A vessel with a cavity for measuring level is disclosed. The vessel includes a differential pressure sensor having a first port and a second port, a reference tube that connects the first port of the differential pressure sensor to a bottom portion of the cavity, and an impulse tube that connects the second port of the differential pressure sensor to an impulse tube ending. At least a portion of the impulse tube extends through the cavity and ends at a fluid inlet. The fluid inlet is located at a level above the reference tube.

An example system includes a fuel tank, fittings mounted through a wall of the fuel tank, and optical sensors positioned within the fittings. A respective optical sensor includes a first pressure sensing end inserted through a fitting and internally into the fuel tank and a second end extending externally from the fuel tank. The system also includes an optical fiber bundle mounted external to the fuel tank, and having an optical fiber connected to each of the plurality of optical sensors for guiding light to each of the plurality of optical sensors.

The invention relates to various means for implementing a method for compensating measured values in capacitive pressure measuring cells using a measuring capacity and at least one reference capacity, comprising the following steps: determination of a pressure-induced capacitance change of the reference capacitance as a function of a pressure-induced capacitance change of the measuring capacitance, determination of a thermal shock-induced capacitance change of the reference capacitance as a function of a thermal shock-induced capacitance change of the measuring capacitance, measurement of the measuring capacitance and of the at least one reference capacitance, determination of the thermal shock-induced capacitance change of the measuring capacitance from a combination of the above dependencies, compensation of the measured measuring capacitance by the thermal shock induced capacitance change of the measuring capacitance, and determination and output of the pressure-induced capacitance change or a quantity derived therefrom.

The invention relates to various means for implementing a method for compensating measured values in capacitive pressure measuring cells using a measuring capacity and at least one reference capacity, comprising the following steps: determination of a pressure-induced capacitance change of the reference capacitance as a function of a pressure-induced capacitance change of the measuring capacitance, determination of a thermal shock-induced capacitance change of the reference capacitance as a function of a thermal shock-induced capacitance change of the measuring capacitance, measurement of the measuring capacitance and of the at least one reference capacitance, determination of the thermal shock-induced capacitance change of the measuring capacitance from a combination of the above dependencies, compensation of the measured measuring capacitance by the thermal shock induced capacitance change of the measuring capacitance, and determination and output of the pressure-induced capacitance change or a quantity derived therefrom.

Disclosed herein are a device and method designed for determining the liquid level in a container through measuring the pressure in the liquid by a pressure sensor located at the bottom of the container within a chamber designed to prevent solid particles dispersed in the liquid from reaching the sensor. Measuring the pressure of the liquid in the container can be based on an upper chamber located above a lower chamber, both adjacent chambers are located within a container. The upper chamber comprises tiny slots allowing the liquid in the container to enter the upper chamber and exert a weight on a diaphragm gasket functioning as a common-wall of the two adjacent chambers. The diaphragm gasket exerts pressure resulting from the liquid weight, on the lower chamber containing the pressure sensor designed to measure the pressure exerted on the lower chamber. In some embodiments, the device and method disclosed herein are used for measuring changes in the pressure at the bottom of the container, wherein the pressure changes are indicative of changes in the liquid level. In some embodiments, the measured pressure can be one or more pressure values measured in a continuously fashion by a one or more pressure sensors.

A wireless pressure sensor for sensing pressure of a liquid in a tank includes a hermetically sealed housing, at least one sensor, at least one photocell array, at least one communication device, and at least one energy storage device. At least a portion of the hermetically sealed housing has a diaphragm. The at least one sensor within the hermetically sealed housing is configured to sense the pressure of the liquid. The at least one photocell array is configured to receive light and generate power from the light. The at least one communication device is configured to transmit data corresponding to the sensed pressure using wireless radio frequency signals. The at least one energy storage device is configured to store power generated by the at least one photocell array and provide power to the at least one sensor and the at least one communication device.

An optically powered pressure sensor for sensing pressure of a liquid in a tank includes a hermetically sealed housing with at least a portion of the housing having a diaphragm, at least one sensor within the hermetically sealed housing, at least one optical emitter, and a photocell array. The hermetically sealed housing forms at least a portion of a hermetically sealed wall of the tank. The at least one sensor within the hermetically sealed housing is configured to sense the pressure of the liquid. The at least one optical emitter is configured to transmit data corresponding to the sensed pressure. The photocell array is configured to receive light and provide power to the at least one sensor and the at least one optical emitter.

A fuel sensing system utilizes a fiber optic sensor comprising a membrane made of a direct band gap semiconductor material (such as gallium arsenide) that forms an optical cavity with an optical fiber inside a hermetically sealed sensor package located at the bottom of a fuel tank. The optical fiber inside the fuel tank is not exposed to the fuel. The optical cavity formed by the bottom surface of the membrane and the surface of the distal end of the internal optical fiber is capable of behaving as a Fabry-Prot interferometer. Multiple light sources operating at different wavelengths and multiple spectrometers can be coupled to the confronting surface of the membrane via the optical fiber inside the fuel tank, a hermetically sealed fiber optic connector that passes through the wall of the fuel tank, and a fiber optic coupler located outside the fuel tank.

A water level gauge according to one aspect of the present invention includes a first communicator configured to receive a first wireless signal indicating an absolute value of water pressure from a water pressure sensor device capable of measuring the absolute value of the water pressure, and a water level calculator configured to calculate a water level on the basis of the absolute value of the water pressure indicated by the first wireless signal received by the first communicator and an atmospheric pressure measured by a barometer.

An example system includes a fuel tank, fittings mounted through a wall of the fuel tank, and optical sensors positioned within the fittings. A respective optical sensor includes a first pressure sensing end inserted through a fitting and internally into the fuel tank and a second end extending externally from the fuel tank. The system also includes an optical fiber bundle mounted external to the fuel tank, and having an optical fiber connected to each of the plurality of optical sensors for guiding light to each of the plurality of optical sensors.