A dynamic electrocardiogram signal simulation generator

Abstract

The invention discloses a dynamic electrocardiogram signal simulation generator, which can output an electrocardiogram signal as low as 1uV-10uV according to its true voltage value, thereby ensuring the accuracy of dynamic electrocardiogram performance detection. The generator includes a touch display screen, a data update interface, a Flash memory, a processor, a digital-to-analog converter, a digital comparator, a signal amplitude adjustment circuit and a 3.5mm coaxial analog signal output interface; the processor is connected to the touch display screen for user operation; the processor is connected to the Flash memory for storing electrocardiogram signals; the processor is connected to the digital-to-analog converter for converting the electrocardiogram signal from a digital quantity to an analog quantity; the processor is connected to the digital comparator; the data comparator determines whether the electrocardiogram signal to be output is less than a set threshold value, and then outputs the comparison result to the signal amplitude adjustment circuit; the digital-to-analog converter is electrically connected to the 3.5mm coaxial analog signal output interface through the signal amplitude adjustment circuit.

Description

Technical Field

[0001] The invention relates to an analog signal generator, in particular to a dynamic electrocardiogram signal analog generator. Background Art

[0002] With the development of economy and the improvement of people's living standards, the incidence of heart disease and the number of people who died suddenly due to heart disease have increased rapidly in recent years. The inspection and early diagnosis equipment for heart disease have shown explosive growth. Among them, the dynamic electrocardiogram, which has the most diagnostic value for heart disease, is the most representative. The dynamic electrocardiogram is different from conventional electrocardiograms and electrocardiogram monitors and other conventional electrocardiogram examination methods. It is a medical device that can record and analyze the patient's electrocardiogram signals and all abnormal waves in daily life, work and activities for 24, 48 or 72 hours. Because it can continuously record long-term dynamic electrocardiogram signals, it makes up for the deficiency of conventional electrocardiograms that can only make short-term static records. Therefore, it can capture myocardial ischemia, myocardial infarction, various occasional, short-term arrhythmias, sudden death, different types of ectopic rhythms or conduction blocks, occasional premature beats, occasional panic, chest tightness, chest pain, dizziness or syncope, and other suspected heart diseases that are difficult to detect with conventional electrocardiograms, greatly improving the detection rate of arrhythmias.

[0003] The main components of dynamic electrocardiogram (hereinafter referred to as HOLTER) products include a collection and recording box and analysis software. The collection and recording box records the patient's electrocardiogram and saves the continuously collected electrocardiogram data as an ECG file, and the analysis software analyzes the ECG file saved by the recording box. The national inspection standard requires manufacturers of dynamic electrocardiogram products to analyze a total of 175 special patient electrocardiogram records from the AHA, MIT, NST and CU standard databases, and compare the analysis results with the standard results given by the database, so as to verify whether the dynamic electrocardiogram products produced by the manufacturer meet the requirements.

[0004] The existing method is to use an ECG signal simulation generator to store 175 record files in four databases and send the record files one by one to the dynamic electrocardiogram for testing, so as to verify whether the dynamic electrocardiogram meets the requirements. However, when the ECG signals stored in the existing ECG signal simulation generator are converted into analog quantities, the weaker signals cannot be output according to their true voltage values ​​(for most ECG signal simulation generators, the analog converter cannot effectively convert signals with voltage values ​​less than 10uV), resulting in output signal distortion, which will affect the accuracy of dynamic electrocardiogram performance testing. Summary of the invention

[0005] In order to solve the problem in the prior art that the ECG signal simulation generator will produce distortion when outputting weak signals, thereby affecting the accuracy of dynamic electrocardiogram performance detection, the present invention proposes a dynamic electrocardiogram signal simulation generator, which can output ECG signals as low as 1uV-10uV according to their true voltage values, thereby ensuring the accuracy of dynamic electrocardiogram performance detection.

[0006] The specific technical solution of the present invention is:

[0007] The present invention provides a dynamic electrocardiogram signal simulation generator, comprising a touch display screen, a Flash memory, a processor, a digital-to-analog converter, a digital comparator, a signal amplitude adjustment circuit and a 3.5mm coaxial analog signal output interface;

[0008] The processor uses the STM32F103RX single-chip microcomputer chip; the Flash memory uses the internal storage space of the STM32F103RX single-chip microcomputer chip; the digital comparator uses the SN74ASA885U6 chip; the digital-to-analog converter uses the DAC1220 chip; the signal amplitude adjustment circuit includes the MCP4012 chip and resistors;

[0009] The STM32F103RX microcontroller chip is connected to the touch screen through the UART pin;

[0010] The SPI pin is electrically connected to the CS pin, SCLK pin and SDIO terminal of the DAC1220 chip;

[0011] Connect the DAT[0:7] pins to the DAT[0:7] pins of the SN74ASA885U6 chip;

[0012] The CS1 and UD pins are electrically connected to the CS1 and UD pins of the MCP4012 chip respectively;

[0013] The ADJ_EN pin of the SN74ASA885U6 chip is connected to the CS1 pin of the MCP4012 chip;

[0014] The VOUT pin of the DAC1220 chip is connected to the resistor end of the MCP4012 chip and the 3.5mm coaxial analog signal output cable through resistors.

[0015] Furthermore, in order to make the threshold range adjustable as needed, the digital comparator further comprises a threshold data setting circuit connected to the threshold signal pin REF; the threshold data setting circuit generates one bit of binary digital quantity data through the dip switch on each bit.

[0016] Furthermore, in order to update the data, the dynamic electrocardiogram signal simulation generator also includes a data update interface.

[0017] Furthermore, the above data update interface is an RS232 interface or a USB interface or an SD card interface or a network interface.

[0018] Furthermore, the DAC1220 chip has a 20-bit resolution, the digital power DVDD and analog power AVDD of the DAC1220 chip use a 5V voltage, the reference voltage VREF is 2.5V; the maximum output voltage is 5V, and the minimum output voltage is 5V / 2 20 .

[0019] Furthermore, the power supply voltage used by the above touch display screen is 5V, and the data interface is UART, wherein TX represents data sent by the processor to the touch display screen, and RX represents data sent by the touch display screen to the processor.

[0020] Furthermore, the voltages of the digital power supply VDD and the analog power supply VDDA of the above-mentioned STM32F103RX single-chip microcomputer chip are both 3.3V.

[0021] The beneficial effects of the present invention are:

[0022] The ECG signal simulation generator constructed by the present invention through a touch display screen, a Flash memory, a processor, a digital comparator, a digital-to-analog converter, a signal amplitude adjustment circuit and a 3.5mm coaxial analog signal output interface can output weak ECG signals of 1uV-10uV according to their true voltage values, thereby solving the problem of distortion when traditional ECG signal simulation generators output weak ECG signals and ensuring the accuracy of dynamic electrocardiogram performance detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the functional block diagram of the ECG simulation generator.

[0024] Figure 2 This is the circuit schematic diagram of the touch display screen.

[0025] Figure 3 A circuit diagram of the processor.

[0026] Figure 4 This is the circuit diagram of the digital-to-analog converter.

[0027] Figure 5 The circuit diagram of the digital comparator.

[0028] Figure 6 This is the circuit diagram of the signal amplitude adjustment circuit.

[0029] The reference numerals are as follows:

[0030] 1-touch display screen, 2-data update interface, 3-Flash memory, 4-processor, 5-digital-to-analog converter, 6-digital comparator, 7-signal amplitude adjustment circuit, 8-3.5mm coaxial analog signal output interface. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

[0032] The present invention provides a dynamic electrocardiogram simulation generator, the basic framework principle of which is as follows: Figure 1 As shown, it includes a touch display screen 1, a data update interface 2, a Flash memory 3, a processor 4, a digital-to-analog converter 5, a digital comparator 6, a signal amplitude adjustment circuit 7 and a 3.5mm coaxial analog signal output interface 8;

[0033] The processor 4 is connected to the touch screen 1, and the touch screen 1 is used for the user to issue operation instructions;

[0034] The processor 4 is connected to the Flash memory 3, and the Flash memory 3 is used to store the ECG signals of the standard ECG database and the ECG signals uploaded by the user;

[0035] The processor 4 is connected to the digital-to-analog converter 5, and the digital-to-analog converter 5 is used to convert the ECG signal from a digital quantity to an analog quantity;

[0036] The processor 4 is connected to the digital comparator 6; the data comparator 6 determines whether the ECG signal to be output is less than a set threshold value (the set threshold value is the minimum digital quantity that can be converted by the digital-to-analog converter), and then outputs the comparison result to the signal amplitude adjustment circuit;

[0037] The digital-to-analog converter 5 is electrically connected to the 3.5 mm coaxial analog signal output interface 8 via the signal amplitude adjustment circuit 7, and is used to output all ECG signals in real voltage values.

[0038] The following is a specific example of a dynamic ECG simulation generator, which introduces the generator in more detail with each circuit.

[0039] The specific circuit of the touch display screen 1 is shown in the attached Figure 2 As shown. The circuit power supply voltage is 5V, and the data interface is UART, wherein TX represents the data sent by the processor 4 to the touch screen, and RX represents the data sent by the touch screen to the processor 4. Under the control of the processor 4, the circuit sends the content to be displayed to the touch screen via TX, and the touch screen sends the user's touch position signal to the processor (3) via RX, thus completing the entire input-output interactive operation.

[0040] The data update interface 2 is used for the user to update the internal ECG data, and the data update interface can be an RS232 interface, a USB interface, an SD card interface, or a network interface. In this embodiment, a USB interface is used.

[0041] The specific circuit of processor 4 is shown in the attached Figure 3 As shown. The STM32F103RX microcontroller is used as the core processor, the digital power supply VDD is powered by 3.3V, and the analog power supply VDDA is powered by 3.3V. Filter capacitors are designed for each pin of VDD and VDDA to ensure the power quality. This circuit design has data interfaces with other circuits, which are:

[0042] The PA pin is connected to the data update interface 2, and the signals are USB_DM and USB_DP;

[0043] UART interface connected to touch screen 1, signals are TX and RX;

[0044] SPI interface with digital-to-analog converter 5, signals are CS, SCLK, SDIO;

[0045] A parallel data interface DAT[0:7] connected to the digital comparator 6, the signal is DAT[0:7];

[0046] UD and CS interfaces connected to the signal amplitude adjustment circuit 7;

[0047] Flash memory 3 uses the internal storage space of STM32F103RX, so no additional design of external circuit is required. Of course, external memory can also be used as needed.

[0048] The specific circuit of the digital-to-analog converter 5 is shown in the attached Figure 4 As shown. The digital-to-analog converter 5 uses a DAC1220 chip; DVDD is the digital power supply of the circuit, using a 5V voltage; AVDD is the analog power supply of the circuit, using a 5V voltage; C1 and C4 are power supplies to filter out clutter; VREF is the reference voltage of the digital-to-analog converter, using a 2.5V reference voltage; X1 provides a clock for the circuit operation, using a 2.5MHz crystal oscillator; CS, SCLK, and SDIO together constitute a digital signal input interface responsible for communicating with the processor 4, CS is a chip select signal, which is valid at a low level and is output to this circuit by the processor 4, SCLK is a clock signal, which provides a clock reference for the digital communication interface and is output to this circuit by the processor 4, SDIO is a serial data signal, and the simulated ECG data that needs to be simulated output in this solution is forwarded by the processor 4 to the serial data signal and output to this circuit, and the data is converted into a signal of a corresponding voltage, and the analog ECG signal output pin is VOUT; the VOUT signal is connected to the signal amplitude adjustment circuit.

[0049] In this embodiment, the digital-to-analog converter adopted has a resolution of 20 bits, VREF is 2.5V, its minimum output voltage is 0V, and its maximum output voltage is 2*Vref, that is, 5V. Therefore, the minimum output voltage of this digital-to-analog converter is 5V / 2 20 That is, 4.8uV.

[0050] The digital comparator 6 uses the SN74ASA885U6 chip. This circuit can automatically identify the size of the data to be converted and output, compare it with the threshold value, and then output the comparison result. Specifically, as Figure 5 shown, the DAT[0:7] pins of the SN74ASA885 chip read the electrocardiogram data or user-defined electrocardiogram data in the standard database of the Flash memory 3 from the processor 4; the REF pin provides the threshold data for this circuit, which can be a value input by the user through the touch screen or a value directly set by a group of DIP switches; (of course, this threshold data can also be set in advance, and this threshold data is the smallest digital quantity signal that the digital-to-analog converter can convert) The comparison result outputs the signal ADJ_EN through the P<QOUT output signal, and this signal is connected to the amplitude adjustment circuit.

[0051] The working principle of this circuit is as follows: The two groups of input data of this circuit are the electrocardiogram data DAT to be converted and the set threshold data REF respectively. When DAT < REF, that is, when the amplitude of the electrocardiogram signal to be output currently is less than the minimum signal amplitude that the digital-to-analog converter can convert, the ADJ_EN signal activates the signal amplitude adjustment circuit to adjust the electrocardiogram data DAT signal that needs to be converted and is less than the threshold data REF. When DAT >= REF, the signal amplitude adjustment circuit does not perform adjustment and directly outputs the converted electrocardiogram signal. Specifically, in this example, setting REF to the corresponding value of 4.8uV, this circuit can automatically adjust the amplitude of the signal less than 4.8uV to ensure that the output signal is not distorted.

[0052] The specific circuit of the signal amplitude adjustment circuit 7 is as shown in the appendix Figure 6As shown, a digital potentiometer MCP4012 and a resistor R1 are used to implement it. The digital potentiometer MCP4012 changes the resistance between its resistor pin 5 and resistor pin 6 (denoted as Ru4) through the control of CS1 and UD receiving processor and digital comparator. SIG is the ECG signal output port, which is used to connect to the 3.5mm coaxial analog signal output interface, so as to output ECG signals to the outside. According to the principle of voltage divider circuit, the output signal SIG of this signal amplitude adjustment circuit is calculated to be Vout*Ru4 / (R1+Ru4). Users can change the output signal amplitude by changing Ru4 according to their needs. When the signal does not need to adjust the amplitude (when DAT is greater than REF), the ADJ_EN signal turns off its function through the CS pin of the digital potentiometer. At this time, the resistor contact between the resistor pin 5 and the resistor pin 6 is disconnected, and the resistance value of Ru4 is infinite. At this time, SIG=VOUT, that is, the signal is directly output without amplitude adjustment.

[0053] When the signal amplitude adjustment circuit R1 is selected as 40KΩ and Ru4 is set to 10KΩ, the output signal amplitude is 4.8 / 5uV=0.96uV.

[0054] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A dynamic electrocardiogram signal simulation generator, characterized in that: It includes a touch screen, a Flash memory, a processor, a digital-to-analog converter, a digital comparator, a signal amplitude adjustment circuit, and a 3.5mm coaxial analog signal output interface; The processor uses the STM32F103RX single-chip microcomputer chip; the Flash memory uses the internal storage space of the STM32F103RX single-chip microcomputer chip; the digital comparator uses the SN74ASA885U6 chip; the digital-to-analog converter uses the DAC1220 chip; the signal amplitude adjustment circuit includes the MCP4012 chip and resistors; The STM32F103RX microcontroller chip is connected to the touch screen through the UART pin; The SPI pin is electrically connected to the CS pin, SCLK pin and SDIO terminal of the DAC1220 chip; Connect the DAT[0:7] pins to the DAT[0:7] pins of the SN74ASA885U6 chip; The CS1 and UD pins are electrically connected to the CS1 and UD pins of the MCP4012 chip respectively; The ADJ_EN pin of the SN74ASA885U6 chip is connected to the CS1 pin of the MCP4012 chip; The VOUT pin of the DAC1220 chip is connected to the resistor end of the MCP4012 chip and the 3.5mm coaxial analog signal output cable through resistors; The voltages of the digital power supply VDD and the analog power supply VDDA of the STM32F103RX single-chip microcomputer chip are both 3.3V, and a filter capacitor is provided at each pin of the digital power supply VDD and the analog power supply VDDA.

2. The dynamic electrocardiogram signal simulation generator according to claim 1, characterized in that: The digital comparator also includes a threshold data setting circuit connected to its threshold signal pin REF; the threshold data setting circuit generates one bit of binary digital quantity data through the dip switch on each bit.

3. The dynamic electrocardiogram signal simulation generator according to claim 2, characterized in that: It also includes a data update interface for updating data.

4. The dynamic electrocardiogram signal simulation generator according to claim 3, characterized in that: The data update interface is RS232 interface, USB interface, SD card interface or network interface.

5. The dynamic electrocardiogram signal simulation generator according to any one of claims 1 to 4, characterized in that: The DAC1220 chip has a 20-bit resolution. The digital power supply DVDD and analog power supply AVDD of the DAC1220 chip use a 5V voltage, and the reference voltage VREF is 2.5V; the maximum output voltage is 5V, and the minimum output voltage is 5V / 2 20 .

6. The dynamic electrocardiogram signal simulation generator according to claim 5, characterized in that: The power supply voltage adopted by the touch display screen is 5V, and the data interface is UART, wherein TX represents the data sent by the processor to the touch display screen, and RX represents the data sent by the touch display screen to the processor.

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