초록 ▼

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

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. The microprocessor controls two independent digital servo loops, one of which is nulled when the microprocessor output is equivalent to the fluid quantity for providing a container configuration independent real time digital display of fluid quantity within a given container, and the other of which is nulled when an in-phase signal of equivalent magnitude and opposite sense to cancel out the real component leakage present across the sensing probes is provided. In addition, the microprocessor may be coupled to another microprocessor which functions to total the signals from a plurality of containers or tanks on board the aircraft to provide a total display of fluid on board.

대표청구항 ▼

In an apparatus responsive to the quantity of a fluid within a container therefor of predetermined volume, said apparatus comprising a capacitive sensing means disposed within said container volume so as to be immersible within said fluid and any air within said container volume, said capacitive sen

In an apparatus responsive to the quantity of a fluid within a container therefor of predetermined volume, said apparatus comprising a capacitive sensing means disposed within said container volume so as to be immersible within said fluid and any air within said container volume, said capacitive sensing means having an associated variable dielectric constant, said dielectric constant being proportional to the proportionate amount of fluid within said container volume, said sensing means capacitance varying in accordance with the variation in said proportionate amount of fluid; a reference capacitive means disposed within said container so as to normally be immersible within said fluid and responsive to variations in the dielectric constant of said fluid due to environmental conditions; the improvement comprising AC reference means operatively connected to said sensing means for providing a signal having a predetermined phase and frequency thereto; first microprocessor control means for providing a control signal output indicative of said fluid quantity; first digital-to-analog conversion means having a magnitude input operatively connected in parallel to said first microprocessor control means control signal output for providing an output in response to said input, said first digital-to-analog conversion means output being operatively connected to said reference capacitive means, said output comprising a signal having a predetermined phase opposite to said AC reference means signal phase and a predetermined frequency identical therewith; said first microprocessor control means being programmable to enable a universal apparatus full scale set compensation for containers for said fluid substantially independent of said container configuration for compensating for variations in full scale capacitance of a given container and to directionally count in response to directional counting command signals provided thereto; first differential amplifier summing means having an input operatively connected to said capacitive sensing means and said capacitive reference means outputs for summing the output signals provided therefrom; first means operatively connected to said first summing means output for providing a directional counting command signal in response to said first summing means output, said counting command signal being operatively connected to said first microprocessor control means input, said first microprocessor control means counting in response to said directional counting command input signal for providing a display control signal output dependent thereon, said first microprocessor control means output further being operatively connected in parallel to a digital display means for controllably providing a digital of said fluid quantity on said digital display means in response to said display control signal output; said AC reference means capacitive sensing means, capacitive reference means, first summing means, first directional counting signal providing means, first microprocessor control means and first digital-to-analog conversion means comprising a first independent digital servo control loop which is nulled when said first microprocessor control means output is equivalent to said fluid quantity, whereby a container configuration independent real time digital display of fluid quantity within a given container is provided.