An apparatus for determining the identity and/or quantity of a liquid fuel contained in a fuel transporting tank of a fuel transporting vehicle can comprise: a longitudinally extensive member having a first end and a second end, an internal volume from which liquid fuel in the tank is excluded, and a mounting arrangement configured for mounting in use of the longitudinally extensive member within and in fixed relation to the tank, said second end configured in use to be immersed in the liquid fuel in the tank. The longitudinally extensive member can further comprise: first and second pressure sensors spaced apart by a fixed distance, each said pressure sensor having a face exposed in use to the local hydrostatic pressure of the liquid fuel in the tank; and a colour sensing device comprising a light emitter and a light detector configured to detect light from the emitter, said emitter and detector being arranged such that in use light from the emitter incident on the detector passes through said liquid fuel in the tank. The apparatus can further comprise a data processing device configured to determine the identity of the liquid fuel based on said pressure measurements from said first and second pressure sensors and colour data from said colour sensing device.

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.

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.

A fluid level measurement system, including an instrument line configured for installation within a fluid storage tank or vessel, the instrument line having a first end configured to be installed below a fluid level of the storage tank and a second end configured to be installed above the fluid level of the storage tank, the first end including a first pressure diaphragm plate configured to communicate with fluid within the storage tank, a pressure sensor configured to be connected to the second end of the instrument line, and a relief valve configured to open and allow high-pressure gas in the tank to escape through a ventilation port in order to depressurize the tank until tank pressure equalizes with the surrounding atmospheric pressure.

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.

Methods, apparatuses, and storage mediums are provided for detecting water shortage for a humidifier. The method includes: obtaining a water level parameter of a water tank; determining a water level state of the water tank according to the water level parameter. When the water level state of the water tank is a water shortage state, energizing a valve connected to a water box so that water can be added to the water tank through the valve. A number of times of energizing the valve is recorded. When the number of times of energizing the valve exceeds a first preset number of times as well as when the water level state of the water tank determined every time after energization of the valve is the water shortage state, confirming that the water box is short of water.

Methods, apparatuses, and storage mediums are provided for detecting water shortage for a humidifier. The method includes: obtaining a water level parameter of a water tank; determining a water level state of the water tank according to the water level parameter. When the water level state of the water tank is a water shortage state, energizing a valve connected to a water box so that water can be added to the water tank through the valve. A number of times of energizing the valve is recorded. When the number of times of energizing the valve exceeds a first preset number of times as well as when the water level state of the water tank determined every time after energization of the valve is the water shortage state, confirming that the water box is short of water.

An apparatus for determining the identity and/or quantity of a liquid fuel contained in a fuel transporting tank of a fuel transporting vehicle can comprise: a longitudinally extensive member having a first end and a second end, an internal volume from which liquid fuel in the tank is excluded, and a mounting arrangement configured for mounting in use of the longitudinally extensive member within and in fixed relation to the tank, said second end configured in use to be immersed in the liquid fuel in the tank. The longitudinally extensive member can further comprise: first and second pressure sensors spaced apart by a fixed distance, each said pressure sensor having a face exposed in use to the local hydrostatic pressure of the liquid fuel in the tank; and a colour sensing device comprising a light emitter and a light detector configured to detect light from the emitter, said emitter and detector being arranged such that in use light from the emitter incident on the detector passes through said liquid fuel in the tank. The apparatus can further comprise a data processing device configured to determine the identity of the liquid fuel based on said pressure measurements from said first and second pressure sensors and colour data from said colour sensing device.

Pressure sensor systems for measuring a liquid pressure and deriving a liquid level from the measured pressure using gas pressure sensing devices. In one embodiment, liquid pressure results in compression or decompression of a trapped gas (as an example, air), wherein the gas pressure is detected by a gas pressure sensing device directly or a gas pressure sensing device that is protected inside a flexible pouch filled with a liquid. In another embodiment, a gas pressure sensing device is packaged in a flexible pouch filled with an inert liquid to protect the sensing device and circuit thereof from external contaminants while accurately transferring pressure from the liquid through a protective barrier. Application of such sensors in a wireless flood or a wireless liquid level measurement system is described as well.

According to one aspect, a lubricant level sensing system for an actuator is provided. The lubricant level sensing system includes a pressure port in an outer housing of the actuator, a pressure sensor, and a pathway from the pressure port to the pressure sensor. The pathway establishes fluid communication between the pressure sensor and a free volume of an internal cavity of the outer housing relative to a lubricant level in the internal cavity such that the pressure sensor detects a pressure of the free volume used to derive the lubricant level.