Txheeb xyuas Qhov Zoo Ntawm Cov Hluav Taws Xob Hluav Taws Xob Hluav Taws Xob

1, Visual tsos qhia:

1. PVC sheath: regular "unevenness" can be seen on the surface of the compressed inner mesh, indicating that the processing technology is good and will not produce relative sliding. It is a good cable. The appearance is smooth, and the "unevenness" of the compressed braided mesh can not be seen. There is looseness when the sheath is pinched by hand, which is a poor cable;

2. Txheeb xyuas cov txheej thaiv thaiv phab ntsa: xyuas seb tus naj npawb braiding puas txaus rau tooj liab netting, xyuas cov khoom siv, khawb cov tinned tooj liab hlau kom pom tias nws yog tooj liab hlau, thiab qhov hardness ntawm aluminium magnesium alloy hlau yog siab dua li ntawm. tooj liab; Sparse network, tsis sib xws thiab xoob qhwv nrog insulating txheej yog cov kab tsis zoo;

3. Kos cov tub ntxhais hlau: txoj kab uas hla - 0.78-0.8mm rau SYV cable thiab 1.0mm rau SYWV cable; Tsis ntev los no, ib lub cable nrog syv75-5 core txoj kab uas hla ntawm 1.0mm tau tshwm sim. Cov yam ntxwv impedance ntawm cov cable no yeej tsis yog 75 ohm thiab tsis siv rau 75 ohm kis tau tus mob;

4. Tshawb xyuas lub zog adhesion ntawm cov tub ntxhais hlau thiab cov txheej insulating: txiav cov txheej insulating obliquely, rub cov tub ntxhais hlau raws li cov kev taw qhia stripping, thiab saib seb cov tub ntxhais hlau thiab cov txheej txheem insulating yog sib koom nrog cov txheej txheem cov ntaub ntawv; Zoo cable muaj zog adhesion loj, tab sis tsis zoo cable tsis adhere;

5. Longitudinal tensile test: take one meter of cable, peel off the core wire, insulation layer, shielding layer and outer sleeve in layers, and leave 10 cm long for each. The method is as follows: two hands hold the adjacent two layers of the cable respectively and pull it in the opposite direction; A good cable can't be pulled by ordinary force, but a poor cable can be easily pulled out without great effort - elevator cable is very important, and many so-called "elevator special cables" have this problem.

2, Kev ntsuas hluav taws

It is difficult for consumers to distinguish whether cable products are added with fake copper wires. Now there are many kinds of fake copper wires on the market, and the simulation degree is high. Ordinary consumers can't distinguish good from bad at all. Next, three types of fake copper wires are collected and sorted out, so that consumers can avoid these three types of cable products when buying.

General pseudocopper hlau: tooj liab clad txhuas, tooj liab clad aluminium magnesium alloy, tooj liab clad hlau, tooj liab clad hlau

High imitation fake tooj liab hlau: tooj liab clad aluminium magnesium alloy yog ntxiv nyob rau hauv ib qho kev faib ua feem nyob rau hauv ntau strand tooj liab hlau. Lwm cov ntaub ntawv yog ua los ntawm electroplating tooj liab. Feem ntau, tus nqi yog kim dua li yav dhau los. Tom qab tag nrho, muaj tiag tooj liab nyob rau hauv nws.

Cov khoom siv tooj liab tsis zoo: cov khoom siv tsis tau kos tooj liab ua los ntawm cov pa oxygen dawb tooj liab, qhov kev sib kis tsis zoo, lossis cov cores tsis txaus

Yog tias koj tsis nco qab qhov kev faib tawm ntawm peb hom ntawm cov tooj liab cuav thaum yuav, koj tuaj yeem sim ua cov hauv qab no:

Raws li cov lus hais mus, kub tiag tiag tsis ntshai hluav taws. Qhov tseeb thiab tsis tseeb SYV, RVV thiab lwm cov xov tooj tooj liab kuj tuaj yeem ua qhov txawv ntawm qhov hluav taws kub. Ua ntej, qhib ib ntu ntawm cov hlau kom nthuav tawm ib ntu ntawm cov hlau tooj liab, thiab faib lawv me ntsis ntxiv (uas yuav muaj txiaj ntsig zoo dua). Feem ntau, ib zaug kub hnyiab nrog lub tshuab cua tsis zoo, nws yuav tshwm sim. Qhov tiag tooj liab hlau yog heev resistant rau kub. Tsis muaj teeb meem kiag li rau ntau tshaj ib feeb. Feem ntau, cov xim yuav hloov me ntsis; Yog tias nws yog tooj liab-clad aluminium thiab tooj liab-clad aluminium magnesium alloy, nws yuav khoov sai sai; Yog tias nws yog tooj liab-clad steel lossis tooj liab-clad hlau, nws yuav tshwm sim thaum nws raug khawb nrog rab riam tom qab hlawv.

3, Kev ntsuas kev sib kis:

Video line, as the name suggests, is a transmission line used to transmit video signals. Since you are transmitting video signals, you should at least understand the transmission characteristics of the transmission line in the 0-6m frequency band, or transmission performance. Here we mainly talk about "oscilloscope measurement method" for reference. Because oscilloscope is a necessary "weapon" for engineers and one of the necessary inspection equipment for qualification examination, the following description is based on being able to skillfully use oscilloscope.

1. The video signal of color camera can be used as "standard video signal source": the amplitude of video output of camera for test project on 75 Ohm load shall be 1Vp-p, that is, from the bottom end of line synchronization head to the "peak peak" of the highest white level of video signal; Note that the amplitude of the line synchronization head is "- 0.3V", and the amplitude of the color synchronization head (4.43M sine wave pulse) is 0.3vp-p; Select the sensitivity of the oscilloscope and turn it to the amplitude calibration state. Select a camera with good indicators as the "video source";

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2. The test cable shall be as long as possible to reduce the measurement error. For example, for 1000 meters, the middle joint of the cable must use "f-joint" and coaxial double-pass (cable TV equipment). Do not use welding method, because the welding method destroys the coaxiality and continuity of characteristic impedance of the cable.

3. Measure the DC resistance data of the cable: for example, if syv75-5 cable is 1000m, the DC resistance core wire is 35-40 ohms, and the resistance of the outer shielding layer is 24-36 ohms when it is 1000m (the resistance varies greatly with the number of shielding layers); Sywv75-5 cable is 1000m, the DC resistance core wire is 18-22 ohms, and the external shielding layer resistance is 24-36 ohms for 1000m; It is very useful to accumulate data in this regard. It can not only judge the quality of cable materials, but also check the quality of engineering wiring and pipe threading. For example, when people wear pipes, the wire is pulled off, the resistance becomes larger, the video signal becomes weaker, and the interference that should not occur also occurs. The probability of this kind of "accident" is very high, but it is often ignored;

4. Measure the high and low frequency attenuation characteristics of cable: measure the amplitude of line head and color synchronization head at the end, and calculate the attenuation based on 0.3V as 0dB. The same line head represents low frequency attenuation, and the color synchronization head represents 4.43M high frequency attenuation. - for example, the measured 1000M line synchronization head is 0.15v, and the DB number of attenuation multiple calculated according to 20log is "- 6dB / 1000m", It is measured that the attenuation amplitude of 4.43M color synchronization head after 1000m is 30mV, i.e. 1 / 10 times, and the attenuation is - 20dB / 1000m; With this method, you can accurately grasp the transmission quality of different cables, and have an intuitive concept of "frequency distortion (attenuation difference between high and low frequencies)". You can accurately measure the difference and performance of SYV and SYWV cables of the same model and structure, and compare the difference and performance of products from different manufacturers, You can also compare the changes of different batches of products from the same manufacturer;

5. Cov txheej txheem saum toj no tseem tuaj yeem txheeb xyuas qhov kev ua tau zoo ntawm kev sib kis video thiab cov khoom siv: piv txwv li, cov yam ntxwv ntawm kev sib kis ntawm txhua coaxial video cable hauv qhov project, cov yam ntxwv ntawm kev sib kis ntawm optical transceiver (txawm nws yog qhov zoo lossis qhov tsis zoo tuaj yeem ntsuas tau, ua tsis xav tias nws zoo tagnrho), RF kis tau tus mob thiab microwave kis tus yam ntxwv, twisted khub kis tau tus mob yam ntxwv, tis yam ntxwv ntawm video distributor, hloov cov yam ntxwv ntawm matrix party, tshwj xeeb yuav tsum tau them rau thaum ntau yam outputs hloov lub input teeb liab tib lub sij hawm. . Yog tias nws pom tias ntau tus lej hloov pauv, qhov ntau dua qhov attenuation, nws tsis raug thiab yuav tsum nyob twj ywm tsis hloov. Tom qab kev sim, koj yuav paub ntau yam khoom tsis tsim nyog;

6. Observe the field signal to see whether the field synchronization position distortion is large (flat and uneven) - it should be flat; At the same time, you can also use an oscilloscope to observe the low-frequency interference: if the field signal fluctuates slowly, it is 50 / 100 cycle interference, there are many "thatch" jumps, mostly frequency conversion harmonic interference, disconnect the remote camera, short circuit the internal and external conductors at the far end of the cable, and directly observe the interference waveform and intensity at the end with a oscilloscope; This method can also check and test the real performance of anti-interference equipment.