Identifikujte kvalitu slaboprúdových káblov

1, Identifikácia vizuálneho vzhľadu:

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. Skontrolujte sieťovinu tieniacej vrstvy: skontrolujte, či je číslo opletenia dostatočné pre medenú sieť, skontrolujte spájkovateľnosť, oškrabte pocínovaný medený drôt, aby ste zistili, či ide o medený drôt a či je tvrdosť drôtu zo zliatiny hliníka a horčíka výrazne vyššia ako tvrdosť drôtu medený drôt; Riedka sieť, nerovnomerné rozmiestnenie a voľné omotanie izolačnou vrstvou sú zlé káble;

3. Skontrolujte žilový vodič: priemer - 0.78-0.8mm pre kábel SYV a 1.0mm pre kábel SYWV; Nedávno sa objavil kábel s priemerom jadra syv75-5 1,0 mm. Charakteristická impedancia tohto kábla určite nie je 75 ohmov a nie je aplikovaná na 75 ohmový prenosový systém;

4. Skontrolujte adhéznu silu medzi jadrovým drôtom a izolačnou vrstvou: šikmo odrežte izolačnú vrstvu, potiahnite jadrový drôt podľa smeru odizolovania a skontrolujte, či sú jadrový drôt a izolačná vrstva spojené procesnými materiálmi; Dobrý kábel má veľkú priľnavosť, ale zlý kábel nepriľne;

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, Skúška ohňom

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.

Všeobecný pseudomedený drôt: hliník potiahnutý meďou, zliatina horčíka potiahnutá meďou, oceľ potiahnutá meďou, železo potiahnuté meďou

Vysoká imitácia falošného medeného drôtu: do viacvláknového medeného drôtu sa v určitom pomere pridáva zliatina hliníka a horčíka pokrytá meďou. Ostatné materiály sa spracovávajú galvanickým pokovovaním medi. Vo všeobecnosti je cena oveľa drahšia ako predchádzajúca. Koniec koncov, je v ňom skutočná meď.

Neštandardný medený drôt: materiál nie je ťahaný medený drôt vyrobený z bezkyslíkatej medi, prenosový výkon je slabý alebo počet jadier nie je dostatočný

Ak pri nákupe zabudnete na klasifikáciu týchto troch druhov falošných medených drôtov, môžete tiež vyskúšať nasledujúcu metódu:

Ako sa hovorí, skutočné zlato sa nebojí ohňa. Pravé a falošné SYV, RVV a iné medené drôty možno rozlíšiť aj ohňom. Najprv otvorte časť drôtu, aby ste odkryli časť medeného drôtu, a rozdeľte ich trochu riedšie (to bude mať lepší efekt). Všeobecne platí, že po spálení vetruodolným zapaľovačom sa objaví. Skutočný medený drôt je veľmi odolný voči vysokej teplote. Neexistuje absolútne žiadny problém dlhšie ako jednu minútu. Maximálne sa farba trochu zmení; Ak ide o hliník potiahnutý meďou- a zliatinu hliníka a horčíka s povlakom medi-, rýchlo sa ohne; Ak ide o medenú-oceľ alebo pomedené-železo, objaví sa, keď sa po spálení oškrabe nožom.

3, Test výkonu prevodovky:

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. Vyššie uvedená metóda môže tiež zistiť výkon video prenosového systému a zariadenia: napríklad prenosové charakteristiky každého koaxiálneho video kábla v projekte, prenosové charakteristiky optického transceivera (je možné zmerať, či je dobrý alebo zlý, nepovažujem to za také ideálne), charakteristiky RF prenosu a mikrovlnného prenosu, prenosové charakteristiky krútenej dvojlinky, distribučné charakteristiky video distribútora, spínacie charakteristiky maticového hostiteľa, Osobitná pozornosť by sa mala venovať tomu, keď viaceré výstupy prepínajú rovnaký vstupný signál v rovnakom čase . Ak sa zistí, že čím väčší je počet spínacích kanálov, tým väčší je útlm, je to nesprávne a malo by zostať nezmenené. Po testovaní zvládnete veľa nekvalifikovaných produktov;

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.