2)Data Transfer Medium

2)Data Transfer Medium

Data transfer medium is twisted pair(as shown in Fig.2.3).

Fig.2.3 The Structure of Twisted Pair

If there is 8-shape mark between the circuit line and the wire,it means there is twisted pair in this circuit,which is mainly used in signal circuit of sensor or data communication circuit(as shown in Fig.2.4)

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Fig.2.4 The Mark of CAN BUS on the Circuit Diagram

There is no appointed receiver for the data from CAN data bus and the data is sent to each control unit through data bus and each control unit will make calculation after receiving.To avoid the external electromagnetic wave interference and outward radiation,CAN BUS adopts two wires with contrary potential(as shown in Fig.2.5)winded together and in work,high voltage of CAN is 2.5-3.5 V and low voltage of CAN is 1.5-2.5 V.When measured in static state,high voltage of CAN is around 2.6 V and low voltage of CAN is around 2.4 V.In this way,CAN-BUS is protected from the interference from the outside electromagnetic field and the outward radiation of CAN-BUS is neutral,namely,no radiation.

Fig.2.5 Potential of Twisted Pair