Multi-frequency-point grounding resistance testing device and method

Abstract

The invention belongs to the technical field of ground resistance measurement, and particularly relates to a multi-frequency-point ground resistance testing device and method, and the device comprises a main control module which is used for generating a frequency point signal; the signal conversion module is used for converting the frequency point signal into a sine wave signal; the power amplification module carries out power amplification on the sine wave signal and couples the sine wave signal to a grounding system; the sampling module is used for sampling a grounding resistance response signal in a grounding system; the signal processing module is used for filtering and amplifying the grounding resistance response signal; and the main control module is also used for receiving the signal processed by the signal processing module and finally outputting a grounding resistance value. According to the device, the grounding resistance can be measured through multiple frequency points, interference caused by multiple harmonic waves of a power frequency signal is avoided, and in addition, a grounding resistance value without interference can be finally obtained through sequential measurement of the multiple frequency points.

Description

Technical Field

[0001] The present application relates to the technical field of ground resistance measurement, and in particular to a multi-frequency ground resistance testing device and method. Background Art

[0002] A ground resistance tester is an instrument used to measure the resistance of a grounding system. It is widely used in fields such as electricity, communications, and construction to ensure the safety and effectiveness of the grounding system. Currently, ground resistance testers are mainly divided into two types: the clamp method and the stake method. The clamp method requires the grounding system to form a loop, which limits the test conditions and reduces the accuracy. The stake method has high measurement accuracy, can perform independent stake measurements, and has a wide range of applications. The grounding system is a bridge connecting electrical equipment and the earth. Due to the diversity of equipment, interference signals of various frequency bands are distributed in the ground network. The ground resistance testers currently on the market all measure at a single frequency point. When a large interference signal at that frequency point also exists in the ground network, the measurement results will be inaccurate.

[0003] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute prior art known to ordinary technicians in this field.

[0004] Application Contents

[0005] In view of at least one of the above technical problems, the present application provides a multi-frequency ground resistance testing device and method, which solves the problem that the ground resistance testers currently on the market all measure at a single frequency point, and when there is a large interference signal at this frequency point in the local network, it will cause inaccurate measurement results.

[0006] In a first aspect, the present application provides a multi-frequency ground resistance testing device, comprising:

[0007] Main control module, which is used to generate frequency signals;

[0008] A signal conversion module is used to convert the frequency point signal into a sine wave signal;

[0009] A power amplifier module, which amplifies the power of the sine wave signal and couples it to the grounding system;

[0010] The sampling module is used to sample the grounding resistance response signal in the grounding system;

[0011] A signal processing module, which is used to filter and amplify the ground resistance response signal;

[0012] The main control module is also used to receive the signal processed by the signal processing module and finally output the ground resistance value.

[0013] One of the above technical solutions has at least one of the following advantages or beneficial effects: the device can measure the grounding resistance through multiple frequency points, thereby avoiding the interference caused by multiple harmonics of the power frequency signal. In addition, by measuring multiple frequency points in sequence, an interference-free grounding resistance value can be finally obtained.

[0014] In some possible implementations, the frequencies of the frequency point signal include: 75 Hz, 130 Hz, 270 Hz, 420 Hz, 650 Hz, 870 Hz, 1170 Hz, 1370 Hz, 1570 Hz, 1870 Hz, 2170 Hz and 2470 Hz.

[0015] In some possible implementations, the main control module sequentially generates frequency signals of different frequencies, and couples them to the grounding system through the signal conversion module and the power amplification module.

[0016] In some possible implementations, the power amplification module includes a push-pull circuit, an input end of the push-pull circuit is connected to the signal conversion module, and an output end of the push-pull circuit is coupled to a ground system.

[0017] In some possible implementations, the push-pull circuit includes a first transistor and a second transistor, the base of the first transistor and the base of the second transistor are connected in common and connected to the signal conversion module, and the emitter of the first transistor and the emitter of the second transistor are connected in common and coupled to the ground system.

[0018] In some possible implementations, a second resistor, a first diode, and a second diode are sequentially connected between the base of the first transistor and the base of the second transistor.

[0019] In some possible implementations, the sampling module includes a first operational amplifier, a second operational amplifier, a third operational amplifier, a third resistor, a fourth resistor, and a fifth resistor. The first input terminal of the first operational amplifier is coupled to the ground system, the output terminal of the first operational amplifier is connected to the first end of the third resistor and the second input terminal of the third operational amplifier, the second input terminal of the first operational amplifier is connected to the second end of the third resistor and the first end of the fourth resistor, the first input terminal of the second operational amplifier is coupled to the ground system, the output terminal of the second operational amplifier is connected to the second end of the fifth resistor and the first input terminal of the third operational amplifier, the second input terminal of the second operational amplifier is connected to the first end of the fifth resistor and the second end of the fourth resistor, and the output terminal of the third operational amplifier is connected to the signal processing module.

[0020] In some possible implementations, the differential amplification gain of the sampling module is calculated as follows:

[0021]

[0022] Wherein, G is the differential amplifier gain, R3 is the third resistor, R4 is the fourth resistor, and R5 is the fifth resistor.

[0023] In some possible implementations, the signal processing module includes: a bandpass filter and a full-wave rectifier circuit. The bandpass filter is connected to the sampling module, the bandpass filter is used to filter the ground resistance response signal, and the full-wave rectifier circuit is connected to the bandpass filter and the main control module respectively. The full-wave rectifier circuit is used to convert the filtered bipolar ground resistance response signal into a unipolar DC signal.

[0024] In a second aspect, the present application provides a multi-frequency ground resistance testing method, comprising:

[0025] Step 100, obtaining multiple frequency points;

[0026] Step 200, generating a frequency point signal corresponding to one of the multiple frequency points according to one of the multiple frequency points;

[0027] Step 300, converting the frequency point signal into a sine wave signal;

[0028] Step 400, power amplifying the sine wave signal and coupling it into the grounding system;

[0029] Step 500: Acquire a grounding resistance response signal in a grounding system, where the grounding resistance response signal corresponds to a frequency point signal;

[0030] Step 600: filtering and amplifying the ground resistance response signal and generating a resistance measurement value;

[0031] Step 700 , repeating the above steps 200 to 600 to generate multiple resistance measurement values;

[0032] Step 800: Determine a ground resistance value based on a plurality of resistance measurements.

[0033] The present application is further described below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0035] Figure 1 A schematic diagram of the structure of a multi-frequency ground resistance test device provided in an embodiment of the present application;

[0036] Figure 2 for Figure 1 Circuit diagram of the medium power amplifier module;

[0037] Figure 3 for Figure 1 Circuit diagram of the sampling module;

[0038] Figure 4 for Figure 1 Circuit diagram of the signal processing module;

[0039] Figure 5 A flow chart of a multi-frequency ground resistance test method according to an embodiment of the present application; DETAILED DESCRIPTION

[0040] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0041] like Figures 1 to 4 As shown, this embodiment provides a multi-frequency ground resistance testing device, including: a main control module 100, a signal conversion module 200, a power amplification module 300, a sampling module 400 and a signal processing module 500.

[0042] The main control module 100 is used to generate a frequency signal; the signal conversion module 200 is used to convert the frequency signal into a sinusoidal wave signal; the power amplification module 300 amplifies the sinusoidal wave signal and couples it to the grounding system; the sampling module 400 is used to sample the grounding resistance response signal in the grounding system; the signal processing module 500 is used to filter and amplify the grounding resistance response signal; the main control module 100 is also used to receive the signal processed by the signal processing module 500 and finally output the grounding resistance value.

[0043] The multi-frequency grounding resistance test device provided in this embodiment can measure the grounding resistance at multiple frequencies, thereby avoiding interference caused by multiple harmonics of the power frequency signal. In addition, by measuring multiple frequencies in sequence, an interference-free grounding resistance value can be finally obtained.

[0044] In this embodiment, the multi-frequency ground resistance testing device may also include: a human-computer interaction module, an interface module and a power supply module. The human-computer interaction module may include: an interface display and buttons to realize human-computer interaction, instruction issuance and measurement display; the interface module may include: a current output terminal, a signal sampling terminal, and a loop terminal for coupling the ground resistance; the power supply module is used to provide a suitable voltage source for other modules.

[0045] In some embodiments, the main control module 100 sequentially generates frequency signals of different frequencies, which are coupled to the grounding system through the signal conversion module 200 and the power amplifier module 300. The frequency signals include 75 Hz, 130 Hz, 270 Hz, 420 Hz, 650 Hz, 870 Hz, 1170 Hz, 1370 Hz, 1570 Hz, 1870 Hz, 2170 Hz, and 2470 Hz.

[0046] During the test, the multi-frequency ground resistance tester will start measuring from 75Hz and analyze the resistance measurement value returned by the test. When the resistance measurement value fluctuates greatly, it is determined that the interference at this frequency point is large, and it will automatically jump to the next frequency point for measurement until the resistance measurement value stabilizes, and the resistance measurement value is determined to be stable and accurate data.

[0047] like Figures 1 to 4 As shown, in some embodiments, the power amplification module 300 includes: a push-pull circuit, an input end of the push-pull circuit is connected to the signal conversion module 200, and an output end of the push-pull circuit is coupled to the ground system.

[0048] like Figures 1 to 4 As shown, in some embodiments, the push-pull circuit includes a first transistor Q1 and a second transistor Q2, the base of the first transistor Q1 and the base of the second transistor Q2 are connected in common and connected to the signal conversion module 200, and the emitter of the first transistor Q1 and the emitter of the second transistor Q2 are connected in common and coupled to the ground system.

[0049] like Figures 1 to 4 As shown, in some embodiments, a second resistor R2 , a first diode D1 , and a second diode D2 are sequentially connected between the base of the first transistor Q1 and the base of the second transistor Q2 .

[0050] Since there is a slight distortion, namely crossover distortion, when the first transistor Q1 and the second transistor Q2 output alternately, the crossover distortion is eliminated by providing the second resistor R2, the first diode D1 and the second diode D2.

[0051] like Figures 1 to 4As shown, in some embodiments, the sampling module 400 includes a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a third resistor R3, a fourth resistor R4 and a fifth resistor R5. The first input terminal of the first operational amplifier U1 is coupled to the ground system, the output terminal of the first operational amplifier U1 is connected to the first end of the third resistor R3 and the second input terminal of the third operational amplifier U3, the second input terminal of the first operational amplifier U1 is connected to the second end of the third resistor R3 and the first end of the fourth resistor R4, the first input terminal of the second operational amplifier U2 is coupled to the ground system, the output terminal of the second operational amplifier U2 is connected to the second end of the fifth resistor R5 and the first input terminal of the third operational amplifier U3, the second input terminal of the second operational amplifier U2 is connected to the first end of the fifth resistor R5 and the second end of the fourth resistor R4, and the output terminal of the third operational amplifier U3 is connected to the signal processing module 500.

[0052] The sampling module 400 effectively amplifies the ground resistance response signal and suppresses noise by amplifying the differential signal and suppressing the common-mode signal. The first operational amplifier U1 and the second operational amplifier U2 constitute a first-stage differential amplifier circuit, which is a combination of two in-phase proportional circuits. The third operational amplifier U3 is a second-stage differential amplifier circuit, whose output is the product of the difference between the first input terminal of the first operational amplifier U1 and the first input terminal of the second operational amplifier U2 and the amplification factor. The amplification factor is the differential amplifier gain, which is calculated as follows:

[0053]

[0054] Wherein, G is the differential amplifier gain, R3 is the third resistor R3, R4 is the fourth resistor R4, and R5 is the fifth resistor R5.

[0055] In some embodiments, the signal processing module 500 includes: a bandpass filter 510 and a full-wave rectifier circuit 520. The bandpass filter 510 is connected to the sampling module 400. The bandpass filter 510 is used to filter the ground resistance response signal. The full-wave rectifier circuit 520 is respectively connected to the bandpass filter 510 and the main control module 100. The full-wave rectifier circuit 520 is used to convert the filtered bipolar ground resistance response signal into a unipolar DC signal.

[0056] like Figure 4 As shown, the bandpass filter 510 is a Butterworth bandpass filter 510, which mainly filters the ground resistance response signal, retains only the signal near the frequency point, and filters out the signals in other frequency bands.

[0057] Continue to refer Figure 4The full-wave rectifier circuit 520 may include a fourth operational amplifier U2B, a fifth operational amplifier U2A, a twelfth diode D12, a twenty-second diode D22 and a thirty-second resistor R32. The second input terminal of the fourth operational amplifier U2B is connected to the band-pass filter 510, the first input terminal of the fourth operational amplifier U2B is grounded, the output terminal of the fourth operational amplifier U2B is connected to the first input terminal of the fourth operational amplifier U2B through the twelfth diode D12, the thirty-second resistor R32 is respectively connected to the anode of the twenty-second diode D22 and the second input terminal of the fourth operational amplifier U2B, and the second input terminal of the fifth operational amplifier U2A is connected to the output terminal of the fourth operational amplifier U2B through the twenty-second diode D22.

[0058] In the full-wave rectifier circuit 520, the fifth operational amplifier U2A and the thirty-second resistor R32 form an inverse proportional operational amplifier. When the input signal of the full-wave rectifier circuit 520 is in the positive half-cycle, the twelfth diode D12 is turned off, the twenty-second diode D22 is turned on, and the current flows from the thirty-second resistor R32 and the twenty-second diode D22 into the fifth operational amplifier U2A. Here, the output voltage of the fifth operational amplifier U2A is greater than 0. When the input signal of the full-wave rectifier circuit 520 is in the negative half-cycle, the twelfth diode D12 is turned on, and the twenty-second diode D22 is turned off. At this time, the fifth operational amplifier U2A is equivalent to an inverse proportional amplifier circuit, and therefore the output voltage is also greater than 0. Therefore, regardless of whether the input signal of the full-wave rectifier circuit 520 is positive or negative, the output is positive, thereby achieving the full-wave rectification function.

[0059] like Figure 5 As shown, this embodiment provides a multi-frequency ground resistance testing method, including:

[0060] Step 100, obtaining multiple frequency points;

[0061] In step 100 , the frequency points are 75 Hz, 130 Hz, 270 Hz, 420 Hz, 650 Hz, 870 Hz, 1170 Hz, 1370 Hz, 1570 Hz, 1870 Hz, 2170 Hz, and 2470 Hz.

[0062] Step 200, generating a frequency point signal corresponding to one of the multiple frequency points according to one of the multiple frequency points;

[0063] Step 300, converting the frequency point signal into a sine wave signal;

[0064] Step 400, power amplifying the sine wave signal and coupling it into the grounding system;

[0065] Step 500: Acquire a grounding resistance response signal in a grounding system, where the grounding resistance response signal corresponds to a frequency point signal;

[0066] Step 600: filtering and amplifying the ground resistance response signal and generating a resistance measurement value;

[0067] Step 700 , repeating the above steps 200 to 600 to generate multiple resistance measurement values;

[0068] In steps 200 to 700, starting from the initial frequency point of 75 Hz, the corresponding frequency point signal is generated. After the resistance measurement value is generated, the frequency point is changed to 130 Hz and the corresponding frequency point signal is generated. The measurement continues until all frequency points are measured.

[0069] Step 800: Determine a ground resistance value based on a plurality of resistance measurements.

[0070] In step 800 , a stable resistance measurement value is selected from a plurality of resistance measurement values as a ground resistance value.

[0071] In the description of the embodiments of this application, unless otherwise specified, " / " represents or. For example, A / B can represent A or B. "And / or" in this article is simply a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of this application, "plurality" means two or more than two.

[0072] In the description of the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more of such features.

[0073] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described below are merely schematic. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or can be electrical, mechanical or other forms of connection.

[0074] The above are merely preferred embodiments of the present application and do not constitute any form of limitation to the present application. Any person skilled in the art can, without departing from the scope of the technical solution of the present application, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present application, or modify it into an equivalent embodiment with equivalent changes. Therefore, all equivalent changes made based on the shape, structure and principle of the present application without departing from the content of the technical solution of the present application should be included in the scope of protection of the present application.

Claims

1. A multi-frequency ground resistance test device, characterized in that: include: A main control module, the main control module is used to generate a frequency signal; A signal conversion module, configured to convert a frequency point signal into a sine wave signal; a power amplification module, which amplifies the power of the sine wave signal and couples it to the grounding system; A sampling module, wherein the sampling module is used to sample a ground resistance response signal in a grounding system; A signal processing module, the signal processing module is used to filter and amplify the ground resistance response signal; The main control module is further configured to receive the signal processed by the signal processing module and ultimately output a ground resistance value.

2. The multi-frequency ground resistance test device according to claim 1, characterized in that: The frequencies of the frequency point signals include: 75 Hz, 130 Hz, 270 Hz, 420 Hz, 650 Hz, 870 Hz, 1170 Hz, 1370 Hz, 1570 Hz, 1870 Hz, 2170 Hz and 2470 Hz.

3. The multi-frequency ground resistance test device according to claim 1, characterized in that: The main control module generates frequency signals of different frequencies in sequence, and couples the signals to the grounding system through the signal conversion module and the power amplification module.

4. The multi-frequency ground resistance test device according to claim 1, characterized in that: The power amplification module includes a push-pull circuit, an input end of the push-pull circuit is connected to the signal conversion module, and an output end of the push-pull circuit is coupled to a grounding system.

5. The multi-frequency ground resistance test device according to claim 4, characterized in that: The push-pull circuit includes a first transistor and a second transistor, the base of the first transistor and the base of the second transistor are connected in common and are connected to the signal conversion module, the emitter of the first transistor and the emitter of the second transistor are connected in common and are coupled to the ground system.

6. The multi-frequency ground resistance test device according to claim 5, characterized in that: A second resistor, a first diode and a second diode are connected in sequence between the base of the first transistor and the base of the second transistor.

7. The multi-frequency ground resistance test device according to claim 1, characterized in that: The sampling module includes a first operational amplifier, a second operational amplifier, a third operational amplifier, a third resistor, a fourth resistor and a fifth resistor. The first input terminal of the first operational amplifier is coupled to the ground system, the output terminal of the first operational amplifier is connected to the first end of the third resistor and the second input terminal of the third operational amplifier, the second input terminal of the first operational amplifier is connected to the second end of the third resistor and the first end of the fourth resistor, the first input terminal of the second operational amplifier is coupled to the ground system, the output terminal of the second operational amplifier is connected to the second end of the fifth resistor and the first input terminal of the third operational amplifier, the second input terminal of the second operational amplifier is connected to the first end of the fifth resistor and the second end of the fourth resistor, and the output terminal of the third operational amplifier is connected to the signal processing module.

8. The multi-frequency ground resistance test device according to claim 7, characterized in that: The calculation formula of the differential amplification gain of the sampling module is: Wherein, G is the differential amplifier gain, R3 is the third resistor, R4 is the fourth resistor, and R5 is the fifth resistor.

9. The multi-frequency ground resistance test device according to claim 1, characterized in that: The signal processing module includes: a bandpass filter and a full-wave rectifier circuit. The bandpass filter is connected to the sampling module. The bandpass filter is used to filter the ground resistance response signal. The full-wave rectifier circuit is respectively connected to the bandpass filter and the main control module. The full-wave rectifier circuit is used to convert the filtered bipolar ground resistance response signal into a unipolar DC signal.

10. A multi-frequency ground resistance testing method, characterized in that: include: Step 100, obtaining multiple frequency points; Step 200, generating a frequency point signal corresponding to one of the multiple frequency points according to one of the multiple frequency points; Step 300, converting the frequency point signal into a sine wave signal; Step 400, power amplifying the sine wave signal and coupling it into the grounding system; Step 500: Acquire a grounding resistance response signal in a grounding system, where the grounding resistance response signal corresponds to the frequency signal; Step 600: filtering and amplifying the ground resistance response signal and generating a resistance measurement value; Step 700 , repeating the above steps 200 to 600 to generate multiple resistance measurement values; Step 800: Determine a ground resistance value based on a plurality of resistance measurements.

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