A cable selection, elevator monitoring
Monitoring applied in the elevator must consider the particularity of its movement up and down continuously, requirements on the wiring is different from the fixed point monitoring wear tube (tank), must use a high mechanical strength pull transmission cables, general engineering contractor in wiring attaches importance to the use of high strength of the cable link, the electrical characteristics of transmission cables did not cause enough attention, the elevator interference phenomenon is widespread.Due to the narrow space of the elevator is an almost closed, and elevator control, lighting, fan, etc. A lot of cable, so add difficulty to the video cable wiring, according to the practical analysis on the choice of cable in the elevator monitoring should follow the following principles.
1, meet the tensile strength: elevator half is used to extend cable, high-rise elevator up to more than 100 meters, one hundred meters of cable is nearly hundred kilograms of weight, so the cable must have enough tensile strength. Now in the market for messenger flat composite elevator monitoring special cable, the cable will be video coaxial cable, power cord, cable and steel strand composite together, make it a flat ribbon cable, so that the whole cable tension by the steel strand to inherit, the tensile strength is very good, not in the elevator running, because gravity pulled signal cable.
2, good electrical parameters: the cable as the elevator up and down movement of the process, there will be a middle segment by the gravity bending deformation, caused by the impedance of the cable and the distributed capacitance electric parameters, such as changing. When quality is bad of cable force deformation, parameter change is big, it will cause the impedance mismatch, the attenuation increases and generate video signal reflection, it is to cause a decline in video signal SNR, video interference, is to try to choose good shielding, wire diameter thick video cable, to prevent interference signal "invasion". Practice has proved that SYWV coaxial cable is better than that of SYV, multi-layer shielding is better than that of single layer shielding.
B The elevator monitoring wiring skills
Elevator control wiring, mostly with other cable strapping were used, but due to the ac signal of the other cable will leak out through transmission cables, video line instead of long distance parallel banding They are tantamount to a "antenna", such interference signal is coupled into the video signal, video interference phenomenon.So try to shorten the video cable and other cable in the wiring of the length of parallel banding, conditional word, can be in the video cable from the elevator shaft fixed intermediate point, from other channel (cable shaft) bring back to the master control room, so that you can avoid ac radiation coupling interference. Conditional engineering, the elevator can be used in the line of control and illumination cable The shielded wire, reduce external radiation, prevent video interference.
C The elevator monitoring frequency conversion governor interference
Now basically is to use ac variable frequency speed regulation technology in the elevator, and frequency conversion governor itself has a strong high frequency parasitic interference, according to the measured results, frequency conversion governor radiation bandwidth of 0 ~ 10
MHz, and the interference signal amplitude is very strong. 0 ~ 6
MHz video baseband signal just in this band, the jamming signal from the power cord and space in two ways to invade the video signal, image monitoring effect. This is the main cause of the elevator interference, which is the most bad solve the problem of interference.
D The power interference and other interference factors
In the elevator monitoring camera power supply best dc power supply, straight from the master control room can't direct power supply can choose from the elevator box lighting power electricity, but most is the elevator manufacturers of the elevator is fluorescent lamp illumination, this kind of lamps and lanterns and use electronic ballast, electronic ballast, also can produce strong ac output parasitic interference, also may interfere with the video signal.
Related Industry Knowledge
- Charging cable requirements
- Charging cable material chosen
- Jingzhou, accelerating the pace of ...
- National ministries to encourage co...
- Ningbo first ultracapacitor energy ...
- Shielded cable
- The purpose of shielding
- Safety rules for indoor fiber optic...
- Weak systems with cable design and ...
- Weak cable transmission media chara...
- Spiral spring cable
- Cable aging and failure
- Safety and protection of cables