基于RS-485总线信号的可靠性研究

在控制系统要求通信距离为几十米到上千米时,广泛采用RS-485串行总线。RS-485可以采用二线与四线方式,二线制可实现真正的多点双向通信。采用差分平衡电气接口,具有较强的抗电磁干扰能力,在石油化工企业,许多控制系统采用支持多节点远距离通信的RS-485总线作为通信网络,它具有较强的核电磁干扰能力,但其节点间易相互干扰,主要表现有两种形式:反射增加了信号畸变程度;外部的干扰由于平衡条件被破坏,共模干扰变成了串模信号进入传输线。通过对RS-485总线信号的物理隔离,达到减小公共阻抗耦合面积,降低节点间相互干扰程度的目的。在化工企业恶劣的电、磁环境中,RS-485HUB星型总线能防止出现节点的静态感应电压过大、瞬态脉冲强压以及信号线差分短接等故障所造成RS-485总线全面瘫痪的情况。

The Reliability Study Based on the RS-485 Bus Signal

In petrochemical enterprises,many controls systems adopt RS-485 bus as communication network,which supports mutipoints and long distance communication.RS-485 bus has a strong anti-electromagnetic interferece,but in practical RS-485 bus does not reach expected results.Although the interfere is different,but in only two;one is reflection increases the signal distortion,the other is interference of the external equilibrium is destroyed,common mode interferece signal becomes series mode signal into the transmmi...