ECG dropout detection method

Abstract

The present invention discloses an ECG detachment detection method, which belongs to the field of ECG signal acquisition and processing. The detection method comprises the following steps: connecting a differential unit in parallel between a first electrode and a second electrode to be detected to be detached, so as to obtain an ECG differential signal between the first electrode and the second electrode; charging the first electrode and the second electrode respectively, and discharging after the charging is completed; after the preset discharge time is over, measuring the voltage at one of the electrodes, and distinguishing the electrode detachment situation according to the measured voltage. Furthermore, the electrode to be measured can also be connected to a single-ended to differential amplifier or a single-ended operational amplifier. The detection method of the present invention can detect the contact status of ECG electrodes in DC and AC modes, and has a wider range of applicable scenarios.

Description

Technical Field

[0001] The present invention relates to the field of ECG signal acquisition and processing, in particular to the field of ECG electrode detachment detection and prompting, and in particular to an ECG detachment detection method. Background Art

[0002] ECG (Electrocardiogram) is an important physiological signal of the human body. It uses an electrocardiogram detection instrument to collect the electrocardiogram signal of each cardiac cycle from the body surface of the subject, and then generates a graph of electrical activity changes based on the electrocardiogram signal of each cardiac cycle. Its measurement results are widely used in cardiac function monitoring and cardiac pathology analysis, so it is necessary to safely, real-time and accurately dynamically detect the basic electrophysiological parameters of the human myocardium.

[0003] When using ECG detection equipment, ECG electrodes may become loose or fall off, which will introduce great interference, cause ECG waveform distortion, and affect the detection results. Therefore, it is necessary to detect the ECG electrode falling off. Traditional ECG electrode falling off detection is mainly based on DC coupling falling off detection, which cannot be used in AC coupling applications. For example, when performing some ECG tests, there are insulating materials such as clothing between the electrode and the skin. In this case, the traditional DC falling off detection method cannot be used. Summary of the invention

[0004] The object of the present invention is to provide an ECG fall-off detection method to solve the problems in the background technology.

[0005] In order to solve the above technical problems, the present invention provides an ECG fall-off detection method, comprising the following steps:

[0006] Connecting a differential unit in parallel between the first electrode to be detected for detachment and the second electrode to obtain an ECG differential signal between the first electrode and the second electrode;

[0007] Charging the first electrode and the second electrode respectively, and discharging after charging is completed;

[0008] After the preset discharge time is over, the voltage at one of the electrodes is measured, and the electrode detachment condition is identified based on the measured voltage.

[0009] In an achievable implementation, the step of distinguishing the electrode detachment situation according to the measured voltage includes:

[0010] If the measured voltage is small, it means that the voltage at the electrode is discharged quickly and both electrodes are not detached;

[0011] If the measured voltage is large, it means that the voltage at the electrode is discharged slowly and both electrodes have fallen off;

[0012] If the measured voltage is in the middle, it means that the voltage discharge speed at the electrode is in the middle, one electrode has fallen off, and the other electrode has not fallen off.

[0013] In an achievable implementation, after the preset discharge time ends, the detection method further includes:

[0014] Connect the electrode to be measured to a single-ended to differential amplifier or a single-ended op amp amplifier.

[0015] In one feasible implementation, the amplifier is a transimpedance amplifier;

[0016] The negative input terminal of the transimpedance amplifier receives the electrode to be measured, the positive input terminal is connected to the reference voltage VREF, and the voltage output by the output terminal is proportional to (V5-VREF).

[0017] In a feasible implementation manner, a sign indicating that the charging of the first electrode and the second electrode is complete is that the voltages of the first electrode and the second electrode are stable.

[0018] In a feasible implementation manner, after the first electrode and the second electrode are fully charged, the voltages therebetween are equal or there is a voltage difference therebetween.

[0019] In a feasible implementation manner, the preset discharge time is greater than a first threshold time and less than a second threshold time.

[0020] In a feasible implementation, between the first threshold time and the second threshold time, discharge curves for three situations, namely, both electrodes are not detached, one electrode is detached, and both electrodes are detached, are different.

[0021] In a feasible implementation manner, the differential unit is a capacitor.

[0022] The ECG fall-off detection method provided by the present invention can detect the contact status of ECG electrodes in DC and AC modes, and has a wider range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of a first embodiment of the ECG fall-off detection method provided by the present invention.

[0025] Figure 2 It is a schematic diagram of a second embodiment of the ECG fall-off detection method provided by the present invention.

[0026] Figure 3 is a schematic diagram of the ECG electrode detachment simulation. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0028] like Figure 1 As shown, the left side of line1 is a human body model, and the resistor R1 and the capacitor C1 are connected in parallel to represent the simplified electrical model of the right-hand electrode; the resistor R2 and the capacitor C2 are connected in parallel to represent the simplified electrical model of the left electrode. The middle of Line1 and Line2 represents the PCB board-level circuit, including capacitors C3 to C6 and resistors R3 to R4; the first end of capacitor C3 and the first end of resistor R3 are both connected to node V1, and the first end of capacitor C4 and the first end of resistor R4 are both connected to node V2; the second end of resistor R3 and the first end of capacitor C6 are both connected to node V3, and the second end of resistor R4 and the first end of capacitor C5 are both connected to node V4; capacitor C5 and capacitor C6 are used for AC coupling of ECG signals. A capacitor C7 is connected between the second end of capacitor C5 and the second end of capacitor C6, and capacitor C7 is used to obtain the differential signal of ECG. The second end of capacitor C5 is connected to node V5, and the second end of capacitor C6 is connected to node V6; node V5 and node V6 are respectively connected to external power supply voltages VDC1 and VDC2 through switches SW1 and SW2; capacitors C5 and C6 are suitable for AC coupling scenarios.

[0029] At time t0, switches SW1 and SW2 are closed (switch on) and connected for a short time, respectively connecting nodes V5 and V6 to a certain voltage value. In this embodiment, 1.8V can be selected, and other voltages can also be selected according to actual conditions; the voltages connected to nodes V5 and V6 can be the same or different. When the voltages at nodes V5 and V6 are stable, switches SW1 and SW2 are disconnected (switch off), so that the voltages at nodes V5 and V6 begin to discharge. The discharge time can be adjusted. Different discharge curves are shown in FIG. Figure 3As shown, they represent different connection situations. Curve 1 is the case where both ECG electrodes fall off, and the discharge speed is the slowest; Curve 2 is the case where only one ECG electrode falls off, and the discharge speed is in the middle; Curve 3 is the case where both ECG electrodes are not fallen off, and the discharge speed is the fastest. The selection standard of the discharge time is that the discharge curves of the three situations of both electrodes not falling off, one electrode falling off, and both electrodes falling off are different. The more obvious the difference between the three, the better, and the more obvious the difference, the easier it is to distinguish.

[0030] After the set discharge time is over, the switch SW3 is closed (switch on), connecting the node V5 to the Figure 1 A single-ended to differential transimpedance amplifier as shown, or Figure 2 The single-ended op amp transimpedance amplifier shown in the figure. During the voltage change of node V5, the charge proportional to (V5-VREF) will be input to the transimpedance amplifier, and then amplified and outputted at the transimpedance amplifier; whether the transimpedance amplifier is a single-ended to differential or single-ended op amp, the purpose is to obtain a voltage output proportional to (V5-VREF). After closing switch SW3, in a very short time, the voltages of nodes V5 and V6 are directly pulled to the input common-mode voltage by the negative feedback of the transimpedance amplifier; at this time, nodes V5 and V6 have two discharge paths, the main discharge path is the newly closed switch SW3, and the secondary discharge path is the circuit on the left of nodes V5 and V6; before switch SW3 is closed (that is, when switch SW3 is open), discharge is carried out by the secondary discharge path.

[0031] Please read first Figure 1 , which is a schematic diagram of the structure of connecting node V5 to single-ended to differential conversion, node V5 is connected to the first end of resistor R7 through switch SW3, the second end of resistor R7 is connected to the negative input end of the transimpedance amplifier, the first end of resistor R5 is connected to the negative input end of the transimpedance amplifier, the second end is connected to node V7, and the positive output end of the transimpedance amplifier is connected to node V7; the positive input end of the transimpedance amplifier is connected to the reference voltage VREF, the first end of resistor R6 is connected to the positive input end of the transimpedance amplifier, the second end is connected to node V8, and the negative output end of the transimpedance amplifier is connected to node V8.

[0032] In this single-ended to differential structure, the voltage relationship between node V7 and node V5 (V5-VREF) / R7=-(V7-VREF) / (R5), the voltage relationship between node V8 and node V5 (V5-VREF) / R7=(V8-VREF) / (R5), and the voltage difference between node V7 and node V8 and the voltage relationship between node V5 (V5-VREF) / R7=-(V7-V8) / (2*R5) can be obtained; the detachment status of the ECG electrode can be distinguished according to the voltage of node V7, the voltage of node V8, or the voltage difference between node V7 and node V8.

[0033] Next, please refer to Figure 2 , which is a structural diagram of connecting node V5 to a single-ended operational amplifier, wherein node V5 is connected to a first end of resistor R7 through switch SW3, and a second end of resistor R7 is connected to a negative input end of the transimpedance amplifier, a first end of resistor R5 is connected to the negative input end of the transimpedance amplifier, and a second end is connected to node V7, and an output end of the transimpedance amplifier is connected to node V7; a positive input end of the transimpedance amplifier is connected to a reference voltage VREF.

[0034] In the structure of the single-ended operational amplifier, the voltage relationship between the node V7 and the node V5 is: (V5-VREF) / R7=(VREF-V7) / R5, and the detachment status of the ECG electrode can be determined based on the voltage of the node V7.

[0035] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0036] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. An ECG dropout detection method, characterized in that: The steps include: Connecting a differential unit in parallel between the first electrode to be detected for detachment and the second electrode to obtain an ECG differential signal between the first electrode and the second electrode; Charging the first electrode and the second electrode respectively, and discharging after charging is completed; After the preset discharge time is over, the voltage at one of the electrodes is measured, and the electrode shedding condition is identified based on the measured voltage; After the set discharge time is over, one of the electrodes is connected to a single-ended to differential transimpedance amplifier or a single-ended op amp transimpedance amplifier by closing the switch; during the voltage change of the electrode charging node, the charge proportional to (V5-VREF) is input to the transimpedance amplifier, amplified and output at the transimpedance amplifier; the transimpedance amplifier is used to obtain a voltage output proportional to (V5-VREF); VREF is a reference voltage connected to the positive input terminal of the transimpedance amplifier, and V5 is the voltage of the electrode charging node; After the first electrode or the second electrode is connected to a single-ended to differential transimpedance amplifier, the voltages of the two electrode charging nodes are directly pulled to the input common-mode voltage by the negative feedback of the transimpedance amplifier; at this time, the two electrode charging nodes have two discharge paths, the main discharge path is a closed switch, and the secondary discharge path is the circuit on the left side of the two electrode charging nodes; when the switch is disconnected, discharge is carried out through the secondary discharge path.

2. The ECG dropout detection method according to claim 1, wherein: The step of distinguishing the electrode detachment situation according to the measured voltage comprises: If the measured voltage is small, it means that the voltage at the electrode is discharged quickly and both electrodes are not detached; If the measured voltage is large, it means that the voltage at the electrode is discharged slowly and both electrodes have fallen off; If the measured voltage is in the middle, it means that the voltage discharge speed at the electrode is in the middle, one electrode has fallen off, and the other electrode has not fallen off.

3. The ECG fall-off detection method according to claim 1, characterized in that: The amplifier is a transimpedance amplifier; The negative input terminal of the transimpedance amplifier receives the electrode to be measured, the positive input terminal is connected to the reference voltage VREF, and the voltage outputted by the output terminal is proportional to (V5-VREF).

4. The ECG fall-off detection method according to claim 1, characterized in that: A sign that the charging of the first electrode and the second electrode is completed is that the voltages of the first electrode and the second electrode are stable.

5. The ECG fall-off detection method according to claim 4, characterized in that: After the first electrode and the second electrode are fully charged, the voltages therebetween are equal or there is a voltage difference therebetween.

6. The ECG dropout detection method according to claim 1, wherein: The preset discharge time is greater than a first threshold time and less than a second threshold time.

7. The ECG dropout detection method according to claim 6, wherein: Between the first threshold time and the second threshold time, the discharge curves of the three situations, namely, both electrodes are not detached, one electrode is detached, and both electrodes are detached, are different.

8. The ECG fall-off detection method according to claim 1, characterized in that: The differential unit is a capacitor.

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