Device for diagnosis of state of tri=state output

摘要

The device comprises a comparator (4) whose two inputs (5,6) are connected via inverse valves (7,8) to a circuit input (2) connectable to the tri-state output (9) of a user interface (10) of a bus coupler (11). With a high ohmic circuit input (2) the comparator output is active. With a low ohmic circuit input the comparator output is inactive. Both comparator inputs define an upper voltage limit and a lower voltage limit. The comparator may be an operational amplifier with a coupling resistor between the comparator output and the non-inverting input.