WO2020073979A1

WO2020073979A1 - Shielded active electrode for physiological electrical detection

Info

Publication number: WO2020073979A1
Application number: PCT/CN2019/110533
Authority: WO
Inventors: 刘红星; 屈永东; 刘乐
Original assignee: 南京大学
Priority date: 2018-10-11
Filing date: 2019-10-11
Publication date: 2020-04-16
Also published as: CN109171700A; CN109171700B

Abstract

Disclosed is a shielded active electrode for physiological electrical detection, which is characterized in that: (1) the shielded active electrode comprises upper, middle and lower PCBs, and the three PCBs are stacked together and are welded into an integral body through welding seams; (2) each of the PCBs is provided with at least two copper-applied shielding layers, and all copper-applied shielding layers of each of the PCBs communicate through copper-plating through holes; (3) shielding bodies of the upper, middle and lower PCBs are welded through welding seams between PCBs to form a complete shielding body; and (4) devices, such as an operational amplifiers, are distributed on an upper surface of the lower PCB or on a lower surface of the upper PCB, and are surrounded by the complete shielding body. According to the solution, the shielded active electrode has firm connection, a compact structure and a good shielding effect, and can effectively restrict interference and noise, especially mobile phone interference.

Description

Shielded active electrode for physiological electrical detection

This application requires the priority of the Chinese patent application submitted to the China Patent Office on October 11, 2018, with the application number CN201811199712.5 and the application name "a shielded active electrode for physiological electrical detection", the entire content of which is cited by reference Incorporated in this application.

Technical field

The present application relates to a shielded active electrode for physiological electrical detection.

Physiological electrical signals refer to electrical signals carrying physiological information, such as electrocardiogram, electroencephalogram, myoelectricity, etc. Active electrodes (Active Electrodes, AE), that is, electrodes with built-in detection circuits, are increasingly used in physiological signal detection, especially in wearable occasions. The reason is: the active electrode is impedance converted by its built-in circuit near the measuring point, and its low output impedance can improve the accuracy of the detection circuit and the robustness to environmental interference, such as suppressing 50Hz or 60Hz AC interference and weakening the cable Motion artifacts (cable motion artifacts), etc. Arrangement of shielding treatment for the active electrode can further suppress the 50Hz or 60Hz AC interference, weaken the artifacts of the cable movement, and at the same time, it can also effectively suppress the radio frequency interference of mobile phones.

Background technique

There are two ways to shield the active electrode. One is to connect the output of the active electrode directly to the shield, and the other is to connect the "virtual" ground of the active electrode to the shield through a voltage follower. As shown in Figure 6 and Figure 7 respectively. Regardless of the shielding circuit, at present, there are mainly two types of shields, one is a single PCB circuit board style, and the other is a single PCB circuit board plus shield cover style.

The first type of shield single PCB circuit board style, as shown in Figure 8, provides a certain shielding effect by providing a shielding layer and a shielding ring, but the shielding surface is not large enough. In the example of FIG. 8, the detection board is connected to the input of the operational amplifier, the output of the operational amplifier is connected to the shield, and the copper-plated through holes communicate with each shield layer / ring, but the operational amplifier and other devices on the upper device layer are bare and unshielded. The active electrode in FIG. 8 is used for non-contact detection, so an insulating layer is provided on the shield ring and the detection disk.

Another type of shielding body-a single PCB circuit board plus a shielding cover, as shown in Figure 9. Although this style increases the shielding area due to the use of the shield, the fixed installation of the shield is inconvenient.

In the patent application "An Active Electrode for Physiological Electrical Signal Detection" (application number 201810180948.8), an application is proposed to protect an active electrode circuit solution, as shown in FIG. 5, characterized in that its circuit includes a voltage following basic The circuit, the "virtual ground" feedback circuit and the DC power supply are three parts. The DC power supply supplies the voltage follower basic circuit and the "virtual ground" feedback circuit; the voltage follower basic circuit is an op amp-based voltage follower whose input is human body measurement Point potential, and output potential to the back-end circuit; "virtual ground" feedback circuit mainly includes a voltage follower based on operational amplifier and a current limiting resistor, "virtual ground" feedback to the human body through the voltage follower and current limiting resistor in turn table. In Figure 5, V + and V- are the positive and negative ends of the DC power supply; the potential vin at the measurement point A on the body surface is input to the operational amplifier A1, and its output vout is connected to the back-end circuit to form the basic circuit of the voltage follower of the active electrode ; Bypass the V + and V- ends of the positive and negative ends of the DC power supply, and connect two equal-value resistors R in series, then the potential of the middle connection point G of the two resistors R is (V ++ V-) / 2, which may be called Point potential points form a "virtual ground", and then input the "virtual ground" potential into the voltage follower A2 based on the operational amplifier, and its output is fed back to another point F on the body surface through the current limiting resistor r, forming a "virtual ground" feedback circuit. This patent application protects the basic circuit part scheme of the active electrode, and does not limit the shielding part of the active electrode.

references:

[1] Jiawei Xu, Srinjoy Mitra, Chris Van Hoof, Refet Firat Yazicioglu and Kofi A. A. Makinwa, Active Electrodes for Wearable EEG Acquisition: Review and Electronics Design Methodology, DOI 10.1109 / RB388.2017.

[2] Liu Hongxing, Qu Yongdong, Liu Le: an active electrode for physiological electrical signal detection, patent application 201810180948.8, application date 20180302

[3] Liu Hongxing, Liu Le, Qu Yongdong: A multifunctional electrocardiographic limb clamp for active electrodes, patent application 201810370809.1, application date 20180424

Summary of the invention

Purpose of the invention.

A shielded active electrode solution for physiological electrical detection is proposed. On the one hand, it has a large shielding area and guarantees the shielding effect. On the other hand, it is convenient and reliable to install and fix.

Technical solutions.

The invention relates to a shielded active electrode for physiological electrical detection, which is characterized in that (1) it includes three PCB boards on the upper, middle and lower sides, the three PCB boards are stacked together, and are welded into a whole by welding seams; (2) Each PCB board has at least 2 copper-clad shielding layers, and all the copper-plated shielding layers of each PCB board are connected through copper-plated through-holes; (3) The shielding bodies of the upper, middle, and lower PCB boards are welded through the welds between the boards To form a complete shield; (4) operational amplifiers and other devices are distributed on the upper surface of the lower PCB or the lower surface of the upper PCB, surrounded by the complete shield. The overall structure is shown in FIG. 1, and the structural schematic diagrams of the upper, middle, and lower PCB boards are shown in FIG. 2, FIG. 3, and FIG. 4, respectively.

According to the above-mentioned shielded active electrode for physiological electrical detection, it is characterized in that its circuit includes a voltage following basic circuit, a "virtual ground" feedback circuit, a shielding circuit and a DC power supply. The DC power supply follows the voltage The basic circuit, the "virtual ground" feedback circuit and the shielding circuit are powered by three parts; the voltage follower basic circuit is a voltage follower based on an operational amplifier, whose input is the human body measuring point potential and outputs the potential to the back-end circuit; "virtual ground" The feedback circuit mainly includes an op amp-based voltage follower and a current-limiting resistor. The "virtual ground" is fed back to the body surface through the voltage follower and the current-limiting resistor in sequence; the shielding circuit connects the output of the voltage-following basic circuit to the shield . See Figure 6. In Figure 6, V + and V- are the positive and negative ends of the DC power supply; the potential vin at the measurement point A on the body surface is input to the operational amplifier A1, and its output vout is connected to the back-end circuit to form the basic circuit of the voltage follower of the active electrode ; Bypass the V + and V- ends of the positive and negative ends of the DC power supply, and connect two equal-value resistors R in series, then the potential of the middle connection point G of the two resistors R is (V ++ V-) / 2, which may be called Point potential point to form a "virtual ground", and then input the "virtual ground" potential to the voltage follower A2 based on the operational amplifier, and its output is fed back to another point F on the body surface through the current limiting resistor r, forming a "virtual ground" feedback circuit; The output vout is connected to the shield at the same time, see point S in FIG. 6 to form a shield circuit.

According to the above-mentioned shielded active electrode for physiological electrical detection, it is characterized in that its circuit includes a voltage following basic circuit, a "virtual ground" feedback circuit, a shielding circuit and a DC power supply. The basic circuit, the "virtual ground" feedback circuit and the shielding circuit are powered by three parts; the voltage follower basic circuit is a voltage follower based on an operational amplifier, whose input is the human body measuring point potential and outputs the potential to the back-end circuit; "virtual ground" The feedback circuit mainly includes a voltage follower based on an operational amplifier and a current limiting resistor. The "virtual ground" is fed back to the body surface through the voltage follower and the current limiting resistor in sequence; the shielding circuit passes the "virtual ground" through a voltage follower circuit. Connect to the shield. See Figure 7. In Figure 7, V + and V- are the positive and negative ends of the DC power supply; the potential vin at the measurement point A on the body surface is input to the operational amplifier A1, and its output vout is connected to the back-end circuit to form the basic circuit of the voltage follower of the active electrode ; Bypass the V + and V- ends of the positive and negative ends of the DC power supply, and connect two equal-value resistors R in series, then the potential of the middle connection point G of the two resistors R is (V ++ V-) / 2, which may be called Point potential point to form a "virtual ground", and then input the "virtual ground" potential to the voltage follower A2 based on the operational amplifier, and its output is fed back to another point F on the body surface through the current limiting resistor r, forming a "virtual ground" feedback circuit; At the same time, the "virtual ground" potential is input to the voltage follower A3 based on the operational amplifier, and the A3 output is connected to the shield, see point S in FIG. 7 to form a shield circuit.

According to the above-mentioned shielded active electrode for physiological electrical detection, it is characterized in that the upper, middle and lower three PCB boards not only have several copper-plated through holes connecting different copper-plated shielding layers in the board, but also each PCB There are two positioning through holes on the board, and the positions of the positioning through holes on the three PCB boards correspond to facilitate the positioning between the three PCB boards when they are stacked and soldered. See Figure 2, Figure 3 and Figure 4.

Beneficial effect.

This shielded active electrode scheme is designed with three PCB boards stacked and welded together. It is very reliable, even one screw is not needed, and the welding seam between the boards also serves as wiring. The structure is compact and clever. On the other hand, it has a more complete shielding body and better shielding effect than the single-board PCB shielding style active electrode.

The inventor made shielded active electrodes according to the proposed technical solution. See the examples for details, and conducted comparative test experiments. The core module of the test device is the USB 6289 module of NI company. Connected to the computer and written the corresponding software, a set of high-precision 2-channel voltage synchronous acquisition system with signal processing function is constructed. Use this system to collect two voltage signals simultaneously in differential mode. One channel is a voltage signal from the left arm to the right arm based on the unshielded active electrode. The two electrode clips near the wrist in Figure 10 are unshielded active electrode clips The other way is based on the voltage signal from the left arm to the right arm of the shielded active electrode of the present invention-the two electrode clips far from the wrist in FIG. 10 are the shielded active electrode of the present invention.

Test experiment. The synchronous sampling rate is set to 128kHz, and two real-time FIR bandpass filters with a passband of 0.5-80Hz are used for the two signals collected synchronously. The unit sample response h (n) length of the filter is taken as 10 seconds. The subject remained quiet and the cable was stationary. During data recording, someone else called the subject's mobile phone to cause interference. Fig. 12 shows the waveforms of the two signals recorded in this case; in Fig. 12, the upper two figures are the signal waveform diagram and the spectrum diagram based on the unshielded active electrode, and the lower two figures are the shielded active diagrams based on the present invention. Electrode signal waveform diagram and spectrum diagram. Obviously, the detection result of the unshielded active electrode shows strong cell phone interference, while the detection result of the shielded active electrode of the present invention is almost invisible. After many experiments by many subjects, the conclusion is consistent. It shows the strong anti-jamming effect of the present invention.

BRIEF DESCRIPTION

FIG. 1 is a schematic diagram of the overall structure of the shielded active electrode of the present invention

FIG. 2 is a schematic diagram of the structure of the PCB board on the shielded active electrode of the present invention

FIG. 3 is a schematic diagram of the structure of the PCB board in the shielded active electrode of the present invention

FIG. 4 is a schematic diagram of the structure of the PCB board under the shielded active electrode of the present invention

FIG. 5 is a schematic diagram of the basic circuit principle of an active electrode invented in the past

FIG. 6 is a schematic diagram of the active electrode output driving shield of the present invention

FIG. 7 is a schematic diagram of the “virtual ground” driving shield of the active electrode circuit of the present invention

Figure 8, the schematic diagram of the traditional single PCB circuit board shield

Figure 9, the traditional single PCB circuit board plus shielding shielding style diagram

Figure 10, Schematic diagram of electrode placement in the comparative test of shielded active and unshielded active electrodes

Figure 11, schematic diagram of the realization of the shielded active electrode clip composition

FIG. 12 is a schematic diagram of the comparative test result of the shielded active electrode of the present invention.

Examples

According to the technical scheme of the present invention, according to the circuit diagram of FIG. 6, the upper, middle, and lower PCBs are designed and made in kind, and the devices of the three boards are welded, and the upper, middle, and lower boards are stacked and welded together to form the shield. The body module of the source electrode, as shown in the upper left figure of Figure 11, at the same time, according to the patent application "a multifunctional ECG detection limb clip facing the active electrode" (application number 201810370809.1 filing date 20180424), a double-column limb clip is made As shown in the upper right diagram of FIG. 11, combining them forms a complete clip-on shield active electrode, as shown in the lower portion of FIG. 11. In the implementation, the DC power supply selected the 3V battery CR2032, the two operational amplifiers A1 and A2 as the core device selected the OPA320, the two resistors R selected 100kΩ, and the current limiting resistor r chose 0Ω for convenience. In the implementation, the connection welds of the three upper, middle and lower PCB boards are arranged as shown in Figure 2, Figure 3 and Figure 4; the device is only arranged on the upper surface of the lower PCB board, and the corresponding four welds are simultaneously The connection between the power supply V +, V-, output vout and shielding board. Both a probe and a feedback connector on the input end use concave buttons, and the connector on the output end uses convex buttons.

The inventor has also implemented the shielding method according to FIG. 7, OP3 was selected for A3, and other parts are basically the same as those in FIG. 6.

For the shielded active electrodes implemented based on the two modes of FIG. 6 and FIG. 7, the above comparative test experiment was conducted, and both achieved excellent shielding effects, as shown in FIG. 12.

Claims

The invention relates to a shielded active electrode for physiological electrical detection, which is characterized in that (1) it includes three PCB boards on the upper, middle and lower sides, the three PCB boards are stacked together, and are welded into a whole by welding seams; (2) Each PCB board has at least 2 copper-clad shielding layers, and all the copper-plated shielding layers of each PCB board are connected through copper-plated through-holes; (3) The shielding bodies of the upper, middle, and lower PCB boards are welded through the welds between the boards To form a complete shield; (4) operational amplifiers and other devices are distributed on the upper surface of the lower PCB or the lower surface of the upper PCB, surrounded by the complete shield.
A shielded active electrode for physiological electrical detection according to claim 1, characterized in that its circuit includes a voltage follower basic circuit, a "virtual ground" feedback circuit, a shielded circuit and a DC power supply. The DC power supply is The voltage-following basic circuit, the "virtual ground" feedback circuit and the shielding circuit are powered by three parts; the voltage-following basic circuit is a voltage follower based on an operational amplifier, whose input is the human body measuring point potential and outputs the potential to the back-end circuit; "virtual The "ground" feedback circuit mainly includes a voltage follower based on an operational amplifier and a current limiting resistor. The "virtual ground" is fed back to the body surface through the voltage follower and the current limiting resistor in sequence; the shielding circuit connects the output of the voltage follower basic circuit to Shield.
A shielded active electrode for physiological electrical detection according to claim 1, characterized in that its circuit includes a voltage follower basic circuit, a "virtual ground" feedback circuit, a shielded circuit and a DC power supply. The DC power supply is The voltage-following basic circuit, the "virtual ground" feedback circuit and the shielding circuit are powered by three parts; the voltage-following basic circuit is a voltage follower based on an operational amplifier, whose input is the human body measuring point potential and outputs the potential to the back-end circuit; "virtual The "ground" feedback circuit mainly includes a voltage follower based on an operational amplifier and a current limiting resistor. The "virtual ground" is fed back to the body surface through the voltage follower and the current limiting resistor in sequence; the shielding circuit follows the "virtual ground" through a voltage Connect to the shield after the circuit.
A shielded active electrode for physiological electrical detection according to claim 1, characterized in that the upper, middle and lower three PCB boards not only have a number of copper-plated through-holes connecting different copper shielding layers in the board, but also each There are two positioning through holes on each PCB, and the positions of the positioning through holes on the three PCB boards correspond to each other to facilitate positioning between the three PCB boards when they are stacked and soldered.