5 mL / h, the metal electrode tip was 15 cm away from the grounded aluminum foil plate, and the applied electric field voltage was 15 kV; (4) The collected nanofibers and aluminum foil were placed in an oven for drying and finally cooled to room temperature.

2. The bracelet-type pulse sensor according to claim 1, wherein: The insulating materials of the first insulating material layer and the second insulating material layer are both elastic insulating materials, and the first conductive material layer and the second conductive material layer are copper powder layers.

3. A bracelet-type heart rate monitor, characterized in that: It comprises the bracelet-type pulse sensor and signal acquisition and processing circuit according to any one of claims 1-2; the signal acquisition and processing circuit comprises a first voltage amplifying unit for amplifying the current generated by the bracelet-type pulse sensor, a rectifier unit, a second voltage amplifying unit for amplifying the direct current output by the rectifier unit, a transistor switch unit, and a data processing and display unit for calculating and displaying the heart rate based on the number and time of current pulses generated by the bracelet-type pulse sensor, the output end of the bracelet-type pulse sensor is connected to the input end of the first voltage amplifying unit, the output end of the first voltage amplifying unit is connected to the input end of the rectifier unit, the output end of the rectifier unit is connected to the input end of the second voltage amplifying unit, the output end of the second voltage amplifying unit is connected to the input end of the transistor switch unit, and the output end of the transistor switch unit is connected to the input end of the data processing and display unit.

4. A bracelet-type heart rate monitor as claimed in claim 3, characterized in that: The first voltage amplification unit includes a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor, wherein the first end of the first resistor is connected to the first end of the second resistor, the second end of the first resistor is connected to the inverting input terminal of the first operational amplifier, the non-inverting input terminal of the first operational amplifier is grounded, and the second end of the second resistor is connected to the output terminal of the first operational amplifier; the first end of the third resistor is connected to the first end of the fourth resistor, the second end of the third resistor is connected to the inverting input terminal of the second operational amplifier, the non-inverting input terminal of the second operational amplifier is grounded, and the second end of the fourth resistor is connected to the output terminal of the second operational amplifier; the power supply terminals of the first operational amplifier and the second operational amplifier are both connected to a DC voltage source, the output terminal of the first operational amplifier and the output terminal of the second operational amplifier are the two output terminals of the first voltage amplification unit, and the first end of the first resistor and the first end of the third resistor are the two input terminals of the first voltage amplification unit; The second voltage amplification unit includes a third operational amplifier, a fourth operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor and an eighth resistor, wherein the first end of the fifth resistor is connected to the first end of the sixth resistor, the second end of the fifth resistor is connected to the inverting input terminal of the third operational amplifier, the output end of the third operational amplifier is respectively connected to the second end of the sixth resistor, the first end of the seventh resistor and the first end of the eighth resistor, the second end of the seventh resistor is connected to the inverting input terminal of the fourth operational amplifier, the output end of the fourth operational amplifier is connected to the second end of the eighth resistor, the non-inverting input terminals of the third operational amplifier and the fourth operational amplifier are both grounded, and the power supply terminals are both connected to a DC voltage source; the first end of the fifth resistor is the input terminal of the second voltage amplification unit, and the output end of the fourth operational amplifier is the output terminal of the second voltage amplification unit.

5. A bracelet-type heart rate monitor as claimed in claim 4, characterized in that: The triode switch unit includes a triode, a ninth resistor, a first capacitor, and a second capacitor, wherein the first capacitor is a polarized capacitor and the second capacitor is a non-polarized capacitor, the base of the triode is respectively connected to the first end of the first capacitor and the first end of the second capacitor, the collector of the triode is connected to the first end of the ninth resistor, the second end of the ninth resistor is connected to a DC voltage source, the second end of the first capacitor, the second end of the second capacitor, and the emitter of the triode are all grounded, the base of the triode is the input end of the triode switch unit, and the second end of the ninth resistor is the output end of the triode switch unit.

6. A bracelet-type heart rate monitor as claimed in claim 5, characterized in that: The data processing and display unit includes a first button switch, a second button switch, a single-chip microcomputer, a clock chip, a crystal oscillator and a character liquid crystal display, wherein the first end of the first button switch, the first end of the second button switch, the reset end of the clock chip, the clock input end of the clock chip, the I / O port of the clock chip and the input end of the display are all connected to the I / O port of the single-chip microcomputer; the second end of the first button switch, the second end of the second button switch and the ground end of the display are all grounded, the power end of the clock chip is connected to a DC voltage source, the two oscillation source interfaces of the clock chip are respectively connected to the two ends of the crystal oscillator, and the power end of the display is connected to the DC voltage source.

7. A bracelet-type heart rate monitor as claimed in claim 6, characterized in that: The single chip microcomputer model is AT89C51, the character liquid crystal display model is LCD1602, the first operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier model are LM324; the rectifier circuit adopts a diode bridge rectifier circuit.

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