Electrocardio analog signal acquisition circuit for teaching experiment
By designing an adjustable analog signal acquisition circuit, the problem of the fixed nature of traditional ECG signal acquisition circuits was solved, enabling flexible adjustment of analog circuit parameters and modular design. This enriched the experimental content, improved students' hands-on skills and experimental results, and bridged the gap between teaching and scientific research.
Patent Information
- Application Number
- CN202423304227.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2026-01-27
- Estimated Expiration
- 2034-12-31
AI Technical Summary
Traditional ECG signal acquisition and processing circuits are fixed designs that cannot meet the diverse needs of different signal characteristics and noise backgrounds. Students find it difficult to intuitively understand the function of analog circuits by adjusting parameters, and there is a lack of experimental diversity and flexibility, resulting in a disconnect between teaching content and scientific research practice.
An adjustable analog signal acquisition circuit was designed, including a multiplexer and a precision resistor and capacitor network, to achieve dynamic adjustment of filter frequency, gain and bias level. Combined with modular design, it covers functional modules such as low-pass filtering, band-pass filtering, level adjustment and signal amplification, and supports a variety of ECG signal processing experiments.
Students can gain a deeper understanding of analog circuit design and application by dynamically adjusting circuit parameters, improve the flexibility and diversity of experiments, meet the needs of complex experiments, cultivate hands-on skills and problem-solving abilities, and bridge the gap between teaching and scientific research practice.
Smart Images
Figure CN223842500U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of electrocardiogram (ECG) signal acquisition circuits, specifically relating to an ECG analog signal acquisition circuit for teaching experiments. Background Technology
[0002] Electrocardiogram (ECG) signal acquisition and processing is a fundamental research area in biomedical engineering and an important component of experimental teaching in related courses. Traditional ECG signal acquisition and processing circuits are mostly based on digital signal processing technology, neglecting the crucial role of analog circuits in the front-end acquisition and conditioning of ECG signals. However, analog circuit design is a core component of electronic information and biomedical engineering disciplines, and it is of great significance for students to master the principles and methods of signal processing.
[0003] In current teaching methods, students typically learn using circuit experiment boxes or virtual simulation platforms with fixed parameters. While this provides some experimental experience, it lacks the ability to deeply explore the process of adjusting core circuit parameters and optimizing performance. For example, in the front-end acquisition of ECG signals, different signal characteristics and noise backgrounds place different demands on the filter cutoff frequency, gain amplification parameters, and signal conditioning levels, which fixed circuit designs cannot meet. Students find it difficult to verify theoretical knowledge through practice, nor can they intuitively understand the role of analog circuits in ECG signal acquisition by manually adjusting circuit parameters.
[0004] The specific technical problems to be solved include:
[0005] 1) The problem of non-adjustable analog circuit parameters: Existing teaching circuits are usually designed with fixed parameters, making it impossible for students to intuitively understand the impact of different resistor and capacitor configurations on ECG signal processing by adjusting the parameters. This invention achieves dynamic adjustment of filter frequency, gain, and bias level through the configuration of multiplexers and precision resistor and capacitor networks, enabling students to verify theoretical formulas and understand the optimization process in actual circuit design;
[0006] 2) The disconnect between teaching content and scientific research practice: Traditional experiments tend to focus on basic circuit verification and lack exploration of the processing characteristics of real electrocardiogram signals. This circuit, through modular design, introduces signal conditioning techniques actually used in scientific research into experimental teaching, enabling students to learn key technologies in scientific research practice through experiments;
[0007] 3) Lack of experimental diversity and flexibility: Fixed experimental circuit designs often only perform a single function, making it difficult to meet the needs of complex experiments. This invention uses a multi-way switch to enable free switching of parameters and functional modules, supporting various ECG signal processing experiments and significantly improving experimental flexibility and diversity. Utility Model Content
[0008] Through the above innovative design, this utility model not only solves the limitations of traditional experimental circuit design, but also provides students with an adjustable and highly flexible ECG signal acquisition experimental platform, helping them to better master the design and application of analog circuits, and laying a solid foundation for future scientific research practice. The technical solution of this utility model is as follows: An ECG analog signal acquisition circuit for teaching experiments, comprising:
[0009] The instrument amplifier circuit includes a first-stage amplifier composed of operational amplifiers U121.1 and U121.2. The amplified signal is AC-coupled through capacitors C1001 and C1002 and transmitted to the next stage. It also includes a second-stage amplifier composed of U126 for further amplification of the signal.
[0010] The bandpass filter circuit includes an operational amplifier U123 and a RC combination formed by multiple capacitors and resistors, which is connected to the operational amplifier U123.
[0011] The low-pass filter circuit includes an operational amplifier U124 and multiple resistors and capacitors forming different RC combinations connected to the operational amplifier U124.
[0012] The level-up circuit, including a multiplexer U129 and different resistor combinations, adjusts the bias level of the input signal through a voltage divider network, raising the reference level of the preceding signal to a DC level range suitable for subsequent processing.
[0013] Based on the aforementioned technical features, operational amplifier U121, including U121.1 and U121.2, performs primary amplification of the signal. Through appropriate gain configuration, determined by external capacitor C1002 and the feedback network, it amplifies weak ECG signals. The core amplifier U126 uses the AD8421ARZ model, which features a high common-mode rejection ratio (CMRR) to effectively suppress common-mode interference introduced during electrode-circuit connection. Its gain is determined by external precision resistors (RG2~RG5). By introducing an adjustable gain network, students can adjust the gain according to experimental needs to observe the processing effect at different signal amplitudes.
[0014] As an improvement of this utility model, the instrument amplification circuit includes a protection circuit module. In the protection circuit module, the input terminals ECG+ and ECG- are connected to diodes E1 and E2 through the ESD protection of the chip PESD5V0S1BA.
[0015] Based on the above technical features, the circuit input terminals (ECG+ and ECG-) are protected by ESD protection diodes E1 and E2 (PESD5V0S1BA) to prevent damage to the circuit from electrostatic discharge. The input terminals also utilize 1 nF capacitors, such as capacitors C101 and C103, to filter high-frequency signals and effectively suppress high-frequency noise.
[0016] As an improvement of this utility model, the instrumentation amplifier circuit includes an input impedance matching module, in which the input signal is connected to the non-inverting input terminal of the operational amplifier through resistors R101 and R104 respectively.
[0017] Based on the above technical features, the input signal is connected to the non-inverting input terminal of the operational amplifier through high-precision resistors, such as R101 and R104, with a resistance of 4.99kΩ and an accuracy of 1%, to match the input impedance and ensure the accuracy of the acquired signal.
[0018] As an improvement of this utility model, the instrument amplification circuit includes a power supply decoupling and filtering module, which includes capacitors C113, C114, C115 and C116. Capacitors C113 and C114 are located between the power supply V+ and ground SGND, and capacitors C115 and C116 are located between the power supply V- and ground SGND.
[0019] Based on the above technical features, decoupling capacitors, such as capacitors C113, C114, C115, and C116, are connected to the power supply pins of the operational amplifier to ensure power supply stability and suppress power supply ripple interference to the signal.
[0020] As an improvement of this utility model, the instrumentation amplifier circuit includes a reference voltage module, which includes U123.2, resistor R1 and bypass capacitor C117.
[0021] Based on the aforementioned technical features, the reference voltage module U123.2 provides a stable reference voltage for the entire circuit to optimize the DC operating point of the instrumentation amplifier. The reference voltage is generated by precision resistors and bypass capacitor C117, ensuring a stable and drift-free output signal.
[0022] As an improvement of this utility model, the low-pass filter circuit includes an operational amplifier, multiple multiplexers, and a low-pass filter network formed by multiple resistors or capacitors. Different resistor-capacitor combinations can be selected by switching multiplexers.
[0023] Based on the aforementioned technical features, the low-pass filter circuit further processes the signal through a low-pass filter module and a gain adjustment module to ensure the smoothness and amplitude controllability of the ECG signal. This module is flexibly designed, including a multiplexer (RS8047H). By switching different RC component configurations, dynamic adjustment of frequency response and gain can be achieved. The low-pass filter module, through operational amplifiers and multiple multiplexers such as U117, U116, and U118, combined with high-precision resistors such as R511, R516, and R519 and capacitors such as C121, C1022, and C1026, implements the low-pass filtering function to suppress high-frequency noise. The filter is designed with a cutoff frequency of 72Hz (-3dB), suitable for the main frequency range of ECG signals. Through multiplexer switching, students can select different RC combinations, such as 410nF, 1uF, 2.2kΩ, and 12.2kΩ, to dynamically adjust the filter's cutoff frequency, gaining a deeper understanding of low-pass filter design and the impact of parameter changes on the signal.
[0024] As an improvement of this utility model, the low-pass filter circuit further includes a gain adjustment module, which includes a resistor network composed of U119 and multiple resistors, and the resistance value of the feedback resistor is adjusted by switching the multiplexer.
[0025] Based on the above technical features, gain adjustment is achieved through a combination of U119 (RS8047H multiplexer) and a resistor network, such as R122, R518, R519, and R520. Students can adjust the value of the feedback resistor by switching the multiplexer, thereby dynamically adjusting the gain of the operational amplifier U124.1 and intuitively experiencing the impact of gain adjustment on the output signal amplitude.
[0026] As an improvement of this utility model, it also includes an operational amplifier U124.2 for amplifying or buffering the signal after level boosting, and a feedback network formed by multiple resistors.
[0027] Based on the aforementioned technical features, the level-up and follow-up module is used to adjust the DC level of the preceding signal and achieve high-precision signal following, ensuring the stability and integrity of the signal output, suitable for subsequent signal processing and analysis. This module uses a multiplexer U129 (RS8047H) combined with high-precision resistors such as R522, R523, R524, and R132 to flexibly adjust the DC level of the input signal. Different resistor combinations, such as 2.49kΩ, 24.9kΩ, 49.9kΩ, and 249kΩ, adjust the bias level of the input signal through a voltage divider network, raising the reference level of the preceding signal to a DC level suitable for subsequent processing. Students can dynamically observe the effect of level adjustment by switching the multiplexer, understanding the practical significance of level-up in eliminating negative voltage or adjusting the operating point in analog signal processing. Operational amplifier U124.2 is used to amplify or buffer the level-up signal, working with feedback network resistors R133 and R134 to achieve high linearity and high-precision signal output.
[0028] As an improvement of this utility model, the level-up circuit further includes a voltage follower circuit, with U125.1 and U125.2 connected in sequence to form a two-stage voltage follower. The input terminal of U125.1 is connected to the output terminal of U124.2, and the output terminal of U125.2 is connected to the ECG-OUT node.
[0029] Based on the aforementioned technical features, U125.1 and U125.2 form a two-stage voltage follower to buffer and stabilize the signal, ensuring that the output signal can adapt to different load conditions: U125.1 receives the boosted signal and, through its low output impedance and high input impedance design, reduces amplitude attenuation and distortion during signal transmission. U125.2 provides strong drive capability, ultimately outputting the signal to the ECG-OUT node, ensuring the stability and reliability of the signal under different application scenarios.
[0030] Compared to existing technologies, the beneficial effects of this invention are as follows: This invention provides an analog circuit design with scientific research value and educational significance. By setting up an adjustable resistor and capacitor network, it achieves the acquisition and conditioning of analog electrocardiogram (ECG) signals. Through dynamic adjustment of circuit parameters, students can gain a deeper understanding of the principles and functions of modules such as low-pass filtering, band-pass filtering, level boosting, signal following, and gain adjustment during experiments. Furthermore, this circuit provides a wealth of experimental combinations, supporting experimental verification of different ECG signal characteristics, effectively improving students' hands-on skills and problem-solving abilities.
[0031] 1) This circuit uses a multiplexer to dynamically adjust the combination of resistors and capacitors, allowing students to easily change the filter's cutoff frequency, gain amplitude, and signal level. Students can observe the effect of parameter changes on ECG signal processing through experiments, thus gaining a more intuitive understanding of the actual function of each module in the analog circuit. This flexibility greatly enriches the content of teaching experiments and helps students explore the optimization process of analog circuit design in depth.
[0032] 2) This circuit adopts a modular design, encompassing functional modules such as low-pass filtering, band-pass filtering, level adjustment, signal amplification, and buffering. Each module operates independently yet collaboratively, facilitating individual student learning of the principles of each module while allowing for the completion of complex ECG signal processing experiments through module combinations. This modular design enhances the hierarchy and applicability of experimental teaching, providing a unified experimental platform for both basic and advanced experiments.
[0033] 3) The design of this circuit fully considers the real needs of ECG signal acquisition, covering practical issues such as signal noise suppression, signal gain adjustment, and signal integrity assurance. Through dynamic adjustment and experimental verification, students can master key technologies such as filtering, amplification, and bias adjustment used in scientific research practice, making up for the deficiency of the disconnect between theory and practice in traditional teaching experiments;
[0034] 4) Compared with traditional fixed-design experimental circuits, this invention allows for flexible parameter adjustment. Students can not only observe the static circuit performance but also understand the circuit response characteristics by adjusting dynamic parameters, thus cultivating their problem analysis and solving abilities. This improvement enhances the applicability and experimental effectiveness of the teaching circuit, better meeting diverse teaching needs. Attached Figure Description
[0035] Figure 1 This is a block diagram of the ECG analog signal acquisition circuit used in teaching experiments;
[0036] Figure 2 This is a connection diagram for the instrument amplifier circuit;
[0037] Figure 3 This is a connection diagram for a bandpass filter circuit;
[0038] Figure 4 This is a connection diagram for a low-pass filter circuit;
[0039] Figure 5 This is a connection diagram for a voltage boost circuit. Detailed Implementation
[0040] 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.
[0041] Example: The connection block diagram of the ECG analog signal acquisition circuit used in this teaching experiment is as follows. Figure 1 shown; specifically:
[0042] like Figure 2 As shown, the instrumentation amplifier circuit includes a first-stage amplifier composed of operational amplifiers U121.1 and U121.2. The amplified signal is AC-coupled through capacitors C1001 and C1002 and transmitted to the next stage. It also includes a second-stage amplifier composed of U126 for further amplification of the signal.
[0043] Operational amplifier U121, comprising U121.1 and U121.2, performs primary amplification of the signal. Through appropriate gain configuration, determined by external capacitor C1002 and the feedback network, it amplifies weak ECG signals. The core amplifier U126 uses the AD8421ARZ model, which features a high common-mode rejection ratio (CMRR) to effectively suppress common-mode interference introduced during electrode-circuit connection. Its gain is determined by external precision resistors (RG2~RG5). By introducing an adjustable gain network, students can adjust the gain according to experimental needs to observe the processing effect at different signal amplitudes.
[0044] Furthermore, the instrument amplification circuit includes a protection circuit module. In the protection circuit module, the input terminals ECG+ and ECG- are connected to diodes E1 and E2 via the ESD protection of the chip PESD5V0S1BA.
[0045] The circuit input terminals ECG+ and ECG- are protected by ESD protection diodes E1 and E2 (PESD5V0S1BA) to prevent damage from electrostatic discharge. The input terminals also utilize 1 nF capacitors, such as capacitors C101 and C103, to filter high-frequency signals and effectively suppress high-frequency noise.
[0046] Furthermore, the instrumentation amplifier circuit includes an input impedance matching module, in which the input signal is connected to the non-inverting input terminal of the operational amplifier through resistors R101 and R104, respectively.
[0047] The input signal is connected to the non-inverting input of the operational amplifier through high-precision resistors, such as R101 and R104, with a resistance of 4.99kΩ and an accuracy of 1%, to match the input impedance and ensure the accuracy of the acquired signal.
[0048] Furthermore, the instrument amplification circuit includes a power supply decoupling and filtering module, which includes capacitors C113, C114, C115, and C116. Capacitors C113 and C114 are located between the power supply V+ and ground SGND, while capacitors C115 and C116 are located between the power supply V- and ground SGND.
[0049] Connect decoupling capacitors, such as C113, C114, C115, and C116, to the op-amp power supply pins to ensure power supply stability and suppress power supply ripple interference with the signal.
[0050] Furthermore, the instrumentation amplifier circuit includes a reference voltage module, which includes U123.2, resistor R1, and bypass capacitor C117.
[0051] The reference voltage module U123.2 provides a stable reference voltage for the entire circuit to optimize the DC operating point of the instrumentation amplifier. The reference voltage is generated by precision resistors and bypass capacitor C117 to ensure a stable and drift-free output signal.
[0052] like Figure 3 As shown, the bandpass filter circuit includes an operational amplifier U123 and a RC combination formed by multiple capacitors and resistors, which is connected to the operational amplifier U123.
[0053] The bandpass filter circuit is used for further filtering, gain adjustment, and characteristic frequency band extraction of the ECG signal. This module includes multiple filtering units and a gain adjustment network, which further enhances the accuracy and adjustability of signal processing through flexible resistor and capacitor configurations.
[0054] The circuit composition and function include an RC high-pass filter section: the high-pass function of the filter consists of a capacitor and a precision resistor network. By adjusting the values of the capacitor and resistor, different cutoff frequencies can be set. The experimental circuit has multiple preset RC combinations for students to switch between and observe the attenuation effect of different cutoff frequencies on high-frequency signals.
[0055] Operational amplifier bandpass and amplification module: The filter circuit uses operational amplifier U123 to achieve signal isolation and amplification. U123 has high input impedance and low output impedance, effectively isolating the signal source and load, and preventing the filter's performance from being affected by load changes. The circuit's amplification factor is adjustable via resistors, and the filter parameters are adjustable via resistors and capacitors.
[0056] Adjustable RC network: The circuit design provides multiple RC switching options, such as the U111 and U113 modules and the RS8047H switching network. Students can select different filtering parameters by jumpers or toggle switches, intuitively observe the changes in filtering effect, and deepen their understanding of filter design principles.
[0057] like Figure 4 As shown, the low-pass filter circuit includes an operational amplifier U124 and multiple resistors and capacitors forming RC combinations, with the multiple resistors and capacitors forming different RC combinations connected to the operational amplifier U124.
[0058] The low-pass filter circuit includes an operational amplifier, multiple multiplexers, and a low-pass filter network formed by multiple resistors or capacitors. Different resistor-capacitor combinations can be selected by switching multiplexers.
[0059] The low-pass filter circuit further processes the signal through a low-pass filter module and a gain adjustment module, ensuring the smoothness and amplitude controllability of the ECG signal. This module is flexibly designed, including a multiplexer (RS8047H). By switching different RC component configurations, the frequency response and gain can be dynamically adjusted. The low-pass filter module, through operational amplifiers and multiple multiplexers such as U117, U116, and U118, combined with high-precision resistors such as R511, R516, and R519, and capacitors such as C121, C1022, and C1026, achieves low-pass filtering and suppresses high-frequency noise. The filter is designed with a cutoff frequency of 72Hz (-3dB), suitable for the main frequency range of ECG signals. Through multiplexer switching, students can select different RC combinations, such as 410nF, 1uF, 2.2kΩ, and 12.2kΩ, to dynamically adjust the filter's cutoff frequency, gaining a deeper understanding of low-pass filter design and the impact of parameter changes on the signal.
[0060] Furthermore, the low-pass filter circuit also includes a gain adjustment module, which includes a resistor network consisting of U119 and multiple resistors, and adjusts the resistance value of the feedback resistor by switching a multiplexer.
[0061] Gain adjustment is achieved through a combination of U119 (RS8047H multiplexer) and a resistor network, such as R122, R518, R519, and R520. Students can adjust the value of the feedback resistor by switching the multiplexer, thereby dynamically adjusting the gain of the operational amplifier U124.1 and intuitively experiencing the impact of gain adjustment on the output signal amplitude.
[0062] In the low-pass and band-pass filtering modules, a network design combining a multiplexer (such as the RS8047H) with high-precision resistors and capacitors allows for adjustable filter cutoff frequency and bandwidth. By switching different RC combinations, students can flexibly adjust filter parameters to meet the experimental needs of different signal characteristics, solving the problem of traditional fixed-parameter circuits being difficult to adapt flexibly. In the signal amplification module, through a dynamically adjustable feedback network design, the gain is determined by the precision resistor selected by the multiplexer. Students can observe changes in signal amplitude by adjusting the gain, gaining an intuitive understanding of the principle of gain adjustment. This improvement significantly enhances the teaching application value and experimental flexibility of the circuit.
[0063] like Figure 5 As shown, the level-up circuit includes a multiplexer U129 and different resistor combinations. It adjusts the bias level of the input signal through a voltage divider network, raising the reference level of the previous stage signal to a DC level range suitable for subsequent processing.
[0064] The level-up circuit also includes an operational amplifier U124.2 for amplifying or buffering the level-up signal, and a feedback network formed by multiple resistors. By introducing a voltage divider network design with multiple switches, the level-up circuit can adjust the signal level bias and, combined with multi-stage buffer amplification, ensures stable signal output, solving the problem of fixed DC bias and difficulty in adapting to different acquisition devices in traditional circuits.
[0065] The level-up and follow module adjusts the DC level of the preceding signal and achieves high-precision signal following, ensuring the stability and integrity of the signal output, suitable for subsequent signal processing and analysis. This module uses a multiplexer U129 (RS8047H) combined with high-precision resistors such as R522, R523, R524, and R132 to flexibly adjust the DC level of the input signal. Different resistor combinations, such as 2.49kΩ, 24.9kΩ, 49.9kΩ, and 249kΩ, adjust the bias level of the input signal through a voltage divider network, raising the reference level of the preceding signal to a suitable DC level range for subsequent processing. Students can dynamically observe the effect of level adjustment by switching the multiplexer, understanding the practical significance of level-up in eliminating negative voltage or adjusting the operating point in analog signal processing. The operational amplifier U124.2 amplifies or buffers the level-up signal, working with feedback network resistors R133 and R134 to achieve high linearity and high-precision signal output.
[0066] Furthermore, the level-up circuit also includes a voltage follower circuit, with U125.1 and U125.2 connected in sequence to form a two-stage voltage follower. The input terminal of U125.1 is connected to the output terminal of U124.2, and the output terminal of U125.2 is connected to the ECG-OUT node.
[0067] U125.1 and U125.2 form a two-stage voltage follower to buffer and stabilize the signal, ensuring that the output signal can adapt to different load conditions: U125.1 receives the boosted signal and reduces amplitude attenuation and distortion during signal transmission through its low output impedance and high input impedance design. U125.2 provides strong drive capability and ultimately outputs the signal to the ECG-OUT node, ensuring the stability and reliability of the signal in different application scenarios.
[0068] 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 circuit for acquiring analog electrocardiogram signals for teaching experiments, characterized in that, include: The instrument amplifier circuit includes a first-stage amplifier composed of operational amplifiers U121.1 and U121.
2. The amplified signal is AC-coupled through capacitors C1001 and C1002 and transmitted to the next stage. It also includes a second-stage amplifier composed of U126 for further amplification of the signal. The bandpass filter circuit includes an operational amplifier U123 and a RC combination formed by multiple capacitors and resistors, which is connected to the operational amplifier U123. The low-pass filter circuit includes an operational amplifier U124 and multiple resistors and capacitors forming different RC combinations connected to the operational amplifier U124. The level-up circuit, including a multiplexer U129 and different resistor combinations, adjusts the bias level of the input signal through a voltage divider network, raising the reference level of the preceding signal to a DC level range suitable for subsequent processing.
2. The electrocardiogram analog signal acquisition circuit for teaching experiments according to claim 1, characterized in that, The instrument amplification circuit includes a protection circuit module. In the protection circuit module, the input terminals ECG+ and ECG- are connected to diodes E1 and E2 via the ESD protection of the chip PESD5V0S1BA.
3. The electrocardiogram analog signal acquisition circuit for teaching experiments according to claim 1, characterized in that, The instrumentation amplifier circuit includes an input impedance matching module. In the input impedance matching module, the input signal is connected to the non-inverting input terminal of the first-stage amplifier through resistors R101 and R104, respectively.
4. The electrocardiogram analog signal acquisition circuit for teaching experiments according to claim 1, characterized in that, The instrument amplification circuit includes a power supply decoupling and filtering module, which includes capacitors C113, C114, C115, and C116. Capacitors C113 and C114 are located between the power supply V+ and ground SGND, while capacitors C115 and C116 are located between the power supply V- and ground SGND.
5. The electrocardiogram analog signal acquisition circuit for teaching experiments according to claim 1, characterized in that, The instrumentation amplifier circuit includes a reference voltage module, which includes U123.2, resistor R1, and bypass capacitor C117.
6. The electrocardiogram analog signal acquisition circuit for teaching experiments according to claim 1, characterized in that, The low-pass filter circuit includes an operational amplifier, multiple multiplexers, and a low-pass filter network formed by multiple resistors or capacitors. Different resistor-capacitor combinations can be selected by switching multiplexers.
7. The electrocardiogram analog signal acquisition circuit for teaching experiments according to claim 1, characterized in that, The low-pass filter circuit also includes a gain adjustment module, which consists of a resistor network composed of U119 and multiple resistors. The resistance value of the feedback resistor is adjusted by switching a multiplexer.
8. The electrocardiogram analog signal acquisition circuit for teaching experiments according to claim 1, characterized in that, It also includes an operational amplifier U124.2 for amplifying or buffering the signal after level boosting, and a feedback network formed by multiple resistors.
9. The electrocardiogram analog signal acquisition circuit for teaching experiments according to claim 8, characterized in that, The level-up circuit also includes a voltage follower circuit. U125.1 and U125.2 are connected in sequence to form a two-stage voltage follower. The input terminal of U125.1 is connected to the output terminal of U124.2, and the output terminal of U125.2 is connected to the ECG-OUT node.