July 17, 2023
With exception of some network cameras, cables are an integral part of surveillance system. The cost of cables is a big cost in entire monitoring system. According to national standards, cost of ordinary cables should reach about 2.25 RMB/m. Poor quality cables bring higher profits. So how do you tell a good cable from a bad one?
How to tell a good cable from a bad one
1. Check weave of shielding layer: is there enough weave:
Copper braided mesh, check solderability, scratch tinned copper computer wire to see if there is copper wire inside, hardness of aluminum-magnesium alloy wire is clearly higher than that of copper wire; woven mesh is sparse, unevenly distributed and not wrapped with an insulating layer. If it is copper-clad aluminum, it is easy to see that inner color is different from outer copper; remove outer sheath and look at braid angle of shielding layer, if it is mostly standing, then you can basically see that braid angle is relatively large, which is result of cutting corners;
2. PVC sheath:
On surface, we see a regular "bump" of braided mesh inside compression, which indicates that processing technology is good and there will be no relative slip, so this is a good cable. The appearance is smooth, and "jumps" of compressed braided net are not visible, and sheath feels loose when pinched by hand, which is a bad cable;
3. Check adhesive strength between core and insulation layer:
Cut insulating layer obliquely, pull strand according to peeling direction, and see if strand and insulating layer are bonded to material to be processed; good cables have a lot of grip, bad cables don't connect ;
4. Check main wire:
The diameter is SYV cable is 0.78-0.8mm, and SYWV cable is 1.0mm, a cable with SYV75-5 core diameter of 1.0mm has recently appeared, characteristic impedance of this cable is definitely not 75 ohm, does not apply to 75 transmission system Ohm; use a caliper to check diameter of inner core of cable;
5. Longitudinal tensile test:
Take a one meter long security cable, strip core, insulation layer, shield layer and outer sheath layer by layer, leaving 10 cm in length each. The method is as follows: hold two adjacent layers of cable with both hands and pull them in opposite directions; good cables cannot be pulled with total force, while bad cables can be easily pulled out without much effort.
What to do if you bought a low-quality cable
Once we know how to distinguish between cables, we will keep a close eye on future purchases, but what do we do if we have already purchased low quality cables?
1. If transmission distance is more than 800 meters, please use SYV-75-5 cable, and find that there is no picture or picture jumps, you can use anti-interference video signal amplification. device using video segmentation method can amplify video signal by 10 times, so that transmission distance can be effectively extended (can not use a simple amplifier, otherwise signal loss will be large);
2. If multiple cables interfere with each other, multi-signal multiplexing equipment can be used to simultaneously transmit 8 channels of video and control signals over one video cable;
3. If you have trouble welding cable, it is recommended to buy pure tin solder and use a powerful soldering iron to quickly solder, and you should not tin slowly;
4. Finally, if you're unsure about video cables, you can also use RF cables to carry multiple video signals. One RF cable can transmit 20 channels of image and control signals. in same time. The transmission distance can reach 3 kilometers, so cost will be more cost-effective.
Generally speaking, cable counterfeiting is also caused by lower margins for engineering companies, and everyone is looking to buy lower products to make more profit. On one hand, engineering companies must pay close attention to advantages and disadvantages of cables, on other hand, they can also introduce new technologies to reduce costs. Only in this way can enterprises benefit from current harsh environment. competition of sharply rising prices for raw materials and labor.