Identifikasi Kualitas Kabel Arus Lemah

1, Identifikasi penampilan visual:

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. Periksa jaring lapisan pelindung: periksa apakah nomor jalinan cukup untuk jaring tembaga, periksa kemampuan solder, kikis kawat tembaga kaleng untuk melihat apakah itu kawat tembaga, dan kekerasan kawat paduan magnesium aluminium secara signifikan lebih tinggi daripada kawat tembaga; Jaringan yang jarang, distribusi yang tidak merata dan pembungkus yang longgar dengan lapisan isolasi adalah kabel yang buruk;

3. Periksa kabel inti: diameter - 0.78-0.8mm untuk kabel SYV dan 1.0mm untuk kabel SYWV; Baru-baru ini, sebuah kabel dengan diameter inti syv75-5 1,0mm telah muncul. Impedansi karakteristik kabel ini tentu tidak 75 ohm dan tidak diterapkan pada sistem transmisi 75 ohm;

4. Periksa kekuatan adhesi antara kawat inti dan lapisan isolasi: potong lapisan isolasi secara miring, tarik kawat inti sesuai dengan arah pengupasan, dan lihat apakah kawat inti dan lapisan isolasi terikat dengan bahan proses; Kabel yang baik memiliki daya rekat yang besar, tetapi kabel yang buruk tidak dapat menempel;

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, uji api

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.

Kawat pseudocopper umum: aluminium berlapis tembaga, paduan magnesium aluminium berlapis tembaga, baja berlapis tembaga, besi berlapis tembaga

Kawat tembaga palsu imitasi tinggi: paduan magnesium aluminium berlapis tembaga ditambahkan dalam proporsi tertentu dalam kawat tembaga multi-untai. Bahan lainnya diproses dengan elektroplating tembaga. Umumnya, harganya jauh lebih mahal dari yang sebelumnya. Lagi pula, ada tembaga asli di dalamnya.

Kawat tembaga di bawah standar: bahan tidak ditarik kawat tembaga terbuat dari tembaga bebas oksigen, kinerja transmisi buruk, atau jumlah inti tidak cukup

Jika Anda lupa klasifikasi ketiga jenis kabel tembaga palsu ini saat membeli, Anda juga bisa mencoba cara berikut ini:

Seperti kata pepatah, emas asli tidak takut api. SYV benar dan salah, RVV dan kabel tembaga lainnya juga dapat dibedakan dengan api. Pertama, buka bagian kawat untuk mengekspos bagian kawat tembaga, dan bagilah sedikit lebih jarang (itu akan memiliki efek yang lebih baik). Umumnya, setelah dibakar dengan korek api tahan angin, itu akan muncul. Kawat tembaga asli sangat tahan terhadap suhu tinggi. Sama sekali tidak ada masalah selama lebih dari satu menit. Paling-paling, warnanya akan sedikit berubah; Jika itu adalah tembaga-aluminium berpakaian dan tembaga-aluminium paduan magnesium, itu akan membungkuk dengan cepat; Jika itu tembaga-baja berlapis atau tembaga-berlapis tembaga, itu akan muncul ketika digores dengan pisau setelah dibakar.

3, Uji kinerja transmisi:

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. Metode di atas juga dapat mendeteksi kinerja sistem dan peralatan transmisi video: misalnya, karakteristik transmisi setiap kabel video koaksial dalam proyek, karakteristik transmisi transceiver optik (baik atau buruk dapat diukur, lakukan tidak berpikir itu sangat ideal), transmisi RF dan karakteristik transmisi gelombang mikro, karakteristik transmisi twisted pair, karakteristik distribusi distributor video, karakteristik switching host matriks, Perhatian khusus harus diberikan ketika beberapa output mengganti sinyal input yang sama pada saat yang sama . Jika ditemukan bahwa semakin banyak jumlah saluran switching, semakin besar redaman, itu salah dan harus tetap tidak berubah. Setelah pengujian, Anda akan menguasai banyak produk yang tidak memenuhi syarat;

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.