Intrinsically safe barrier device

A protection barrier device comprising:

• first and second input terminals adapted for connection of the device with an associated direct current voltage source;
• first and second output terminals adapted for connection of the device with an associated device disposed in a hazardous area, the first output terminal being in a first low-impedance series path with the first input terminal and the second output terminal being in second low-impedance series path with the second input terminal;
• current sensing means for sensing current in at least one of the first and second series paths;
• excess current level signal generating means for generating an excess current level signal consisting of current in excess of a preselected level;
• amplifier means, powered at least in part by excess current in at least on of the first and second series paths, for amplifying the excess current level signal provided by the excess current level signal generating means to form a trigger signal;
• crowbar circuit means for providing a low resistance crowbar circuit current path between the first and second series paths in accordance with the trigger signal;
• reverse polarity protection means for providing a low resistance reverse polarity current path between the first and second series paths in an event wherein a voltage potentials thereacross is inverted;
• and
• switching means for impeding current flow through at least one of the first and second series paths in accordance with current passing through at least one of the crowbar circuit current path and the reverse polarity current path.

A method for controlling electricity levels communicated to a hazardous area comprising the steps of:

• sensing current in at least one of first and second series paths, the first non-inductive series path extending between a first input terminal and a first output terminal of an protection barrier device, and the second non-inductive series path extending between a second input terminal and a second output terminal of the protection barrier device;
• generating an excess current level signal in accordance with a sensed current level in excess of a selected current level;
• amplifying the excess current level signal to form a trigger signal;
• selectively providing a low resistance crowbar current path between the first and second series paths in accordance with the trigger signal;
• selectively providing a low resistance reverse polarity current path between the first and second series paths in an event wherein a voltage potentials thereacross is inverted;
• and
• impeding current flow through at least one of the first and second series paths in accordance with current passing through at least one of the crowbar circuit current path and the reverse polarity current path.