Abstract: A method of data communication with a selected sensor of multiple liquid level detection sensors connected to a central processing unit includes the steps of: a) transmitting by the central processing unit directly or indirectly a communication signal to the selected sensor of the series of multiple sensors, b) upon receipt of the communication signal by the selected sensor, processing the communication signal in the selected sensor. A liquid level detection system, in particular a liquid overfill prevention system for multi compartment liquid tank trucks, includes two or more liquid level detection sensors, preferably arranged in series, and a central processing unit, where at least one of the two or more sensors includes a sensor processing unit comprising a storage unit.

Abstract: An optical liquid level detection sensor includes a light source for emitting a light beam, a liquid contact surface, and a light detector, where the light source is arranged to emit a light beam towards the liquid contact surface, which liquid contact surface reflects or transmits the light beam in dependence of liquid being present on the liquid contact surface, where the light detector is arranged to receive the light beam after reflection on the liquid contact surface, where the sensor includes an at least partially transparent ring element, and where the liquid contact surface is formed by an outer surface of the ring element.

Abstract: A method of data communication with a selected sensor of multiple liquid level detection sensors connected to a central processing unit includes the steps of: a) transmitting by the central processing unit directly or indirectly a communication signal to the selected sensor of the series of multiple sensors, b) upon receipt of the communication signal by the selected sensor, processing the communication signal in the selected sensor. A liquid level detection system, in particular a liquid overfill prevention system for multi compartment liquid tank trucks, includes two or more liquid level detection sensors, preferably arranged in series, and a central processing unit, where at least one of the two or more sensors includes a sensor processing unit comprising a storage unit.

Abstract: An optical liquid level detection sensor includes a light source for emitting a light beam, a liquid contact surface, and a light detector, where the light source is arranged to emit a light beam towards the liquid contact surface, which liquid contact surface reflects or transmits the light beam in dependence of liquid being present on the liquid contact surface, where the light detector is arranged to receive the light beam after reflection on the liquid contact surface, where the sensor includes an at least partially transparent ring element, and where the liquid contact surface is formed by an outer surface of the ring element.

Abstract: A valve assembly for a liquid storage tank, the storage tank having a wall, the assembly comprising: a pressure relief conduit; a gas inlet valve device having a gas inlet aperture through which gas may pass into the tank; and a gas outlet valve device having a gas outlet aperture through which gas may pass out from the tank, the inlet valve device and outlet valve device being arranged to control a flow of gas into and out from the storage tank, respectively, whereby a pressure of gas in the tank may be maintained between an upper pressure value being a value in excess of a reference pressure value by a prescribed amount and a lower pressure value being a value below the reference pressure value by a prescribed amount, the gas inlet and outlet apertures being provided in gaseous communication with the pressure relief conduit, the pressure relief of conduit being arranged such that gas flowing into or out from the storage tank by means of an operation of the value assembly is caused to pass through the condui