Grounding resistance tester for SPD

Abstract

The utility model belongs to the technical field of grounding resistance testers, and particularly relates to a grounding resistance tester for an SPD (surge protective device), which comprises a signal amplification main circuit, a single chip microcomputer circuit, a signal inverter circuit, an excitation coil, an acquisition coil, a grounding resistor, a logic gate circuit and a communication circuit. The single-chip microcomputer circuit is connected with the signal inverter circuit through a wire, and the signal inverter circuit is connected with the excitation coil through a wire. According to the utility model, a loop method is provided on the basis of the principle of a two-pole method, only one auxiliary earth pole is needed, wiring is not needed, and only a connecting line between the auxiliary earth pole and the earth pole to be detected needs to pass through the coil, so that the product cost, the construction cost and the installation cost are greatly reduced; and signals are sent out and collected in an induction mode through a coil technology and a two-stage method principle, so that the product use problem caused by a wiring terminal is completely eradicated.

Description

TECHNICAL FIELD

[0001] The utility model relates to grounding resistance tester circuit field, concretely is a grounding resistance tester for SPD. BACKGROUND

[0002] The power lightning protection device (SPD) is also called lightning arrester, surge protector and electric surge protector. In the information age, computer networks and communication equipment are more and more precise, and their working environment requirements are also higher and higher. Lightning and the instantaneous overvoltage of large electrical equipment will more and more frequently invade indoor electrical equipment and network equipment through power supply, antenna, radio signal transceiver equipment and other lines, causing equipment or component damage, personnel injury, transmission or storage data interference or loss, even making electronic equipment malfunction or temporarily paralyzed, system pause, data transmission interruption, LAN and even WAN destruction. Its harm is shocking, and indirect loss is generally much larger than direct economic loss. The power lightning protection device is a device that prevents lightning strike through modern electricity and other technologies. The grounding resistance tester is an instrument for measuring the resistance value of the grounding system, which is usually used to detect whether the grounding system of a building, equipment or facility meets safety standards and requirements.

[0003] After retrieval, the invention patent with publication number CN112505425A discloses a grounding resistance testing device and method, which comprises an electrode, a first insulating rod and a second insulating rod. The electrode, the first insulating rod and the second insulating rod are respectively inserted into the ground to be measured. The first insulating rod is arranged between the electrode and the second insulating rod. A plurality of first metal contacts at different heights are arranged on the first insulating rod. A plurality of second metal contacts at different heights are arranged on the second insulating rod. The plurality of first metal contacts correspond to the plurality of second metal contacts one by one, and the corresponding first metal contacts and second metal contacts are located at the same depth.

[0004] The existing product has the following problems: its principle is complex, and the three-pole method is generally used to measure the grounding resistance of the measured grounding body. Although higher precision can be obtained, two auxiliary test ground poles are needed, which increases the size of the product, greatly increases the product cost, construction cost and installation cost. Therefore, improvement is needed. UTILITY MODEL CONTENT

[0005] The utility model aims at providing a grounding resistance tester for SPD, solving the problem of high use cost of the existing grounding resistance tester.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a grounding resistance tester for SPDs, comprising a signal amplification main circuit, a microcontroller circuit, a signal inverter circuit, an excitation coil, a acquisition coil, a grounding resistor, a logic gate circuit, and a communication circuit. The signal amplification main circuit is connected to the microcontroller circuit via wires. The microcontroller circuit is connected to the signal inverter circuit via wires. The signal inverter circuit is connected to the excitation coil via wires. The acquisition coil is connected to the signal amplification main circuit via wires. Both the acquisition coil and the excitation coil are connected to the grounding resistor via wires. The logic gate circuit is connected to the signal amplification main circuit via wires.

[0007] Preferably, the communication circuit is connected to the main signal amplification circuit via a wire. It can send commands to the 485 chip via URAT communication, and then the 485 chip converts them into RS485 bus signals to communicate with the host computer using the standard MODBUS protocol.

[0008] Preferably, the main signal amplification circuit includes signal amplification circuit one, signal amplification circuit two, and signal amplification circuit three, which are connected sequentially by wires. The main signal amplification circuit converts the signal collected by the acquisition coil into a DC signal using an operational amplifier, amplifies it proportionally, and sends it to the microcontroller for acquisition and calculation.

[0009] Preferably, the microcontroller circuit includes a reset circuit, an external crystal oscillator circuit, an external storage circuit, and a filtering circuit. It provides the microcontroller with timer, data storage, and stable power supply functions. Simultaneously, the microcontroller can generate high-frequency square waves, greatly facilitating testing.

[0010] Preferably, the signal inverter circuit is located between the microcontroller circuit and the excitation coil. The signal inverter circuit uses a TLC2252CDR chip to convert the high-frequency square wave generated by the microcontroller into a sine wave. Compared with DC inverter, square wave inverter has higher efficiency and lower loss. Moreover, the signal frequency generated by the microcontroller is sufficient, eliminating the need for inverter chip boosting, further reducing the load on the inverter chip. The test signal is then sent to the excitation coil.

[0011] Preferably, the logic gate circuit consists of analog switches and logic switches. They are controlled by a microcontroller. When the signal returned from the signal amplification circuit is too weak, the microcontroller controls the logic gate switches to send the signal to a signal amplification circuit with a larger amplification ratio, thereby improving the acquisition accuracy. This is because the sampling range of the grounding resistance is from 0.01Ω to 1000Ω; directly comparing it with the microcontroller's sampling range of 0-3.3V would significantly reduce accuracy.

[0012] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0013] 1. This utility model introduces a loop method based on the principle of the two-electrode method. It only requires one auxiliary grounding electrode and does not require wiring. The connection between the auxiliary grounding electrode and the grounding electrode under test is simply passed through the coil, which greatly reduces product cost, construction cost and installation cost. Moreover, by using coil technology and the principle of the two-electrode method to send and collect signals through induction, it completely eliminates product usage problems caused by wiring terminals.

[0014] 2. This utility model generates a high-frequency sine wave by using the periodic square wave of the inverter microcontroller and enhances the signal strength by using a coil, which greatly reduces the power and size of the product. At the same time, by utilizing the characteristic of the microcontroller itself to generate a high-frequency square wave, the inverter chip can more easily realize the measurement waveform of the high-frequency sine wave. Attached Figure Description

[0015] Figure 1 This is the overall circuit diagram of this utility model;

[0016] Figure 2 For the present utility model Figure 1 The circuit diagram of the microcontroller;

[0017] Figure 3 For the present utility model Figure 1 Signal inverter circuit diagram;

[0018] Figure 4 For the present utility model Figure 1 Communication circuit diagram;

[0019] Figure 5 For the present utility model Figure 1 The logic gate circuit diagram.

[0020] In the diagram: 1. Signal amplification main circuit; 11. Signal amplification circuit one; 12. Signal amplification circuit two; 13. Signal amplification circuit three; 2. Microcontroller circuit; 3. Signal inverter circuit; 4. Excitation coil; 5. Acquisition coil; 6. Grounding resistor; 7. Logic gate circuit; 8. Communication circuit. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] Please see Figures 1-5A grounding resistance tester for SPDs includes a signal amplification main circuit 1, a microcontroller circuit 2, a signal inverter circuit 3, an excitation coil 4, a acquisition coil 5, a grounding resistance 6, a logic gate circuit 7, and a communication circuit 8. The signal amplification main circuit 1 includes signal amplification circuit one 11, signal amplification circuit two 12, and signal amplification circuit three 13, which are connected sequentially by wires. The signal amplification main circuit 1 converts the signal acquired by the acquisition coil 5 into a DC signal using an operational amplifier, amplifies it proportionally, and sends it to the microcontroller for acquisition and calculation. The signal amplification main circuit 1 is connected to the microcontroller circuit 2 via wires. The microcontroller circuit 2 includes a reset circuit, an external crystal oscillator circuit, an external storage circuit, and a filtering circuit. This circuit provides the microcontroller with timer, data storage, and stable power supply functions. Simultaneously, the microcontroller can generate high-frequency square waves, greatly facilitating testing. Microcontroller circuit 2 is connected to signal inverter circuit 3 via wires, and signal inverter circuit 3 is connected to excitation coil 4 via wires. Signal inverter circuit 3 is positioned between microcontroller circuit 2 and excitation coil 4. The signal inverter circuit 3 uses a TLC2252CDR chip to convert the high-frequency square wave generated by the microcontroller into a sine wave. Compared to DC inverters, square wave inverters are more efficient and have lower losses. Furthermore, the signal frequency generated by the microcontroller is sufficient, eliminating the need for inverter chip boosting, further reducing the load on the inverter chip. The test signal is then sent to excitation coil 4.

[0023] Please see Figures 1-5 The acquisition coil 5 is connected to the main signal amplification circuit 1 via a wire. Both the acquisition coil 5 and the excitation coil 4 are connected to the grounding resistor 6 via wires. The logic gate circuit 7 is connected to the main signal amplification circuit 1 via a wire. The communication circuit 8 is connected to the main signal amplification circuit 1 via a wire. The logic gate circuit 7 consists of analog switches and logic switches. They are controlled by the microcontroller. When the signal returned from the signal amplification circuit is too small, the microcontroller will control the logic gate switches to send the signal to the signal amplification circuit with a larger amplification ratio, thereby improving the acquisition accuracy. Because the sampling range of the grounding resistor 6 is from 0.01Ω to 1000Ω, directly comparing it with the microcontroller's sampling range of 0-3.3V will greatly reduce the accuracy. The communication circuit can send commands to the 485 chip via URAT communication, and then the 485 chip converts them into RS485 bus and uses the standard MODBUS protocol to communicate with the host computer.

[0024] The specific implementation process of this utility model is as follows: First, the main signal amplification circuit 1 converts the signal collected by the acquisition coil 5 into a DC signal through an operational amplifier, and amplifies it proportionally before sending it to the microcontroller for acquisition and calculation. Then, the high-frequency square wave generated by the microcontroller in the microcontroller circuit 2 is converted into a sine wave. Compared with DC inverter, square wave inverter has higher efficiency and lower loss. Moreover, the signal frequency generated by the microcontroller is sufficient, eliminating the need for inverter chip boosting and further reducing the load on the inverter chip. Then, the test signal is sent to the excitation coil 4. When the signal returned by the signal amplification circuit is too small, the microcontroller will control the logic gate switch to send the signal to the signal amplification circuit with a larger amplification ratio, thereby improving the acquisition accuracy. Because the sampling range of the grounding resistance is from 0.01Ω to 1000Ω, if they are directly compared with the microcontroller sampling range of 0-3.3V, the accuracy will be greatly reduced.

[0025] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A grounding resistance tester for SPD, comprising a signal amplification main circuit (1), a microcontroller circuit (2), a signal inverter circuit (3), an excitation coil (4), a acquisition coil (5), a grounding resistance (6), a logic gate circuit (7), and a communication circuit (8), characterized in that: The signal amplification main circuit (1) is connected to the microcontroller circuit (2) via wires. The microcontroller circuit (2) is connected to the signal inverter circuit (3) via wires. The signal inverter circuit (3) is connected to the excitation coil (4) via wires. The acquisition coil (5) is connected to the signal amplification main circuit (1) via wires. Both the acquisition coil (5) and the excitation coil (4) are connected to the grounding resistor (6) via wires. The logic gate circuit (7) is connected to the signal amplification main circuit (1) via wires.

2. A grounding resistance tester for SPD according to claim 1, characterized in that: The communication circuit (8) is connected to the signal amplification main circuit (1) via a wire.

3. A grounding resistance tester for SPD according to claim 1, characterized in that: The main signal amplification circuit (1) includes a first signal amplification circuit (11), a second signal amplification circuit (12), and a third signal amplification circuit (13), which are connected in sequence by wires.

4. A grounding resistance tester for SPD according to claim 1, characterized in that: The microcontroller circuit (2) includes a reset circuit, an external crystal oscillator circuit, an external storage circuit, and a filter circuit.

5. A grounding resistance tester for SPD according to claim 1, characterized in that: The signal inverter circuit (3) is located between the microcontroller circuit (2) and the excitation coil (4).

6. A grounding resistance tester for SPD according to claim 1, characterized in that: The logic gate circuit (7) consists of analog switches and logic switches.

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