INTRINSICALLY SAFE FIELD BUS SYSTEM

摘要

An intrinsically safe field bus system (1) comprising a field bus (2), a power source (3), a terminating resistor (7) and at least one field bus device (4) connected to the field bus (2). The power source (3) is connected to a first end (5) of the field bus (2) and the terminating resistor (8) terminates the field bus (2) on the other end (7). The power source (3) generates a periodic alternating signal, has a reactance (ZAbsch) as a terminating resistor (8) and a unit for control and adjustment (13) of the power source (3) according to the input impedance (ZBus) of the field bus (2). The field bus input current (IBus) is kept constant when the input impedance (ZBus) in a first range of operation (I) is smaller than the wave impedance (ZW) of the field bus line, and the field bus input voltage (UBus) is adjusted to a constant maximum voltage (Umax) and the field bus input current (IBus) is adjusted according to the input impedance (ZBus) if the input impedance (ZBus) exceeds the value of the wave impedance (Zw) in a second operating range (II).