弱電流ケーブルの品質を特定する

1、外観の識別：

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.シールド層ネットを確認します。編組数が銅ネットに十分かどうかを確認し、はんだ付け性を確認し、錫メッキされた銅線をこすって銅線であるかどうかを確認します。アルミニウムマグネシウム合金線の硬度は、銅線よりも大幅に高くなっています。銅線; 疎なネットワーク、不均一な分布、および絶縁層による緩い巻き付けは、不十分なケーブルです。

3.コアワイヤを確認します。SYVケーブルの場合は直径- 0。78-0。8mm、SYWVケーブルの場合は1。0 mm。 最近、syv75-5コア径1.0mmのケーブルが登場しました。 このケーブルの特性インピーダンスは確かに75オームではなく、75オームの伝送システムには適用されません。

4.芯線と絶縁層の接着力を確認します。絶縁層を斜めに切断し、剥離方向に応じて芯線を引っ張り、芯線と絶縁層がプロセス材料で接着されているかどうかを確認します。 良いケーブルは接着力が大きいですが、悪いケーブルは接着しません。

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、火災試験

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.

一般的な疑似銅線：銅被覆アルミニウム、銅被覆アルミニウムマグネシウム合金、銅被覆鋼、銅被覆鉄

高模倣偽銅線：銅被覆アルミニウムマグネシウム合金は、マルチストランド銅線に一定の割合で追加されます。 その他の材料は、銅を電気めっきすることによって処理されます。 一般的に、価格は前のものよりはるかに高価です。 結局のところ、その中に本物の銅があります。

標準以下の銅線：材料が無酸素銅製の銅線を引き抜いていない、伝送性能が悪い、またはコアの数が不足している

購入時にこれら3種類の偽銅線の分類を忘れた場合は、次の方法を試すこともできます。

ことわざにあるように、本物の金は火を恐れていません。 真と偽のSYV、RVV、およびその他の銅線も、火災によって区別できます。 まず、ワイヤーのセクションを開いて銅線のセクションを露出させ、それらをもう少しまばらに分割します（これにより効果が向上します）。 一般的に、防風ライターで燃やすと表示されます。 本物の銅線は高温に対して非常に耐性があります。 1分以上は全く問題ありません。 せいぜい、色は少し変わります。 銅-クラッドアルミニウムと銅-クラッドアルミニウムマグネシウム合金の場合、すぐに曲がります。 銅-クラッド鋼または銅-クラッド鉄の場合、燃焼後にナイフでこすったときに表示されます。

3、伝送性能テスト：

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.上記の方法では、ビデオ伝送システムおよび機器のパフォーマンスも検出できます。たとえば、プロジェクト内の各同軸ビデオケーブルの伝送特性、光トランシーバーの伝送特性（良し悪しを測定できるかどうか）を実行します。あまり理想的ではないと思います）、RF伝送とマイクロ波伝送特性、ツイストペア伝送特性、ビデオディストリビュータの分配特性、マトリックスホストのスイッチング特性、複数の出力が同時に同じ入力信号を切り替える場合は特に注意が必要です。 。 スイッチングチャネルの数が多いほど減衰が大きくなることがわかった場合、それは誤りであり、変更しないでおく必要があります。 テスト後、多くの認定されていない製品を習得します。

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.