Circuit of cable fault detector

Abstract

The utility model provides a circuit of a cable fault detector. The circuit comprises a relay switch on-off circuit; the cable length measuring circuit is connected to the relay switch on-off circuit, and the cable length measuring circuit is used for calculating the length of the coaxial cable; the resistance measuring circuit is connected to the relay switch on-off circuit, and the resistance measuring circuit is used for calculating the resistance of the cable; the capacitance measuring circuit is connected to the relay switch on-off circuit, and the capacitance measuring circuit is used for measuring the capacitance value of the cable; the direct current bias circuit is connected to the cable length measuring circuit; the relay switch on-off circuit, the cable length measuring circuit, the resistance measuring circuit, the capacitance measuring circuit and the direct current bias circuit are all connected to the power supply circuit, and the power supply circuit is used for supplying power to all the circuits.

Description

Technical Field

[0001] The utility model relates to the field of cable fault detectors, and more specifically, to a circuit of a cable fault detector. Background Art

[0002] Cable fault detector is an important tool that helps the normal operation of cable lines and maintains various cables. It is a new generation of high-tech products with multiple fault detection methods, applying the most advanced electronic technology achievements of the contemporary era, and using computers and special electronic technologies. It is intelligent and full-featured.

[0003] At present, driven by the rapid development of domestic power, communication and energy industries, the cable market is expanding, which in turn drives the rapid development of the cable detection industry. The use of cables is increasing, and cable failures are also common. The emergence of cable fault detectors provides an effective means for the detection of cable faults and has become one of the important equipment in the power industry and the communication industry.

[0004] Principle of measuring fault point: TDR, also known as time domain reflection measurement, can be realized by shape reflection. The time detection of the rising edge of two pulses is detected, so the reflection time can be calculated, and the length can be calculated according to the calculation equation of the coaxial cable. Establish SPI communication between STM32 and FPGA, collect the return signal frequency and the square wave return time at both ends of the coaxial cable, calculate the pulse width time and duty cycle, so as to calculate the signal reflection time, and thus calculate the length of the coaxial cable.

[0005] Principle of measuring duty cycle: the measured signal and the standard signal will be counted simultaneously within the same time, and the D trigger will ensure that the actual gate time is synchronized with the measured signal to eliminate the counting error of the measured signal; the data reading module will read the data of the two technical modules simultaneously and send them to the data processing module for processing; the data processing module will calculate the frequency and duty cycle of the read data and send them to the display module; the display module will display the frequency and duty cycle on the screen.

[0006] However, the measurement accuracy of current cable fault detectors needs to be improved. Due to technical and financial limitations, when the fault point is very close, the measured distance to the fault point will have an error of about 1m. Summary of the invention

[0007] The utility model aims to provide a circuit of a cable fault detector.

[0008] The utility model aims to solve the problems existing in the prior art.

[0009] Compared with the prior art, the technical solution of the utility model and its beneficial effects are as follows:

[0010] A circuit of a cable fault detector comprises: a relay switch on-off circuit; a cable length measuring circuit, the cable length measuring circuit is connected to the relay switch on-off circuit, and the cable length measuring circuit is used to calculate the length of a coaxial cable; a resistance measuring circuit, the resistance measuring circuit is connected to the relay switch on-off circuit, and the resistance measuring circuit is used to calculate the resistance of a cable; a capacitance measuring circuit, the capacitance measuring circuit is connected to the relay switch on-off circuit, and the capacitance measuring circuit is used to measure the capacitance value of a cable; a DC bias circuit, the DC bias circuit is connected to the cable length measuring circuit; and a power supply circuit, the relay switch on-off circuit, the cable length measuring circuit, the resistance measuring circuit, the capacitance measuring circuit, and the DC bias circuit are all connected to the power supply circuit, and the power supply circuit is used to supply power to each circuit.

[0011] As a further improvement, the relay switch on-off circuit includes: the 1st and 4th ends of the microcontroller U6 are both connected to the +5V voltage end, the 2nd end of the microcontroller U6 is connected to one end of the resistor R21, the other end of the resistor R21 is connected to one end of the plug J4, the 3rd end of the microcontroller U6 is connected to one end of the resistor R19, the other end of the resistor R19 is connected to one end of the resistor R15, and the other end of the resistor R15 is grounded; and the other end of the resistor R19 is connected to the base of the transistor Q2, the collector of the transistor Q2 is connected to the +5V voltage end, the emitter of the transistor Q2 is connected to one end of the resistor R11, the other end of the resistor R11 is connected to the positive electrode of the lamp LED2, and the negative electrode of the lamp LED2 is grounded; the negative electrode of the diode D1 is connected to the emitter of the transistor Q2, and the positive electrode of the diode D1 is grounded; the 1st end of the relay RELAY2 is connected to the emitter of the transistor Q2, the 4th end of the relay RELAY2 is grounded, and the 5th end of the relay RELAY2 is connected At the 2nd end of relay RELAY1; the 1st end and the 4th end of the microcontroller U4 are both connected to the +5V voltage end, the 2nd end of the microcontroller U4 is connected to one end of the resistor R10, the other end of the resistor R10 is connected to the other end of the plug J4, the 3rd end of the microcontroller U4 is connected to one end of the resistor R12, the other end of the resistor R12 is connected to one end of the resistor R16, and the other end of the resistor R16 is grounded; and the other end of the resistor R12 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to the +5V voltage end, the emitter of the transistor Q1 is connected to one end of the resistor R20, the other end of the resistor R20 is connected to the positive electrode of the lamp LED3, and the negative electrode of the lamp LED3 is grounded; the negative electrode of the diode D3 is connected to the emitter of the transistor Q1, and the positive electrode of the diode D3 is grounded; the 1st end of the relay RELAY1 is connected to the emitter of the transistor Q1, the 4th end of the relay RELAY1 is grounded, and the 5th end of the relay RELAY1 is connected to the cable interface RF6.

[0012] As a further improvement, the cable length measurement circuit includes: one end of capacitor C1 is connected to the cable interface RF1, the other end of capacitor C1 is connected to one end of resistor R1, the other end of resistor R1 is connected to one end of resistor R2, and the other end of resistor R2 is grounded; the other end of resistor R1 is connected to terminal 1 of controller U1; one end of capacitor C2 is connected to the relay switch on-off circuit, the other end of capacitor C2 is connected to one end of resistor R3, the other end of resistor R3 is connected to one end of resistor R4 and connected to the third end of controller U1, and the other end of resistor R4 is grounded; the eighth end of controller U1 is connected to the +2.5V voltage terminal and to one end of capacitor C3, and the other end of capacitor C3 is grounded; the eighth end of controller U1 is connected to one end of capacitor C4, and the other end of capacitor C4 is grounded; one end of resistor R5 is connected to the seventh end of controller U1, and the other end of resistor R5 is connected to the relay switch on-off circuit; one end of resistor R6 is connected to the sixth end of controller U1, and the other end of resistor R6 is connected to cable interface RF4.

[0013] As a further improvement, the resistance measurement circuit includes: one end of the resistor R8 is connected to the +2.5V voltage terminal and connected to the interface J1, and the other end of the resistor R8 is connected to the relay switch on-off circuit and connected to the interface J2.

[0014] As a further improvement, the capacitance measurement circuit includes: one end of capacitor C10 is connected to terminal 1 of controller U2, and the other end of capacitor C10 is connected to terminal 5 of controller U2; one end of resistor R18 is connected to terminal 4 of controller U2, and the other end of resistor R18 is connected to terminal 7 of controller U2; one end of resistor R17 is connected to terminal 7 of controller U2, and the other end of resistor R17 is connected to terminals 2 and 6 of controller U2; terminal 2 of controller U2 is connected to the relay switch on-off circuit, and terminals 4 and 8 of controller U2 are connected to the +5V voltage terminal.

[0015] The beneficial effects of the utility model are:

[0016] The utility model provides a circuit for a cable fault detector, which improves the measurement accuracy of the cable fault detector and greatly reduces labor costs. The cable fault detector using the circuit is easy to carry, is integrated in equipment manufacturing, occupies a small space, and can cope with relatively special geographical environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the on-off circuit of the relay switch provided in the embodiment of the utility model.

[0018] Figure 2 It is a schematic diagram of a cable length measurement circuit provided by an embodiment of the utility model.

[0019] Figure 3 It is a schematic diagram of a capacitance measurement circuit provided by an embodiment of the utility model.

[0020] Figure 4 It is a schematic diagram of a DC bias circuit provided by an embodiment of the utility model.

[0021] Figure 5 It is a schematic diagram of a power supply circuit provided by an embodiment of the utility model.

[0022] Figure 6 It is a schematic diagram of a digital-analog-to-ground isolation circuit provided by an embodiment of the utility model.

[0023] Figure 7 It is a schematic diagram of a resistance measurement circuit provided by an embodiment of the utility model. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Therefore, the following detailed description of the embodiments of the utility model provided in the drawings is not intended to limit the scope of the utility model for which protection is sought, but merely represents the selected embodiments of the utility model. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0025] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0026] Reference Figures 1 to 7As shown, a circuit of a cable fault detector includes: a relay switch on-off circuit; a cable length measurement circuit, the cable length measurement circuit is connected to the relay switch on-off circuit, and the cable length measurement circuit is used to calculate the length of the coaxial cable; a resistance measurement circuit, the resistance measurement circuit is connected to the relay switch on-off circuit, and the resistance measurement circuit is used to calculate the resistance of the cable; a capacitance measurement circuit, the capacitance measurement circuit is connected to the relay switch on-off circuit, and the capacitance measurement circuit is used to measure the capacitance value of the cable; a DC bias circuit, the DC bias circuit is connected to the cable length measurement circuit; a power supply circuit, the relay switch on-off circuit, the cable length measurement circuit, the resistance measurement circuit, the capacitance measurement circuit, and the DC bias circuit are all connected to the power supply circuit, and the power supply circuit is used to supply power to each circuit.

[0027] The relay switch on-off circuit includes: the 1st and 4th ends of the microcontroller U6 are both connected to the +5V voltage end, the 2nd end of the microcontroller U6 is connected to one end of the resistor R21, the other end of the resistor R21 is connected to one end of the plug J4, the 3rd end of the microcontroller U6 is connected to one end of the resistor R19, the other end of the resistor R19 is connected to one end of the resistor R15, and the other end of the resistor R15 is grounded; and the other end of the resistor R19 is connected to the base of the transistor Q2, the collector of the transistor Q2 is connected to the +5V voltage end, the emitter of the transistor Q2 is connected to one end of the resistor R11, the other end of the resistor R11 is connected to the positive electrode of the lamp LED2, and the negative electrode of the lamp LED2 is grounded; the negative electrode of the diode D1 is connected to the emitter of the transistor Q2, and the positive electrode of the diode D1 is grounded; the 1st end of the relay RELAY2 is connected to the emitter of the transistor Q2, the 4th end of the relay RELAY2 is grounded, and the 5th end of the relay RELAY2 is connected to the relay R 2 ends of ELAY1; 1 end and 4 end of the microcontroller U4 are both connected to the +5V voltage end, 2 end of the microcontroller U4 is connected to one end of the resistor R10, the other end of the resistor R10 is connected to the other end of the plug J4, 3 end of the microcontroller U4 is connected to one end of the resistor R12, the other end of the resistor R12 is connected to one end of the resistor R16, and the other end of the resistor R16 is grounded; and the other end of the resistor R12 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to the +5V voltage end, the emitter of the transistor Q1 is connected to one end of the resistor R20, the other end of the resistor R20 is connected to the positive electrode of the lamp LED3, and the negative electrode of the lamp LED3 is grounded; the negative electrode of the diode D3 is connected to the emitter of the transistor Q1, and the positive electrode of the diode D3 is grounded; 1 end of the relay RELAY1 is connected to the emitter of the transistor Q1, 4 end of the relay RELAY1 is grounded, and 5 end of the relay RELAY1 is connected to the cable interface RF6.

[0028] The cable length measurement circuit includes: one end of a capacitor C1 is connected to a cable interface RF1, the other end of the capacitor C1 is connected to one end of a resistor R1, the other end of the resistor R1 is connected to one end of a resistor R2, and the other end of the resistor R2 is grounded; the other end of the resistor R1 is connected to the 1 end of the controller U1; one end of the capacitor C2 is connected to the relay switch on-off circuit, the other end of the capacitor C2 is connected to one end of a resistor R3, the other end of the resistor R3 is connected to one end of a resistor R4 and connected to the 3rd end of the controller U1, and the other end of the resistor R4 is grounded; the 8th end of the controller U1 is connected to the +2.5V voltage end and to one end of the capacitor C3, and the other end of the capacitor C3 is grounded; the 8th end of the controller U1 is connected to one end of the capacitor C4, and the other end of the capacitor C4 is grounded; one end of the resistor R5 is connected to the 7th end of the controller U1, and the other end of the resistor R5 is connected to the relay switch on-off circuit; one end of the resistor R6 is connected to the 6th end of the controller U1, and the other end of the resistor R6 is connected to the cable interface RF4.

[0029] The time domain reflectometry (TDR) method involved in the cable length measurement circuit can be realized by shape reflection. The time detection of the rising edge of two pulses is detected, so the reflection time can be calculated, and the length can be calculated according to the calculation equation of the coaxial cable. Establish SPI communication between STM32 and FPGA, collect the return signal frequency and the square wave return time at both ends of the coaxial cable, calculate the pulse width time and duty cycle, so as to calculate the signal reflection time, and thus calculate the length of the coaxial cable.

[0030] The resistance measurement circuit includes: one end of the resistor R8 is connected to the +2.5V voltage terminal and to the interface J1, and the other end of the resistor R8 is connected to the relay switch on-off circuit and to the interface J2.

[0031] The resistance measurement circuit uses the resistance voltage divider method to add a standard resistor to the front end of the cable and measure the voltage across the standard resistor. Through Ohm's law, the current of the serial circuit can be calculated, and therefore the resistance of the cable can be calculated.

[0032] The capacitance measurement circuit includes: one end of capacitor C10 is connected to terminal 1 of controller U2, and the other end of capacitor C10 is connected to terminal 5 of controller U2; one end of resistor R18 is connected to terminal 4 of controller U2, and the other end of resistor R18 is connected to terminal 7 of controller U2; one end of resistor R17 is connected to terminal 7 of controller U2, and the other end of resistor R17 is connected to terminals 2 and 6 of controller U2; terminal 2 of controller U2 is connected to the relay switch on-off circuit, and terminals 4 and 8 of controller U2 are connected to the +5V voltage terminal.

[0033] The capacitance measurement circuit uses the microcontroller to collect the period of the square wave at the OUT end. According to T=ln2(R22+2*R23)*C, the sum of the cable and load capacitance can be obtained. Through measurement, it is found that the capacitance value of the cable is much larger than the required capacitance value (about 10 times), and this part of the capacitance is the integrated capacitance generated by the cable core conductor and the ground wire, which cannot be eliminated. It is found that this part of the capacitance and the load capacitance are in parallel, and the capacitance value of the parallel capacitance is added. Therefore, the total capacitance of the cable and the load can be measured, and then the capacitance of the unloaded cable can be detected at the beginning of the length detection. The final result is the capacitance value we require. After actual measurement, the capacitance value obtained is within the required error, realizing the capacitance measurement function.

[0034] The main function of a power supply circuit is to convert the input voltage or current into a stable voltage or current suitable for electronic equipment and ensure its quality. Rectification and filtering: If the input is an AC power supply, the power supply circuit first needs to convert the AC voltage into a DC voltage. In order to reduce the ripple in the output, a filter capacitor needs to be added to smooth the output voltage. A stable voltage or current is very important. A voltage regulator is a commonly used component in a power supply circuit, which ensures that the output voltage or current remains stable when the load changes or the input fluctuates.

[0035] The above embodiments are only used to explain the technical solution of the utility model rather than to limit it. Those skilled in the art should understand that any modification and equivalent substitution that does not deviate from the spirit and scope of the utility model should fall within the scope of protection of the claims of the utility model.

Claims

1. A circuit of a cable fault detector, characterized in that: include: Relay switches on and off the circuit; A cable length measurement circuit, the cable length measurement circuit is connected to the relay switch on-off circuit, and the cable length measurement circuit is used to calculate the length of the coaxial cable; A resistance measuring circuit, the resistance measuring circuit is connected to the relay switch on-off circuit, and the resistance measuring circuit is used to calculate the resistance of the cable; A capacitance measuring circuit, the capacitance measuring circuit is connected to the relay switch on-off circuit, and the capacitance measuring circuit is used to measure the capacitance value of the cable; A DC bias circuit, the DC bias circuit being connected to the cable length measurement circuit; The power supply circuit, the relay switch on-off circuit, the cable length measurement circuit, the resistance measurement circuit, the capacitance measurement circuit, and the DC bias circuit are all connected to the power supply circuit, and the power supply circuit is used to supply power to each circuit.

2. The circuit of a cable fault detector according to claim 1, characterized in that: The relay switch on-off circuit comprises: Terminals 1 and 4 of the microcontroller U6 are both connected to the +5V voltage terminal, terminal 2 of the microcontroller U6 is connected to one end of a resistor R21, the other end of the resistor R21 is connected to one end of a plug J4, terminal 3 of the microcontroller U6 is connected to one end of a resistor R19, the other end of the resistor R19 is connected to one end of a resistor R15, and the other end of the resistor R15 is grounded; and the other end of the resistor R19 is connected to the base of the transistor Q2, the collector of the transistor Q2 is connected to the +5V voltage terminal, the emitter of the transistor Q2 is connected to one end of the resistor R11, the other end of the resistor R11 is connected to the positive electrode of the lamp LED2, and the negative electrode of the lamp LED2 is grounded; the negative electrode of the diode D1 is connected to the emitter of the transistor Q2, and the positive electrode of the diode D1 is grounded; Terminal 1 of relay RELAY2 is connected to the emitter of transistor Q2, terminal 4 of relay RELAY2 is grounded, and terminal 5 of relay RELAY2 is connected to terminal 2 of relay RELAY1; The 1st and 4th terminals of the microcontroller U4 are both connected to the +5V voltage terminal, the 2nd terminal of the microcontroller U4 is connected to one end of the resistor R10, the other end of the resistor R10 is connected to the other end of the plug J4, the 3rd terminal of the microcontroller U4 is connected to one end of the resistor R12, the other end of the resistor R12 is connected to one end of the resistor R16, and the other end of the resistor R16 is grounded; and the other end of the resistor R12 is connected to the base of the transistor Q1, the collector of the transistor Q1 is connected to the +5V voltage terminal, the emitter of the transistor Q1 is connected to one end of the resistor R20, the other end of the resistor R20 is connected to the positive electrode of the lamp LED3, and the negative electrode of the lamp LED3 is grounded; the negative electrode of the diode D3 is connected to the emitter of the transistor Q1, and the positive electrode of the diode D3 is grounded; Terminal 1 of the relay RELAY1 is connected to the emitter of the transistor Q1 , terminal 4 of the relay RELAY1 is grounded, and terminal 5 of the relay RELAY1 is connected to the cable interface RF6 .

3. The circuit of a cable fault detector according to claim 1, characterized in that: The cable length measurement circuit comprises: One end of the capacitor C1 is connected to the cable interface RF1, the other end of the capacitor C1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to one end of the resistor R2, the other end of the resistor R2 is grounded; the other end of the resistor R1 is connected to the 1 end of the controller U1; One end of the capacitor C2 is connected to the relay switch on-off circuit, the other end of the capacitor C2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to one end of the resistor R4 and connected to the third end of the controller U1, and the other end of the resistor R4 is grounded; The 8th terminal of the controller U1 is connected to the +2.5V voltage terminal and to one end of the capacitor C3, and the other end of the capacitor C3 is grounded; the 8th terminal of the controller U1 is connected to one end of the capacitor C4, and the other end of the capacitor C4 is grounded; One end of the resistor R5 is connected to the 7th terminal of the controller U1, and the other end of the resistor R5 is connected to the relay switch on-off circuit; One end of the resistor R6 is connected to the sixth terminal of the controller U1 , and the other end of the resistor R6 is connected to the cable interface RF4 .

4. The circuit of a cable fault detector according to claim 1, characterized in that: The resistance measurement circuit comprises: One end of the resistor R8 is connected to the +2.5V voltage terminal and to the interface J1 , and the other end of the resistor R8 is connected to the relay switch on / off circuit and to the interface J2 .

5. The circuit of a cable fault detector according to claim 1, characterized in that: The capacitance measurement circuit comprises: One end of the capacitor C10 is connected to terminal 1 of the controller U2, and the other end of the capacitor C10 is connected to terminal 5 of the controller U2; One end of the resistor R18 is connected to terminal 4 of the controller U2, and the other end of the resistor R18 is connected to terminal 7 of the controller U2; One end of the resistor R17 is connected to the terminal 7 of the controller U2, and the other end of the resistor R17 is connected to the terminals 2 and 6 of the controller U2; Terminal 2 of the controller U2 is connected to the relay switch on-off circuit, and terminals 4 and 8 of the controller U2 are connected to the +5V voltage terminal.

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