CN113679391B - Electrocardiogram baseline drift filter device, electrocardiosignal sampling system and sampling method - Google Patents
Electrocardiogram baseline drift filter device, electrocardiosignal sampling system and sampling method Download PDFInfo
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/30—Input circuits therefor
- A61B5/307—Input circuits therefor specially adapted for particular uses
- A61B5/308—Input circuits therefor specially adapted for particular uses for electrocardiography [ECG]
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/316—Modalities, i.e. specific diagnostic methods
- A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/316—Modalities, i.e. specific diagnostic methods
- A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
- A61B5/319—Circuits for simulating ECG signals
Abstract
The application relates to an electrocardiosignal baseline drift filtering device, an electrocardiosignal sampling system and a sampling method, wherein the device comprises a signal amplifying module, a control module, a switch module and an analog integrator; the switch module is used for acquiring the filter frequency adjustment instruction change-over switch transmitted by the control module so as to change the cut-off frequency of the analog integrator; the analog integrator is used for integrating the electrocardiosignals amplified by the signal amplifying module according to the cut-off frequency and feeding the integration result back to the signal amplifying module so as to enable the signal amplifying module to output electrocardiosignal amplified signals with constant direct current voltage; the signal amplifying module is used for acquiring electrocardiosignals of a human body, amplifying the electrocardiosignals and outputting the electrocardiosignals to the analog integrator, and outputting electrocardiosignal amplified signals with constant direct current voltage to the control module; and the control module is used for filtering and sampling the electrocardio amplified signals to obtain electrocardio digital signals. The baseline drift filtering frequency can be adjusted, and the applicability and effect of baseline drift hardware filtering are improved.
Description
Technical Field
The application relates to the technical field of signal filtering, in particular to an electrocardiosignal baseline drift filtering device, an electrocardiosignal sampling system and a sampling method.
Background
Currently, human electrocardiographic detection is commonly used in medical equipment, and acquired human electrocardiographic signals may have baseline drift. When the baseline drift filtering of the existing dynamic electrocardiograph adopts hardware filtering, the filtering frequency is generally fixed, so that the disadvantage is that if the frequency is set too low, the adjusting time of the myoelectric filtering is long, i.e. the adjusting time of filtering the myoelectric signal from the electrocardiograph is long. If the frequency setting is high, the dynamic electrocardiograph cannot have the function of measuring the ST segment in the electrocardiogram, because the frequency of the ST segment can reach 0.05Hz at the lowest. Therefore, when baseline drift filtering is performed based on hardware of the dynamic electrocardiograph, the single filtering frequency cannot better meet the actual requirements.
Disclosure of Invention
In view of this, the application provides an electrocardiograph baseline drift filtering device, an electrocardiograph signal sampling system and a sampling method, which are used for solving the technical problem that the baseline drift hardware filtering frequency of the existing dynamic electrocardiograph is not adjustable.
In order to solve the above problems, in a first aspect, the present application provides an electrocardiograph baseline wander filtering device, where the device includes a signal amplifying module, a control module, a switch module, and an analog integrator; the signal amplifying module is electrically connected with the control module, the switch module and the analog integrator are sequentially and electrically connected, and the analog integrator is electrically connected with the signal amplifying module;
the control module is used for acquiring a filtering frequency adjusting instruction and transmitting the filtering frequency adjusting instruction to the switch module;
the switch module is used for switching a switch according to the filtering frequency adjusting instruction so as to change the cut-off frequency of the analog integrator;
the analog integrator is used for integrating the electrocardiosignals amplified by the signal amplifying module according to the cut-off frequency and feeding the integration result back to the signal amplifying module so as to enable the signal amplifying module to output electrocardiosignal amplified signals with constant direct current voltage;
the signal amplification module is used for obtaining an electrocardiosignal of a human body, amplifying the electrocardiosignal to be output to the analog integrator, and outputting an electrocardiosignal amplified signal with constant direct current voltage to the control module;
the control module is also used for carrying out low-pass filtering and AD sampling on the electrocardio amplified signals to obtain filtered electrocardio digital signals.
Optionally, the switching module includes a supply voltage conversion unit and a switching unit, where the supply voltage conversion unit is electrically connected with the switching unit, the supply voltage conversion unit is electrically connected with the control module, and the switching unit is electrically connected with the integrator;
the power supply voltage conversion unit is used for converting the single power supply control signal output by the control module into a double power supply control signal and transmitting the double power supply control signal to the switch switching unit;
the switch switching unit is used for controlling the working state of the switch according to the dual-power control signal so as to switch the key resistance of the analog integrator and change the cut-off frequency of the analog integrator.
Optionally, the analog integrator includes an operational amplifier U3A, a capacitor C271, a resistor R484 and a resistor R486;
the non-inverting input end of the operational amplifier U3A is grounded, the inverting input end is respectively connected with one end of a resistor R484 and one end of a resistor R486, the other end of the resistor R484 and the other end of the resistor R486 are both connected with the switch switching unit, and the capacitor C271 is connected in series between the inverting input end and the output end of the operational amplifier U3A; the other end of the resistor R484 is connected with the signal amplifying module;
according to the switch working state controlled by the switch switching unit, when the resistor R484 and the resistor R486 of the analog integrator are simultaneously connected, the cut-off frequency of the analog integrator is the first cut-off frequency, and the cut-off frequency is 0.47-0.67 Hz; when the analog integrator is only connected with the resistor R484, the cut-off frequency of the analog integrator is the second cut-off frequency, and the size is 0.04-0.05 Hz.
Optionally, the switch switching unit adopts a single-pole single-throw analog switch; the power supply voltage conversion unit adopts a mos tube voltage conversion circuit;
the mos transistor voltage conversion circuit comprises a mos transistor Q1, a resistor R487, a resistor R488, a resistor R489, a resistor R490, a capacitor C274 and a capacitor C275;
the grid electrode of the mos tube Q1 is connected with one end of the resistor R487, and the other end of the resistor R487 is used as the input end of the mos tube voltage conversion circuit; one end of the resistor R488 is connected between the grid electrode of the mos tube Q1 and the resistor R487, and the other end of the resistor R488 is grounded; the source electrode of the mos tube Q1 is connected with a positive power supply voltage end, and the drain electrode is connected with a negative power supply voltage end through a resistor R489; one end of the capacitor C274 is connected with the source electrode of the mos tube Q1, and the other end of the capacitor C is grounded; one end of the capacitor C275 is connected between the resistor R489 and the negative voltage end of the power supply, and the other end of the capacitor C275 is grounded; one end of the resistor R490 is connected with the drain electrode of the mos transistor Q1, and the other end is used as the output end of the mos transistor voltage conversion circuit.
Optionally, the device further comprises a signal input module, wherein the signal input module is used for acquiring electrocardiosignals of a human body and transmitting the electrocardiosignals to the signal amplification module; the signal input module adopts a buffer circuit.
Optionally, the signal amplifying module comprises a primary amplifying unit and a secondary amplifying unit, wherein the output end of the primary amplifying unit is electrically connected with the input end of the secondary amplifying unit, and the output end of the secondary amplifying unit is electrically connected with the input end of the control module; the input end and the output end of the primary amplifying unit are respectively and electrically connected with the analog integrator;
the first-stage amplifying unit is used for amplifying the electrocardiosignals according to a preset first amplifying multiple, and counteracting a direct-current baseline drifting part in the input electrocardiosignals according to an integration result by acquiring the integration result fed back by the analog integrator so as to output electrocardiosignals with constant direct-current voltage, and transmitting the electrocardiosignals with the constant direct-current voltage to the second-stage amplifying unit;
the secondary amplifying unit is used for amplifying the electrocardiosignals amplified by the primary amplifying unit according to a preset second amplifying multiple so as to output electrocardiosignal amplifying signals to the control module.
Optionally, the first-stage amplifying unit adopts a differential amplifying mode, and the first amplifying factor is 3 times or 6 times; the second-stage amplifying unit adopts an operational amplifying mode, and the second amplifying factor is 100-200 times.
Optionally, the control module comprises a low-pass filtering unit and a main control unit; the low-pass filtering unit is electrically connected with the AD sampling end of the main control unit, the input end of the low-pass filtering unit is electrically connected with the output end of the signal amplifying module, and the output end of the main control module is electrically connected with the input end of the switch module;
the low-pass filtering unit is used for carrying out low-pass filtering denoising on the electrocardio-amplified signals output by the signal amplifying module and transmitting the electrocardio-amplified signals subjected to the low-pass filtering denoising to the main control unit;
and the main control unit is used for carrying out AD sampling on the electrocardio amplified signals after low-pass filtering and denoising so as to obtain filtered electrocardio digital signals.
In a second aspect, the application provides an electrocardiograph signal sampling system, which comprises a sensing module, an electrocardiograph baseline drift filtering device and/or an instruction input module; the sensing module is electrically connected with the electrocardio baseline drift filter device, and/or the instruction input module is electrically connected with the electrocardio baseline drift filter device; the sensing device adopts an acceleration sensor;
the sensing module is used for detecting human body movement information and transmitting the human body movement information to the electrocardio baseline drift filter device;
the instruction input module is used for manually inputting a filtering frequency adjustment instruction;
the electrocardio baseline filtering device is used for triggering an internal filtering frequency adjusting instruction to switch the cut-off frequency of a corresponding analog integrator when the human body movement information exceeds a preset threshold value so as to realize baseline filtering of different frequencies;
and/or the electrocardio baseline filtering device is used for acquiring the filtering frequency adjusting instruction transmitted by the instruction input module so as to switch the cut-off frequency of the corresponding analog integrator to realize baseline filtering of different frequencies.
In a third aspect, the present application provides an electrocardiograph signal sampling method, which is applied to the electrocardiograph signal sampling system, and the method includes:
acquiring human body movement information, wherein the movement information comprises movement acceleration and duration;
judging whether the human body movement acceleration exceeds a preset acceleration threshold value or not, and judging whether the duration exceeds a preset time threshold value or not;
if yes, triggering a first filtering frequency adjusting instruction to enable the electrocardiosignal baseline filtering device to be switched to a first cut-off frequency to filter and sample electrocardiosignal baseline noise, and obtaining a filtered electrocardiosignal digital signal; wherein the first cutoff frequency is greater than the second cutoff frequency;
if not, triggering a second filtering frequency adjusting instruction to enable the electrocardiosignal baseline filtering device to be switched to a second cut-off frequency to filter and sample electrocardiosignal baseline noise, and obtaining a filtered electrocardiosignal digital signal.
The beneficial effects of adopting the embodiment are as follows: acquiring and amplifying a human electrocardiosignal through a signal amplifying module; acquiring a filtering frequency adjusting instruction through a switch module to change the cut-off frequency of the analog integrator, so that the subsequent baseline filtering frequency is adjustable; the analog integrator integrates the electrocardiosignals amplified by the signal amplifying module according to the cut-off frequency and feeds the integration result back to the signal amplifying module so that the signal amplifying module outputs electrocardiosignals with constant direct current voltage, and the signal amplifying module can keep constant direct current output voltage even if skin contact resistance changes in the electrocardiosignal acquisition process, so that baseline drift interference is reduced; and filtering and sampling the electrocardio-amplified signals through a control module to finally obtain electrocardio-digital signals which are convenient to analyze. The baseline drift filtering frequency can be adjusted, and the applicability and the filtering effect of baseline drift hardware filtering are improved.
Drawings
FIG. 1 is a schematic block diagram of an embodiment of an electrocardiographic baseline wander filter device provided herein;
FIG. 2 is a circuit diagram of an embodiment of a buffer circuit provided herein;
FIG. 3 is a circuit diagram of a switching unit, an analog integrator, and a first stage amplifying unit according to an embodiment of the present disclosure;
FIG. 4 is a circuit diagram of an embodiment of a two-stage amplifying unit provided in the present application;
FIG. 5 is a circuit diagram of an embodiment of a power supply voltage conversion unit provided in the present application;
fig. 6 is a flowchart of a method for sampling an electrocardiograph signal according to an embodiment of the present application.
Detailed Description
Preferred embodiments of the present application are described in detail below with reference to the attached drawing figures, which form a part of the present application and, together with the embodiments of the present application, serve to explain the principles of the present application and are not intended to limit the scope of the present application.
At present, the electrical signal of the human body electrocardio waveform collected by the dynamic electrocardio equipment through the electrode is generally 1mv peak value, and contains rich harmonic waves. In order to make this signal available for analysis, a magnification of about 200 times or more is required. The human body electrocardio waveform is not single frequency, and the electrocardio signal contains rich harmonic waves. If the electrocardiograph has the same gain for signals of different frequencies, the waveform traced will not be distorted, but the amplification capability of the amplifier for signals of different frequencies is not necessarily exactly the same. The hardware baseline filtering of the existing dynamic electrocardiograph equipment is generally fixed in filtering frequency, and when baseline drift filtering is carried out, a single filtering frequency cannot respond to signals with different frequencies well.
Referring to fig. 1, an embodiment of the present application provides an electrocardiographic baseline wander filtering device, which includes a signal amplifying module 101, a control module 102, a switch module 103, and an analog integrator 104; the signal amplifying module is electrically connected with the control module, the switch module and the analog integrator are sequentially electrically connected, and the analog integrator is electrically connected with the signal amplifying module.
The control module 102 is configured to obtain a filtering frequency adjustment instruction, and transmit the filtering frequency adjustment instruction to the switch module; a switch module 103 for switching the switch according to the filter frequency adjustment instruction to change the cut-off frequency of the analog integrator; the analog integrator 104 is configured to integrate the electrocardiosignal amplified by the signal amplifying module according to the cutoff frequency, and feed back an integration result to the signal amplifying module, so that the signal amplifying module outputs an electrocardiosignal amplified signal with constant direct current voltage; the signal amplification module 101 is configured to obtain an electrocardiograph signal of a human body, amplify the electrocardiograph signal to output the electrocardiograph signal to the analog integrator, and output an electrocardiograph amplified signal of constant dc voltage to the control module; the control module 102 is further configured to filter and AD sample the electrocardiograph amplified signal, and obtain a filtered electrocardiograph digital signal.
The embodiment obtains and amplifies the electrocardiosignals of the human body through a signal amplification module; acquiring a filtering frequency adjusting instruction through a switch module to change the cut-off frequency of the analog integrator, so that the subsequent baseline filtering frequency is adjustable; the analog integrator integrates the electrocardiosignals amplified by the signal amplifying module according to the cut-off frequency and feeds the integration result back to the signal amplifying module so that the signal amplifying module outputs electrocardiosignals with constant direct current voltage, and the signal amplifying module can keep constant direct current output voltage even if skin contact resistance changes in the electrocardiosignal acquisition process, so that baseline drift interference is reduced; and filtering and sampling the electrocardio-amplified signals through a control module to finally obtain electrocardio-digital signals which are convenient to analyze. The baseline drift filtering frequency can be adjusted, and the applicability and the filtering effect of baseline drift hardware filtering are improved.
In an embodiment, the electrocardiograph baseline drift filtering device further comprises a signal input module, wherein the signal input module is used for acquiring electrocardiograph signals of a human body and transmitting the electrocardiograph signals to the signal amplification module; the signal input module adopts a buffer circuit. In a specific application embodiment, as shown in fig. 2, the signal input end of the buffer circuit only shows two electrodes, which are used for detecting electrocardiosignals in contact with the skin of a human body, and in some specific embodiments, five electrodes, ten electrodes, 12 electrodes, and the like can also be used.
It should be noted that, because the amplification factor of the signal amplification module is larger, the signal at the filtering sampling end of the control module is very sensitive to the change of the contact resistance between the electrode and the skin, which can cause baseline drift interference on the finally generated electrocardiogram, and even affect the sampling at the filtering sampling end of the control module, so the embodiment solves the problem of baseline drift interference through the analog integrator, and further describes the analog integrator later.
In one embodiment, the signal amplifying module comprises a first-stage amplifying unit and a second-stage amplifying unit, wherein the output end of the first-stage amplifying unit is electrically connected with the input end of the second-stage amplifying unit, and the output end of the second-stage amplifying unit is electrically connected with the input end of the control module; the input end and the output end of the first-stage amplifying unit are respectively and electrically connected with the analog integrator.
The first-stage amplifying unit is used for amplifying the electrocardiosignals according to a preset first amplifying multiple, counteracting a direct-current baseline drift part in the input electrocardiosignals according to an integration result fed back by the analog integrator by acquiring the integration result so as to output electrocardiosignals with constant direct-current voltage, and transmitting the electrocardiosignals with the constant direct-current voltage to the second-stage amplifying unit; and the second-stage amplifying unit is used for amplifying the electrocardiosignals amplified by the first-stage amplifying unit according to a preset second amplifying multiple so as to output electrocardiosignal amplifying signals to the control module.
In one embodiment, the first-stage amplifying unit adopts a differential amplifying mode, and the first amplifying factor is 3 times or 6 times; the second-stage amplifying unit adopts an operational amplifying mode, and the second amplifying factor is 100-200 times. In a specific embodiment, as shown in fig. 3, the first-stage amplifying unit uses an instrumentation amplifier U2, and the model may be INA317; the second-stage amplification unit may employ a low-power op-amp with a gain-bandwidth product greater than 1MHz, as shown in fig. 4. In other embodiments, the specific types of the primary amplifying unit and the secondary amplifying unit may be determined according to actual situations, which is not limited herein.
It should be noted that, the input end and the output end of the first-stage amplifying unit are respectively and electrically connected with the analog integrator, referring to fig. 3, the output end of the analog integrator is electrically connected with the 5 th port of the instrumentation amplifier U2, so that the analog integrator integrates the direct current component of the electrocardiosignal amplified by the first-stage amplifying unit, and then feeds back the integration result to the first-stage amplifying unit, and counteracts the direct current baseline wander part in the input electrocardiosignal according to the integration result, thereby solving the problem of baseline wander. Further, as shown in fig. 3, in the present embodiment, the first-stage amplification unit is connected to the second-stage amplification unit through the 6 th port.
In an embodiment, the control module comprises a low-pass filtering unit and a main control unit; the low-pass filter unit is electrically connected with the AD sampling end of the main control unit, the input end of the low-pass filter unit is electrically connected with the output end of the signal amplifying module, and the output end of the main control module is electrically connected with the input end of the switch module.
The low-pass filter unit is used for carrying out low-pass filtering denoising on the electrocardio amplified signals output by the signal amplifying module and transmitting the electrocardio amplified signals subjected to the low-pass filtering denoising to the main control unit; and the main control unit is used for sampling the electrocardio amplified signals after low-pass filtering and denoising so as to obtain filtered electrocardio digital signals.
In this embodiment, the main control unit may use an MCU singlechip, where the MCU singlechip is provided with an AD sampling end; in the embodiment, the human body electrocardiosignals are acquired through the electrodes, the signals enter a first-stage differential amplification after being buffered, then a second-stage amplification is carried out, and finally, the signals are filtered and sent to an AD sampling end of the MCU singlechip. In addition, in the present embodiment, the low-pass filter unit adopts a filter circuit of an op-amp structure; in other embodiments, filtering may be implemented by adopting a capacitive mode and a resistive mode, and may be specifically determined according to practical situations.
In an embodiment, the switching module includes a supply voltage conversion unit and a switching unit, where the supply voltage conversion unit is electrically connected to the switching unit, the supply voltage conversion unit is electrically connected to the control module, and the switching unit is electrically connected to the analog integrator, as shown in fig. 3.
The power supply voltage conversion unit is used for converting the single power supply control signal output by the control module into a double power supply control signal and transmitting the double power supply control signal to the switch switching unit; and the switch switching unit is used for controlling the working state of the switch according to the dual-power control signal so as to switch the key resistance of the analog integrator and change the cut-off frequency of the analog integrator.
In an embodiment, the switch switching unit adopts a single-pole single-throw analog switch, as in fig. 3, the single-pole single-throw analog switch is an analog switch U5; the power supply voltage conversion unit adopts a mos tube voltage conversion circuit.
Referring to fig. 5, the mos transistor voltage conversion circuit includes a mos transistor Q1, a resistor R487, a resistor R488, a resistor R489, a resistor R490, a capacitor C274, and a capacitor C275; the grid electrode of the mos tube Q1 is connected with one end of a resistor R487, and the other end of the resistor R487 is used as the input end of the mos tube voltage conversion circuit; one end of the resistor R488 is connected between the grid electrode of the mos tube Q1 and the resistor R487, and the other end of the resistor R488 is grounded; the source electrode of the mos tube Q1 is connected with a positive voltage end of a power supply, and the drain electrode is connected with a negative voltage end of the power supply through a resistor R489; one end of the capacitor C274 is connected with the source electrode of the mos tube Q1, and the other end of the capacitor C is grounded; one end of the capacitor C275 is connected between the resistor R489 and the negative voltage end of the power supply, and the other end of the capacitor C275 is grounded; one end of the resistor R490 is connected with the drain electrode of the mos transistor Q1, and the other end is used as the output end of the mos transistor voltage conversion circuit.
It should be noted that, because the low level of the MCU singlechip output control level is 0V, the high level is 3.3V, and the working voltage of the analog switch U5 is + -2.7V, direct control is not possible. The mos transistor voltage conversion circuit is simple and practical, and converts a single power supply control signal into a double power supply control signal, so that the mos transistor voltage conversion circuit outputs-2.7V when the MCU singlechip outputs high level; when the MCU singlechip outputs low level, the mos tube voltage conversion circuit outputs +2.7V, so that the analog switch U5 is controlled to switch the enabling pin, as shown in fig. 3 and 5, the output end BASELINE_CON of the mos tube voltage conversion circuit is connected with the 7 th port of the analog switch U5 of the switch switching unit, and the switch switching control is realized.
In one embodiment, referring to FIG. 3, the analog integrator comprises an operational amplifier U3A, a capacitor C271, a resistor R484 and a resistor R486; the non-inverting input end of the operational amplifier U3A is grounded, the inverting input end is respectively connected with one end of a resistor R484 and one end of a resistor R486, the other end of the resistor R484 and the other end of the resistor R486 are both connected with a switch switching unit, and a capacitor C271 is connected in series between the inverting input end and the output end of the operational amplifier U3A; and the other end of the resistor R484 is connected with the signal amplifying module. According to the switch working state controlled by the switch switching unit, when the resistor R484 and the resistor R486 of the analog integrator are simultaneously connected, the cut-off frequency of the analog integrator is the first cut-off frequency, and the cut-off frequency is 0.47-0.67 Hz; when the analog integrator is only connected with the resistor R484, the cut-off frequency of the analog integrator is the second cut-off frequency, and the size is 0.04-0.05 Hz.
The MCU singlechip is used for controlling the single-pole single-throw analog switch U5, and key resistors R484 and R486 of the analog integrator are switched. In this embodiment, when the resistors R486 and R484 are connected to the circuit at the same time, the cut-off frequency of the analog integrator may be 0.67Hz, and when only the resistor R484 is connected to the circuit, the cut-off frequency of the analog integrator may be 0.04-0.05 Hz, specifically may be 0.04Hz or may be 0.05Hz, so as to realize the adjustable hardware baseline filtering frequency.
In this embodiment, the cut-off frequency of the analog integrator is determined by the resistor R484, the resistor R486, and the capacitor C271, and the calculation formula is as follows:
wherein V is REF Representing the output voltage of the analog integrator, V o-ac Represents the alternating component of the electrocardiographic signal, τ represents the time constant, τ=rc (r=r484// R486), and f represents the cut-off frequency of the analog integrator.
When determining the cut-off frequency of the analog integrator, the magnitudes of the resistor R484, the resistor R486, and the capacitor C271 may be determined reversely by the RC circuit, and the specific values may be determined according to the actual situation.
Different from the prior art, the embodiment acquires and amplifies the electrocardiosignals of the human body through a signal amplification module; acquiring a filtering frequency adjusting instruction through a switch module to change the cut-off frequency of the analog integrator, so that the subsequent baseline filtering frequency is adjustable; the analog integrator integrates the electrocardiosignals amplified by the signal amplifying module according to the cut-off frequency and feeds the integration result back to the signal amplifying module so that the signal amplifying module outputs electrocardiosignals with constant direct current voltage, and the signal amplifying module can keep constant direct current output voltage even if skin contact resistance changes in the electrocardiosignal acquisition process, so that baseline drift interference is reduced; and filtering and sampling the electrocardio-amplified signals through a control module to finally obtain electrocardio-digital signals which are convenient to analyze. The baseline drift filtering frequency can be adjusted, and the applicability and the filtering effect of baseline drift hardware filtering are improved.
The application also provides an electrocardiosignal sampling system which comprises a sensing module, an electrocardiosignal baseline drift filtering device and/or an instruction input module; the sensing module is electrically connected with the electrocardio baseline drift filter device, and/or the instruction input module is electrically connected with the electrocardio baseline drift filter device; the sensing device adopts an acceleration sensor.
The sensing module is used for detecting the movement information of the human body and transmitting the movement information to the electrocardio baseline drift filter device; the instruction input module is used for manually inputting a filtering frequency adjustment instruction; the electrocardio baseline filtering device is used for triggering an internal filtering frequency adjusting instruction to switch the cut-off frequency of the corresponding analog integrator when the human body movement information exceeds a preset threshold value so as to realize baseline filtering of different frequencies; and/or an electrocardio baseline filtering device, which is used for acquiring a filtering frequency adjusting instruction transmitted by the instruction input module so as to switch the cut-off frequency of the corresponding analog integrator to realize baseline filtering of different frequencies.
In the present embodiment, the acceleration sensor may employ a triaxial acceleration sensor; the instruction input module can be a mouse key device or a touch screen; the preset threshold is determined according to actual conditions.
It should be noted that, the baseline filtering frequency can be automatically adjusted by the sensing module and the electrocardiograph baseline filtering device; the baseline filtering frequency can be adjusted by manually inputting a filtering frequency adjusting instruction on the mouse key device or the touch screen and then by an electrocardio baseline filtering device.
Referring to fig. 6, the present application further provides an electrocardiograph signal sampling method, which is applied to an electrocardiograph signal sampling system of the present application, and the method includes:
s1: acquiring human body movement information, wherein the movement information comprises movement acceleration and duration;
s2: judging whether the human body movement acceleration exceeds a preset acceleration threshold value or not, and judging whether the duration exceeds a preset time threshold value or not;
s3: if yes, triggering a first filtering frequency adjusting instruction to enable the electrocardiosignal baseline filtering device to be switched to a first cut-off frequency to filter and sample electrocardiosignal baseline noise, and obtaining a filtered electrocardiosignal digital signal; wherein the first cutoff frequency is greater than the second cutoff frequency;
s4: if not, triggering a second filtering frequency adjusting instruction to enable the electrocardiosignal baseline filtering device to be switched to a second cut-off frequency to filter and sample electrocardiosignal baseline noise, and obtaining a filtered electrocardiosignal digital signal.
In this embodiment, the first filtering frequency adjustment instruction refers to a control instruction to switch to relatively high frequency filtering; the first cut-off frequency is 0.67Hz or 0.47Hz; the second filtering frequency adjusting instruction refers to a control instruction for switching to relatively low frequency filtering; the second cut-off frequency is 0.05Hz or 0.04Hz.
It should be noted that, in the three-axis acceleration sensor adopted in this embodiment, three axes respectively correspond to three directions of human body movement, then data processing is performed on the accelerations in the three directions, in this embodiment, a square sum quadratic root method is adopted to calculate the accelerations in the three directions, so as to obtain a final moving acceleration, when the moving acceleration of the human body exceeds an acceleration threshold value, and the duration exceeds a preset time threshold value, a first filtering frequency adjustment instruction is triggered, so that the electrocardio baseline filtering device performs filtering sampling relative to a high frequency to obtain a corresponding filtering signal; when the moving acceleration of the human body does not exceed the acceleration threshold value or the duration time does not exceed the preset time threshold value, triggering a second filtering frequency adjusting instruction to enable the electrocardio baseline filtering device to perform filtering sampling at a relatively low frequency so as to obtain a corresponding filtering signal. In an embodiment, the time threshold of the duration may be 2s, 3s or 4s, and the acceleration threshold may be determined according to practical situations.
In addition, the electrocardiosignal sampling method can be a main control unit written into the electrocardiosignal baseline filtering device in an embedded mode, and can also be integrated in independent electronic equipment.
The electrocardiosignal sampling method can automatically adjust the filtering frequency according to the movement condition of the human body, so that the validity of electrocardiosignal filtering and sampling is improved, and the electrocardiosignal sampling method is more intelligent and convenient.
Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above.
The foregoing is merely a preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the technical scope of the present application should be covered by the scope of the present application.
Claims (6)
1. The electrocardio baseline drift filtering system is characterized by comprising a sensing module, an electrocardio baseline drift filtering device and an instruction input module; the sensing module is electrically connected with the electrocardio baseline drift filter device; the instruction input module is electrically connected with the electrocardio baseline drift filter device;
the sensing module is used for detecting human body movement information and transmitting the human body movement information to the electrocardio baseline drift filtering device, wherein the movement information comprises movement acceleration and duration;
judging whether the human body movement acceleration exceeds a preset acceleration threshold value or not, and judging whether the duration exceeds a preset time threshold value or not;
if yes, triggering a first filtering frequency adjusting instruction to enable the electrocardiosignal baseline filtering device to be switched to a first cut-off frequency to filter and sample electrocardiosignal baseline noise, and obtaining a filtered electrocardiosignal digital signal; wherein the first cutoff frequency is greater than the second cutoff frequency;
if not, triggering a second filtering frequency adjusting instruction to enable the electrocardiosignal baseline filtering device to be switched to a second cut-off frequency to filter and sample electrocardiosignal baseline noise, and obtaining a filtered electrocardiosignal digital signal;
the instruction input module is used for manually inputting a filtering frequency adjustment instruction;
the electrocardio baseline filtering device is used for triggering an internal filtering frequency adjusting instruction to switch the cut-off frequency of a corresponding analog integrator when the human body movement information exceeds a preset threshold value, so as to realize baseline filtering of different frequencies, and specifically comprises the following steps:
the electrocardio baseline drift filter device comprises a signal amplifying module, a control module, a switch module and an analog integrator; the signal amplifying module is electrically connected with the control module, the switch module and the analog integrator are sequentially and electrically connected, and the analog integrator is electrically connected with the signal amplifying module;
the control module is used for acquiring a filtering frequency adjusting instruction and transmitting the filtering frequency adjusting instruction to the switch module;
the switch module is used for switching a switch according to the filtering frequency adjusting instruction so as to change the cut-off frequency of the analog integrator;
the analog integrator is used for integrating the electrocardiosignals amplified by the signal amplifying module according to the cut-off frequency and feeding the integration result back to the signal amplifying module so as to enable the signal amplifying module to output electrocardiosignal amplified signals with constant direct current voltage;
the signal amplification module is used for obtaining an electrocardiosignal of a human body, amplifying the electrocardiosignal to be output to the analog integrator, and outputting an electrocardiosignal amplified signal with constant direct current voltage to the control module;
the control module is also used for carrying out low-pass filtering and AD sampling on the electrocardio-amplified signals to obtain filtered electrocardio-digital signals;
the switching module comprises a power supply voltage conversion unit and a switching unit, wherein the power supply voltage conversion unit is electrically connected with the switching unit, the power supply voltage conversion unit is electrically connected with the control module, and the switching unit is electrically connected with the integrator;
the power supply voltage conversion unit is used for converting the single power supply control signal output by the control module into a double power supply control signal and transmitting the double power supply control signal to the switch switching unit;
the switch switching unit is used for controlling the working state of the switch according to the dual-power control signal so as to switch the key resistance of the analog integrator and change the cut-off frequency of the analog integrator;
the analog integrator comprises an operational amplifier U3A, a capacitor C271, a resistor R484 and a resistor R486;
the non-inverting input end of the operational amplifier U3A is grounded, the inverting input end is respectively connected with one end of a resistor R484 and one end of a resistor R486, the other end of the resistor R484 and the other end of the resistor R486 are both connected with the switch switching unit, and the capacitor C271 is connected in series between the inverting input end and the output end of the operational amplifier U3A; the other end of the resistor R484 is connected with the signal amplifying module;
according to the switch working state controlled by the switch switching unit, when the resistor R484 and the resistor R486 of the analog integrator are simultaneously connected, the cut-off frequency of the analog integrator is a first cut-off frequency, and the cut-off frequency is 0.47-0.67 Hz; when the analog integrator is only connected with the resistor R484, the cut-off frequency of the analog integrator is the second cut-off frequency, and the size is 0.04-0.05 Hz.
2. The system of claim 1, wherein the switch-switching unit employs a single pole single throw analog switch; the power supply voltage conversion unit adopts a mos tube voltage conversion circuit;
the mos transistor voltage conversion circuit comprises a mos transistor Q1, a resistor R487, a resistor R488, a resistor R489, a resistor R490, a capacitor C274 and a capacitor C275;
the grid electrode of the mos tube Q1 is connected with one end of the resistor R487, and the other end of the resistor R487 is used as the input end of the mos tube voltage conversion circuit; one end of the resistor R488 is connected between the grid electrode of the mos tube Q1 and the resistor R487, and the other end of the resistor R488 is grounded; the source electrode of the mos tube Q1 is connected with a positive power supply voltage end, and the drain electrode is connected with a negative power supply voltage end through a resistor R489; one end of the capacitor C274 is connected with the source electrode of the mos tube Q1, and the other end of the capacitor C is grounded; one end of the capacitor C275 is connected between the resistor R489 and the negative voltage end of the power supply, and the other end of the capacitor C275 is grounded; one end of the resistor R490 is connected with the drain electrode of the mos transistor Q1, and the other end is used as the output end of the mos transistor voltage conversion circuit.
3. The system of claim 1, wherein the device further comprises a signal input module for acquiring an electrocardiographic signal of a human body and transmitting the electrocardiographic signal to the signal amplification module; the signal input module adopts a buffer circuit.
4. The electrocardiographic baseline wander filtering system according to claim 1, wherein the signal amplification module comprises a primary amplification unit and a secondary amplification unit, the output end of the primary amplification unit is electrically connected with the input end of the secondary amplification unit, and the output end of the secondary amplification unit is electrically connected with the input end of the control module; the input end and the output end of the primary amplifying unit are respectively and electrically connected with the analog integrator;
the first-stage amplifying unit is used for amplifying the electrocardiosignals according to a preset first amplifying multiple, and counteracting a direct-current baseline drifting part in the input electrocardiosignals according to an integration result by acquiring the integration result fed back by the analog integrator so as to output electrocardiosignals with constant direct-current voltage, and transmitting the electrocardiosignals with the constant direct-current voltage to the second-stage amplifying unit;
the secondary amplifying unit is used for amplifying the electrocardiosignals amplified by the primary amplifying unit according to a preset second amplifying multiple so as to output electrocardiosignal amplifying signals to the control module.
5. The system of claim 4, wherein the first-stage amplification unit adopts a differential amplification mode, and the first amplification factor is 3 times or 6 times; the second-stage amplifying unit adopts an operational amplifying mode, and the second amplifying time is 100-200 times.
6. The system of claim 1, wherein the control module comprises a low pass filter unit and a master control unit; the low-pass filtering unit is electrically connected with the AD sampling end of the main control unit, the input end of the low-pass filtering unit is electrically connected with the output end of the signal amplifying module, and the output end of the main control module is electrically connected with the input end of the switch module;
the low-pass filtering unit is used for carrying out low-pass filtering denoising on the electrocardio-amplified signals output by the signal amplifying module and transmitting the electrocardio-amplified signals subjected to the low-pass filtering denoising to the main control unit;
and the main control unit is used for carrying out AD sampling on the electrocardio amplified signals after low-pass filtering and denoising so as to obtain filtered electrocardio digital signals.
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| US4147990A (en) * | 1978-03-07 | 1979-04-03 | American Optical Corporation | Fast-recovery circuit |
| US4255769A (en) * | 1979-06-28 | 1981-03-10 | American Optical Corporation | Low-noise preamplifier |
| JP2003144404A (en) * | 2001-11-14 | 2003-05-20 | Noritz Corp | Electrocardiographic signal processor |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US4147990A (en) * | 1978-03-07 | 1979-04-03 | American Optical Corporation | Fast-recovery circuit |
| US4255769A (en) * | 1979-06-28 | 1981-03-10 | American Optical Corporation | Low-noise preamplifier |
| JP2003144404A (en) * | 2001-11-14 | 2003-05-20 | Noritz Corp | Electrocardiographic signal processor |
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