Method and apparatus for monitoring liquid volume/mass in tanks

A method for measuring the quantity of a mass of fluid material stored in a tank comprising the steps of:

• (a) coupling R.F. energy to an antenna inserted in the tank said antenna adapted to propagate said energy within said tank in an axially symmetric wave mode in which the electric field strength of the wave varies principally as a function of the axial length of said tank;
• (b) sweeping the frequency of the R.F. energy across a range of frequencies;
• (c) detecting and measuring the power not absorbed in said tank across said range of frequencies;
• (d) from the measurements in step (c), determining the Q said tank at several resonance points;
• (e) from the measurements in step (d), determining the amount of material stored in the tank.

A system comprising:

• a metallic fuel tank having input and output ports, said tank forming an inner longitudinally extended cavity in which a dielectric fuel may be stored and metered out to the output port;
• a sweep oscillator for generating a variable frequency range of electromagnetic energy;
• an antenna within said tank disposed along the longitudinal axis thereof and coupled to said sweep oscillator for propagating a voltage standing wave of said energy within said tank, the electric field strength of said wave varying principally as a function of the axial length of said tank;
• and
• measurement means responsive to the amount of energy absorbed by the fuel to gauge the amount of fuel in said tank, wherein the measurement means determines the ratio of th voltage standing wave of the electromagnetic energy entering said tank versus the voltage standing wave of the electromagnetic energy reflected from said tank to derive the amount of fuel in the tank.