Open type AC voltage sampling device and AC cable voltage detection system

Abstract

The invention provides an open-type AC voltage sampling device and an AC cable voltage detection system, and the device comprises a printed circuit board which comprises an insulating substrate integrated with a first electrode plate, a second electrode plate and an analog signal conditioning circuit, the analog signal conditioning circuit is used for generating a differential signal according to a first voltage signal from the first electrode plate and a second voltage signal from the second electrode plate; the insulating shell comprises a wire passing hole used for placing an alternating current cable, an opening used for placing the alternating current cable into the wire passing hole and a containing cavity used for installing a printed circuit board, the containing cavity is located on one side of the wire passing hole, and the center line of the wire passing hole is parallel to the printed circuit board installed in the containing cavity; and the overlapped part of the vertical projection of the first electrode plate and the vertical projection of the second electrode plate completely covers the vertical projection of the wire passing hole on the printed circuit board. Installation can be completed without powering off electric equipment.

Description

Technical Field

[0001] The present invention relates to the field of AC voltage detection, and more specifically, to an open-type AC voltage sampling device and an AC cable voltage detection system. Background Art

[0002] At present, the equipment for non-contact detection of AC voltage mainly uses the principle of capacitive coupling. The distributed capacitance between the cable under test and the probe sensing electrode is used to couple the voltage signal. The signal coupled to the probe sensing electrode is then sent to the back-end analog conditioning and digital filtering circuit for processing to obtain the voltage amplitude in the cable under test.

[0003] In the above detection equipment, the probe is generally of the perforated type. During on-site installation, one end of the cable to be tested needs to be removed and passed through the probe's perforation. This requires the on-site equipment to be powered off to install the probe, but this is often unacceptable in the power industry because it will cause power outages in production and power supply equipment, which has a significant impact on user electricity use and production processes. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide an open-type AC voltage sampling device and an AC cable voltage detection system in view of the problem that the on-site equipment needs to be powered off during installation of the above-mentioned non-contact AC voltage detection equipment.

[0005] The technical solution of the present invention to solve the above technical problem is to provide an open-type AC voltage sampling device for sampling the voltage of an AC cable, wherein the open-type AC voltage sampling device comprises: A printed circuit board, comprising an insulating substrate integrated with a first electrode plate, a second electrode plate and an analog signal conditioning circuit, wherein the first electrode plate and the second electrode plate are respectively located on different layers of the insulating substrate and are insulated from each other, and vertical projections of at least a portion of the first electrode plate and the second electrode plate overlap; the analog signal conditioning circuit is electrically connected to the first electrode plate and the second electrode plate, respectively, and is used to generate a differential signal according to a first voltage signal from the first electrode plate and a second voltage signal from the second electrode plate, and the voltage of the AC cable is generated according to the differential signal; The insulating shell comprises a wire-passing hole for placing an AC cable, an opening for inserting the AC cable in a powered state into the wire-passing hole, and a receiving cavity for installing the printed circuit board, wherein the receiving cavity is located on one side of the wire-passing hole, and a center line of the wire-passing hole is parallel to the printed circuit board installed in the receiving cavity, and the overlapping part of the vertical projections of the first electrode plate and the second electrode plate completely covers the vertical projection of the wire-passing hole on the printed circuit board. As a further improvement of the present invention, the insulating housing comprises a bottom shell and an upper cover, the bottom shell and the upper cover are hinged together by a pin shaft, and the upper cover is rotated around the pin shaft away from the bottom shell to form the opening; The wire hole is formed by a first through slot on the upper surface of the bottom shell and a lower surface of the upper cover, or the wire hole is formed by a first through slot on the upper surface of the bottom shell and a second through slot on the lower surface of the upper cover.

[0006] As a further improvement of the present invention, a first buckle is provided on a side of the bottom shell away from the pin shaft, a second buckle is provided on a side of the top cover away from the pin shaft, and the bottom shell and the top cover are locked and fixed together by the first buckle and the second buckle; The bottom shell or the upper cover is provided with a plurality of fixing structures, and the insulating shell is fixed to the AC cable through a locking piece matched with the fixing structures.

[0007] As a further improvement of the present invention, the open-type AC voltage sampling device includes an electromagnetic shielding sheet, which is located between the bottom shell and the upper cover and covers the opening of the first through slot, and the electromagnetic shielding sheet is electrically connected to the reference ground of the printed circuit board.

[0008] As a further improvement of the present invention, the first electrode plate and the second electrode plate have the same size, and the vertical projections of the first electrode plate and the second electrode plate completely overlap.

[0009] As a further improvement of the present invention, the printed circuit board includes a top-layer circuit located on the upper surface of an insulating substrate and a bottom-layer circuit located on the bottom layer of the insulating substrate, and the first electrode plate and the second electrode plate are located respectively between the top-layer circuit and the bottom-layer circuit; the analog signal conditioning circuit is composed of a top-layer circuit, a bottom-layer circuit and a plurality of electronic components soldered on the top-layer circuit and the bottom-layer circuit.

[0010] As a further improvement of the present invention, the analog signal conditioning circuit includes a first filtering unit, a second filtering unit and an analog signal amplifying unit, the first electrode plate is electrically connected to the first input end of the analog signal amplifying unit via the first filtering unit, the second electrode plate is electrically connected to the second input end of the analog signal amplifying unit via the second filtering unit, and a differential signal is formed and output by the analog signal amplifying unit.

[0011] As a further improvement of the present invention, the analog signal amplification unit includes an instrument amplifier and an operational amplifier, the non-phase input terminal and the inverting input terminal of the instrument amplifier are respectively connected to the output terminals of the first filtering unit and the second filtering unit, and the non-phase input terminal of the operational amplifier is connected to the output terminal of the instrument amplifier.

[0012] As a further improvement of the present invention, the distance between the first electrode plate and the wire-through hole is greater than the distance between the second electrode plate and the wire-through hole; the first filtering unit includes a first capacitor and a first resistor connected in parallel between the first electrode plate and the reference ground, and the first electrode plate is electrically connected to the non-inverting input terminal of the instrument amplifier; the second filtering unit includes a second capacitor and a second resistor connected in parallel between the second electrode plate and the reference ground, and the second electrode plate is electrically connected to the inverting input terminal of the instrument amplifier; the resistance values ​​of the first resistor and the second resistor are both R, the capacitance values ​​of the first capacitor and the second capacitor are both C, and the transfer function of the instrument amplifier is:

[0013] Among them, C p1 is the capacitance value of the capacitor formed by the first electrode plate and the AC cable in the cable hole, C p2 is the capacitance value of the capacitor formed by the second electrode plate and the AC cable in the cable hole, Vo is the output voltage value of the instrument amplifier, and Vi is the voltage value of the AC cable in the cable hole.

[0014] The present invention also provides an AC cable voltage detection system, comprising a first probe, a second probe and a non-contact digital processing module, wherein the first probe and the second probe are both composed of the open-type AC voltage sampling device as described above, and the non-contact digital processing module is respectively connected to the first probe and the second probe signals and generates the line voltages of two AC cables according to the signals from the first probe and the second probe.

[0015] The present invention has the following beneficial effects: by arranging an opening in the insulating shell for inserting the cable into the wire hole, integrating the first electrode plate and the second electrode plate on the printed circuit board below the wire hole, and generating a signal according to the signals of the first electrode plate and the second electrode plate to obtain the AC voltage, the equipment installation can be completed without cutting off the power of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of an open-type AC voltage sampling device provided in an embodiment of the present invention.

[0017] Figure 2 It is a schematic diagram of the cross-sectional structure of a printed circuit board in an open-type AC voltage sampling device provided in an embodiment of the present invention.

[0018] Figure 3 It is a schematic diagram of a capacitor formed by a first electrode plate, a second electrode plate and an AC cable in an open-type AC voltage sampling device provided by an embodiment of the present invention.

[0019] Figure 4 It is a schematic diagram of an analog signal conditioning circuit in an open-type AC voltage sampling device provided in an embodiment of the present invention.

[0020] Figure 5 A schematic diagram of an AC cable voltage detection system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] like Figure 1 , Figure 2 , which is a schematic diagram of an open-type AC voltage sampling device of the present invention, the open-type AC voltage sampling device can be directly fixed to an AC cable in a power supply state, and samples the voltage of the AC cable. The open-type AC voltage sampling device of this embodiment includes an insulating housing 10 and a printed circuit board 20, wherein the insulating housing 10 can be made of engineering plastics such as ABS and PC, and the printed circuit board 20 is installed in the insulating housing 10 and protected by the insulating housing 20.

[0023] The printed circuit board 20 includes an insulating substrate 25, which is in the form of a flat plate and is integrated with a first electrode plate 21 and a second electrode plate 22. Similar to the existing printed circuit board (PCB), the insulating substrate 25 can be made of epoxy resin glass fiber cloth, polytetrafluoroethylene, polyimide, CEM-1 / CEM-3, ceramic substrate, etc. The first electrode plate 21 and the second electrode plate 22 can be made of a conductive material layer (such as copper foil) printed on the surface or middle layer of the insulating substrate 25, and the first electrode plate 21 and the second electrode plate 22 are both in the form of a continuous film with a thickness of not less than 1 mil. In this embodiment, the first electrode plate 21 and the second electrode plate 22 are respectively located on different layers of the insulating substrate 25 (that is, the first electrode plate 21 and the second electrode plate 22 are parallel to each other) and are insulated from each other, and the vertical projections of at least a portion of the first electrode plate 21 and the second electrode plate 22 overlap. Figure 2 It is only used to illustrate the structure of the printed circuit board 20. In a specific implementation, the actual size and proportion of each layer are irrelevant to this figure.

[0024] An analog signal conditioning circuit is also integrated on the insulating substrate 25, which is electrically connected to the first electrode plate 21 and the second electrode plate 22 respectively, and is used to generate a differential signal based on a first voltage signal from the first electrode plate 21 and a second voltage signal from the second electrode plate 22, and the voltage of the AC cable is generated based on the above differential signal.

[0025] The insulating housing 10 includes a wire hole for placing an AC cable, an opening for placing the AC cable in a powered state into the wire hole, and a receiving cavity for installing the printed circuit board 20. Specifically, the opening can be a movable opening or a fixed opening. The wire hole passes through two oppositely disposed surfaces of the insulating housing 10, and the size of the cross section of the wire hole is adapted to the size of the cross section of the AC cable (for example, the size of the cross section of the wire hole is equal to or slightly larger than the size of the cross section of the AC cable) to ensure that the AC cable will not loosen in the wire hole.

[0026] The accommodating cavity is located on one side of the wire hole, and the center line of the wire hole is parallel to the printed circuit board installed in the accommodating cavity. That is, different from the existing way of surrounding the AC cable with the electrode plate, the first electrode plate 21 and the second electrode plate 22 in this embodiment are located in two planes on the same side of the AC cable, and the overlapping part of the vertical projections of the first electrode plate 21 and the second electrode plate 22 completely covers the vertical projection of the wire hole on the printed circuit board 20. That is, the size of the overlapping part of the first electrode plate 21 and the second electrode plate 22 is not less than the size of the maximum axial cross-section of the wire hole. Those skilled in the art can understand that the above-mentioned opening refers to a structure in which the AC cable can be placed into the through hole under certain conditions. In order to ensure safety and accuracy, the opening can be closed when the open AC voltage sampling device is in normal working condition.

[0027] When in use, the open-type AC voltage sampling device can be directly fixed to an AC cable in normal working condition, that is, the AC cable in the energized state is allowed to enter the wire-passing hole through the opening. At this time, the first electrode plate 21 and the second electrode plate 22 on the printed circuit board 20 in the accommodating cavity of the insulating shell 10 respectively generate induced voltages under the action of the AC current in the AC cable. The analog signal conditioning circuit processes the induced voltages on the first electrode plate 21 and the second electrode plate 22 respectively and generates a differential signal corresponding to the voltage in the AC cable. Since the distance d1 between the first electrode plate 21 and the AC cable in the wire-passing hole and the distance d2 between the second electrode plate 22 and the AC cable in the wire-passing hole are different, as shown in FIG. Figure 3 As shown, the first electrode plate 21 and the second electrode plate 22 will form Cp1 and Cp2 with a large difference in capacitance. At this time, there is a potential difference between the potentials sensed by the two layers of the first electrode plate 21 and the second electrode plate 22 (experiments have confirmed that the potential difference is linear with the potential in the measured cable). Therefore, by detecting this potential difference and inversely calculating through the transfer function, the voltage of the AC power in the AC cable can be obtained.

[0028] The above-mentioned open-type AC voltage sampling device, by providing an opening for the AC cable to be placed in the wire hole in the insulating housing 10, and integrating the first electrode plate 21 and the second electrode plate 22 on the printed circuit board 20 below the wire hole, and generating signals according to the signals of the first electrode plate 21 and the second electrode plate 22 to obtain the AC voltage, can complete the equipment installation without powering off the equipment, can better meet the requirements of live installation without disconnection on site, and improve the application scope of non-contact voltage detection. In addition, non-contact measurement is achieved by coupling through the electric field, without any direct contact with the system under test, and the entire measurement process has no effect on the cable under test, which has extremely high safety.

[0029] In one embodiment of the present invention, the insulating housing 10 includes a bottom shell 11 and an upper cover 12, wherein the bottom shell 11 and the upper cover 12 are hinged together by a pin, that is, the bottom shell 11 and the upper cover 12 can rotate relative to each other around the pin, so as to realize the opening or closing of the bottom shell 11 and the upper cover 12. In addition, the upper cover 12 rotates away from the bottom shell 11 around the pin to form an opening for inserting the AC cable into the wire hole, that is, the opening adopts a movable opening.

[0030] Specifically, the wire-passing hole can be formed by the first through-slot 111 located on the upper surface of the bottom shell 11 and the lower surface of the upper cover 12, that is, only a first through-slot 111 penetrating through the two side walls of the bottom shell 11 is opened on the upper surface of the bottom shell 11, and the depth of the first through-slot 111 is adapted to the diameter of the AC cable, and the wire-passing hole is formed when the upper cover 12 is buckled onto the bottom shell 11. In addition, the above-mentioned wire-passing hole can also be formed by the first through-slot 111 on the upper surface of the bottom shell 11 and the second through-slot 121 on the lower surface of the upper cover 12, that is, the position of the first through-slot 111 on the bottom shell 11 corresponds to the position of the second through-slot 121 on the upper cover 12, and the sum of the depths of the first through-slot 111 and the second through-slot 121 is adapted to the diameter of the AC cable, and when the upper cover 12 is buckled onto the bottom shell 11, the first through-slot 111 and the second through-slot 121 are combined to form the wire-passing hole. In addition, in order to improve the insulation performance, an insulating rubber pad may be provided in the first through groove 111 and / or the second through groove 121 to further improve the safety.

[0031] The above-mentioned opening and closing structure of the upper cover 12 and the bottom shell 11 and the wire hole structure facilitate fixing the open-type AC voltage sampling device to the AC cable. In practical applications, the wire hole can also be formed by the second through groove 121 on the upper surface of the bottom shell 11 and the lower surface of the upper cover 12, and the depth of the second through groove 121 is adapted to the diameter of the AC cable.

[0032] In order to achieve stable fixation of the AC cable, the side of the bottom shell 11 away from the pin shaft has a first buckle 112, and correspondingly, the side of the upper cover 12 away from the pin shaft has a second buckle 122, and the bottom shell 11 and the upper cover 12 are locked and fixed together by the first buckle 112 and the second buckle 122 to prevent the AC cable from falling out of the wire hole after installation. In addition, the bottom shell 11 or the upper cover 12 has a plurality of fixing structures 113, and the insulating shell 10 is fixed to the AC cable by a locking member matched with the fixing structure 113. For example, the above-mentioned fixing structure can be two fixing holes respectively located on two back-facing sides of the bottom shell 11, and the insulating shell 10 is fixed to the AC cable by bundling with insulating straps passing through the two fixing holes respectively. Through the above structure, the open-type AC voltage sampling device can be conveniently installed on the AC cable, so that the open-type AC voltage sampling device can continuously sample the voltage in the AC cable.

[0033] In order to improve the accuracy of the sampled voltage, in one embodiment of the present invention, the above-mentioned open-type AC voltage sampling device further includes an electromagnetic shielding sheet 14, which is located between the bottom shell 11 and the upper cover 12 and covers the opening of the first through slot 111. The electromagnetic shielding sheet 14 can be specifically made of metal materials (such as aluminum, copper or silver), conductive rubber, conductive cloth and magnetic materials, and can shield electromagnetic interference. The electromagnetic shielding sheet 14 is electrically connected to the reference ground of the printed circuit board 20, for example, the electromagnetic shielding sheet 14 is directly welded on the printed circuit board 20, and extends through the bottom shell 11 to the upper surface of the bottom shell 11. When the open-type AC voltage sampling device is assembled to the AC cable, the electromagnetic shielding sheet 14 can be first lifted from the upper surface of the bottom shell 11, and then the electromagnetic shielding sheet 14 can be put down after the AC cable is placed in the first through slot 111, so that the electromagnetic shielding sheet 14 covers the side of the AC cable facing away from the first through slot 111, and then the upper cover 12 is buckled on the bottom shell 11.

[0034] The above structure can effectively shield the same frequency interference, so that the measurement lower limit of the open-type AC voltage sampling device can reach 50mV. If reasonable materials and structural design are adopted, the insulation performance of the open-type AC voltage sampling device can fully meet the relevant industry standards or national standards, and its theoretical maximum detection range has no upper limit.

[0035] In one embodiment of the present invention, the first electrode plate 21 and the second electrode plate 22 on the printed circuit board 20 have the same size, and the vertical projections of the first electrode plate 21 and the second electrode plate 22 completely overlap. That is, the width of the first electrode plate 21 and the second electrode plate 22 is greater than the diameter of the AC cable, the length of the first electrode plate 21 and the second electrode plate 22 is adapted to the length of the AC cable in the wire hole, and the vertical projection of the AC cable in the wire hole on the printed circuit board 20 is completely on the first electrode plate 21 and the second electrode plate 22. Through the above structure, the first electrode plate 21 and the second electrode plate 22 can generate induced voltage to the maximum extent, thereby improving the accuracy of the final voltage detection result.

[0036] like Figure 2 As shown, in one embodiment of the present invention, the printed circuit board 20 comprises a top line 23 located on the upper surface of an insulating substrate 25 and a bottom line 24 located on the bottom of the insulating substrate 25, wherein the top line 23 and the bottom line 24 are respectively formed of printed conductive films, and the first electrode plate 21 and the second electrode plate 22 are sequentially located between the top line 23 and the bottom line 24. The analog signal conditioning circuit is composed of the top line 23, the bottom line 24 and a plurality of electronic components soldered on the top line 23 and the bottom line 24.

[0037] Specifically, the thickness of the first electrode plate 21, the second electrode plate 22, the top circuit 23 and the bottom circuit 24 are about 1.4 mil, respectively, and the interval between the top circuit 23 and the first electrode plate 21, the interval between the first electrode plate 21 and the second circuit board 22, and the interval between the second electrode plate 22 and the bottom circuit 24 are about 12.6 mil. In addition, a solder resist layer can be added on the upper surface of the top circuit 23 and the lower surface of the bottom circuit 24, and the thickness of the solder resist layer is about 0.4 mil. The above structure can well realize the AC voltage sampling function, while making the volume of the printed circuit board 20 relatively small.

[0038] In one embodiment of the present invention, the analog signal conditioning circuit on the printed circuit board 20 includes a first filtering unit, a second filtering unit and an analog signal amplifying unit, and the first electrode plate 21 is electrically connected to the first input terminal of the analog signal amplifying unit via the first filtering unit, and the second electrode plate 22 is electrically connected to the second input terminal of the analog signal amplifying unit via the second filtering unit, and the analog signal amplifying unit forms a differential signal and outputs it. The first filtering unit and the second filtering unit can filter the analog signals from the first electrode plate 21 and the second electrode plate 22, respectively, to filter out interference signals and improve the accuracy of the signals. The analog signal amplifying unit can amplify the filtered signals and generate corresponding differential signals.

[0039] like Figure 4As shown, in one embodiment of the present invention, the analog signal amplification unit includes an instrument amplifier U1 and an operational amplifier U3B, wherein the non-inverting input terminal and the inverting input terminal of the instrument amplifier U1 are respectively connected to the output terminal of the first filtering unit and the output terminal of the second filtering unit, and the non-inverting input terminal of the operational amplifier U3B is connected to the output terminal of the instrument amplifier U1. The instrument amplifier U1 can perform differential amplification processing on the voltage of the output terminal P1 of the first filtering unit and the voltage of the output terminal P2 of the second filtering unit, and the operational amplifier U3B can further amplify the output signal of the instrument amplifier U1.

[0040] Combination Figure 3 , Figure 4 As shown, in one embodiment of the present invention, the distance d1 between the first electrode plate 21 and the wire hole is greater than the distance d2 between the second electrode plate 22 and the wire hole. Accordingly, the first filtering unit includes a first capacitor C4 and a first resistor R2 connected in parallel between the output end P1 of the first electrode plate 21 and the reference ground COM, and the output end P1 of the first electrode plate 21 is electrically connected to the positive input end of the instrument amplifier U1 (there is also a body capacitor C2 on the transmission line between the output end P1 of the first electrode plate 21 and the instrument amplifier U1); the second filtering unit includes a second resistor R1 and a second capacitor C3 connected in parallel between the output end P2 of the second electrode plate 22 and the reference ground COM, and the output end P2 of the second electrode plate 22 is electrically connected to the inverting input end of the instrument amplifier U1 (there is also a body capacitor C1 on the transmission line between the output end P2 of the second electrode plate 22 and the instrument amplifier U1). In addition, the resistance values ​​of the first resistor R2 and the second resistor R1 are both R, the capacitance values ​​of the first capacitor C4 and the second capacitor C3 are both C, and the transfer function of the instrument amplifier U1 is: (1) Among them, C p1 is the capacitance value of the capacitor formed by the first electrode plate 21 and the AC cable in the cable hole, C p2 is the capacitance value of the capacitor formed by the second electrode plate 22 and the AC cable in the cable hole, Vo is the output voltage value of the instrument amplifier, Vi is the voltage value of the AC cable in the cable hole, s is an independent variable, which is related to the frequency of the voltage in the measured cable (for example, s= jω, ω=2πf, j is an imaginary unit, and f is the frequency of the voltage in the measured cable). The s value can be set in advance according to the frequency of the voltage in the measured cable. p1 , C p2 known (for example, through factory calibration); in addition, the first capacitor C4, the second capacitor C3, the first resistor R2 and the second resistor R1 can be appropriately set so that C p1 Much smaller than C, C p2 Much smaller than C, frequency |sCR|<1, the above formula (1) can be simplified to: (2) By testing and calibrating (i.e. calibrating various parameters) after on-site installation, the voltage in the tested cable is linearly related to the output of the analog signal conditioning circuit (i.e. the difference between the voltage on the second electrode plate 22 and the voltage on the first electrode plate 21), so that the voltage measurement accuracy can be achieved within 1%.

[0041] like Figure 5 As shown, the present invention also provides an AC cable voltage detection system, which includes a first probe, a second probe and a non-contact digital processing module, wherein the first probe and the second probe are both composed of the open-type AC voltage sampling device as described above, and the non-contact digital processing module is respectively connected to the first probe and the second probe signals and generates the line voltages of the two AC cables according to the signals from the first probe and the second probe.

[0042] The non-contact digital processing module can be independent of the first probe and the second probe, and connected to the first probe and the second probe via waterproof cables respectively. The non-contact digital processing module can specifically include a digital filtering and compensation module, an output transmission module and a power supply module.

[0043] Considering that the signal collected by the first probe and the second probe is very weak and easily interfered by external signals, the digital filtering and compensation module eliminates interference by filtering. Due to the inherent characteristics of the capacitor, such as the frequency characteristics and temperature characteristics, the first probe and the second probe have different voltage collection amounts at different frequencies, and the change in ambient temperature affects the capacitance of the capacitor, which all produce measurement errors. The digital filtering and compensation module uses digital compensation to correct the sampling signal, offset the measurement error, and ensure the measurement accuracy. For example, the temperature coefficient of the first probe and the second probe is tested first. For example, within the range of -40℃~85℃, the input voltage remains unchanged, and the output values ​​of the first probe and the second probe are tested at every 10℃ step to obtain temperature data. Then, with 20℃ (or other points, determined according to the application) as the reference, the compensation coefficient value at this temperature point is set to 1, and the compensation coefficient values ​​of the output at other temperature points are obtained based on this output value, that is, the output value at each temperature point is multiplied by the compensation coefficient and the output is close to the reference output value. This value is written into the digital filtering and compensation module, and the compensation for the temperature drift of the probe is completed.

[0044] The output transmitter module is used to transform the voltage signal after filtering and compensation by the digital filtering and compensation module into the required signal quantity and transmit it in and out (wired or wirelessly). For example, it can be converted into a standard industrial analog signal, digital RS485 / RS232 / CAN (various standard and non-standard transmission protocols), wireless interface and transmitted to the cloud (including: Bluetooth, NB-IOT, GPRS), etc.

[0045] The power module is used to supply power to the first probe, the second probe, the digital filtering and compensation module, the output transmission module, etc.

[0046] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An open-type AC voltage sampling device for sampling the voltage of an AC cable, characterized in that: The open-type AC voltage sampling device comprises: A printed circuit board, comprising an insulating substrate integrated with a first electrode plate, a second electrode plate and an analog signal conditioning circuit, wherein the first electrode plate and the second electrode plate are respectively located on different layers of the insulating substrate and are insulated from each other, and vertical projections of at least a portion of the first electrode plate and the second electrode plate overlap; the analog signal conditioning circuit is electrically connected to the first electrode plate and the second electrode plate, respectively, and is used to generate a differential signal according to a first voltage signal from the first electrode plate and a second voltage signal from the second electrode plate, and the voltage of the AC cable is generated according to the differential signal; The insulating shell comprises a wire-passing hole for placing an AC cable, an opening for inserting the AC cable in a powered state into the wire-passing hole, and a receiving cavity for installing the printed circuit board, wherein the receiving cavity is located on one side of the wire-passing hole, and a center line of the wire-passing hole is parallel to the printed circuit board installed in the receiving cavity, and the overlapping part of the vertical projections of the first electrode plate and the second electrode plate completely covers the vertical projection of the wire-passing hole on the printed circuit board.

2. The open-type AC voltage sampling device according to claim 1, characterized in that: The insulating shell comprises a bottom shell and an upper cover, wherein the bottom shell and the upper cover are hinged together by a pin shaft, and the upper cover is rotated around the pin shaft away from the bottom shell to form the opening; The wire hole is formed by a first through slot on the upper surface of the bottom shell and a lower surface of the upper cover, or the wire hole is formed by a first through slot on the upper surface of the bottom shell and a second through slot on the lower surface of the upper cover.

3. The open-type AC voltage sampling device according to claim 2, characterized in that: The bottom shell has a first buckle on one side away from the pin shaft, the top cover has a second buckle on one side away from the pin shaft, and the bottom shell and the top cover are locked and fixed together by the first buckle and the second buckle; The bottom shell or the upper cover is provided with a plurality of fixing structures, and the insulating shell is fixed to the AC cable through a locking piece matched with the fixing structures.

4. The open-type AC voltage sampling device according to claim 2 or 3, characterized in that: The open-type AC voltage sampling device comprises an electromagnetic shielding sheet, which is located between the bottom shell and the upper cover and covers the opening of the first through slot, and is electrically connected to the reference ground of the printed circuit board.

5. The open-type AC voltage sampling device according to claim 1, characterized in that: The first electrode plate and the second electrode plate have the same size, and vertical projections of the first electrode plate and the second electrode plate completely overlap.

6. The open-type AC voltage sampling device according to claim 1, characterized in that: The printed circuit board includes a top-layer circuit located on the upper surface of an insulating substrate and a bottom-layer circuit located on the bottom layer of the insulating substrate, and the first electrode plate and the second electrode plate are located between the top-layer circuit and the bottom-layer circuit in sequence; the analog signal conditioning circuit is composed of a top-layer circuit, a bottom-layer circuit and a plurality of electronic components soldered on the top-layer circuit and the bottom-layer circuit.

7. The open-type AC voltage sampling device according to claim 1, characterized in that: The analog signal conditioning circuit includes a first filtering unit, a second filtering unit and an analog signal amplifying unit. The first electrode plate is electrically connected to the first input end of the analog signal amplifying unit via the first filtering unit, the second electrode plate is electrically connected to the second input end of the analog signal amplifying unit via the second filtering unit, and a differential signal is formed and output by the analog signal amplifying unit.

8. The open-type AC voltage sampling device according to claim 7, characterized in that: The analog signal amplifying unit comprises an instrument amplifier and an operational amplifier, wherein the non-inverting input terminal and the inverting input terminal of the instrument amplifier are respectively connected to the output terminals of the first filtering unit and the second filtering unit, and the non-inverting input terminal of the operational amplifier is connected to the output terminal of the instrument amplifier.

9. The open-type AC voltage sampling device according to claim 8, characterized in that: The distance between the first electrode plate and the wire-through hole is greater than the distance between the second electrode plate and the wire-through hole; the first filtering unit comprises a first capacitor and a first resistor connected in parallel between the first electrode plate and a reference ground, and the first electrode plate is electrically connected to a non-inverting input terminal of the instrument amplifier; The second filtering unit includes a second capacitor and a second resistor connected in parallel between a second electrode plate and a reference ground, and the second electrode plate is electrically connected to the inverting input terminal of the instrument amplifier; the resistance values ​​of the first resistor and the second resistor are both R, the capacitance values ​​of the first capacitor and the second capacitor are both C, and the transfer function of the instrument amplifier is: Among them, C p1 is the capacitance value of the capacitor formed by the first electrode plate and the AC cable in the cable hole, C p2 is the capacitance value of the capacitor formed by the second electrode plate and the AC cable in the cable hole, Vo is the output voltage value of the instrument amplifier, and Vi is the voltage value of the AC cable in the cable hole.

10. An AC cable voltage detection system, characterized in that: It includes a first probe, a second probe and a non-contact digital processing module, wherein the first probe and the second probe are both composed of an open-type AC voltage sampling device as described in any one of claims 1 to 9, and the non-contact digital processing module is respectively connected to the first probe and the second probe signals and generates line voltages of two AC cables according to the signals from the first probe and the second probe.

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