Vega Grieshaber Kg

Albert Woehrle

Juergen Motzer

Ralf Schaetzle

Ralf Koernle

A driver circuit for an electric device of an intrinsically safe circuit is provided, including a coupling capacitor configured to be open to AC voltage signals and to decouple DC voltage signals, the coupling capacitor includes first and second terminals, and is electrically connected to a first output line of the driver circuit by the first terminal; a first circuit configured to detect an output current of the coupling capacitor, which flows from the first terminal to the first output line; a switchable element electrically connected to the second terminal; a switching behaviour of the element being controllable by switching the element from an electrically blocking state to an electrically conductive state when the output current at the first terminal exceeds a predefined threshold, so that the element in the conductive state causes discharge of the coupling capacitor via the second terminal.

Driver circuit for intrinsically safe circuits

A two-wire sensor () is attached to one pole of a voltage distribution source (U) by an initial connecting line (V) in which a current-limiting resistor (R) is positioned and is attached to the other pole by a second connecting line (V). Parallel to the series connection consisting of the two-wire sensor (S) and the current-limiting resistor (R) is at least one limiting diode (D). A current regulator (SR) which is attached to the poles of the power source (U) regulates a parallel current (I) which runs parallel to the current through the two-wire sensor (D), so that there is a sum current at the poles of the power source (U) that always corresponds to the measured value delivered by the two-wire sensor (S). The regulating inputs of the current regulator (SR) are connected to the terminals of a current-sensing resistor (R) positioned in a connecting line (V). When a HART&#xae;-interface is used with the two-wire sensor (S) a HART&#xae;-resistor (RH) is positioned in one of the two connecting lines (V).

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Aichhalden, Germany

Albert Woehrle