Transient suppression apparatus for potentially explosive environments

A system for determining a quantity of fuel in a container, said system comprising:

• at least one sensor disposed at said container for sensing a quantity of fuel in the container;
• sensor excitation system coupled to each of said at least one sensor through an electrical pathway for providing an excitation signal thereto;
• transient suppression apparatus disposed in series with each said electrical pathway for limiting current, voltage and energy to the container, said apparatus comprising:
• an impedance element coupled in series with said electrical pathway to conduct current to the sensor to which it is coupled, said current causing a voltage potential across said impedance element;
• at least one first field effect transistor coupled to said impedance element in series with said current path upstream of said impedance element, each said at least one first field effect transistor having a source and gate connected respectively to an upstream side and a downstream side of said impedance element, and controlled directly by the voltage potential across said impedance element to impose a series resistance to said current of said electrical pathway proportional to the voltage potential of a first polarity across said impedance element;
• and
• at least one second field effect transistor coupled to said impedance element in series with said current path downstream of said impedance element, each said at least one second field effect transistor having a source and gate connected respectively to the downstream side and the upstream side of said impedance element, and controlled directly by the voltage potential across said impedance element to impose a series resistance to said current of said electrical pathway proportional to the voltage potential of a second polarity across said impedance element.