Piezoelectric Oscillator Gas Density Measurement
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Solution Overview
Problem
Existing methods for accurately measuring the contents of a gas cylinder under high pressure face challenges due to temperature-pressure relationships, gas compressibility, and convection currents, which lead to inaccurate measurements and noise in gas properties.
Innovation Solution
A sensor assembly using a piezoelectric oscillator housed within a shielding structure with two chambers, allowing direct measurement of gas density and mass within the cylinder, immune to temperature and compressibility corrections, and reducing noise from convection currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pressure sensors (elastic diaphragm with strain gauge) are used to measure gas pressure, then the measurement can be obtained, but the sensor becomes relatively large in size, mechanically complex, expensive to manufacture, and fragile requiring calibration and temperature compensation
Solution Approach 1:
The patent replaces the mechanical elastic diaphragm structure with a piezoelectric crystal oscillator system. The piezoelectric effect converts mechanical stress from gas pressure directly into electrical frequency changes, eliminating the need for mechanical strain gauge elements and complex elastic structures. This substitution reduces mechanical complexity while maintaining measurement precision.
Solution Approach 2:
The patent introduces a piezoelectric crystal as an intermediary between gas pressure and measurement. Instead of directly measuring pressure with complex mechanical sensors, the crystal oscillator serves as a mediator that converts pressure into frequency signals, simplifying the overall sensor structure while enabling accurate measurements.
2Measurement precision
If Bourdon gauge is used to measure pressure, then the measurement can be obtained, but the gauge becomes fragile with delicate components vulnerable to damage from high pressures
Solution Approach 1:
The patent replaces the fragile Bourdon gauge mechanical structure with a piezoelectric crystal oscillator. The crystal's piezoelectric properties allow it to withstand high pressures without the delicate curved tube structure that is prone to damage. The frequency-based measurement approach eliminates mechanical fragility while maintaining pressure measurement capability.
3Measurement precision
If pressure measurement is used to determine gas contents, then the measurement can be obtained, but temperature variations cause pressure to fluctuate proportionally, leading to inaccurate gas content determination
Solution Approach 1:
The patent substitutes pressure-based measurement with direct density measurement using a piezoelectric crystal oscillator. The oscillator measures the density of gas molecules directly through their mass effect on crystal vibration frequency, rather than indirectly through pressure. This direct density measurement is independent of temperature variations, eliminating the temperature-pressure measurement correlation problem.
4Measurement precision
If conventional pressure gauges are used in high pressure cylinders, then pressure can be measured, but gas compressibility at high pressure causes deviation from ideal gas behavior, complicating accurate gas content determination
Solution Approach 1:
The patent replaces indirect pressure-based gas content calculation with direct density measurement using piezoelectric crystal oscillation. By measuring the actual density of gas molecules through their mass effect on crystal frequency, the system obtains direct information about gas content that is not affected by compressibility corrections or ideal gas law deviations at high pressures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise and accurate measurement of gas mass and flow rates within the cylinder, independent of temperature and compressibility, with reduced noise from convection currents, improving measurement reliability and accuracy.
Implementation Method 1
a piezoelectric oscillator for immersion in the gas within the gas cylinder... utilising said piezoelectric oscillator to measure the density of the gas within the gas cylinder
Data Source
AI summary
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.