Device for measuring current
By using Hall effect sensors and multi-stage comparison circuits in high-voltage DC circuits, the problem of inaccurate measurement of microamperes to milliamperes in the prior art is solved, and more accurate and efficient current measurement is achieved.
Patent Information
- Application Number
- CN202411781431.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-05
- Publication Date
- 2025-03-04
AI Technical Summary
In high voltage DC circuits, it is difficult for the prior art to accurately measure currents from microamperes to milliamperes, resulting in distortion of the test results.
Using a measurement circuit including a Hall effect sensor, a multi-stage comparison circuit, a series-out shift register, a digital-to-analog converter and a controller MCU, the wire is clamped through the jaw of a clamp ammeter, the current is measured and communicated with the industrial control machine through an optical fiber interface.
Accurate measurement of microampere to milliampere currents is achieved, avoiding the operational complexity and risks caused by circuit disconnection and improving work efficiency.
Smart Images
Figure CN119555986A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of measurement technology, and in particular to a device for measuring current. Background Art
[0002] The basic principle of DC high voltage test: like Figure 1 As shown, the existing method for measuring the leakage current of the lightning arrester is to connect a high-voltage microammeter in series in the high-voltage circuit, use an AC power supply, raise the AC voltage through a transformer, then perform voltage doubling rectification based on a diode D and a resistor R, and perform filtering based on a capacitor C to convert the AC power into a stable DC high voltage, and adjust the output voltage to gradually increase until the test requirements are met.
[0003] The significance of measuring leakage current: When DC high voltage is applied to the device under test Cx, polarization current, absorption current and leakage current will be generated in the insulation material of the device. Polarization current and absorption current gradually decay over time, while leakage current is a stable DC current, and its magnitude reflects the conductivity and insulation condition of the insulation material. Changes in leakage current can reflect subtle defects in the insulation material.
[0004] like Figure 2 As shown, the high-voltage microammeter includes a shielding cap 6-1, a liquid crystal screen 6-2, a connecting nut 6-3, a high-voltage lead-out jack 6-4 and a microammeter optical fiber interface 6-5. The high-voltage microammeter is connected in series in the high-voltage circuit and measures the leakage current by direct display or optical fiber data transmission. At this time, the high-voltage lead of the test product needs to be rewired to connect the microammeter to the circuit. This process consumes a lot of time and manpower at the test site. If you do not want to remove the high-voltage lead during the test, you can use the existing clamp ammeter on the market for external measurement, but the range accuracy of this ammeter is not enough, and the minimum current can only measure the milliampere level, and it cannot accurately measure the current from microampere to milliampere, which will cause distortion of the test results.
[0005] like Figure 3As shown, the clamp type AC ammeter includes a clamp body 7-1, a first clamp body 7-2, a second clamp body 7-3, a button 7-4, a transmission mechanism, a switch arranged on the clamp body 7-1, a reset button and a knob, a tension spring and a measuring circuit arranged in the clamp body 7-1, a first coil arranged on the first clamp body 7-2 and a second coil arranged on the second clamp body 7-3, the first clamp body 7-2 is rotatably connected to the clamp body 7-1, the second clamp body 7-3 is rotatably connected to the clamp body 7-1, and the button 7-4 is rotatably connected to the clamp body 7-1. Connection, button 7-4 is connected to the first caliper body 7-2 and the second caliper body 7-3 respectively through the transmission mechanism, one end of the tension spring is fixedly connected to the inner wall of the caliper body 7-1, and the other end of the tension spring is fixedly connected to the transmission mechanism. When the button 7-4 is pressed, the button 7-4 pushes the transmission mechanism, and the transmission mechanism pushes the first caliper body 7-2 and the second caliper body 7-3 to open. When the button 7-4 is released, the tension spring naturally contracts and drives the transmission mechanism to move, and the moving transmission mechanism pulls the first caliper body 7-2 and the second caliper body 7-3 to close.
[0006] In high-voltage DC circuits, the circuit needs to be disconnected to measure current, which makes the operation complicated and risky, and the current measurement is inaccurate. Inaccurate current measurement has become a technical problem that needs to be solved urgently. Summary of the invention
[0007] The invention provides a device for measuring current, which solves the technical problem of inaccurate current measurement.
[0008] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows: A device for measuring current includes a measuring circuit, wherein the measuring circuit includes a first ferrite core, a second ferrite core, a Hall effect sensor, a multi-stage comparison circuit, a parallel-input and serial-output shift register, a digital-to-analog converter and a controller MCU, one side of the Hall effect sensor corresponds to one end of the first ferrite core, the other side of the Hall effect sensor corresponds to one end of the second ferrite core, and the free end of the first ferrite core away from the Hall effect sensor and the free end of the second ferrite core are connected together or separated; the multi-stage comparison circuit includes first to nth voltage-dividing resistors R1 to Rn and first to nth operational amplifiers O P1~OPn, the output terminal Vout of the Hall effect sensor is electrically connected to the non-inverting input terminal of each operational amplifier in the multi-stage comparison circuit, the output terminal of each operational amplifier in the multi-stage comparison circuit is respectively electrically connected to the input terminal of the parallel-input serial-output shift register, the output terminal of the parallel-input serial-output shift register is electrically connected to the input terminal of the controller, the control terminal of the controller MCU is electrically connected to the control terminal of the analog-to-digital converter, the output terminal Vref of the analog-to-digital converter is grounded via the first voltage-dividing resistor R1 to the nth voltage-dividing resistor Rn in sequence, and the input terminal of each voltage-dividing resistor in the multi-stage comparison circuit is electrically connected to the inverting input terminal of a corresponding operational amplifier.
[0009] A further technical solution is that the input end of each voltage-dividing resistor in the multi-stage comparison circuit is electrically connected to the inverting input end of a corresponding operational amplifier, that is, the output end Vref of the analog-to-digital converter is electrically connected to the inverting input end of the first operational amplifier OP1, the inverting input end of the second operational amplifier OP2 is electrically connected to the junction of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, the inverting input end of the third operational amplifier OP2 is electrically connected to the junction of the second voltage-dividing resistor R2 and the third voltage-dividing resistor R3, until the inverting input end of the nth operational amplifier OPn is electrically connected to the junction of the n-1th voltage-dividing resistor Rn-1 and the nth voltage-dividing resistor Rn.
[0010] A further technical solution is: it also includes an industrial computer, which is connected to and communicates with the controller MCU.
[0011] A further technical solution is: it also includes an optical fiber interface, and the controller MCU is connected and communicates with the industrial computer via the optical fiber interface.
[0012] A further technical solution is that it also includes a support part, the support part includes a clamp body, a first clamp body, a second clamp body, a button, a transmission mechanism and a tension spring fixed in the clamp body, the first clamp body is rotatably connected to the clamp body, the second clamp body is rotatably connected to the clamp body, the button is rotatably connected to the clamp body, the button is respectively connected to the first clamp body and the second clamp body through the transmission mechanism, one end of the tension spring is fixedly connected to the inner wall of the clamp body, and the other end of the tension spring is fixedly connected to the transmission mechanism. When the button is pressed, the button pushes the transmission mechanism, and the transmission mechanism pushes the first clamp body and the second clamp body to open. When the button is released, the tension spring naturally contracts and drives the transmission mechanism to move, and the moving transmission mechanism pulls the first clamp body and the second clamp body to close; the first ferrite core is fixedly connected to the inside of the first clamp body, the second ferrite core is fixedly connected to the inside of the second clamp body, the Hall effect sensor, the multi-stage comparison circuit, the parallel input and output shift register, the digital-to-analog converter and the controller MCU are fixedly connected to the inside of the clamp body, an optical fiber interface is embedded and fixed on the clamp body, the controller MCU is electrically connected to the optical fiber interface, and a switch is fixedly connected to the clamp body, and the switch is electrically connected to the controller MCU.
[0013] A further technical solution is that the multi-stage comparison circuit is a ten-stage comparison circuit, n=10, the ten-stage comparison circuit includes first to tenth voltage-dividing resistors R1~R10 and first to tenth operational amplifiers OP1~OP10, the output terminal Vref of the analog-to-digital converter is grounded via the first voltage-dividing resistor R1 to the tenth voltage-dividing resistor R10 in sequence, the input terminal of each voltage-dividing resistor in the ten-stage comparison circuit is electrically connected to the inverting input terminal of a corresponding operational amplifier, that is, the output terminal Vref of the analog-to-digital converter is electrically connected to the inverting input terminal of the first operational amplifier OP1, the inverting input terminal of the second operational amplifier OP2 is electrically connected to the junction of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, the inverting input terminal of the third operational amplifier OP2 is electrically connected to the junction of the second voltage-dividing resistor R2 and the third voltage-dividing resistor R3, until the inverting input terminal of the tenth operational amplifier OP10 is electrically connected to the junction of the ninth voltage-dividing resistor R9 and the tenth voltage-dividing resistor R10.
[0014] A further technical solution is that: the multi-stage comparison circuit is a two-stage comparison circuit, n=2, the two-stage comparison circuit includes a first voltage-dividing resistor R1, a second voltage-dividing resistor R2, a first operational amplifier OP1 and a second operational amplifier OP2, the output end Vout of the Hall effect sensor is electrically connected to the positive phase input end of the first operational amplifier OP1, the output end Vout of the Hall effect sensor is electrically connected to the positive phase input end of the second operational amplifier OP2, the output end of the first operational amplifier OP1 is electrically connected to the input end of the parallel-in-serial-output shift register, the output end of the second operational amplifier OP2 is electrically connected to the input end of the parallel-in-serial-output shift register, the output end Vref of the analog-to-digital converter is grounded via the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 in sequence, the output end Vref of the analog-to-digital converter is electrically connected to the inverting input end of the first operational amplifier OP1, and the inverting input end of the second operational amplifier OP2 is electrically connected to the junction of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2.
[0015] A further technical solution is that it also includes a battery and a switch, wherein the battery is electrically connected to the controller MCU via the switch and supplies power, and the controller MCU is respectively connected to the Hall effect sensor, the multi-stage comparison circuit, the parallel input and serial output shift register and the digital-to-analog converter and supplies power.
[0016] The beneficial effects of adopting the above technical solution are: A device for measuring current includes a measuring circuit, wherein the measuring circuit includes a first ferrite core, a second ferrite core, a Hall effect sensor, a multi-stage comparison circuit, an in-line and out-line shift register, a digital-to-analog converter and a controller MCU; the device measures current more accurately through the multi-stage comparison circuit, the in-line and out-line shift register, the digital-to-analog converter and the controller MCU.
[0017] Please refer to the detailed description of the specific implementation method. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a schematic diagram of a DC high voltage test in the prior art; Figure 2 It is a structural diagram of a high voltage microammeter in the prior art; Figure 3 It is a structural diagram of a clamp-on AC ammeter in the prior art; Figure 4 It is a structural diagram of the support portion of the present invention; Figure 5 It is a principle block diagram of the present invention.
[0019] Among them: 1-1 the first ferrite core, 1-2 the second ferrite core, 2 the Hall effect sensor, 6-1 the shielding cap, 6-2 the LCD screen, 6-3 the connecting nut, 6-4 the high voltage lead-out jack, 6-5 the microammeter optical fiber interface, 7-1 the clamp body, 7-2 the first clamp body, 7-3 the second clamp body, 7-4 the button, 7-5 the switch, 7-6 the optical fiber interface. DETAILED DESCRIPTION
[0020] The present application adopts the measurement method of a clamp ammeter and improves the measurement circuit principle, so that the measurement is accurate and the operational complexity and risk caused by circuit disconnection are avoided, especially in high-voltage DC circuits.
[0021] Measuring principle: When a DC current flows through a conductor, it generates a constant magnetic field around it, and the strength of the magnetic field is proportional to the current: The magnetic core in the jaws will concentrate the magnetic field generated by the wire to the Hall sensor. After the Hall sensor senses the magnetic field, it will output a Hall voltage proportional to the magnetic field strength according to the Hall effect, which is then converted into a corresponding current value through the internal multi-stage comparison circuit.
[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0023] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.
[0024] Embodiment 1: like Figure 4 and Figure 5 As shown, the present invention discloses a device for measuring current, which includes a support portion, a measuring circuit fixed in the support portion, and an industrial computer outside the support portion.
[0025] like Figure 4 As shown, the support part includes a pliers body 7-1, a first pliers body 7-2, a second pliers body 7-3, a button 7-4, a transmission mechanism and a tension spring fixed in the pliers body 7-1. The first pliers body 7-2 is rotationally connected to the pliers body 7-1, the second pliers body 7-3 is rotationally connected to the pliers body 7-1, the button 7-4 is rotationally connected to the pliers body 7-1, the button 7-4 is respectively connected to the first pliers body 7-2 and the second pliers body 7-3 via the transmission mechanism, one end of the tension spring is fixedly connected to the inner wall of the pliers body 7-1, and the other end of the tension spring is fixedly connected to the transmission mechanism. When the button 7-4 is pressed, the button 7-4 pushes the transmission mechanism, and the transmission mechanism pushes the first pliers body 7-2 and the second pliers body 7-3 to open. When the button 7-4 is released, the tension spring naturally contracts and drives the transmission mechanism to move, and the moving transmission mechanism pulls the first pliers body 7-2 and the second pliers body 7-3 to close.
[0026] like Figure 4 and Figure 5 As shown, the measuring circuit includes a first ferrite core 1-1 fixedly connected in the first clamp body 7-2, a second ferrite core 1-2 fixedly connected in the second clamp body 7-3, a battery fixed in the clamp body 7-1, a Hall effect sensor 2, a multi-stage comparison circuit, an in-line and out-line shift register, a digital-to-analog converter and a controller MCU, and a switch 7-5 and an optical fiber interface 7-6 embedded and fixed on the clamp body 7-1. One side of the Hall effect sensor 2 corresponds to one end of the first ferrite core 1-1, and the other side of the Hall effect sensor 2 corresponds to one end of the second ferrite core 1-2. The free end of the first ferrite core 1-1 away from the Hall effect sensor 2 and the free end of the second ferrite core 1-2 are connected together or separated.
[0027] The battery is electrically connected to the controller MCU via the switch 7 - 5 and supplies power. The controller MCU is separately connected to the Hall effect sensor 2 , the multi-stage comparison circuit, the parallel-input and serial-output shift register and the digital-to-analog converter and supplies power.
[0028] The multi-stage comparison circuit includes first to n-th voltage-dividing resistors R1-Rn and first to n-th operational amplifiers OP1-OPn. The output terminal Vout of the Hall effect sensor 2 is electrically connected to the non-inverting input terminal of each operational amplifier in the multi-stage comparison circuit. The output terminal of each operational amplifier in the multi-stage comparison circuit is electrically connected to the input terminal of the parallel-input-serial-output shift register, the output terminal of the parallel-input-serial-output shift register is electrically connected to the input terminal of the controller, the control terminal of the controller MCU is electrically connected to the control terminal of the analog-to-digital converter, and the output terminal Vref of the analog-to-digital converter is grounded via the first voltage-dividing resistor R1 to the n-th voltage-dividing resistor Rn in sequence. The input end of each voltage-dividing resistor in the multi-stage comparison circuit is electrically connected to the inverting input end of a corresponding operational amplifier, that is, the output end Vref of the analog-to-digital converter is electrically connected to the inverting input end of the first operational amplifier OP1, the inverting input end of the second operational amplifier OP2 is electrically connected to the junction of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, the inverting input end of the third operational amplifier OP2 is electrically connected to the junction of the second voltage-dividing resistor R2 and the third voltage-dividing resistor R3, until the inverting input end of the nth operational amplifier OPn is electrically connected to the junction of the n-1th voltage-dividing resistor Rn-1 and the nth voltage-dividing resistor Rn.
[0029] like Figure 5 As shown, the present application places two high-conductivity ferrite cores in the jaws, and the jaws clamp the wire to form a complete ferrite core. Since the high-conductivity ferrite has a high relative magnetic permeability μ, the μ value is 5000-15000, it can better concentrate the magnetic flux lines generated by the current so that it passes through the Hall element. Since the leakage current measured in the test is small, usually in the microampere to milliampere level, the magnetic induction intensity generated is weak, the measurement is difficult, and the ordinary clamp ammeter cannot accurately measure it, so the present application uses a Hall effect sensor, model AD22151, which is a high-precision, high-resolution Hall effect sensor that integrates Hall elements, temperature compensation and amplifier circuits. Its minimum resolution for magnetic induction intensity can reach 0.15Gs, and its sensitivity is 6.5mV / Gs. When 100uA DC current flows through the wire, the distance from the Hall element measurement point to the wire is R=1cm, and the relative magnetic permeability μ=10000 is used for calculation. At this time, the magnetic induction intensity B=0.2Gs, then the voltage Vout output by the Hall sensor AD22151 is about 1.3mV. When testing the arrester with DC high voltage, the test current is generally 0 to 1000uA. Then a ten-level comparison circuit can be used to determine whether the current reaches 100uA, 200uA, ..., 1000uA. This method can solve the problem of insufficient precision and inaccuracy of ordinary clamp ammeters for micro-current measurement.
[0030] In the first embodiment, n=10, the multi-stage comparison circuit is a ten-stage comparison circuit, n=10, and the ten-stage comparison circuit includes first to tenth ten-stage voltage resistors R1-R10 and first to tenth operational amplifiers OP1-OP10.
[0031] like Figure 5 As shown, the multi-level comparison circuit uses a precision operational amplifier as a comparator, and the controller MCU controls a high-resolution and high-stability digital-to-analog converter. The model of the digital-to-analog converter is AD5791. The digital-to-analog converter generates an analog voltage Vref and divides it through a high-precision resistor as the reference voltage for each level of the comparator. The minimum step value of the digital-to-analog converter AD5791 can reach 4.77 µV, so when the application is debugged and calibrated by a standard current source, the controller MCU can be used to control and generate a suitable and accurate reference voltage. This application takes a ten-level comparison circuit as an example. At this time, the digital-to-analog converter AD5791 is controlled to output Vref=13mV. Assuming R1=R2=…=R10, the voltage of the reverse input terminal of the tenth operational amplifier OP10 divided by the tenth voltage resistor R10 is 1.3mV. When the current reaches 100uA, the output voltage Vref of the digital-to-analog converter AD22151 is 1.3mV. At this time, all the op amps in-phase input terminals are 1.3mV, and because the reverse input terminals of other op amps After voltage division, all the terminals are greater than 1.3mV, so at this time only the output level of the tenth operational amplifier OP10 will be set from low to high, which also means that the current reaches 100uA, and then the parallel-in-serial-out shift register transmits the output levels of all operational amplifiers to the controller MCU. The model of the parallel-in-serial-out shift register is 74HC165. 74HC165 is an eight-bit parallel-in-serial-out shift register, which can only provide eight input terminals. Two 74HC165s can be used. The controller MCU can determine the current size and transmit the data through the optical fiber interface and the optical fiber communication line to the test control system of the industrial computer for processing and display.
[0032] In actual operation, variable resistors can also be used as voltage divider resistors, so that the voltage at the inverting input terminal of each stage of the op amp can be more accurately controlled during calibration to achieve a more accurate indication of the current size. In this way, the current can be measured by clamping the wire with the jaws of the ammeter without disconnecting the circuit. The operational complexity and risks caused by circuit disconnection are avoided, especially in high-voltage circuits. Compared with traditional methods, the operation steps are reduced and the work efficiency is greatly improved.
[0033] Embodiment 2: Embodiment 2 is different from Embodiment 1 in that the multi-stage comparison circuit can also reduce the number of operational amplifiers according to actual needs. For example, if it is only necessary to determine whether the current reaches 500uA and 1000uA in the test, it can be reduced to a two-stage comparison circuit.
[0034] The present invention discloses a device for measuring current, comprising a support part, a measuring circuit fixed in the support part and an industrial computer outside the support part, wherein the multi-stage comparison circuit comprises a first voltage-dividing resistor R1, a second voltage-dividing resistor R2, a first operational amplifier OP1 and a second operational amplifier OP2, an output end Vout of a Hall effect sensor 2 is electrically connected to a positive phase input end of the first operational amplifier OP1, an output end Vout of the Hall effect sensor 2 is electrically connected to a positive phase input end of the second operational amplifier OP2, an output end of the first operational amplifier OP1 is electrically connected to an input end of a parallel-input-serial-output shift register, and a first operational amplifier OP2 is electrically connected to an input end of a parallel-input-serial-output shift register. The output end of the second operational amplifier OP2 is electrically connected to the input end of the parallel-in-serial-output shift register, the output end of the parallel-in-serial-output shift register is electrically connected to the input end of the controller, the control end of the controller MCU is electrically connected to the control end of the analog-to-digital converter, the output end Vref of the analog-to-digital converter is grounded via the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 in sequence, the output end Vref of the analog-to-digital converter is electrically connected to the inverting input end of the first operational amplifier OP1, and the inverting input end of the second operational amplifier OP2 is electrically connected to the junction of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2. The similarities are not repeated here.
[0035] Embodiment 3: Embodiment 3 is different from Embodiment 1 in that an industrial computer is not included.
[0036] The present invention discloses a device for measuring current, which includes a support part and a measuring circuit fixed in the support part. The similarities are not repeated here. The support part and the measuring circuit fixed in the support part form a separate complete measuring device.
[0037] When measuring, connect to the industrial computer via optical fiber for use.
[0038] Embodiment 4: Embodiment 4 is different from Embodiment 3 in that it does not include a supporting portion and an optical fiber interface.
[0039] The present invention discloses a device for measuring current, including a measuring circuit, and similarities are not repeated here.
[0040] The most basic current measurement can be completed through the measurement circuit. When using it, the current measurement can be achieved by simply fixing the ferrite.
[0041] Compared with the above-mentioned embodiment 1, a parallel-input-serial-output shift register of model Max6921 can also be used. This parallel-input-serial-output shift register has a 16-bit parallel input, and one can be used.
Claims
1. A device for measuring current, characterized in that: The invention comprises a measuring circuit, wherein the measuring circuit comprises a first ferrite core (1-1), a second ferrite core (1-2), a Hall effect sensor (2), a multi-stage comparison circuit, a parallel input and output shift register, a digital-to-analog converter and a controller MCU; one end of the first ferrite core (1-1) is placed on one side of the Hall effect sensor (2) correspondingly, and one end of the second ferrite core (1-2) is placed on the other side of the Hall effect sensor (2) correspondingly; a free end of the first ferrite core (1-1) away from the Hall effect sensor (2) and a free end of the second ferrite core (1-2) are connected together or separated; the multi-stage comparison circuit comprises first to nth voltage-dividing resistors R1 to R2; Rn and the first to nth operational amplifiers OP1-OPn, the output terminal Vout of the Hall effect sensor (2) is electrically connected to the non-inverting input terminal of each operational amplifier in the multi-stage comparison circuit, the output terminal of each operational amplifier in the multi-stage comparison circuit is respectively electrically connected to the input terminal of the parallel-input-serial-output shift register, the output terminal of the parallel-input-serial-output shift register is electrically connected to the input terminal of the controller, the control terminal of the controller MCU is electrically connected to the control terminal of the analog-to-digital converter, the output terminal Vref of the analog-to-digital converter is connected to the ground via the first voltage-dividing resistor R1 to the nth voltage-dividing resistor Rn in sequence, and the input terminal of each voltage-dividing resistor in the multi-stage comparison circuit is electrically connected to the inverting input terminal of a corresponding operational amplifier.
2. A device for measuring current according to claim 1, characterized in that: The input end of each voltage-dividing resistor in the multi-stage comparison circuit is electrically connected to the inverting input end of a corresponding operational amplifier, that is, the output end Vref of the analog-to-digital converter is electrically connected to the inverting input end of the first operational amplifier OP1, the inverting input end of the second operational amplifier OP2 is electrically connected to the junction of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, the inverting input end of the third operational amplifier OP2 is electrically connected to the junction of the second voltage-dividing resistor R2 and the third voltage-dividing resistor R3, until the inverting input end of the nth operational amplifier OPn is electrically connected to the junction of the n-1th voltage-dividing resistor Rn-1 and the nth voltage-dividing resistor Rn.
3. The device for measuring current according to claim 1, characterized in that: It also includes an industrial computer, which is connected to and communicates with the controller MCU.
4. A device for measuring current according to claim 3, characterized in that: It also includes an optical fiber interface (7-6), and the controller MCU is connected to and communicates with the industrial computer via the optical fiber interface (7-6).
5. The device for measuring current according to claim 1, characterized in that: The invention also comprises a support part, wherein the support part comprises a clamp body (7-1), a first clamp body (7-2), a second clamp body (7-3), a button (7-4), a transmission mechanism and a tension spring fixed in the clamp body (7-1); the first clamp body (7-2) is rotationally connected to the clamp body (7-1); the second clamp body (7-3) is rotationally connected to the clamp body (7-1); the button (7-4) is rotationally connected to the clamp body (7-1); the button (7-4) is respectively connected to the first clamp body (7-2) and the second clamp body (7-3) via the transmission mechanism; one end of the tension spring is fixedly connected to the inner wall of the clamp body (7-1); the other end of the tension spring is fixedly connected to the transmission mechanism; when the button (7-4) is pressed, the button (7-4) pushes the transmission mechanism, and the transmission mechanism pushes the first clamp body (7-2) and the second clamp body (7-3) to open; when the button (7-4) is released, the first clamp body (7-2) and the second clamp body (7-3) are opened. The first ferrite core (1-1) is fixedly connected inside the first pliers body (7-2), the second ferrite core (1-2) is fixedly connected inside the second pliers body (7-3), the Hall effect sensor (2), the multi-stage comparison circuit, the parallel input and output shift register, the digital-to-analog converter and the controller MCU are fixedly connected inside the pliers body (7-1), an optical fiber interface (7-6) is embedded and fixed on the pliers body (7-1), the controller MCU is electrically connected to the optical fiber interface (7-6), and a switch (7-5) is fixedly connected to the pliers body (7-1), the switch (7-5) is electrically connected to the controller MCU.
6. The device for measuring current according to claim 1, characterized in that: The multi-stage comparison circuit is a ten-stage comparison circuit, n=10, the ten-stage comparison circuit includes first to tenth voltage-dividing resistors R1~R10 and first to tenth operational amplifiers OP1~OP10, the output end Vref of the analog-to-digital converter is grounded via the first voltage-dividing resistor R1 to the tenth voltage-dividing resistor R10 in sequence, the input end of each voltage-dividing resistor in the ten-stage comparison circuit is electrically connected to the inverting input end of a corresponding operational amplifier, that is, the output end Vref of the analog-to-digital converter is electrically connected to the inverting input end of the first operational amplifier OP1, the inverting input end of the second operational amplifier OP2 is electrically connected to the junction of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, the inverting input end of the third operational amplifier OP2 is electrically connected to the junction of the second voltage-dividing resistor R2 and the third voltage-dividing resistor R3, until the inverting input end of the tenth operational amplifier OP10 is electrically connected to the junction of the ninth voltage-dividing resistor R9 and the tenth voltage-dividing resistor R10.
7. The device for measuring current according to claim 1, characterized in that: The multi-stage comparison circuit is a two-stage comparison circuit, n=2, the two-stage comparison circuit comprises a first voltage-dividing resistor R1, a second voltage-dividing resistor R2, a first operational amplifier OP1 and a second operational amplifier OP2, the output end Vout of the Hall effect sensor (2) is electrically connected to the positive phase input end of the first operational amplifier OP1, the output end Vout of the Hall effect sensor (2) is electrically connected to the positive phase input end of the second operational amplifier OP2, the output end of the first operational amplifier OP1 is electrically connected to the input end of the parallel-input serial-output shift register, the output end of the second operational amplifier OP2 is electrically connected to the input end of the parallel-input serial-output shift register, the output end Vref of the analog-to-digital converter is connected to ground via the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 in sequence, the output end Vref of the analog-to-digital converter is electrically connected to the inverting input end of the first operational amplifier OP1, and the inverting input end of the second operational amplifier OP2 is electrically connected to the junction of the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2.
8. The device for measuring current according to claim 1, characterized in that: It also includes a battery and a switch (7-5), wherein the battery is electrically connected to the controller MCU via the switch (7-5) and supplies power, and the controller MCU is respectively connected to the Hall effect sensor (2), the multi-stage comparison circuit, the parallel-input and serial-output shift register, and the digital-to-analog converter and supplies power.