Safety measure

Doing away with the electric leads connected to fuel gauges in car and
aircraft fuel tanks could improve safety, say engineers at Penn State
University, so they have developed an optical fuel gauge. Srivatsan Chakravarthy
shines a pair of intersecting light beams through a window in the top of the
tank. The distance between the two spots where the beams strike the surface of
the fuel reveals how full the tank is. Chakravarthy is now refining the system
to cope with jolting, sloshing fuel in a fast moving vehicle.