Method of, and apparatus for, measuring the true contents of a cylinder of gas under pressure

摘要

There is provided a sensor assembly (200) for measuring physical properties of a gas under pressure within a pressure vessel (100). The sensor assembly (200) comprises a housing and a piezoelectric oscillator (202) for immersion in the gas within the pressure vessel (100). The sensor assembly (200) is arranged, when immersed in said gas, to measure the density of the gas within the pressure vessel (100). The housing comprises a first chamber and a second chamber. The first chamber is in fluid communication with the second chamber and substantially encloses said piezoelectric oscillator. The second chamber is in fluid communication with the interior of the pressure vessel. By providing such an arrangement, the true contents (i.e. mass) of fluid in a pressure vessel such as a cylinder can be measured directly and accurately. The housing of the present invention alleviates noise and errors generated by convective currents within a gas cylinder 100, enabling an accurate determination of mass, or rate of change of mass. through direct derivation from the density of the gas in the cylinder.

主权项

1. A sensor assembly for measuring physical properties of a gas under pressure within a gas cylinder comprising: a gas cylinder body and a valve arrangement defining a fixed internal volume of the gas cylinder, the sensor assembly comprising a housing, a piezoelectric oscillator for immersion in the gas within the gas cylinder and a drive circuit operable to drive the piezoelectric oscillator such that the piezoelectric oscillator resonates at a resonant frequency, the sensor assembly being arranged to determine the density of the gas within the gas cylinder from the resonant frequency of the piezoelectric oscillator when immersed in said gas, wherein, in use, the housing is located within the fixed internal volume of the gas cylinder and comprises a first chamber and a second chamber, the first chamber being in fluid communication with the second chamber and substantially enclosing said piezoelectric oscillator, and the second chamber being in fluid communication with the interior of the gas cylinder;
wherein the sensor assembly further comprises a processor arranged to determine, from the density measurement and from the internal volume of said gas cylinder, the mass of the gas within the gas cylinder.