As we all know, the electrical interface module can only transmit within 100m because it is connected with a network cable, which can transmit up to 100M. If the data exceeds 100M, stable transmission cannot be guaranteed, and the packet is severely dropped or not connected at all.
But why can it only reach 100M?
The signal is represented by binary 0 and 1 in the process of transmission. Generally, the default voltage is 5~15V to represent 1, -5~15V to represent 0, and -3~3V will be regarded as a signal with no logical meaning, that is, white noise, and will be discarded. This is the rate of packet loss. Therefore, the fault-tolerant voltage of the signal in the network cable is U=2V.
The characteristic impedance of the network cable is R=100Ω, according to Ohm’s law, I am 0.02A, the core diameter is 0.5mm, so the area of a single wire is S=0.1965m㎡. The definition of resistance is R=ρ*L/S, and the resistivity of oxygen-free copper is p=0.0175Ω*mm2/M, it can be calculated that L≈112M. The voltage loss of the 12M cable is about 0.02V. Therefore, the voltage loss of a 100M cable is 1.98V. Therefore, the longest transmission distance of network cable is 112M.
Of course, this is not a rigorous calculation. In fact, the transmission speed, length as well as bending and pressing of the network cable, will all affect it. Considering the redundancy and aging of the line in the future, it's better not to exceed 90 meters.