Density sensor and density sensor manufacturing method

A density sensor to measure density of a gas having a density ranging from 30 gram per cubic meter to 150 kilogram per cubic meter and a working pressure ranging from 0 to 100 bar comprising:

• a resonator housing defining a chamber isolated from the gas, the resonator housing comprising an area of reduced thickness defining a membrane separating the chamber from the gas;
• an actuating/detecting module positioned within the chamber so as to be isolated from the gas and mechanically coupled to the membrane;
• a resonating element arranged to be immersed in the gas, the resonating element being mechanically coupled to the membrane by a pedestal;
• wherein the membrane, the pedestal and the resonator housing are made of metal;
• wherein the membrane has a thickness enabling transfer of mechanical vibration between the actuating/detecting module and the resonating element through the pedestal;
• wherein the resonating element is a resonating disk having a thickness ranging from 25 μm to 200 μm and a diameter ranging from 4 mm to 12 mm, the resonating disk extending parallelly to the membrane or being angled relatively to the membrane, and being coupled by its center to the pedestal, the resonating disk being made of a metal chosen among a group comprising stainless steel, nickel-iron alloy and Molybdenum;
• and wherein the resonating disk comprises two opposing major surfaces, one major surface having at least one undulation creating a dissymmetry between the two major surfaces such as to generate an anisotropic resonating disk.

A method of using a density sensor to measure density of a gas having a density ranging from 30 gram per cubic meter to 150 kilogram per cubic meter and a working pressure ranging from 0 to 100 bar within a tubing or a container comprising:

• tightly coupling the density sensor to a wall of the tubing or the container, or immersing the density sensor into a first chamber, said density sensor comprising:
• a resonator housing defining a second chamber isolated from the gas, the resonator housing comprising an area of reduced thickness defining a membrane separating the second chamber from the gas;
• an actuating/detecting module positioned within the second chamber so as to be isolated from the gas and mechanically coupled to the membrane;
• a resonating element arranged to be immersed in the gas, the resonating element being mechanically coupled to the membrane by a pedestal;
• wherein the membrane, the pedestal and the resonator housing are made of metal;
• wherein the membrane has a thickness enabling transfer of mechanical vibration between the actuating/detecting module and the resonating element through the pedestal;
• wherein the resonating element is a resonating disk having a thickness ranging from 25 μm to 200 μm and a diameter ranging from 4 mm to 12 mm, the resonating disk extending parallelly to the membrane or being angled relatively to the membrane, and being coupled by its center to the pedestal, the resonating disk being made of a metal chosen among a group comprising stainless steel, nickel-iron alloy and Molybdenum;
• and
• wherein the resonating disk comprises two opposing major surfaces, one major surface having a thinned or tapered edge forming a shoulder creating a dissymmetry between the two major surfaces such as to generate an anisotropic resonating disk;
• the method further comprising:
• immersing the resonating element into the gas;
• transferring mechanical vibration from the actuating/detecting module through the membrane to the resonator via the pedestal;
• measuring by the actuating/detecting module a signal representative of the vibration of the resonating element;
• and
• amplifying and processing the signal representative of the vibration of the resonating element by:
• determining a resonance frequency;
• and
• determining the density of the gas by comparing the resonance frequency to calibration measurements.

A method of using a density sensor to measure density of a gas having a density ranging from 30 gram per cubic meter to 150 kilogram per cubic meter and a working pressure ranging from 0 to 100 bar within a tubing or a container comprising:

• tightly coupling the density sensor to a wall of the tubing or the container, or immersing the density sensor into a first chamber, said density sensor comprising:
• a resonator housing defining a second chamber isolated from the gas, the resonator housing comprising an area of reduced thickness defining a membrane separating the second chamber from the gas;
• an actuating/detecting module positioned within the second chamber so as to be isolated from the gas and mechanically coupled to the membrane;
• a resonating element arranged to be immersed in the gas, the resonating element being mechanically coupled to the membrane by a pedestal;
• wherein the membrane, the pedestal and the resonator housing are made of metal;
• wherein the membrane has a thickness enabling transfer of mechanical vibration between the actuating/detecting module and the resonating element through the pedestal;
• wherein the resonating element is a resonating disk having a thickness ranging from 25 μm to 200 μm and a diameter ranging from 4 mm to 12 mm, the resonating disk extending parallelly to the membrane or being angled relatively to the membrane, and being coupled by its center to the pedestal, the resonating disk being made of a metal chosen among a group comprising stainless steel, nickel-iron alloy and Molybdenum;
• and
• wherein the resonating disk comprises two opposing major surfaces, one major surface having at least one undulation creating a dissymmetry between the two major surfaces such as to generate an anisotropic resonating disk;
• the method further comprising:
• immersing the resonating element into the gas;
• transferring mechanical vibration from the actuating/detecting module through the membrane to the resonator via the pedestal;
• measuring by the actuating/detecting module a signal representative of the vibration of the resonating element;
• and
• amplifying and processing the signal representative of the vibration of the resonating element by:
• determining a resonance frequency;
• and
• determining the density of the gas by comparing the resonance frequency to calibration measurements.