Device and method for testing ideal shielding coefficient of multi-frequency cable

Abstract

The invention belongs to the technical field of cable shielding coefficient testing, and relates to a multi-frequency cable ideal shielding coefficient testing device and method. The device comprises a digital level oscillator, a power amplifier, an impedance converter, a fixed straightening device, an interference level digital frequency-selecting electric meter and an induction level digital frequency-selecting electric meter. Hardware fitting units are arranged at the two ends of the fixed straightening device, and each hardware fitting unit comprises a cable connecting hardware fitting, a current testing hardware fitting and a voltage testing hardware fitting; during testing, the cable connection fitting is connected with the current testing fitting; one end of the impedance converter is connected with one current test fitting, and the other end of the impedance converter is connected with the other current test fitting; one end of the interference level digital frequency-selecting ammeter is connected with one voltage test fitting, and the other end is connected with the other voltage test fitting; one end of the induction level digital frequency-selecting ammeter is connected with the voltage test fitting, and the other end is connected with the to-be-tested cable. The problem that the ideal shielding coefficient of the multi-frequency cable cannot be tested is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of cable shielding coefficient testing, and in particular relates to a device and method for testing an ideal shielding coefficient of a multi-frequency cable. Background Art

[0002] With the rapid development of railways, railway signal technology is developing towards digitalization, intelligence, networking and integration, resulting in a large number of railway communication and signal cables with new uses and new structures. When laying cables, railway communication and signal cables are laid in the same trench as power cables. In normal operation, in places such as transmission lines, AC electrified railways and radio stations that form electromagnetic interference to communication cables, signal cables and communication cables used in electrified railways or sections with strong electromagnetic interference are required to have excellent shielding performance to prevent external electromagnetic wave interference or prevent themselves from interfering with the outside, so as to ensure the safety and reliability of the line. The ideal shielding coefficient is a technical parameter to measure the shielding performance.

[0003] Currently, there are only devices on the market that test the ideal shielding coefficient of 50Hz power frequency. The test of 50Hz ideal shielding coefficient uses the power supply used in daily life, which cannot directly produce signal sources of other frequencies, so only the 50Hz ideal shielding coefficient can be tested. However, new communication cables and railway digital signal cables use more frequencies, specifically 0.8kHz, 1.7kHz, 2.0kHz, 2.3kHz, 2.6kHz, etc. In order to evaluate the anti-interference ability of these signal cables in the frequency bands used, multi-frequency cable ideal shielding coefficient test devices and methods are needed.

[0004] However, there is currently no device or method for evaluating the anti-electromagnetic interference capability of digital signal cables at various operating frequencies. Summary of the invention

[0005] The purpose of the present invention is to provide a device and method for testing the ideal shielding coefficient of a multi-frequency cable, which solves the problem that the prior art cannot test the ideal shielding coefficient of a multi-frequency cable.

[0006] The present invention is achieved through the following technical solutions:

[0007] The invention discloses a multi-frequency cable ideal shielding coefficient test device, comprising a digital level oscillator, a power amplifier, an impedance converter, a fixed straightening device, an interference level digital frequency selective meter and an induction level digital frequency selective meter;

[0008] Both ends of the fixed straightening device are provided with hardware units, which include cable connection hardware, current test hardware and voltage test hardware;

[0009] A digital level oscillator, a power amplifier and an impedance converter are connected in sequence;

[0010] During the test, the cable connection fitting is connected to the current test fitting; one end of the impedance converter is connected to one of the current test fittings, and the other end is connected to the other current test fitting;

[0011] One end of the interference level digital frequency-selective meter is connected to one of the voltage test fixtures, and the other end is connected to another voltage test fixture;

[0012] One end of the induction level digital frequency-selective meter is connected to the voltage test fixture, and the other end is connected to the cable to be tested.

[0013] Furthermore, the cable connection fittings serve as current test lead-out terminals, and the voltage test fittings serve as voltage test lead-out terminals.

[0014] Furthermore, the fixing and straightening device is an epoxy resin insulation tube.

[0015] Furthermore, a plurality of calibration knobs are provided on the fixed straightening device, and the calibration knobs are used to fix and calibrate the cable to be tested.

[0016] Furthermore, the multi-frequency cable ideal shielding coefficient test device also includes an insulating base, and a digital level oscillator, a power amplifier, an impedance converter, a fixed straightening device, an interference level digital frequency selective meter and an induction level digital frequency selective meter are all fixed on the insulating base.

[0017] Furthermore, the insulating base is an L-shaped base consisting of a horizontal platform and a vertical platform, the fixed straightening device and the hardware unit are arranged on the horizontal platform, and the digital level oscillator, power amplifier, impedance converter, interference level digital frequency selective meter and induction level digital frequency selective meter are arranged on the vertical platform.

[0018] Furthermore, the insulating base is made of epoxy resin insulating board.

[0019] Furthermore, the multi-frequency cable ideal shielding coefficient test device also includes a control system, the control system includes a processor and a display panel, and the processor stores a cable ideal shielding coefficient calculation formula, specifically:

[0020] γ=POWER(10,(P0-P^) / 20);

[0021] Among them, γ is the ideal shielding coefficient of the cable, P0 is the induction level value, and P^ is the interference level value;

[0022] The display panel is connected with the processor, the interference level digital frequency-selective meter and the induction level digital frequency-selective meter, and is used for displaying the ideal shielding coefficient of the cable, the interference level value and the induction level value.

[0023] The present invention also discloses a testing method of the multi-frequency cable ideal shielding coefficient testing device, comprising the following process:

[0024] Adjust the level of the digital level oscillator and the amplitude of the power amplifier, use the digital level oscillator to generate level electrical signals of various frequencies and waveforms, and process the level electrical signals through the power amplifier and the impedance converter to generate artificial interference electric fields under multiple frequencies to achieve the interference level value required for the test, and record the interference level value displayed by the interference level digital frequency selective meter and the induction level value of the induction level digital frequency selective meter respectively;

[0025] The ideal shielding factor of the cable is calculated based on the interference level and induction level values.

[0026] Furthermore, before adjusting the level of the digital level oscillator and the amplitude of the power amplifier, it is necessary to calibrate and adjust the digital level oscillator, the interference level digital frequency selective meter and the induction level digital frequency selective meter.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] The invention discloses a multi-frequency cable ideal shielding coefficient test device, including a digital level oscillator, a power amplifier, an impedance converter, a digital frequency-selective level meter, a test fixture, and a cable connection fitting. The digital level oscillator is used to generate level electrical signals of various frequencies and waveforms. After the power amplifier and the impedance converter process the signal, an artificial interference electric field under multiple frequencies is generated. The interference level value and the induction level value are obtained through the interference level digital frequency-selective level meter and the induction level digital frequency-selective level meter, thereby achieving the purpose of testing the ideal shielding coefficient of the multi-frequency cable. The digital level oscillator, the digital frequency-selective level meter, the impedance converter, and the power amplifier have strong anti-interference, low distortion, high sensitivity, and convenient reading performance, and can ensure the accuracy of the test data, provide technical support for the high quality and excellent performance evaluation of the product and the improvement of the cable testing technology, and the high anti-interference performance of the product ensures the reliable and safe operation of the digital and intelligent railway.

[0029] Furthermore, the insulating base is made of epoxy resin material, which has good insulation performance, ensures the safety of operation and reduces test influencing factors, thereby ensuring accurate test results.

[0030] The invention also discloses a testing method for the multi-frequency cable ideal shielding coefficient testing device. When the system is working, the output frequency, amplitude, modulation coefficient, etc. of the digital level oscillator are continuously adjustable within a certain range, and the reading is accurate, stable, and well-shielded, providing an interference level at the test frequency. The power amplifier converts the low-power signal of the digital level oscillator into a high-power signal required for the test with high gain and low distortion. After the high-power signal passes through the impedance converter, it is output as a large test current. This current passes through the shielding layer and copper rod of the test cable sample to form a large current loop, artificially create an interference circuit, and the frequency-selective level meter responds to the frequency of the level oscillator to test the interference level applied to the cable and the induction level of the cable core, record the values ​​of the interference level and the induction level at this time, and calculate according to the ideal shielding coefficient formula to obtain the ideal shielding coefficient result of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of a multi-frequency cable ideal shielding coefficient testing device of the present invention;

[0032] Figure 2 It is a schematic diagram of the testing principle of the ideal shielding coefficient of the cable of the present invention;

[0033] Figure 3 The present invention is an electrical connection diagram of a multi-frequency cable ideal shielding coefficient testing device.

[0034] Among them: 1. Power switch; 2. Cable connection fittings; 3. Digital level oscillator; 4. Power amplifier; 5. Impedance converter; 6. Fixed straightening device; 7. Interference level digital frequency selective meter; 8. Induction level digital frequency selective meter; 9. Current test fittings; 10. Voltage test fittings; 11. Calibration knob; 12. Insulation base. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to 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 used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0036] The components described and shown in the drawings and embodiments of the present invention may be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0037] It should be noted that the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, so that a process, element, method, article or equipment that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or equipment.

[0038] The features and performances of the present invention are further described in detail below in conjunction with the embodiments.

[0039] like Figure 1 As shown, the present invention discloses a multi-frequency cable ideal shielding coefficient testing device, including a power switch 1, a cable connection fitting 2, a digital level oscillator 3, a power amplifier 4, an impedance converter 5, a fixed straightening device 6, an interference level digital frequency-selective meter 7, an induction level digital frequency-selective meter 8, a current test fitting 9, a voltage test fitting 10, a calibration knob 11, and an insulating base 12.

[0040] like Figure 1 As shown, the fixed straightening device 6 is horizontally arranged on an insulating base 12 , and hardware units are provided at both ends of the fixed straightening device 6 , and the hardware units include a cable connection hardware 2 , a current test hardware 9 and a voltage test hardware 10 .

[0041] The insulating base 12 is a mechanical support device for the instrument and an insulating device for the cable test line, and is made of epoxy resin insulating board.

[0042] The insulating base 12 is designed as an L-shaped base consisting of a horizontal platform and a vertical platform. The fixed straightening device 6 and the hardware unit are arranged on the horizontal platform, and the digital level oscillator 3, the power amplifier 4, the impedance converter 5, the interference level digital frequency selective meter 7 and the induction level digital frequency selective meter 8 are arranged on the vertical platform.

[0043] The cable connection fitting 2 is composed of a copper nut and a screw to form a current test lead-out end. The current test fitting 9 is a soft copper brush, which is used for electrical connection of the inner and outer shielding layers of the cable. It is the current end of the entire test circuit, has excellent conductivity, reduces internal and external contact resistance, and increases test accuracy.

[0044] The voltage test fitting 10 is a voltage test lead-out terminal composed of a copper nut and a screw, and is a voltage common terminal for interference voltage and induced voltage.

[0045] The soft brush can better ensure that the test cable and the current loop are in good contact, reduce contact resistance, and improve test accuracy; the voltage test fixture 10 adopts copper nuts and screws to ensure good contact at the voltage end; it is good and easy to operate.

[0046] The fixed straightening device 6 is an epoxy resin insulating tube. The fixed straightening device 6 is an open and adjustable tube. Because in normal tests, cable samples often have bending phenomena, which affects the test results, the fixed straightening device 6 is used to correct and straighten the bent cables to improve the test efficiency.

[0047] The fixed straightening device 6 is provided with a plurality of calibration knobs 11, which are epoxy resin insulated fastening knobs. The fixed straightening device 6 and the calibration knobs 11 are used together to fix and calibrate the cable sample, so as to reduce the test length error.

[0048] like Figure 2 As shown, a schematic diagram of the connection of a digital level oscillator 3, a power amplifier 4, an impedance converter 5 and a digital frequency-selective ammeter is shown. The digital level oscillator 3 generates level electrical signals of various frequencies and waveforms, which are processed by the power amplifier 4 and the impedance converter 5 to generate artificial interference electric fields at multiple frequencies.

[0049] like Figure 3 As shown, the interference level digital frequency selective meter 7 and the induction level digital frequency selective meter 8 are independent of each other. When testing the level, there is a common end, and the other end is connected to different circuits to test the interference level and the induction level respectively. Specifically, one end of the interference level digital frequency selective meter 7 is connected to one of the voltage test fittings 10, and the other end is connected to another voltage test fitting 10; one end of the induction level digital frequency selective meter 8 is connected to the voltage test fitting 10, and the other end is connected to one of the core wires in the cable to be tested.

[0050] Specifically, the digital level oscillator 3 is used to generate level electrical signals of various frequencies and waveforms. The level electrical signals output by the digital level oscillator 3 are low-power signals.

[0051] The power amplifier 4 is used to convert the low-power signal generated by the digital level oscillator 3 into a high-power signal required for testing.

[0052] The impedance converter 5 is used to convert the low-current mA level of the high-power signal of the power amplifier 4 into the high-interference current of level A required for the test.

[0053] Interference level digital frequency selective meter 7 is used to test the interference level of the ideal shielding coefficient test.

[0054] The induction level digital frequency selective ammeter 8 is used to test the induction level of the ideal shielding coefficient test.

[0055] When the system is working, the digital level oscillator 3 outputs a signal with frequency, amplitude, modulation coefficient, etc. that is continuously adjustable within a certain range, and the reading is accurate, stable, and well-shielded, providing the interference level at the test frequency; the power amplifier 4 converts the low-power signal of the digital level oscillator 3 into a high-power signal required for the test; the high-power signal passes through the impedance converter 5 and is output as a large test current; this large test current passes through the shielding layer and copper rod of the test cable sample to form a large current loop, artificially create an interference circuit, and the frequency-selective ammeter responds to the frequency of the level oscillator to test the interference level applied to the cable and the induction level of the cable core.

[0056] Among them, first, a cable sample to be tested is made, the cable sample is placed in a cable straightening device 6, the calibration knob 11 is adjusted, the cable sample is fixed, the two ends of the cable connecting fittings 2 are connected to the interference current circuit, the two voltage test fittings 10 are connected to the interference level digital frequency selective meter 7 for testing the interference level, and one of the core wires in the cable sample and the voltage test fittings 10 are connected to the induction level digital frequency selective meter 8 for testing the induction level.

[0057] The present invention also discloses a testing method based on the above-mentioned testing device, which is specifically:

[0058] Turn on the power switch 1, and adjust the test frequencies of the digital level oscillator 3, the interference level digital frequency selective meter 7, and the induction level digital frequency selective meter 8;

[0059] Adjust the level of the digital level oscillator 3 and the amplitude of the power amplifier 4 to achieve the interference level value required for the test, and record the interference level value P^ displayed by the interference level digital frequency selective meter 7 and the induction level value P0 displayed by the induction level digital frequency selective meter 8, complete the test, and record the interference level value P^ and the induction level value P0;

[0060] The interference level value P^ and the induction level value P0 are input into the processor, and the processor calculates according to the following formula to obtain the ideal shielding coefficient result of the cable, stores and uses the result for statistical analysis, and draws the result chart.

[0061] Calculation formula for ideal shielding factor of cable:

[0062] γ=POWER(10,(P0-P^) / 20)

[0063] Where γ is the ideal shielding coefficient of the cable, P0 is the induction level value, and P^ is the interference level value.

[0064] The application of this method and device is simple to implement. It uses the level oscillator to generate equipment performance of various frequencies, waveforms and output level electrical signals. After the power amplifier 4 and the impedance converter 5 process the signal, it generates a considered interference electric field under multiple frequencies. By testing the interference signal strength and the induced signal strength, the ideal shielding coefficient test purpose of the multi-frequency cable is achieved. In addition, the digital level oscillator 3, the digital frequency selection level meter, the impedance converter, and the power amplifier 4 equipment have strong anti-interference, low distortion, high sensitivity, and convenient reading performance, which improves the accuracy of the test data, provides technical support for the high quality and excellent performance evaluation of the product and the improvement of the cable testing technology, and the high anti-interference performance of the product ensures the reliable and safe operation of the digital and intelligent railway.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A multi-frequency cable ideal shielding coefficient test device, characterized in that: It comprises a digital level oscillator (3), a power amplifier (4), an impedance converter (5), a fixed straightening device (6), an interference level digital frequency selective meter (7) and an induction level digital frequency selective meter (8); Both ends of the fixed straightening device (6) are provided with hardware units, the hardware units comprising a cable connection hardware (2), a current test hardware (9) and a voltage test hardware (10); A digital level oscillator (3), a power amplifier (4) and an impedance converter (5) are connected in sequence; During testing, the cable connection fitting (2) is connected to the current test fitting (9); one end of the impedance converter (5) is connected to one of the current test fittings (9), and the other end is connected to the other current test fitting (9); One end of the interference level digital frequency-selective electric meter (7) is connected to one of the voltage test fittings (10), and the other end is connected to another voltage test fitting (10); One end of the induction level digital frequency-selective ammeter (8) is connected to a voltage test fixture (10), and the other end is connected to a cable to be tested.

2. A multi-frequency cable ideal shielding coefficient test device according to claim 1, characterized in that: The cable connection fitting (2) serves as a current test lead-out terminal, and the voltage test fitting (10) serves as a voltage test lead-out terminal.

3. A multi-frequency cable ideal shielding coefficient test device according to claim 1, characterized in that: The fixing and straightening device (6) is an epoxy resin insulating tube.

4. A multi-frequency cable ideal shielding coefficient test device according to claim 1, characterized in that: A plurality of calibration knobs (11) are provided on the fixed straightening device (6), and the calibration knobs (11) are used to fix and calibrate the cable to be tested.

5. A multi-frequency cable ideal shielding coefficient test device according to claim 1, characterized in that: The multi-frequency cable ideal shielding coefficient test device also includes an insulating base (12), on which a digital level oscillator (3), a power amplifier (4), an impedance converter (5), a fixed straightening device (6), an interference level digital frequency-selective meter (7) and an induction level digital frequency-selective meter (8) are all fixed.

6. A multi-frequency cable ideal shielding coefficient test device according to claim 5, characterized in that: The insulating base (12) is an L-shaped base consisting of a horizontal platform and a vertical platform. The fixing and straightening device (6) and the hardware unit are arranged on the horizontal platform, and the digital level oscillator (3), the power amplifier (4), the impedance converter (5), the interference level digital frequency selective meter (7) and the induction level digital frequency selective meter (8) are arranged on the vertical platform.

7. A multi-frequency cable ideal shielding coefficient test device according to claim 1, characterized in that: The insulating base (12) is made of an epoxy resin insulating board.

8. A multi-frequency cable ideal shielding coefficient test device according to any one of claims 1 to 7, characterized in that: The multi-frequency cable ideal shielding coefficient test device also includes a control system, which includes a processor and a display panel. The processor stores a cable ideal shielding coefficient calculation formula, which is specifically: γ=POWER(10,(P0-P^) / 20); Among them, γ is the ideal shielding coefficient of the cable, P0 is the induction level value, and P^ is the interference level value; The display panel is connected to the processor, the interference level digital frequency-selective ammeter (7) and the induction level digital frequency-selective ammeter (8), and is used to display the ideal shielding coefficient of the cable, the interference level value and the induction level value.

9. The testing method of the multi-frequency cable ideal shielding coefficient testing device according to any one of claims 1 to 8, characterized in that: The process includes: The level of the digital level oscillator (3) and the amplitude of the power amplifier (4) are adjusted, and the digital level oscillator (3) is used to generate level electrical signals of various frequencies and waveforms. The level electrical signals are processed by the power amplifier (4) and the impedance converter (5) to generate artificial interference electric fields at multiple frequencies to achieve the interference level value required for the test, and the interference level value displayed by the interference level digital frequency selective meter (7) and the induction level value of the induction level digital frequency selective meter (8) are recorded respectively; The ideal shielding factor of the cable is calculated based on the interference level and induction level values.

10. The testing method according to claim 9, characterized in that: Before adjusting the level of the digital level oscillator (3) and the amplitude of the power amplifier (4), it is necessary to first calibrate and adjust the digital level oscillator (3), the interference level digital frequency selective meter (7) and the induction level digital frequency selective meter (8).

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