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由于现场总线的数字化通信特征,使得现场总 线与模拟信号(4～20mA)电缆的敷设有很大区别。 1.电缆类型 有许多种类型的电缆可以用于现场总线,但一般推荐使用屏蔽双绞线。电缆的允许长度是与电缆的类型有关的。表1所列的是IEC/ISA物理层标准中指定的电缆类型。 在各类电缆中,优先推荐A型电缆,因为它的传输性能最好,允许的传输距离也最远,因此对于新建项目,一般选择这种类型的电缆。
Due to the characteristics of the fieldbus digital communications, making the field bus and analog signals (4 ~ 20mA) cable laying is very different. 1. Types of Cables There are many types of cables that can be used for fieldbus, but shielded twisted pair cables are generally recommended. The allowable length of the cable depends on the type of cable. Table 1 lists the cable types specified in the IEC / ISA physical layer standard. Among all types of cables, type A cables are preferred because they offer the best transmission performance and the longest transmission distance possible, so this type of cable is generally recommended for new projects.