Abstract: A system for providing an airtight/particle tight hermetically sealed clean room environment (20) from which air is passed through a filter (22) includes a panel supporting grid member (24, 24a) having a negative pressure return (32) integrally formed therein for preventing air leakage into the clean room environment (20) with the grid member (24) comprising a circumferential mounting frame having an aperture therein, and a filter panel (22) which is mounted in the frame (24, 24a) in hermetically sealing engagement therewith for closing the aperture. The mounted filter panel (22) and the integral grid member (24, 24a) comprises a negative pressure plenum cavity (32) with the grid member (24, 24a) per se comprising a plenum member which allows negative pressure to be carried around the mounted filter panel (22).

Abstract: A universal fuel quantity indicator apparatus (100,102) includes a digital fuel quantity indicator (100) having an internal microprocessor control unit (104) and a removably connectable digital calibration trim unit interface (102) which enables the fuel quantity indicator (100) to be reconfigured for different fuel tanks by varying selectable fuel tank parameters, such as constants associated with a fuel quantity determination based on calculations of capacitance of a tank capacitor array (110) and a compensator capacitor (112).

Abstract: A system for providing a hermetically sealed clean room environment (34) from which air enters through a filter (20, 20a) includes a magnetically permissive ceiling grid (22, 26, 54), a filter panel (20, 20a) removably mountable in the grid (22, 26, 54) and a magnetic sealing and mounting arrangement (38, 40, 42, 44, 52) associated with the filter panel (20, 20a) for effectuating an airtight/particle-tight hermetic seal. A permanent magnet (42, 52) extends circumferentially around the periphery of the filter panel (20, 20a) and is bonded thereto, with the magnet (42) being embedded in a gasket (38) in one instance and comprising a magnet blade (52) in another instance.

Abstract: An improved fluid quantity indicator, such as for aviation fuel, of the type utilizing capacitive type sensing probes in which a capacitance change occurs proportional to the amount of fluid in a tank or container due to the dielectric constant of the fluid being different from that of air, in which the improvement comprises microprocessor control means for providing display and totalizing control in conjunction with automatic compensation for the zero fluid capacitance variation in a tank and automatic adjustment of the fluid full scale reading for variation in fluid tank capacitance.

Abstract: An improved fluid quantity indicator, such as for aviation fuel, of the type utilizing capacitive type sensing probes in which a capacitance change occurs proportional to the amount of fluid in a tank due to the dielectric constant of the fluid, such as aviation fuel, being different from that of air, in which the improvement comprises automatic compensation for the zero fluid capacitance variation in a tank and automatic adjustment of the fluid full scale reading for variation in fluid tank capacitance. Programmable digital to analog convertors are utilized to provide a universal apparatus full scale set compensation for containers for the fluid substantially independent of the container configuration for compensating for variation in full scale capacitance of a given container and to provide a universal apparatus zero set compensation for containers for the fluid substantially independent of the container configuration for compensating for variations in zero fluid capacitance of a given container.