Capacitive coupling electrode for weak current pulse signal detection

Abstract

The invention relates to the field of electric signal measurement, and particularly provides a capacitive coupling electrode for weak current pulse signal detection, the electrode sequentially comprises a first insulating layer, a conductive layer, a second insulating layer and a covering layer from bottom to top, the surface of the conductive layer is provided with a convex structure, the convex structure is arranged on the plane of one side, close to the first insulating layer, of the conductive layer, and the second insulating layer is arranged on the covering layer. The convex structure extends into the first insulating layer; the first insulating layer is in contact with the to-be-detected plane. According to the electrode, capacitive coupling exists between the conducting layer and the detection surface, the lower surface of the conducting layer is provided with the protruding structure, the distance between the protruding structure and the detection surface is small, a plurality of coupling points are formed, and each protruding unit corresponds to the coupling point. The coupling points enable the capacitance between the detection surface and the conductive layer to be kept stable, and the capacitance is not easy to change due to the influence of position change and the like, so that the capacitance is stable; meanwhile, the protruding structures further have the effects of gathering the electric field, increasing the induction area and reducing dielectric impedance, the signal-to-noise ratio is further increased, and the detection accuracy is improved.

Description

Technical Field

[0001] The present application relates to the field of electrical signal measurement, and in particular to a capacitive coupling electrode for detecting weak electrical pulse signals. Background Art

[0002] Weak electric pulse signals refer to electrical signals with low amplitude and power, which can reflect temperature, pressure, acceleration, life activities, etc. They are widely used in fault detection, material property detection, organism detection, weather monitoring, etc. For example, the microstructure and surface characteristics of materials can be detected through weak electric pulse signals on the surface of materials, and the vital signs of organisms can be detected through bioelectric signals on the surface of organisms.

[0003] The intensity of weak current pulse signals is small and mixed with the surrounding noise, making them difficult to distinguish. This results in a low signal-to-noise ratio for weak current pulse signals and attenuation during transmission. Therefore, weak current pulse signals are difficult to detect accurately. Since low-frequency noise can be filtered out and the signal-to-noise ratio can be improved, capacitive coupling is often used to detect weak current pulse signals. The cutoff frequency of the capacitor is less than or equal to the frequency of the weak current pulse signal. In this way, the weak current pulse signal to be detected can be turned on and the lower frequency noise signal cannot pass through, thereby playing the role of detecting weak current pulse signals. Compared with direct wire connection, capacitive coupling can transmit signals without contact, reducing transmission loss and energy consumption and improving transmission efficiency.

[0004] However, changes in ambient temperature and mechanical stress will cause changes in capacitance. Due to changes in capacitance, the signal-to-noise ratio of existing capacitive coupling electrodes is relatively low. Capacitance changes will cause the response frequency to change. The reduction in capacitance will cause more useful low-frequency signals to be attenuated, reducing the amplitude of the effective signal, relatively increasing the impact of noise and reducing the signal-to-noise ratio. The increase in capacitance will allow more low-frequency components to pass through. These low-frequency components contain noise, which may increase the noise level and reduce the signal-to-noise ratio. Therefore, there is a lack of coupling electrodes that have a high detection signal-to-noise ratio and can accurately detect weak electrical pulse signals. Summary of the invention

[0005] The purpose of the present invention is to provide a capacitive coupling electrode for detecting weak electric pulse signals in view of the above-mentioned deficiencies in the prior art, so as to solve the problem of low signal-to-noise ratio and poor accuracy of electrode detection of weak electric pulse signals in the prior art.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: The present application provides a capacitive coupling electrode for detecting weak electric pulse signals, which comprises, from bottom to top, a first insulating layer, a conductive layer, a second insulating layer, and a covering layer. A protruding structure is arranged on the surface of the conductive layer, the protruding structure is arranged on a plane of the conductive layer close to one side of the first insulating layer, and the protruding structure extends into the first insulating layer; the first insulating layer is in contact with the plane to be detected.

[0007] Furthermore, a non-penetrating hole is arranged on the surface of the first insulating layer away from the conductive layer.

[0008] Furthermore, the sum of the depth of the hole and the height of the protruding structure is less than four fifths of the thickness of the first insulating layer and greater than one half of the thickness of the first insulating layer.

[0009] Furthermore, the holes and the protrusions are arranged alternately.

[0010] Furthermore, the size of the lower side of the hole is larger than the size of the side close to the conductive layer, forming a cone shape that is wider at the bottom and narrower at the top.

[0011] Furthermore, a protrusion is arranged on the surface of the cover layer away from the second insulating layer.

[0012] Furthermore, the material of the conductive layer is one of carbon material, gold, silver and platinum.

[0013] Furthermore, the material of the protrusion structure is carbon nanotube.

[0014] Furthermore, the material of the first insulating layer and the second insulating layer is one of polyamide, polyethylene and polypropylene.

[0015] Furthermore, the material of the covering layer is aluminum or copper.

[0016] Compared with the prior art, the present invention has the following beneficial effects: in the electrode of the present application, there is capacitive coupling between the conductive layer and the detection surface, a protruding structure is provided on the lower surface of the conductive layer, and the top of the protruding structure (close to the side of the first insulating layer) is close to the detection surface, forming multiple coupling points, and each protruding unit corresponds to a coupling point. The coupling points keep the capacitance between the detection surface and the conductive layer stable and not easily affected by position changes, so the capacitance is relatively stable, the signal-to-noise ratio of the weak current pulse signal is higher, and the detection is more accurate.

[0017] The raised structure also enhances the electric field strength, forms a stronger local electric field, improves the sensing ability of the conductive layer, and increases the strength of the induced signal; at the same time, the raised structure reduces the dielectric impedance, improves the signal transmission efficiency, weakens the signal attenuation, and improves the signal-to-noise ratio; the raised structure increases the sensing area, and the larger sensing area increases the induced charge, thereby increasing the signal level, increasing the signal strength, improving the signal-to-noise ratio, and making the detection results more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of a capacitive coupling electrode for detecting weak electric pulse signals provided by the present invention; Figure 2 A schematic diagram of a first insulating layer in another capacitive coupling electrode for detecting weak electric pulse signals provided by the present invention.

[0019] Icon: 1-first insulating layer; 2-conductive layer; 3-second insulating layer; 4-covering layer. DETAILED DESCRIPTION

[0020] In order to make the implementation process of the present invention clearer, it will be described in detail below with reference to the accompanying drawings.

[0021] The present invention provides a capacitive coupling electrode for detecting weak electric pulse signals, such as Figure 1 As shown, the electrode includes a first insulating layer 1, a conductive layer 2, a second insulating layer 3, and a covering layer 4. The first insulating layer 1 is arranged at the bottom, the conductive layer 2 is arranged on the upper side of the first insulating layer 1, the second insulating layer 3 is arranged on the side of the conductive layer 2 away from the first insulating layer 1, and the covering layer 4 is arranged on the side of the second insulating layer 3 away from the conductive layer 2. The lower side of the first insulating layer 1 contacts the detection surface.

[0022] The materials of the first insulating layer 1 and the second insulating layer 3 are polyamide, polyethylene or polypropylene, which have good insulation properties and can provide a stable insulation environment between the detection surface and the conductive layer 2 and between the conductive layer 2 and the covering layer 4, avoiding short circuits and signal interference, that is, good electrical insulation properties, preventing short circuits between the conductive layer 2 and the surrounding environment or the detection surface; at the same time, these materials have good thermal stability, and the heat generated during the use of the electrode will not cause deformation of the insulating layer or reduction of the insulation properties, and still maintain good insulation properties. In addition to the role of electrical insulation, the first insulating layer 1 also plays a mechanical role in supporting the upper structure. The material of the conductive layer 2 is one of carbon materials, gold, silver, and platinum; it has good conductivity. The material of the covering layer 4 is aluminum or copper, which has good electromagnetic shielding ability, can effectively block external electromagnetic interference, and avoid affecting the detected weak electric pulse signal. Since the intensity of the weak electric pulse signal is low and sensitive to the external environment, the external electromagnetic interference will change the amplitude, frequency and phase of the weak electric pulse signal, causing signal distortion, and will also produce noise superposition, which greatly reduces the accuracy of signal detection. The thickness of the first insulating layer 1 is 5-10 μm. Thus, the thinner thickness is conducive to the weak electric pulse signal on the detection surface to induce more charges in the conductive layer 2, thereby improving the detection accuracy; at the same time, it can also ensure the insulation effect and avoid the transmission of DC signals. The first insulating layer 1, the conductive layer 2, the second insulating layer 3, and the covering layer 4 are collinear and perpendicular to the central axis of the plane where they are located, and in the vertical downward direction.

[0023] A raised structure is arranged on the lower surface of the conductive layer 2, that is, the raised structure is arranged on the plane of the conductive layer 2 close to the first insulating layer 1, and the raised structure extends into the first insulating layer 1; the top of the raised structure (close to the first insulating layer 1) is closer to the detection surface; in this way, a stable coupling point is formed between the raised structure and the detection surface, reducing the capacitance change caused by the relative position change between the detection surface and the electrode. At the same time, it also plays a role in improving the strength of the induced signal. Specifically, in the first aspect, the raised structure concentrates the electric field and enhances the electric field strength. The raised structure increases the contact area between the conductive layer 2 and the first insulating layer 1, and forms a stronger local electric field between the conductive layer 2 and the detection surface. The strong local electric field can more effectively sense the weak electric signal on the detection surface, and the concentrated electric field helps to improve the charge sensing ability and the overall strength of the signal; the raised structure also increases the effective sensing area of ​​the conductive layer 2, which can sense more signal charges, improve the signal level, increase the signal-to-noise ratio, and improve accuracy. Secondly, the raised structure can reduce the dielectric impedance in the signal path. The lower dielectric impedance helps to reduce signal attenuation and improve signal transmission efficiency. Specifically, the increased contact area reduces the current density per unit area, thereby reducing the contact resistance, making it easier for electrical signals to be transmitted to the conductive layer 2, and the larger contact area provides more paths for current to pass through, thereby reducing the loss and attenuation of the signal during transmission; due to the presence of the raised structure, some parts of the conductive layer 2 are closer to the detection surface, reducing the thickness of the insulating layer between the conductive layer 2 and the detection surface. For AC signals, the impedance is inversely proportional to the capacitance, and increasing the capacitance value will lead to a decrease in impedance, thereby making signal transmission more efficient; the raised structure reduces the thickness of the insulating material in the signal path, and the current can reach the conductive layer 2 through a shorter path, reducing the loss of the signal during transmission, and also reducing parasitic resistance and inductance. These parasitic effects usually introduce additional noise and loss in high-frequency signals. Thirdly, a larger sensing area can sense more signal charges, and the charges are converted into higher signal levels, that is, the strength of the signal is increased. A larger signal strength makes it easier to distinguish the signal from the noise and improve the signal-to-noise ratio. However, noise is usually random and dispersed. When the sensing area increases, the noise from different areas will cancel each other out or average out in general. This averaging effect makes the noise contribution per unit area smaller, so the overall noise level is relatively reduced. In other words, the increase in the sensing area directly increases the amount of the sensed signal, and the interference of external noise on the signal is evenly distributed over the increased area. Therefore, the rate of increase of the signal is usually greater than the rate of increase of the noise, resulting in an overall improvement in the signal-to-noise ratio.

[0024] Preferably, the raised structure is composed of a plurality of raised units arranged in an array, and the arrangement can be a rectangular array, and the spacing between adjacent raised units is 1-1.5 times the size of the raised units, so that more raised units can be set without causing excessive local electric field strength. The shape of the raised structure can be a pointed cone, a hemispherical shape, a rectangular parallelepiped, etc. The raised structure is a pointed cone, and the lower part forms a tip, which can concentrate the electric field, making the electric field stronger in the top area of ​​the raised structure, which helps to more sensitively sense the charge of weak electric pulse signals, improve signal strength, and enhance the signal-to-noise ratio; the raised structure is a hemispherical shape, which can provide a more uniform electric field distribution, reduce the risk of electrical breakdown or discharge caused by excessive local electric fields, and have stronger stability; the raised structure is a rectangular parallelepiped, which is simple to prepare and has good stability. The size of the raised unit is between 500nm-20μm. Too large a size will introduce stray noise and reduce the signal-to-noise ratio; too small a raised structure has limited ability to sense charge, resulting in less signal strength enhancement and a low signal-to-noise ratio.

[0025] The material of the protruding structure can be the same as or different from the material of the conductive layer 2. Preferably, the material of the protruding structure can be highly conductive gold, silver, carbon nanotubes, etc. More preferably, the material of the protruding structure of the present application is carbon nanotubes, which are stacked together to form the protruding structure. Carbon nanotubes are a nanoscale tubular structure material composed of carbon atoms, which has good conductivity and a large specific surface area. Specifically, the nanoscale size and columnar structure of carbon nanotubes generate an extremely strong electric field at their tips. The electric field enhancement effect of carbon nanotubes amplifies weak signals in the tip area, thereby increasing the signal level, significantly enhancing the electric field strength, and improving the signal-to-noise ratio of weak electric pulse signals. The larger specific surface area increases the sensing area of ​​the charge. The large surface area of ​​carbon nanotubes can better disperse the influence of external noise, so that the noise is averaged over the entire sensing area, reducing the interference of local noise. At the same time, more charges are induced, the overall strength of the signal is improved, and the signal-to-noise ratio is improved. The better the conductivity, the conductivity can be close to or exceed that of traditional metals such as copper. Carbon nanotubes can effectively conduct the sensing signals and reduce the loss during signal transmission, thereby improving the signal strength and the signal-to-noise ratio. In addition, carbon nanotubes have a high thermal conductivity. Carbon nanotubes can quickly conduct heat and reduce the accumulation of heat at the interface. The accumulation of heat will cause the resistance of the material to increase with the increase in temperature, causing signal distortion.

[0026] When in use, the first insulating layer 1 is in contact with the surface to be detected away from the side of the conductive layer 2, and a weak electric pulse signal is transmitted on the surface to be detected. During detection, an electric field is formed between the detection surface and the conductive layer 2. When there is an electric signal on the detection surface (such as skin, material surface, etc.), these signals will induce corresponding charge changes on the conductive layer 2, and the weak electric pulse signal on the detection surface can be effectively sensed in the conductive layer 2, and the conductive layer 2 senses and transmits the electric signal on the detection surface. The capacitive coupling method reduces the contact noise caused by direct electrical contact, and can also block the transmission of DC signals, only transmit AC signals, and avoid the influence of DC offset; because the signal transmission is purer and the noise level is low, it is conducive to accurate detection of weak signals. The raised structure on the lower side of the conductive layer 2 plays a role in concentrating the electric field, enhancing the electric field strength, improving the signal level, and increasing the signal-to-noise ratio; reducing the dielectric impedance in the signal path, and improving the transmission efficiency of the signal; increasing the sensing area, and converting the charge into a higher signal level, that is, increasing the strength of the signal. The coupling electrode of the present application can accurately detect weak electric pulse signals.

[0027] Furthermore, a non-penetrating hole is arranged on the surface of the first insulating layer 1 away from the conductive layer 2. The holes are arranged alternately with the protrusion structures, that is, the holes are arranged between adjacent protrusion units, not opposite to the protrusion units, such as Figure 2 As shown. In this way, on the one hand, the existence of the hole reduces the effective capacitance of the first insulating layer 1, thereby reducing the influence of the capacitance change on the detected weak electric pulse signal and improving the signal-to-noise ratio.

[0028] On the other hand, the presence of holes concentrates the electric field around the holes, gathers the electric field, and enhances the electric field strength in these areas, which is equivalent to increasing the weak electric pulse signal to be detected, making the weak signal easier to detect; at the same time, the non-penetrating holes have a shielding effect, and the insulating material around the holes can block part of the external electromagnetic noise, reduce the impact of external electromagnetic interference, thereby reducing the impact of noise on the signal and improving the signal-to-noise ratio. On the other hand, the holes reduce the direct contact area between the conductive layer 2 and the detection surface, reducing the parasitic capacitance effect. The parasitic capacitance will cause additional signal loss and noise. Reducing the parasitic capacitance through the holes can improve the purity of the signal and enhance the signal-to-noise ratio. On the other hand, the signal crosstalk is reduced; when the holes are not set, the signal sensed at the protruding structure depends on multiple coupling sources, which is the superposition of the effects of multiple coupling sources; the presence of the holes disperses the electric field, reduces the crosstalk between the protruding units, and makes the coupled signal more accurate. Furthermore, the sum of the depth of the hole and the height of the protruding structure is less than four-fifths of the thickness of the first insulating layer 1 and greater than one-half of the thickness of the first insulating layer 1; holes that are too shallow and smaller protruding structures have a weaker effect in guiding the electric field, which will lead to uneven electric field distribution, local hot spots and areas with weak signals, while holes that are too deep and protruding structures that are too high will cause the electric field to be too concentrated, increasing parasitic capacitance and electric field interference.

[0029] Furthermore, the size of the bottom side of the hole is larger than the size of the side close to the conductive layer 2, forming a cone shape that is wide at the bottom and narrow at the top. In this way, the shape of the cone-shaped hole that is wide at the bottom and narrow at the top allows the electric field lines to be effectively guided and gathered when passing through the hole, and the wider opening at the bottom of the hole gathers more electric fields, forming a stronger electric field concentration area, which increases the electric field strength in the bottom area of ​​the hole, helps to increase signal strength and improve the signal-to-noise ratio; at the same time, the upper part of the cone-shaped hole is narrow, which effectively limits the path of external electromagnetic noise entering the hole, reduces the impact of external electromagnetic interference on the signal, reduces the introduction of noise, and thus improves the signal-to-noise ratio.

[0030] Furthermore, a protrusion is provided on the surface of the side of the covering layer 4 away from the second insulating layer 3, and the shape of the protrusion is a pointed cone with the tip facing upward, and the material of the protrusion is the same as that of the covering layer 4. In this way, the protrusion increases the distance between the covering layer 4 and the external environment, thereby enhancing the shielding effect against external electromagnetic interference. The pointed cone-shaped structure causes the electric field lines to gradually converge to the tip, and the electric field gathers toward the tip, thereby enhancing the concentration of the electric field at the tip. Through the electric field focusing effect of the pointed cone-shaped structure, the influence of external interference signals on the electrode can be reduced, the noise level can be reduced, and the signal-to-noise ratio can be improved.

[0031] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A capacitive coupling electrode for detecting weak electric pulse signals, characterized in that: The electrode includes, from bottom to top, a first insulating layer, a conductive layer, a second insulating layer, and a covering layer. A protruding structure is arranged on the surface of the conductive layer. The protruding structure is arranged on a plane of the conductive layer close to the first insulating layer, and the protruding structure extends into the first insulating layer. The first insulating layer is in contact with the plane to be detected.

2. The capacitive coupling electrode for detecting weak electric pulse signals according to claim 1, characterized in that: A non-penetrating hole is arranged on the surface of the first insulating layer away from the conductive layer.

3. The capacitive coupling electrode for detecting weak electric pulse signals according to claim 2, characterized in that: The sum of the depth of the hole and the height of the protruding structure is less than four fifths of the thickness of the first insulating layer and greater than one half of the thickness of the first insulating layer.

4. The capacitive coupling electrode for detecting weak electric pulse signals according to claim 3, characterized in that: The holes and the protruding structures are arranged alternately.

5. The capacitive coupling electrode for detecting weak electric pulse signals according to claim 4, characterized in that: The size of the lower side of the hole is larger than the size of the side close to the conductive layer, forming a cone shape that is wider at the bottom and narrower at the top.

6. The capacitive coupling electrode for detecting weak electric pulse signals according to claim 5, characterized in that: A protrusion is arranged on the surface of the cover layer at a side away from the second insulating layer.

7. The capacitive coupling electrode for detecting weak electric pulse signals according to claim 6, characterized in that: The material of the conductive layer is one of carbon material, gold, silver and platinum.

8. The capacitive coupling electrode for detecting weak electric pulse signals according to claim 7, characterized in that: The material of the protrusion structure is carbon nanotube.

9. The capacitive coupling electrode for detecting weak electric pulse signals according to claim 1, characterized in that: The material of the first insulating layer and the second insulating layer is one of polyamide, polyethylene and polypropylene.

10. The capacitive coupling electrode for detecting weak electric pulse signals according to claim 1, characterized in that: The material of the covering layer is aluminum or copper.

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