CN203149060U

CN203149060U - Time-domain reflection cable tester

Info

Publication number: CN203149060U
Application number: CN 201320022620
Authority: CN
Inventors: 林烨
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-01-16
Filing date: 2013-01-16
Publication date: 2013-08-21
Anticipated expiration: 2023-01-16

Abstract

The utility model discloses a time-domain reflection cable tester which comprises a central processing circuit, a gating circuit, a wiring terminal and an operational amplifier circuit. The central processing circuit is connected with the gating circuit and is used for sending a probe pulse; the gating circuit is connected with the wiring terminal and is used for sending the probe pulse to a tested cable and receiving a reflected pulse returned by the tested cable through the wiring terminal; and the operational amplifier circuit is connected with the central processing circuit and the gating circuit and is used for offsetting the probe pulse of the central processing circuit, carrying out operational amplification on the reflected pulse transmitted by the gating circuit to form an amplified pulse and sending the amplified pulse to the central processing circuit. Compared with the prior art, with the time-domain reflection cable tester adopted, the probe pulse is offset, the reflected pulse is amplified, a device can capture a reflected signal more conveniently, the measurement range is expanded, and the measurement precision is improved.

Description

The Time Domain Reflectometry cable tester

Technical field

The utility model relates to length of cable and trouble spot field tests, relates more specifically to a kind of Time Domain Reflectometry cable tester.

Background technology

Time-domain reflectomer is a kind of instrument that utilizes the work of echo-bearing principle, and main application is to search and determine broken string in one section electric wire or the cable and the position of short circuit trouble point.During work, instrument initiatively to circuit emission electromagnetic signal, can propagate along circuit by electromagnetic signal.If not broken string or short trouble in the circuit, signal can be propagated along circuit always, if similar fault is arranged in the circuit, electromagnetic signal propagation will produce reflected signal during to this point, and reflected signal can back be propagated along circuit, and is received by instrument.Electromagnetic wave has definite velocity of propagation in the line, electromagnetic wave from emitted by instrument run into the trouble spot again time of being experienced of reflected back instrument can be got off by instrument record, instrument is according to the distance that just can calculate the trouble spot during this period of time with electromagnetic wave velocity of propagation in the line.

Yet electromagnetic wave has attenuation characteristic when propagating in the line, just when electromagnetic wave is propagated to larger distance, electromagnetic signal intensity can decay thereupon, when the long and trouble spot of circuit distance is distant, the reflected signal that obtains through transmission attenuation is crossed and lowly may be caused and can not be received by instrument, thereby cause the test of long distance line is restricted, measurement range is less.

Therefore, thus being badly in need of a kind of can the amplification reflected signal is conducive to the cable tester that equipment catches reflected signal and enlarge measurement range and overcomes above-mentioned defective.

The utility model content

Thereby the purpose of this utility model provides a kind of Time Domain Reflectometry cable tester to be conducive to equipment seizure reflected signal and to enlarge measurement range so that reflected signal is amplified, and improves measuring accuracy.

For achieving the above object, the utility model provides a kind of Time Domain Reflectometry cable tester, comprise central processing circuit, gating circuit, connection terminal and discharge circuit, described central processing circuit is connected with described gating circuit and sends direct impulse, described gating circuit is connected with described connection terminal, described direct impulse is sent to tested cable and receives the reflected impulse that described tested cable returns by described connection terminal, described discharge circuit is connected with described gating circuit with described central processing circuit, the direct impulse of described central processing circuit offset and the reflected impulse that described gating circuit transmits is carried out computing amplify to form and amplify pulse, and described amplification pulse is sent to described central processing circuit.

Compared with prior art, Time Domain Reflectometry cable tester of the present utility model, send a direct impulse to an input end of tested cable and discharge circuit by central processing circuit, direct impulse can form a pulse in the same way when transmitting in tested cable, direct impulse is simultaneously transmitted in tested cable and is produced a reflected impulse when running into barrier point, with another input end of pulse and the equal input operational amplifier of reflected impulse in the same way, discharge circuit is with direct impulse and pulse in the same way cancel out each other (namely offsetting direct impulse), amplify reflected impulse simultaneously obtaining amplifying pulse, last central processing circuit calculates direct impulse and the mistiming of amplifying pulse and obtains cable fault point distance according to the described mistiming; Namely this cable tester has amplified reflected impulse, is conducive to equipment more and catches reflected signal, has enlarged measurement range and has improved measuring accuracy.

Preferably, described discharge circuit is the voltage comparison amplifier.

Particularly, described gating circuit comprises interconnective two groups of electronic switches (SW1, SW2), and the interconnective end of two groups of electronic switches (SW1, SW2) is connected with described connection terminal, the other end of electronic switch (SW1) is connected with the positive input of described central processing circuit and described voltage comparison amplifier, and the other end of electronic switch (SW2) is connected with the reverse input end of described voltage comparison amplifier.

By following description also by reference to the accompanying drawings, it is more clear that the utility model will become, and these accompanying drawings are used for explaining embodiment of the present utility model.

Description of drawings

Fig. 1 is the structured flowchart of the utility model Time Domain Reflectometry cable tester one embodiment.

Fig. 2 is the circuit theory diagrams of Fig. 1.

Embodiment

With reference now to accompanying drawing, describe embodiment of the present utility model, the similar elements label represents similar elements in the accompanying drawing.

Please refer to Fig. 1, described the structured flowchart of the utility model Time Domain Reflectometry cable tester 100 1 embodiment.As shown in Figure 1, described Time Domain Reflectometry cable tester 100 comprises central processing circuit 10, discharge circuit 11, gating circuit 12 and connection terminal 13.Central processing circuit 10 is connected with gating circuit 12 and discharge circuit 11, central processing circuit 10 be used for sending direct impulse to discharge circuit 11 and gating circuit 12, receive discharge circuit 11 outputs the amplification pulse that is obtained through amplification by reflected impulse, calculate direct impulse and the mistiming of amplifying pulse and calculate length of cable or trouble spot distance according to the mistiming; Gating circuit 12 is connected with connection terminal 13, gating circuit 12 be used for the tested cable of gating inner core, by connection terminal 13 direct impulse is sent to tested cable and receives the reflected impulse that tested cable returns; Discharge circuit 11 is connected with gating circuit 12 with central processing circuit 10, is used for the direct impulse that central processing circuit 10 sends to be offset and the reflected impulse that gating circuit 12 transmits is carried out computing amplify formation amplification pulse and described amplification pulse is sent to central processing circuit 10.

Wherein, direct impulse transmission speed in cable is certain, and therefore the pulse width difference of fixing has the cable fault point distance of a correspondence; Tested cable is telephone wire, concentric cable or netting twine, and different tested cables is to there being different cable interfaces, if tested cable is netting twine, then connection terminal 13 is RJ45, and tested cable is netting twine in the present embodiment.

Please refer to Fig. 2, described the circuit theory diagrams of Fig. 1.As shown in Figure 2, it is a fpga chip that central authorities handle moding circuit 10, and discharge circuit 11 is the voltage comparison amplifier, and gating circuit 12 comprises interconnective two groups of electronic switches (SW1, SW2), and connection terminal 13 is RJ45.The input pin in the same way 3 of voltage comparison amplifier 11 is connected with 1,2,3,4,5,6,7,8 pin of the output pin IO1 of fpga chip 10 and electronic switch SW2, the reverse input pin 4 of voltage comparison amplifier 11 is connected with 1,2,3,4,5,6,7,8 pin of electronic switch SW1, and the output pin 1 of voltage comparison amplifier 11 is connected with the input pin IO2 of fpga chip 10; 16 pin of electronic switch SW1 and 16 pin of electronic switch SW2 interconnect the back and link to each other with 1 pin of RJ45 terminal, 15 pin of electronic switch SW1 and 15 pin of electronic switch SW2 interconnect the back and link to each other with 2 pin of RJ45 terminal, and in

like manner

14,13,12,11,10,9 pin of Dui Ying electronic switch SW1 and SW2 are connected with

RJ45 terminal

3,4,5,6,7,8; The other end of RJ45 terminal connects tested netting twine.

The principle of work of the utility model Time Domain Reflectometry cable tester is as follows:

Two inner cores of FPGA control electronic switch SW2 and the tested netting twine of electronic switch SW1 gating, as: gating inner core 1 and inner core 2, send direct impulse v1 by the IO1 pin to inner core 1 wherein, in inner core 2, can produce an in the same way pulse v2 identical with direct impulse simultaneously, direct impulse v1 transmits in inner core 1, when running into barrier point such as short dot or open circuit point, can reflect, produce a reflected impulse v3, reflected impulse v3 inputs to the input pin in the same way 3 of voltage comparator through electronic switch SW2, pulse v2 inputs to the reverse input pin 4 of voltage comparison amplifier in the same way, because the IO1 pin of FPGA is imported direct impulse v1 to the input pin in the same way 3 of voltage comparison amplifier 11 simultaneously, therefore the processing procedure of voltage comparison amplifier 11 is: direct impulse v1 and pulse v2 in the same way cancel out each other (namely offsetting direct impulse v1), reflected impulse v3 amplified obtain the IO2 pin that amplifies pulse v4 and export FPGA to, FPGA calculates direct impulse v1 and amplifies the mistiming of pulse v4 and calculate the trouble spot distance of inner core 1 relative inner core 2 according to the mistiming; In like manner, gating inner core 1 and inner core 3, inner core 1 and inner core 4 ... inner core 1 and inner core 8 will draw the trouble spot distance of inner core 1 relative inner core 3 to 8 according to said method, more above-mentioned trouble spot distance value are averaged, and finally obtain the trouble spot distance of inner core 1.Repeat above-mentioned steps, just can record the trouble spot distance of all the other 7 inner cores.

As can be seen from the above description, can offset direct impulse and reflected impulse is amplified by tester of the present utility model, make FPGA can be easy to capture reflected impulse and then calculate cable fault point distance when long or trouble spot distance is far away at tested cable, enlarged measurement range and improved measuring accuracy.

It should be noted that, when testing, inner core that can gating have 1-2,1-3,1-4 ... 7-8 combination in totally 56, wherein gating 1-2,1-3,1-4,1-5,1-6,1-7,1-8 and in inner core 1, send direct impulse successively, the value that at every turn records the average average length that is inner core 1 or the mean value of trouble spot distance, data are more accurate; In like manner the rest may be inferred during other inner core of survey line cable.In addition, if the IO2 pin of FPGA can not receive the amplification pulse always, then strengthen the cycle of direct impulse till can receiving the amplification pulse of returning; If the cycle of direct impulse still fails to measure the amplification pulse of returning when being enlarged to upper limit 200ns, then stop test, give tacit consent to tested cable not in the range ability of the utility model cable tester.

Abovely in conjunction with most preferred embodiment the utility model is described, but the utility model is not limited to the embodiment of above announcement, and should contains various modification, equivalent combinations of carrying out according to essence of the present utility model.

Claims

1. Time Domain Reflectometry cable tester, comprise central processing circuit, gating circuit and connection terminal, described central processing circuit is connected with described gating circuit and sends direct impulse, described gating circuit is connected with described connection terminal, by described connection terminal described direct impulse is sent to tested cable and receives the reflected impulse that described tested cable returns, it is characterized in that: also comprise discharge circuit, described discharge circuit is connected with described gating circuit with described central processing circuit, the direct impulse of described central processing circuit offset and the reflected impulse that described gating circuit transmits is carried out computing amplify to form and amplify pulse, and described amplification pulse is sent to described central processing circuit.

2. Time Domain Reflectometry cable tester as claimed in claim 1, it is characterized in that: described discharge circuit is the voltage comparison amplifier.

3. Time Domain Reflectometry cable tester as claimed in claim 2, it is characterized in that: described gating circuit comprises interconnective two groups of electronic switches (SW1, SW2), and the interconnective end of two groups of electronic switches (SW1, SW2) is connected with described connection terminal, the other end of electronic switch (SW1) is connected with the positive input of described central processing circuit and described voltage comparison amplifier, and the other end of electronic switch (SW2) is connected with the reverse input end of described voltage comparison amplifier.