Video line, radio frequency line, shielded and unshielded, signal line, control line, etc., various models, newcomers are often confused. The following are the differences between several commonly used models: RVV and KVVRVVP and KVVP.
The line used in RVV and RVVP is a flexible line composed of multiple strands of thin copper wire, that is, RV wire. The line used in KVV and KVVP is a hard line composed of a single thick copper wire, that is, BV wire. The difference between AVVR and RVVP: things are the same, except that the name of the internal section less than 0.75 mm² is AVVR, and the name of the section greater than or equal to 0.75 mm² is RVVP.
Identification of Monitoring Cables in Monitoring Projects
The identification of the quality of the cable, the real detection is the need for special equipment and instruments. These equipment and instruments are not available in design and engineering units.
In engineering practice, how should we identify good and bad:
1. PVC sheath: the surface can see the regular "unevenness" of the braided net inside the compact, indicating that the processing technology is good, no relative sliding occurs, and it is a good cable. The appearance is smooth, and the "unevenness" of the compacted braid cannot be seen. The sheath is loosened by hand, which is a poor cable;
2. Check the braiding of the shielding layer: is the braiding number enough? Braiding of copper material, check the solderability, scratch the tin-plated copper computer wire to see if it is copper wire, and the hardness of the aluminum-magnesium alloy wire is obviously greater than that of the copper wire; the braiding is sparse, the distribution is uneven, and the insulation layer is not tightly wrapped, etc. The cable is poor;
3. Check core wire: diameter -- SYV cable is 0.78-0.8mm,SYWV cable is 1.0mm; Recently, a cable with a SYV75-5 core diameter of 1.0mm has appeared. The characteristic impedance of this cable is definitely not 75 ohms and should not be used in 75 ohms transmission system;
4. Check the adhesion force between the core wire and the insulating layer: cut the insulating layer obliquely, pull the core wire apart according to the peeling direction, and see if the core wire and the insulating layer have any bonding process materials; Good cables have greater adhesion force, while poor cables have no adhesion;
5. Longitudinal tensile test: Take one meter of cable, strip the core wire, insulation layer, shielding layer and outer cover in layers, leaving 10cm long each. The method is: two hands respectively hold the adjacent two layers of the cable and pull it in the opposite direction; Good cables cannot be pulled by general strength, while poor cables can be easily pulled out without great effort.
