Bus interface unit for interposing in a two-wire current loop, as well as a transducer, position controller and analog input and output module with such a bus interface unit

摘要

A bus interface unit is provided for intermediate switching in a two-wire current loop, wherein the bus interface unit has a transformer for potential-free decoupling of an alternating current signal modulated with digital receive data and/or for coupling in of an alternating current signal to be modulated with digital send data. The alternating current signal is modulated onto a direct current signal of a two-wire current loop. The bus interface unit has a bidirectional modem unit connected on the secondary side to the transformer for output of the receive data on a data bus and for input of the send data from the data bus. The transformer has two primary windings, which are interconnected such that the magnetic fields generated by the two-wire loop current flowing through it cancel each other out. A lowpass and/or a highpass filter for the alternating current signal is connected upstream from the at least one primary winding.