method for measuring the molecular weight of a gas, meter for measuring the molecular weight of a ga

专利摘要:
METHOD FOR MEASURING THE MOLECULAR WEIGHT OF A GAS, METER FOR MEASURING THE MOLECULAR WEIGHT OF A GAS, COMPUTER PROGRAM PRODUCT EXECUTABLE BY A PROGRAMMABLE PROCESSING EQUIPMENT, AND COMPUTER STORAGE MEDIA A molecular weight meter is displayed a gas the meter comprising a housing having an entrance and interior to accommodate said gas to be measured, a detector assembly comprising a high frequency flat piezoelectric crystal oscillator located within said housing, so that, in use, the oscillator of piezoelectric crystal is in contact with said gas, said detector set being arranged: to activate the piezoelectric crystal oscillator, so that the piezoelectric crystal oscillator resonates on a single resonant frequency; for measuring said single resonant frequency of said piezoelectric crystal oscillator, in order to determine the gas density; and to determine, through density, determined or predetermined pressure of the gas and determined or predetermined temperature of the gas, the molecular weight of the gas.
公开号:BR112013013328B1
申请号:R112013013328-7
申请日:2011-11-28
公开日:2020-10-20
发明作者:Neil Alexander Dowie
申请人:Air Products And Chemicals, Inc；
IPC主号:

专利说明:

[0001] The present invention relates to a method and apparatus for measuring the molecular weight of a gas. More particularly, the present invention relates to a method and apparatus for measuring the molecular weight of a gas (or the average molecular weight, in the case of a mixture of gases), using a piezoelectric crystal oscillator.
[0002] The methods and apparatus described here can be applied to systems, where fluids with relatively high pressure (for example, about 10 bars or more) are present, such as, for example, the supply of fluids in high cylinders. pressure, or factories that use high pressure fluids. The present invention relates particularly to "clean" gases, that is, gases with little or no impurity or contaminants, such as water vapor or dust.
[0003] The present invention is particularly applicable to permanent gases. Permanent gases are gases, which cannot be liquefied by pressure alone and, for example, can be supplied in cylinders at pressures up to 450 bar g (where bar g is a measure of the pressure in bar above atmospheric pressure). Examples are argon and nitrogen. However, this is not to be taken as a limitation and the term gas can be considered, as covering a wider range of gases, for example, a permanent gas and a vapor of a liquefied gas.
[0004] Vapors of liquefied gases are present above the liquid inside a cylinder of compressed gas. Gases, which liquefy under pressure, as they are compressed to fill in a cylinder, are not permanent gases, and are more precisely described as liquefied gases under pressure, or as vapors of liquefied gases. As an example, nitrous oxide is supplied inside a cylinder in liquid form, with an equilibrium vapor pressure of 44.4 bar g at 15 ° C. These vapors are not permanent or real gases, since they are liquefied by pressure or temperature around environmental conditions.
[0005] A compressed gas cylinder is a pressure vessel designed to contain gases at high pressures, that is, at pressures significantly above atmospheric pressure. Compressed gas cylinders are used in a wide range of markets, from the generally low-cost industrial market, through the medical market, to higher-cost applications, such as the manufacture of electronics using high-purity, corrosive special gases, toxic or pyrophoric. Pressurized gas containers commonly comprise steel, aluminum or compounds, and are capable of storing compressed, liquefied or dissolved gases with a maximum filling pressure of up to 450 bar g for most gases, and up to 900 bar g for gases, like hydrogen and helium.
[0006] In many cases, it is desirable, and sometimes critical, to know the type of gas inside a cylinder, or at a point downstream of a cylinder; for example, in a pipe during the welding process. An example of such a situation would be to know, when the purge occurred.
[0007] Molecular weights are usually measured using mass spectrometers. Such arrangements measure the mass to charge ratio of a gas in order to directly determine the molecular weight. A commonly used device is a matrix-assisted laser desorption / ionization source in combination with a time-o f-flight mass analyzer (known as MALDI-TOF). However, such devices are bulky, expensive and unsuitable for many applications, where portability and cost can be of relevance.
[0008] An alternative type of meter, which can be used to measure molecular weights, is a vibrating gas density meter, as shown and described in "Suzuki GD Series Vibratory Gas Density Meters", Report Technician Yokogawa N °. 29 (2000). Such a device comprises a thin-walled metal cylinder arranged in such a way that gas is able to flow in and out of the cylinder. Two pairs of piezoelectric elements are located on the cylinder - a pair of drive elements and a pair of detection elements. The density of the gas is obtained from a measurement of two different resonant frequencies, to compensate for variations due to temperature. The resonant frequencies used are very low and on the order of a few hundred Hz.
[0009] The above device is complex, relatively expensive and highly vulnerable to the effects of vibration. This is because the resonant frequencies used are comparable to the frequencies generated by external vibrations. In addition, a complicated excitation and detection arrangement is necessary to compensate for the effects of temperature.
[00010] According to a first aspect of the present invention, a method is provided to measure the molecular weight of a gas with a high frequency flat piezoelectric crystal oscillator in contact with the gas, the method comprising: a) using said piezoelectric crystal oscillator to measure gas density by: using a drive circuit to drive the piezoelectric oscillator, so that the piezoelectric crystal oscillator resonates to a single resonant frequency; and measuring said single resonant frequency of said piezoelectric crystal to determine the density of the gas; and b) determining, from the density, determined or predetermined pressure and determined or predetermined temperature of the gas, the molecular weight of the gas.
[00011] By providing such a method, the molecular weight of a gas (or average molecular weight in the case of a gas mixture) can be easily determined using a robust and relatively inexpensive piezoelectric crystal oscillator, for example, a crystal oscillator of quartz. Such an oscillator works both as a source of excitation (by oscillating in response to being triggered by a drive circuit), and as a detector (by having a single resonant frequency, which is dependent on the medium in which the oscillator is located).
[00012] A flat crystal oscillator is compact and robust and, as a result, is not relatively insensitive to environmental disturbances. Furthermore, due to the fact that the oscillator's oscillation frequency is high (in the order of kHz), the oscillator is relatively insensitive to localized vibrations (which tend to have frequencies in the order of Hz). This is in contrast to the known molecular weight detection arrangements.
[00013] In one embodiment, the method comprises measuring the pressure of the gas.
[00014] In one embodiment, the gas pressure is measured using an electronic pressure sensor. In one embodiment, the electronic pressure sensor comprises a piezo-resistive diaphragm sensor.
[00015] In one embodiment, the predetermined pressure of the gas is the fixed outlet pressure of a gas regulator located upstream of said oscillator.
[00016] In one embodiment, the predetermined pressure of the gas is atmospheric pressure.
[00017] In one embodiment, the method further comprises measuring the temperature of the gas with a temperature sensor. In one embodiment, the temperature sensor comprises a thermistor or a temperature dependent resistance.
[00018] In one embodiment, the quartz crystal is composed of at least one tooth. In one arrangement, said piezoelectric crystal oscillator comprises at least two flat teeth.
[00019] In one embodiment, the quartz crystal is cut in AT or SC.
[00020] In a variation, the surface of the quartz crystal is directly exposed to the gas.
[00021] In one embodiment, said piezoelectric crystal oscillator has a resonant frequency of 32 kHz or more.
[00022] In one embodiment, the detector assembly comprises a source of energy. In one arrangement, the power supply consists of a lithium-ion battery.
[00023] In one embodiment, the detector assembly comprises a processor.
[00024] According to any second embodiment of the present invention, there is provided a meter for measuring the molecular weight of a gas, the apparatus comprising a housing having an inlet and an interior to accommodate said gas to be measured, a detector assembly comprising a high frequency flat piezoelectric crystal oscillator located inside said housing, so that, in use, the piezoelectric crystal oscillator is in contact with said gas, said detector set being arranged: to drive the oscillator piezoelectric crystal, so that the piezoelectric crystal oscillator resonates to a single resonant frequency; to measure said single resonant frequency of said piezoelectric crystal oscillator, to determine the density of the gas; and to determine, from the density, determined or predetermined pressure of the gas, and determined or predetermined temperature of the gas, the molecular weight of the gas.
[00025] By providing such an arrangement, the molecular weight of a gas (or average molecular weight, in the case of a gas mixture) can be easily determined using a robust and relatively inexpensive piezoelectric crystal oscillator, for example, a crystal oscillator of quartz. Such an oscillator works both as a source of excitation (by oscillating in response to be triggered by a drive circuit) and as a detector (by having a single resonant frequency, which is dependent on the medium in which the oscillator is located).
[00026] A flat crystal oscillator is compact and robust and, as a result, is not relatively insensitive to environmental disturbances. Furthermore, due to the fact that the oscillator's oscillation frequency is high (in the order of kHz), the oscillator is relatively insensitive to localized vibrations (which tend to have frequencies in the order of Hz). This is in contrast to the known molecular weight detection arrangements.
[00027] In one embodiment, the meter further comprises one or more of a drive circuit, a processor and a power source.
[00028] In one embodiment, the detector assembly comprises a drive circuit, which comprises a Darlington pair arranged in a feedback configuration from a common emitter amplifier.
[00029] In one embodiment, the meter further comprises a pressure sensor to measure the pressure of the gas.
[00030] In one embodiment, said pressure sensor is an electronic pressure sensor. In one embodiment, the electronic pressure sensor comprises a piezo-resistive diaphragm sensor.
[00031] In one embodiment, the meter is located downstream of a fixed pressure regulator, and the gas pressure has a predetermined value, based on the output of said fixed pressure regulator.
[00032] In one embodiment, the meter further comprises a restrictive orifice upstream of said inlet and an outlet to the atmosphere downstream of said inlet, wherein said predetermined gas pressure is atmospheric pressure.
[00033] In one embodiment, the method further comprises measuring the temperature of the gas with a temperature sensor. In one embodiment, the temperature sensor comprises a thermistor or a temperature dependent resistance.
[00034] In one embodiment, the quartz crystal is composed of at least one tooth. In a variation, the quartz crystal comprises a pair of flat teeth.
[00035] In one embodiment, the quartz crystal is cut in AT or SC.
[00036] In a variation, the surface of the quartz crystal is directly exposed to the gas.
[00037] In one embodiment, the piezoelectric crystal oscillator has a resonant frequency of 32 kHz or more.
[00038] In one embodiment, the meter includes a filter located at the entrance. In one embodiment, the filter has a pore size in the range of 5 to 10 pm.
[00039] In one embodiment, the meter includes a heating element located within the housing. In one embodiment, the heating element is located adjacent to the piezoelectric crystal oscillator. In another arrangement, the heating element is in contact with the piezoelectric crystal oscillator.
[00040] In one embodiment, the detector assembly comprises a source of energy. In one arrangement, the power supply consists of a lithium ion battery.
[00041] In one embodiment, the detector assembly comprises a processor.
[00042] In one embodiment, the meter includes a monitor.
[00043] In one embodiment, the meter includes an antenna connected to the detector assembly and arranged to allow wireless data transmission from the meter. In one embodiment, the meter is operable to transmit data wirelessly to a remote display unit.
[00044] According to a third embodiment of the present invention, there is provided a computer program product executable by a programmable processing apparatus, which comprises one or more segments of software to perform the steps of the first aspect.
[00045] According to a fourth embodiment of the present invention, a computer-usable storage medium is provided having a computer program product, according to the fourth aspect, stored therein.
[00046] In addition, a gas mixing arrangement is provided, the gas mixing arrangement comprising a first gas source to supply a first gas, a second gas source to supply a second gas other than said first gas, and a mixer located downstream of the first and second gas sources and arranged, in use, to mix the first and second gases, to provide a gas mixture, the gas mixing arrangement further comprising a meter arranged to measure the average molecular weight of the gas mixture and to control the relative proportion of the first and second gases in said gas mixture, in response to the measured average molecular weight of said gas mixture.
[00047] In one embodiment, the first and second gas sources each comprise a pressure regulating device arranged to selectively control the flow of gas from the respective gas source. In one embodiment, one or each of said pressure regulating devices comprises a pressure regulator, or a valve.
[00048] In one embodiment, the meter controls at least one of the pressure regulating devices in response to the measured average molecular weight of the gas mixture. In one embodiment, at least one of the pressure regulating devices is an electronic pressure regulating device. In one embodiment, at least one of the pressure regulating devices comprises a solenoid valve.
[00049] In one embodiment, the meter comprises a detector assembly, including a piezoelectric crystal oscillator which, in use, is in contact with said gas mixture, said detector assembly being arranged: to drive the piezoelectric crystal oscillator, so that the piezoelectric crystal oscillator resonates at a resonant frequency; to measure the resonant frequency of said piezoelectric crystal oscillator, to determine the density of the gas; and to determine, from the density, determined or predetermined pressure of the gas, and determined or predetermined temperature of the gas, the molecular weight of the gas.
[00050] In one embodiment, the meter comprises the second aspect meter.
[00051] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a gas cylinder and regulator assembly; Figure 2 is a schematic diagram showing a regulator assembly and a molecular weight meter, according to a first embodiment of the invention; Figure 3 is a schematic diagram, showing a regulator assembly and a molecular weight meter, according to a second embodiment of the invention; Figure 4 is a schematic diagram, showing a regulator assembly and a molecular weight meter, according to a third embodiment of the invention; Figure 5 is a schematic diagram, showing a molecular weight meter, according to a fourth embodiment of the invention; Figure 6 is a schematic diagram of a drive circuit for use with any of the first to fourth embodiments; Figure 7 is a schematic diagram showing an alternative to the drive circuit for use with any of the first to fourth embodiments; Figure 8 is a schematic diagram, showing the parameters entered and transmitted from a processor for use with any of the first to fourth embodiments; Figure 9 shows a graph of the quartz crystal frequency (kHz) on the Y axis as a function of density (kg / m3) for a number of different gases; Figure 10 shows a graph of gas density (in kg / m3) on the Y axis as a function of pressure (bar g) on the X axis for argon, oxygen and argon: carbon dioxide: oxygen at pressures up to 300 bar g; Figure 11 shows a graph of gas density (kg / m3) on the Y axis as a function of pressure (bar g) on the X axis for argon, oxygen and a mixture of argon: carbon dioxide: oxygen at pressures up to at 100 bar g; Figure 12 is a graph, showing the change of frequency (in Hz) on the Y axis as a function of time (in seconds) on the X axis, when gases are purged; Figure 13 is a graph, which corresponds to Figure 13, showing the change in the calculated molecular weight (on the Y axis) as a function of time (in seconds), on the X axis; Figure 14 is a flow chart, illustrating a method, according to a described embodiment; Figure 15 shows a schematic diagram of a fifth embodiment of the present invention, showing a gas mixing arrangement; Figure 16 shows a graph of the frequency behavior of different types of crystals; Figure 17 is a schematic diagram showing an alternative detector assembly, comprising two quartz crystals; and Figure 18 shows an alternative arrangement, which uses an electronic remote data unit.
[00052] Figure 1 shows a schematic view of a gas cylinder assembly 10, according to an embodiment of the invention.
[00053] Figure 1 shows a schematic view of a situation, in which the present invention can be used. A gas cylinder 100, regulator 150 and molecular weight meter 200 are provided.
[00054] The gas cylinder 100 has a gas cylinder body 102 and a valve 104. The gas cylinder body 102 comprises a generally cylindrical pressure vessel, having a flat base 102a arranged to allow the gas cylinder assembly gas 10 stand on a flat surface.
[00055] The gas cylinder body 102 is formed from steel, aluminum and / or composite materials and is adapted and arranged to withstand internal pressures up to about 900 bar g. An opening 106 is located at a proximal end of the body of the gas cylinder 102 opposite the base 102a, and comprises a helical thread (not shown) adapted to accommodate the valve 104.
[00056] The gas cylinder 100 defines a pressure vessel having an internal volume V. Any suitable fluid can be contained within the gas cylinder 100. However, the present embodiment refers to, but is not limited to, exclusively , purified permanent gases, which are free of impurities, such as dust and / or moisture. Non-exhaustive examples of such gases may be: oxygen, nitrogen, argon, helium, hydrogen, methane, nitrogen trifluoride, carbon monoxide, krypton or neon.
[00057] The valve 104 comprises a housing 108, an outlet 110, a valve body 112, and a valve seat 114. The housing 108 comprises a complementary helical thread for engagement with the opening 106 of the gas cylinder body 102. Output 110 is adapted and arranged to allow gas cylinder 100 to be connected to other components in a gas assembly; for example, hoses, pipes, or other valves or pressure regulators. Valve 104 may optionally comprise a VIPR (Integrated Pressure Reducing Valve). In this situation, regulator 150 can be omitted.
[00058] The valve body 112 can be axially adjusted towards or away from the valve seat 114, by rotating a lever 116 to selectively open or close the outlet 110. In other words, the movement of the valve body 112 towards or away from the valve seat 112 selectively controls the area of the communication passageway between the interior of the gas cylinder body 102 and the outlet 110. This, in turn, controls the flow of gas from from the interior of the gas cylinder assembly 100 to the external environment.
[00059] A regulator 150 is located downstream of outlet 110. Regulator 150 has an inlet 152 and an outlet 154. Inlet 152 of regulator 150 is connected to an inlet tube 156, which provides a communication path between outlet 110 of gas cylinder 100 and regulator 150. Inlet 152 of regulator 150 is arranged to accommodate gas at a high pressure from outlet 110 of gas cylinder 100. This can be any suitable pressure; however, in general, the pressure of the gas leaving outlet 110 will be greater than 20 bar and is more likely to be in the range of 100 - 900 bar.
[00060] Output 154 is connected to an outlet tube 158. A coupling 160 is located at the distal end of the outlet tube 158 and is adapted for connection to other ducts or devices (not shown), for which gas is required .
[00061] A molecular weight meter 200 is located in communication with outlet tube 158 between outlet 154 and coupling 160. The molecular weight meter 200 is located immediately downstream of regulator 150, and is arranged to determine the weight molecular weight of the gas (or average molecular weight of a gas mixture), downstream of regulator 150.
[00062] Regulator 150 and molecular weight meter 200, according to a first embodiment of the present invention, are shown in greater detail in Figure 2.
[00063] In this embodiment, regulator 150 comprises a single diaphragm regulator. However, the person skilled in the art should be readily aware of the variations that can be used with the present invention, for example, a two-diaphragm regulator or other device.
[00064] Regulator 150 comprises a valve region 162 in communication with inlet 152 and outlet 154. Valve region 162 comprises a pressure regulating valve 164 located adjacent to a valve seat 166. Pressure regulating valve 164 it is connected to a diaphragm 168, which is configured to allow the translation movement of the pressure regulating valve 164 towards and away from the valve seat 166, to open and close, respectively, an opening 170 between them. Diaphragm 168 is resilient by a spring 172 located on an axis 174.
[00065] The regulator 150 is operable to receive gas from the outlet 110 at a total pressure of the cylinder (for example, 100 bar), but to distribute the gas at substantially constant fixed low pressure (for example, 5 bar), for the outlet 154. This is achieved by a feedback mechanism, whereby the gas pressure downstream of opening 170 is operable to act on diaphragm 168 as opposed to the pressure force of spring 172. In the embodiment of Figure 2, the regulator 150 is a fixed pressure regulator and is arranged to supply gas from outlet 154 at a fixed and known pressure. The pressure is determined by the relative spring force 172.
[00066] If the gas pressure in the region adjacent to diaphragm 168 exceeds the specified level, diaphragm 168 is operable to move upwards (in relation to Figure 2). As a result, pressure regulating valve 164 is moved closer to valve seat 166, reducing the size of opening 170 and, consequently, restricting the flow of gas from inlet 152 to outlet 154. In general, forces opposite the resistance of the spring 172 and the gas pressure will result in an equilibrium position of the diaphragm and, therefore, the supply of a constant pressure of gas at the outlet 154.
[00067] The molecular weight meter 200 comprises housing 202 and detector assembly 204. Housing 202 can comprise any suitable material, for example, steel, aluminum or composites. The housing has an interior 206, which is in communication with the interior of the outlet tube 158, through a short supply tube 208. Consequently, the interior 206 of the housing 202 is at the same pressure as the interior of the outlet tube 158. In use, housing 202 is generally sealed and isolated from the outside atmosphere. The molecular weight meter 200 is arranged to measure the molecular weight of the gas inside the housing 202. Alternatively, the molecular weight meter 200 can measure the average molecular weight of a homogeneous mixture of gases inside the housing 202.
[00068] Alternatively, housing 202 can be provided as an integral part of outlet tube 158. For example, a part of outlet tube 158 can be extended to accommodate detector assembly 204. Alternatively, only a part of detector assembly 204 can be located inside tube 158, the remainder being located outside or spaced from them.
[00069] In addition, housing 202 may form an integral part of regulator 150. For example, detector assembly 204 can be located entirely within outlet 154 of regulator 150. The expert should be readily aware of the variations and alternatives that affect within the scope of the present invention.
[00070] The detector assembly 204 comprises a quartz crystal oscillator 210 connected to a drive unit 212, a temperature sensor 214 and a battery 216. These components are located inside housing 202.
[00071] The drive circuit 212 and quartz crystal oscillator 210 will be described in detail later with reference to Figures 6 and 7. The temperature sensor 214 includes a thermistor. Any suitable thermistor can be used. High precision is not required on the part of the thermistor. For example, an accuracy of 0.5 ° C is suitable for this embodiment. Therefore, cheap and small components can be used.
[00072] A processor 230 (shown and described later with reference to Figure 8) can also be provided, either separately or as part of the drive circuit 212.
[00073] In this arrangement, the quartz crystal oscillator 210 is constantly under isostatic pressure within housing 202 of the molecular weight meter 200 and, consequently, does not have a pressure gradient. In other words, any mechanical stress arising from the pressure difference between the external atmosphere and the internal components of the molecular weight meter 200 is expressed throughout the housing 202.
[00074] However, this need not be so. For example, only the quartz crystal oscillator 210 and the temperature sensor 214 can be located inside housing 202, with the remainder of detector assembly 204 being located outside it.
[00075] The inventors have found that only some of the components of the detector assembly 204 are sensitive to high pressure. In particular, larger components, such as batteries, may be susceptible to high pressures. However, lithium ion batteries have been found to behave particularly well under high pressures arising within the gas cylinder 100. Consequently, battery 216 comprises lithium ion cells. However, suitable alternative energy sources will be easily contemplated by qualified people.
[00076] The location of detector assembly 204 fully within housing 202 provides additional flexibility when configuring regulators 150. In particular, the location of relatively fragile electronic components entirely within the strong metal or composite walls of housing 202 provides considerable protection against environmental or accidental damage. This is particularly important, for example, in storage areas or depots, where gas cylinders 100 comprising regulators 150 are located adjacent to gas cylinders, heavy machinery or rough surfaces.
[00077] In addition, the internal location of detector assembly 204 protects these components from environmental conditions, such as salt, water and other contaminants. This will allow, for example, a high impedance circuit, which is highly sensitive to salt and water damage, to be used as part of the detector assembly 204.
[00078] The benefits of the internal location of detector assembly 204 are unique to solid-state detector devices, such as the quartz crystal oscillator 210. For example, a conventional pressure sensor, such as a Bourdon meter, cannot be located this way. Although a crystal-based sensor can operate fully immersed in the gas at constant pressure, a conventional pressure sensor is not capable of measuring isostatic pressure, and requires a pressure gradient in order to function. Therefore, a conventional pressure gauge must be located between the high pressure to be measured and the atmosphere. This increases the risk of damage to the external components of the 200 molecular weight meter.
[00079] A second embodiment of the invention is shown in Figure 3. The characteristics of the second embodiment shown in Figure 3, which are in common with the first embodiment of Figure 2, are assigned with the same reference numbers, and will not be described here again.
[00080] In the embodiment of Figure 3, regulator 250 differs from regulator 150 from the embodiment of Figure 2, in which regulator 250 is arranged to provide a variable gas outlet pressure at outlet 154.
[00081] In this regard, a lever 252 is provided, to allow a user to adjust the pressure force of the spring 172. This moves the equilibrium position of diaphragm 168 and, as a result, adjusts the balance spacing between the regulating valve pressure valve 164 and valve seat 166. This allows adjustment of the dimensions of the opening 170, through which the flow of high pressure gas through the outlet 110 can pass.
[00082] The pressure can typically vary up to about 20 bar g. However, the person skilled in the art should be readily aware of alternative arrangements and pressures, which can be provided by regulator 250. In addition, the regulator may comprise secondary phases for use in situations, such as welding with oxy-acetylene, where it is necessary precise pressure regulation.
[00083] The second embodiment comprises a molecular weight meter 300. The components of the molecular weight meter 300, in common with the molecular weight meter 200, are assigned the same reference numbers for clarity.
[00084] The molecular weight meter 300 is substantially similar to the molecular weight meter 200 of the first embodiment. However, the molecular weight meter 300 still comprises a pressure sensor 302 located inside housing 202. Any suitable pressure sensor can be used.
[00085] For example, pressure sensor 302 may comprise a piezo-resistive diaphragm sensor. Such a pressure sensor typically comprises a machined silicon diaphragm having piezo-resistive strain gauges formed therein. The diaphragm is fused with a silicon or glass back plate. Strain gauges are usually connected to form a Wheatstone bridge, the output of which is directly proportional to the measured pressure. The output of the pressure sensor 302 can then be inserted into the processor 230.
[00086] The expert should be readily aware of alternative electronic pressure sensors, which can be used with the present invention. In other words, the pressure sensor 302 can comprise any sensor capable of measuring the pressure of a gas and providing an electronic output for that measurement.
[00087] In this arrangement, the quartz crystal oscillator 210 and pressure sensor 302 are constantly under isostatic pressure within housing 202 of the molecular weight meter 200 and, consequently, do not have a pressure gradient. In other words, any mechanical stress arising from the pressure difference between the external atmosphere and the internal components of the molecular weight meter 300 is expressed throughout the housing 202.
[00088] A third embodiment of the invention is shown in Figure 4. The characteristics of the third embodiment shown in Figure 4, which are in common with the second embodiment of Figure 3, are assigned with the same reference numbers and will not be described here again.
[00089] In the embodiment of Figure 4, regulator 250 corresponds to regulator 250 of the second embodiment, and is arranged to provide a variable gas outlet pressure through outlet 154. The components of regulator 250 have already been described and not will be described more here.
[00090] The third embodiment comprises a molecular weight meter 400. The components of the molecular weight meter 400, in common with the molecular weight meters 200, 300, are assigned the same reference numbers for clarity.
[00091] The molecular weight meter 400 is substantially similar to the molecular weight meters 200, 300 of the first and second embodiments. However, the molecular weight meter 400 is operable with a variable pressure regulator 250, without requiring the pressure sensor 302 of the second embodiment.
[00092] The molecular weight meter 400 comprises a conduit 402. The interior of conduit 402 is in communication with the interior 206 of housing 202. A proximal end of conduit 402 comprises a restrictor orifice 404 located immediately downstream of short tube 208 and in communication with outlet 154. The restrictor orifice 404 is arranged to provide a physical restriction, to limit the pressure of the gas entering the conduit 402 from the outlet 154. Therefore, the pressure of the gas inside the conduit 402 downstream of the restrictor orifice 404 is considerably lower than at outlet 154.
[00093] A distal end 406 of conduit 402 is open to the atmosphere. The distal end 406 is located at the end of a section of conduit 402 downstream of housing 202. For typical applications, a suitable conduit 402 will have a hole in the region of 2 mm and a length of about 100 mm. This is to ensure that there is no counter-diffusion of atmospheric gases into the interior 206 of housing 202, to avoid possible errors in measurement.
[00094] Although conduit 402 is shown to be essentially linear in Figure 4, conduit 402 can be of any suitable form. For example, a more compact arrangement would be to arrange conduit 402 in a labyrinthine or coil shape, in order to adjust the conduit in a smaller space.
[00095] Therefore, the combined effect of restrictor orifice 404 and remote distal end 406 of conduit 402 (which is at atmospheric pressure) is that the interior 206 of housing 202 is always at, or close to, atmospheric pressure. This is independent of the gas pressure downstream of outlet 154 and upstream of restrictor orifice 404.
[00096] As a result, no pressure gauge is necessary, as pressure can always be considered as atmospheric pressure. If a correction is needed (for example, when operating at high altitudes, where the atmospheric pressure is lower), it can be entered manually into the 230 processor.
[00097] Therefore, under particular conditions, no pressure sensor is necessary, since the pressure value can be adjusted automatically, or manually entered by a user, and the resulting pressure value used by the processor 230 to determine the molecular weight of the gas or gases to be detected.
[00098] A fourth embodiment of the present invention is shown in Figure 5. The fourth embodiment refers to a 500 molecular weight meter. The 500 molecular weight meter can be portable, and can be placed in locations where it is desired to quickly and easily determine the type of gas within a specific location; for example, inside a tube during an orbital welding process. Alternatively, the molecular weight meter 500 can be placed at the outlet of a tube to detect, for example, the purging of one type of gas, with another type of gas.
[00099] The molecular weight meter 500 comprises a housing 502. Housing 502 has walls 504, which delimit an opening 506. Opening 506 provides a communication path between the inside and outside of housing 504. The remaining components of the meter molecular weight of 500 are similar to those of molecular weight meters 200, 300, 400 of the first to third embodiments, and will not be described hereinafter.
[000100] In order for the 210 quartz crystal oscillator to provide an accurate measurement, the 210 quartz crystal oscillator must be kept free of dirt, moisture and other contaminants. Although this is not a problem for packaged, commercially supplied gases (which are extremely clean), the 500 molecular weight meter can be used in situations where environmental contamination can be a significant problem.
[000101] Therefore, the molecular weight meter 500 is provided with a filter 508 located in the opening 506. The filter 508 can be of any suitable pore size. The pore sizes are in the range of 5 - 10 pm, and are particularly suitable for this application. Filter 508 (or a similar filter) can be applied to any of the first to third embodiments described above.
[000102] Alternatively, the filter 508 can be omitted if the opening 506 is small enough to prevent the penetration of dirt or other contaminants. For example, an aperture size of 0.25 millimeter would be suitable for use without a filter.
[000103] Additionally, the 500 molecular weight meter can be subjected to environments, where moisture is present. An incorrect measurement can result if any portion of moisture condenses on the quartz crystal oscillator 210. Therefore, in order to mitigate these effects, a heater 510 adjacent to the quartz crystal oscillator 210 can be provided in order to ensure let moisture not condense on oscillator 210. Heating apparatus 510 may comprise a single heated wire, or may comprise a solid resistive element, for converting electrical energy into thermal energy. The heating apparatus 510 can be located in contact with the quartz crystal oscillator 210.
[000104] If a heater is used, it is desirable that the temperature sensor 214 is located as close as possible to the 210 quartz crystal oscillator, so that an accurate measurement of the gas temperature around the 210 quartz crystal oscillator can be done. The heater 510, or any other suitable heater, can also be used with any of the first to third embodiments.
[000105] The molecular weight meter 500 is shown in Figure 5, comprising a pressure sensor 302, in common with the molecular weight meter 300 of the second embodiment. Such an arrangement can be beneficial when used inside a pressurized apparatus, such as high pressure tubes, or inside pressure vessels.
[000106] However, in situations where the pressure is known to a degree of general accuracy, the pressure sensor 302 can be omitted, as in the first and third embodiments. Such a situation may arise when the 500 molecular weight meter is used at ambient atmospheric pressure; for example, when measuring the molecular weight (or average molecular weight) of gas exiting a tube into the atmosphere, or inside tubes at atmospheric pressure. In this situation, no pressure sensor is necessary, since the pressure value can be adjusted automatically or manually entered by a user, and the resulting pressure value used by the processor 230 to determine the molecular weight of the gas or gases to be detected .
[000107] Any of the first to fourth embodiments can additionally comprise a monitor (not shown) to show a user the results of measurements made on the detected gas. Alternatively, the display can be located at a distance from the molecular weight meters 200, 300, 400, 500, and the relevant data can be communicated remotely.
[000108] For example, any of the first to fourth embodiments can further comprise an antenna (not shown) for remote communication with, for example, a base station. This will be discussed later. In this case, the antenna can be located outside housing 202 and connected to detector assembly 204 by means of a wire connector or equivalent.
[000109] The antenna itself can be adapted and arranged to use any appropriate communication protocol; for example, a non-complete list may be transmission over RFID, Bluetooth, infrared (IR), 802.11 wireless, frequency modulation (FM), or a cellular network.
[000110] Alternatively, wired communication can be implemented. Wired communication needs only a single metallic conductor to communicate: the "return" path of the circuit is provided by capacitive coupling through the air between the communication devices. The expert should be promptly aware of the alternatives of the antenna (and associated transmission hardware), which can be used with the embodiments discussed here.
[000111] For example, communication can be carried out by means of acoustic transmission, from inside cylinder 100. A transmitter located inside housing 202 can carry out acoustic transmission. The transmitter may comprise, for example, a simple fixed frequency piezoelectric resonator.
[000112] A complementary receiver is also required and this component can be located away from the 200, 300, 400, 500 molecular weight meter, and can comprise hardware, such as, for example, a phase-locked circuit tone detector integrated with a microphone.
[000113] Detector assembly 204 will now be described in more detail with reference to Figures 6 and 7. The quartz crystal oscillator 210 comprises a flat section of cut quartz. Quartz shows piezoelectric behavior, that is, the application of a tension along the crystal causes the crystal to change its shape, generating a mechanical force. On the other hand, a mechanical force applied to the crystal produces an electrical charge.
[000114] Two parallel surfaces of the 210 quartz crystal oscillator are metallized in order to provide electrical connections through the raw crystal. When a voltage is applied through the crystal through the metal contacts, the crystal changes shape. By applying an alternating voltage to the crystal, the crystal can be made to oscillate.
[000115] The size and physical thickness of the quartz crystal determines the characteristic or resonant frequency of the quartz crystal. In effect, the characteristic or resonant frequency of crystal 210 is inversely proportional to the physical thickness between the two metallized surfaces. Quartz crystal oscillators are well known in the art and, therefore, the structure of the quartz crystal oscillator 210 will not be described in more detail here.
[000116] In addition, the frequency of resonant vibration of a quartz crystal will vary, depending on the environment, in which the crystal is located. In a vacuum, the crystal has a specific frequency. However, this frequency will change in different environments. For example, in a fluid, the vibration of the crystal will be attenuated by the surrounding molecules, which will affect the resonant frequency and the energy required to oscillate the crystal in a given amplitude.
[000117] In addition, the deposition of adjacent materials on the crystal will affect the mass of the vibrating crystal, changing the resonant frequency. Such adsorption or deposition of material forms the basis for the normally used selective gas analyzers, in which an absorbent layer is formed on the crystal and increases in mass when gas is absorbed.
[000118] However, in the present case, no coating is applied to the 210 quartz crystal oscillator. Indeed, the adsorption or deposition of material on the 210 quartz crystal oscillator is undesirable in the present process, since the accuracy measurement may be affected.
[000119] As shown in Figure 6, the quartz crystal oscillator 210 of the present embodiment is in the form of a tuning fork, and comprises a pair of teeth 210a approximately 5 mm in length, arranged to oscillate at a resonant frequency of 32.768 kHz. Teeth 210a are formed in the flat section of quartz. The tines 210a of the tuning fork normally oscillate in their fundamental mode, in which they move synchronously close and far apart at the resonant frequency.
[000120] Fused (or non-crystalline) quartz has a very low expansion coefficient as a function of temperature and a low elasticity coefficient. This reduces the dependence of the fundamental frequency on the temperature and, as will be shown, the effects of the temperature are minimal.
[000121] In addition, it is desirable to use quartz, which is cut in AT or SC. In other words, the flat section of quartz is cut at specific angles, so that the temperature coefficient of the oscillation frequency can be arranged to be parabolic, with a peak width close to the ambient temperature. Thus, the crystal oscillator can be arranged in such a way that the inclination at the top of the peak is precisely zero.
[000122] These quartz crystals are commonly available at a relatively low cost. In contrast to most quartz crystal oscillators, which are used in a vacuum, in the present embodiment, the quartz crystal oscillator 210 is exposed to gas under pressure in housing 202.
[000123] The drive circuit 212 to drive the quartz crystal oscillator 210 is shown in Figure 6. The drive circuit 212 must meet a series of specific criteria. First, the quartz crystal oscillator 210 of the present invention can be exposed to a range of gas pressures; potentially, pressures can range from atmospheric pressure (when gas cylinder 100 is empty) to about 900 bar g, if the gas cylinder contains a pressurized gas, such as hydrogen. Thus, the 210 quartz crystal oscillator is required to operate (and restart after a period of non-use) under a wide range of pressures.
[000124] Therefore, the quality factor (Q) of the 210 quartz crystal oscillator will vary considerably during use. The Q factor is a dimensionless parameter related to the attenuation rate of an oscillator or resonator. Equally, it can characterize a resonator's bandwidth relative to its central frequency.
[000125] In general, the higher the Q factor of an oscillator, the lower the rate of energy loss in relation to the stored energy of the oscillator. In other words, the oscillations of an oscillator with a high Q factor are reduced in amplitude more slowly, in the absence of an external force. Sinusoidally activated resonators with higher Q factors resonate with greater amplitudes at the resonant frequency, but have a lower frequency bandwidth around that frequency, to which they resonate.
[000126] The drive circuit 212 must be capable of driving the quartz crystal oscillator 210, despite the variable Q factor. As the pressure in the gas cylinder 100 increases, the oscillator of the quartz crystal oscillator 210 will become more and more attenuated, and the Q factor will drop. The falling Q factor requires a greater gain to be provided by an amplifier in the drive circuit 212. However, if a very high amplification is supplied to the drive circuit 212, the response from the quartz crystal oscillator 210 can make it is difficult to distinguish. In this case, the drive circuit 212 can simply oscillate with an unrelated frequency, or the frequency in a non-fundamental way of the quartz crystal oscillator 210.
[000127] As an additional limitation, the drive circuit 212 must be of low power, to operate with small low power batteries for a long time, with or without supplementary power, such as photovoltaic cells.
[000128] The drive circuit 212 will now be described with reference to Figure 6. In order to drive the quartz crystal oscillator 210, the drive circuit 212 essentially receives a voltage signal from the quartz crystal oscillator 210, amplifies it, and feeds that signal back to the quartz crystal oscillator 210. The fundamental resonant frequency of the quartz crystal oscillator 210 is, in essence, a function of the rate of expansion and contraction of the quartz. This is determined, in general, by the cut and size of the crystal.
[000129] However, external factors also affect the resonant frequency. When the energy of the generated output frequencies coincides with the losses in the circuit, an oscillation can be sustained. The drive circuit 212 is arranged to detect and maintain that oscillation frequency. The frequency can then be measured by processor 230, used to calculate the appropriate gas property required by the user and, if necessary, output to an appropriate display medium (as will be described later).
[000130] Drive circuit 212 is powered by a 6 V 216 battery. Battery 216, in this embodiment, comprises a lithium ion battery. However, alternative energy sources will be readily apparent to a person skilled in the art; for example, other types of batteries, rechargeable and non-rechargeable, and an array of solar cells.
[000131] Drive circuit 212 still comprises a common emitter amplifier with Darlington pair 218. A Darlington pair comprises a composite structure consisting of two bipolar NPN transistors configured in such a way that the current amplified by a first transistor is further amplified more by the second transistor. This configuration allows a higher current gain to be obtained, when compared to each transistor obtained separately. Alternatively, bipolar PNP transistors can be used.
[000132] The Darlington pair 218 is arranged in a feedback configuration by a common single-transistor (Ti) 220 emitter amplifier. An NPN bipolar junction transistor is shown in Figure 4. However, the expert must be aware of alternative transistor arrangements, which can be used; for example, a bipolar junction PNP transistor or Metal Oxide Semiconductor Field Effect Transistors (MOSFETs).
[000133] As a variant, automatic gain control (not shown) can be implemented in the feedback circuit between the Darlington pair 218 and the common emitter amplifier 220. This can take the form of a potentiometer, variable resistor, or other suitable component located in place of, for example, the rightmost 22 k resistor shown in Figure 6.
[000134] Automatic gain control allows compensation for changes in the Q factor with pressure, and changes in the supply voltage (for example, in low battery conditions). Automatic gain control can be particularly applicable for low pressure applications.
[000135] The drive circuit 212 comprises another transistor T2 following an NPN emitter, which acts as a non-inverting amplifier 222. The non-inverting amplifier 222 is arranged to function as a buffer between the circuit and the external environment. However, this feature is optional and may not be mandatory; for example, a FET can be directly connected to drive circuit 212.
[000136] A capacitor 224 is located in series with the quartz crystal oscillator 210. Capacitor 224, in this example, has a value of 100 pF, and activates the drive circuit 212 to drive the quartz crystal oscillator 210 in situations where the crystal has become contaminated, for example, by salts or other deposited materials.
[000137] An alternate drive circuit 260 will now be described with reference to Figure 7. The drive circuit shown in Figure 7 is configured similarly to a Pierce oscillator. Pierce oscillators are known from digital IC clock oscillators. In essence, the drive circuit 260 comprises a single digital converter (in the form of a transistor) T, three resistors Ri, R2 and Rs, two capacitors Ci, C2, and the quartz crystal oscillator 210.
[000138] In this arrangement, the 210 quartz crystal oscillator functions as a highly selective filter element. Resistor Ri acts as a load resistor for transistor T. Resistor R2 acts as a feedback resistor, polarizing the inverter T in its linear region of operation. This effectively allows the T inverter to function as a high gain inversion amplifier. Another resistance Rs is used between the output of the T converter and the quartz crystal oscillator 210, to limit the gain and to attenuate unwanted oscillations in the circuit.
[000139] The 210 quartz crystal oscillator, in combination with Ci and C2, forms a Pi bandpass filter. This allows for a 180 degree phase shift and voltage gain from the output to the input at approximately the resonant frequency of the quartz crystal oscillator. The drive circuit 260 described above is safe and inexpensive to manufacture, since it comprises a relatively small number of components.
[000140] As discussed above, the detector assembly 204 can include a processor 230, which receives inputs from the quartz crystal oscillator 210 and the drive circuit 212. Processor 230 may comprise a suitable arrangement, such as an ASIC or FPGA.
[000141] Processor 230 is programmed to calculate and, if necessary, present and report a determination of the molecular weight of the gas (or average molecular weight of a homogeneous mixture of gases). A schematic of the main inputs and outputs of processor 230 is shown in Figure 8.
[000142] When used with the quartz crystal oscillator 210, the processor 230 can be configured to measure the frequency / or period of the signal from the drive circuit 212. This can be achieved, for example, by counting oscillations at the over a fixed time, and converting that frequency to a density value, using an algorithm or a look-up table. This value is transferred to processor 230.
[000143] Processor 230 also receives temperature T measured from temperature sensor 214. In addition, processor 230 receives a pressure value from a pressure sensor 302 (if present), or from a fixed pressure value. This value can be adjusted automatically, for example, in situations where the molecular weight meter 400, 500 must be used only at atmospheric pressure, or it must be used when outputting a fixed pressure regulator, as is the case with the molecular weight 200. In this situation, the fixed pressure value is inserted into processor 230. Alternatively, the fixed pressure value can be entered manually by a user.
[000144] Processor 230 is prepared to perform, based on the inputs provided, a calculation to determine the molecular weight of the gas, in which the quartz crystal oscillator 210 is immersed.
[000145] Once the molecular weight has been determined, this data can be stored in a local memory, can be shown on a display screen, or can be transmitted to a remote station.
[000146] Processor 230 can optionally be designed so that mass production is identical across the 200 molecular weight meter, with different characteristics in the software and hardware enabled for different gases.
[000147] In addition, processor 230 can also be configured to minimize power consumption by implementing standby or "sleep" modes, which can cover processor 230 and additional components, such as drive circuit 212 and the 210 quartz crystal oscillator.
[000148] Various schemes can be implemented; for example, processor 230 may be at rest for 10 seconds every 11 seconds. In addition, the processor 230 can control the quartz crystal oscillator 210 and the drive circuit 212, in such a way that these components are put on hold by it most of the time, with only the most energy-poor components being energized by U second every 30 seconds.
[000149] The theory and operation of detector assembly 204 will now be described with reference to Figures 9 to 13.
[000150] The quartz crystal oscillator 210 has a resonant frequency, which is dependent on the density of the fluid, in which it is found. The exposure of a flat crystal oscillator of the type oscillating tuning fork to a gas leads to a displacement and attenuation of the resonant frequency of the crystal (when compared to the resonant frequency of the crystal in a vacuum). There are a number of reasons for this. Although there is no gas attenuation effect on the crystal oscillations, the gas adjacent to the vibrating teeth 210a of the tuning fork type 210 oscillator increases the effective mass of the oscillator. This leads to a reduction in the resonant frequency of the quartz crystal oscillator, according to the movement of a fixed, unilateral elastic beam:
Where
is the relative change in the resonant angular frequency, p is the density of the gas, t is the thickness of the quartz oscillator, pq is the density of the quartz oscillator, and w is the width of the tuning fork; ci and C2 are geometrically dependent constants and δ is the thickness of the gas's surface layer, as defined by:
Where η is the viscosity dependent on the gas temperature.
[000151] The two parts of equation 1) concern the a) mass of gas additive on the teeth of the 210 quartz crystal oscillator and b) shear forces that arise in the outermost layer of the teeth during oscillation.
[000152] The equation can thus be rewritten in terms of frequency and simplified to:
Where
, C is a displacement constant and was the natural resonant frequency of the crystal in a vacuum.
[000153] It was discovered by the inventors, that a good approximation can be adequately obtained by the approximation:

[000154] Therefore, for a good approximation, the change in frequency is proportional to the change in gas density, to which the quartz crystal oscillator is exposed. Figure 9 shows, for a series of different gases / gas mixtures, that the resonant frequency of the 210 quartz crystal oscillator varies linearly as a function of density.
[000155] In general, the sensitivity of the 210 quartz crystal oscillator is that a change in frequency of 5% is seen, for example, with oxygen gas (having the atomic mass number 32) at 250 bar, when compared to atmospheric pressure. Such gas pressures and densities are typical of cylinders used for storing permanent gases, which are typically between 137 and 450 bar g for most gases, and up to 700 bar or 900 g for helium and hydrogen.
[000156] The 210 quartz crystal oscillator is particularly suitable for use as a density sensor as part of a molecular weight meter for commercially supplied gases. In order to correctly detect the density of a gas, it is necessary that the gas be free of dust and liquid droplets, which is guaranteed in gases supplied commercially, but not with air, or in most pressure control situations.
[000157] Since the density value is obtained from the quartz crystal oscillator 210, the molecular weight of the gas can be determined from:
where P is the gas pressure, V is the gas volume, n is the number of moles of gas, R is the gas constant, and T is the temperature. Then, to eliminate V:
where MW is the molecular weight of the gas and M is the mass of the gas. Thus, replacing V in equation 5) results in:
where α is a constant equal to RT, where R is the gas constant, and T is the absolute temperature in degrees Kelvin. Consequently, for a known pressure, density and temperature of a gas, the molecular weight of the gas (or average molecular weight, in the case of a mixture of gases) can be determined. The above derivations assume that the gas is close to an ideal gas.
[000158] Based on equation 8) above, if the pressure is known (for example, when the pressure is atmospheric, or at the outlet of a fixed pressure regulator), then only the temperature and density of the gas are necessary to provide an accurate determination of the molecular weight. At the same time, if the pressure and temperature are known to a reasonable degree, the molecular weight of the gas is effectively proportional to the density or, in other words, the resonant frequency of the quartz crystal oscillator, multiplied by a predetermined factor.
[000159] Consequently, the molecular weight of the gas (or average of a mixture) can be determined from the pressure gradient as a function of density, in which, rearranging equation 8, it provides:

[000160] Figures 10 and 11 illustrate experimental molecular weight measurement data. Both graphs show the density (kg / mJ) on the Y axis as a function of pressure (in bar g) on the X axis for the same four gases. The two graphs are identical, with the exception that Figure 10 illustrates pressures up to 300 bar g, while Figure 11 shows only pressures up to 100 bar g.
[000161] The four gases used are Ferromax 15 (a mixture of argon: carbon dioxide: oxygen), helium, carbon dioxide and oxygen, as shown in Figure 9. The gradient of the line is proportional to the molecular weight (assuming that RT constant for all three). Therefore, the quartz crystal oscillator 210 can easily determine the molecular weight of the gas or mixture of gases.
[000162] Furthermore, the high precision of the 210 quartz crystal oscillator allows measurement with very high precision, with a resolution of parts per million. Together with the linear response of the 202 quartz density sensor to high densities and pressures, the high precision allows the molecular weight of very light gases, such as H2 and He, to be accurately measured.
[000163] A useful application of this technology is in the purge detection. Figures 12 and 13 illustrate experimental data for gas purge detection. Such information is vital in situations, such as automatic orbital welding of pipelines.
[000164] Figure 12 shows a graph of frequencies (Hz) on the Y axis as a function of time (in seconds) on the X axis, for an argon flow of 5 liters / minute in a nitrogen environment, followed by refilling with nitrogen. Clearly, the radical change in frequency is easily measured with high precision.
[000165] Figure 13 shows the same data, except that, in this case, the Y axis was calibrated to read molecular weight (in units of mass).
[000166] These Figures clearly illustrate that, for many normal uses, the molecular weight of the gas can be easily determined using a quartz crystal oscillator. In addition, the change in molecular weight that occurs when one gas is purged with another is clearly defined and identifiable. Therefore, the change in molecular weight during a gas purge can be calculated with sufficient precision and time resolution, using the quartz crystal oscillator 210 and the drive circuit 204.
[000167] A method, according to an embodiment of the present invention, will now be described with reference to Figure 14. The method described below is applicable to each of the first to fourth embodiments described above. Step 550: initialize measurement
[000168] In step 550, the measurement of the molecular weight of the gas inside the housing 202 is initialized. This can be activated, for example, by a user by pressing a button outside the housing 202. Alternatively, the measurement can be initiated via a remote connection, for example, a signal transmitted over a wireless network and received by the molecular weight meter 200, 300, 400, 500 through an antenna.
[000169] As another alternative, or in addition, the molecular weight meter 200, 300, 400, 500 can be configured to start up remotely, or with a timer. The method proceeds to step 552. Step 552: activate the quartz crystal oscillator
[000170] Once started, the drive circuit 212 is used to drive the quartz crystal oscillator 210. During start-up, the drive circuit 212 applies a random noise AC voltage across the crystal 210. At least a portion of the said random voltage will be at an appropriate frequency, to cause the crystal 210 to oscillate. The 210 crystal will then begin to oscillate in sync with this signal.
[000171] As will be noticed, the quartz crystal oscillator 210 is, in essence, a detector and autonomous trigger, since the resonant frequency of the crystal itself is being measured.
[000172] Through the piezoelectric effect, the movement of the quartz crystal oscillator 210 will then generate a voltage in the resonant frequency range of the quartz crystal oscillator 210. The drive circuit 212 then amplifies the generated signal by the quartz crystal oscillator 210, in such a way that the signals generated in the frequency band of the quartz crystal resonator 202 dominate the output of the drive circuit 212. The narrow resonant band of the quartz crystal removes by filtration all unwanted frequencies and the drive circuit 212 then drives the crystal quartz oscillator 210 at the fundamental resonant frequency f. Once the quartz crystal oscillator 210 has stabilized at a particular resonant frequency, the method proceeds to step 554. Step 554: Measure the resonant frequency of the quartz crystal oscillator
[000173] The resonant frequency f is dependent on the environmental conditions inside the housing 202. In the present embodiment, the change in the resonant frequency Δfé, for a good approximation, proportional in magnitude to the change in the gas density inside 206 of the housing 202 and will decrease with increasing density.
[000174] In order to make a measurement, the frequency of the 210 quartz crystal oscillator is measured over a period of approximately 1 s. This is to allow the reading to stabilize, and for sufficient swings to be counted, in order to determine an accurate measurement. Frequency measurement is performed on processor 230. Processor 230 can also record the time, Ti, when the measurement was started.
[000175] Once the frequency has been measured, the method proceeds to step 556. Step 556: measure gas temperature
[000176] In step 556, temperature sensor 214 measures the temperature of the gas inside housing 202. This measurement is carried out in order to improve the accuracy of the molecular weight calculation, from the frequency change measured in step 554.
[000177] The temperature measurement need not be particularly accurate. For example, if the temperature sensor 214 is accurate to 0.5 ° C, then this corresponds to an error of only about one part in six hundred (assuming normal atmospheric temperatures) over the absolute temperature value required for calculating the molecular weight in later stages.
[000178] Alternatively, this step may simply involve a fixed temperature value to be entered into the 230 processor. This can occur, for example, in situations where a known temperature environment is used. In this case, the temperature sensor 214 is not necessary. Step 558: determine the gas pressure
[000179] Since the frequency of the quartz crystal oscillator 210 was measured satisfactorily in step 554 and the temperature measured in step 556, processor 230 then determines the gas pressure inside 206 of housing 202.
[000180] This can be done with a pressure sensor input value 302 (if provided), which provides an electrical signal proportional to the pressure measured in housing 202. This applies to the second and fourth embodiments.
[000181] Alternatively, the pressure value can be entered into processor 230, manually or automatically, when the pressure is known to a reasonable degree. This can correspond to the output of a fixed pressure regulator (as in the first embodiment), or it can correspond to atmospheric pressure (as in the third embodiment). Step 560: determine the molecular weight of the gas
[000182] This is done using equation 8) above, where the density p, pressure P and temperature T of the gas are known. Thus, knowing the resonant frequency, measured in step 554, the known temperature T of the gas in housing 202, measured in step 556, and the known pressure of the gas, as determined in step 558, an exact measurement of the molecular weight (or molecular weight medium for a homogeneous mixture of gases) can be made. The method then proceeds to step 562. Step 562: communicate and store results
[000183] The molecular weight of the gas can be presented in several ways. For example, a display (not shown) connected to housing 202 or regulator 150, 250 can display the molecular weight (or average molecular weight) of the gas. Alternatively, the pressure measurement can be remotely communicated to a base station, or to a meter located in an adjacent accessory, as will be described later.
[000184] Since the molecular weight meter 200, 300, 400, 500 for future recovery. As yet another alternative, the gas pressure at time Ti can be stored in a local memory, for said processor 230 to generate a time stamp.
[000185] The method then proceeds to step 564. Step 564: turn off detector assembly
[000186] It is not necessary to keep the molecular weight meter 200, 300, 400, 500 operational at all times. On the contrary, it is beneficial to reduce energy consumption by turning off the molecular weight meter 200, 300, 400, 500, when not in use. This extends the life of the 216 battery.
[000187] The configuration of the drive circuit 212 allows the quartz crystal oscillator 210 to be restarted, regardless of the pressure in the housing 202. Therefore, the molecular weight meter 200, 300, 400, 500 can be turned off, when necessary, in order to save the battery.
[000188] Another application of the molecular weight meter, according to the present invention, consists of a feedback type gas mixer. In such an arrangement, two different gases are needed to be mixed in precise concentrations and proportions. This may be necessary in situations such as, for example, welding applications, where a mixture of argon and carbon dioxide is required, the percentage of carbon dioxide being well defined. In addition, for medical applications, the relative percentage of a particular type of gas may be required to be known to a high degree of accuracy.
[000189] A fifth embodiment of the present invention is shown in Figure 15. Figure 15 shows a gas mixer 600 and a molecular weight meter 650, according to a fifth embodiment of the present invention.
[000190] The gas mixer 600 comprises a first gas source 602 and a second gas source 604. In this embodiment, the gas sources 602, 604 comprise gas cylinders, which are arranged to store permanent gases under high pressure . Each cylinder comprises a valve (not shown), which may be similar to the valve 104 shown in the first embodiment.
[000191] The gases contained inside each gas cylinder are different and are chosen according to the required use. For example, in welding applications, a mixture of argon and carbon dioxide is used. Alternatively, for medical applications, a mixture of oxygen and nitrogen may be required.
[000192] The first and second gas sources 602, 604 are connected, respectively, to the first and second supply lines 606, 608. Check valves 610, 612 are located, respectively, in the first and second supply lines downstream of the respective first and second gas sources 602, 604, to prevent the flow of gases back to the gas sources 602, 604.
[000193] In addition, a main valve 614 is located on the first supply line 606 downstream of the check valve 610. The main valve 614 is operated manually and can take any suitable shape. For example, main valve 614 can take the form of a simple on / off valve, or it can comprise an adjustable flow valve, VIPR or regulator. Alternatively, main valve 614 can be controlled electronically by a remote user from gas mixer 600. The total flow of the gas mixture (described later) is defined by main valve 614.
[000194] A solenoid valve 616 is located on the second supply line 608 downstream of the check valve 612. The solenoid valve 616 comprises an armature (not shown), which is mobile in response to an electric current through a set of coils (not shown) located in the body of the solenoid valve 616. The armature is movable to open or close the solenoid valve 616, to allow gas to flow through the solenoid valve 616 to the components downstream of the same.
[000195] The 616 solenoid valve can be in the normally open state. In other words, in the absence of an electric current through the solenoid valve 616, the armature is in a retracted position, such that the solenoid valve 616 is opened, namely, the gas from the second gas source 604 is able to flow through from it to the downstream components of the solenoid valve 616. If a current is applied to the solenoid valve 616, the armature will retract, and the solenoid valve 616 will be closed, preventing gas from flowing through it. In this embodiment, the solenoid valve 616 is continuously variable in a linear direction.
[000196] An expert should be readily aware of the different types of solenoid valve, which can be used with the present invention. For example, the armature can act directly as a selectively operable flow restriction. Alternatively, the armature can act directly on a diaphragm. As another alternative, the armature can control the flow through a narrow duct, in communication with the supply line 608 downstream of the solenoid valve 616, in order to regulate the movement of a diaphragm. Such an arrangement is known as a pilot diaphragm valve. The solenoid valve 616 is controlled by the molecular weight meter 650, as will be described later.
[000197] The first and second feed lines 606, 608 are both connected to a mixing unit 618. The mixing unit 618 can be operated to combine the two flows of the first and second feed lines, 606, 608 and to pass the flow combined for a third feed line 620. The mixing unit 618 acts merely to combine the two flows and does not change the gas or pressure ratio in each flow.
[000198] A fixed pressure regulator 622 is located on the third supply line 620 downstream of mixing unit 618. Pressure regulator 622 is substantially similar to the fixed pressure regulator 150 described with reference to the first embodiment and therefore it will not be described in detail here. The fixed pressure regulator 622 is arranged to regulate the pressure of the gas received from the mixing unit 618 and to supply gas to portions of the third supply line 620 downstream of the fixed pressure regulator 622, at a constant pressure. This pressure can be, for example, 5 bar.
[000199] The fifth embodiment comprises a molecular weight meter 650. The components of the molecular weight meter 650 are substantially similar to those of the molecular weight meter 200 of the first embodiment and therefore will not be described in detail here. However, the molecular weight meter 650 still comprises an electronic solenoid unit 652 connected to the solenoid valve 616 and the detector assembly 204 of the molecular weight meter 650.
[000200] The solenoid unit 652 is arranged to receive a signal from the detector assembly 204, and to control the solenoid valve 616 in response to that signal. Therefore, the molecular weight meter 650 is operable to control the flow of gas through the solenoid valve 616. In other words, the molecular weight meter 650 and the solenoid valve 616 form a feedback circuit, which allows for pressure regulation accurate and remote gas flow along the second feed line 608 to mixer 618. Therefore, the proportion of the mixed gases in mixer unit 618 can be precisely controlled, as will be described later.
[000201] The solenoid unit 652 can comprise any drive circuit suitable for controlling the solenoid valve 616. A suitable circuit can be an operational amplifier arrangement having an input from the detector assembly 204 to the negative terminal of the operational amplifier. Therefore, a variable resistance can be connected to the positive terminal. The variable resistance can be arranged to provide a constant reference level and act as a comparator. The reference level can be varied automatically or manually.
[000202] An entry from detector assembly 204 to solenoid unit 652 will cause solenoid valve 616 to function. For example, if the input signal from detector assembly 204 (or, alternatively, from processor 230) exceeds one At a certain threshold level, solenoid unit 652 can energize solenoid valve 616. Solenoid valve 616 can be controlled digitally (i.e., on or off), where a DC voltage is varied between a minimum and maximum value. Alternatively, the DC voltage from the solenoid unit 652 can be continuously variable to fine-tune the flow restrictor through the 616 solenoid valve.
[000203] Additionally or alternatively, solenoid unit 652 can control solenoid valve 616, via a DC outlet, which comprises an AC component. Since the armature extension of the 616 solenoid valve is approximately proportional to the applied current, this causes the armature of the 616 solenoid valve to oscillate. Such oscillations mitigate the static friction of the armature, that is, they help prevent the armature from getting stuck or jammed.
[000204] Alternatively, other control systems, such as FETs, processors or ASICs, can be used appropriately to control the operation of the 616 solenoid valve. In addition, the 616 solenoid valve can operate in any of the digital modes ( that is, on / off) or analog (that is, continuously variable), to allow the exact movement of the armature or similar.
[000205] In Figure 15, the main components of the molecular weight meter 650 are presented separately from the solenoid valve 616. In such a situation, the solenoid valve 616 can be controlled remotely by wireless communication means between the detector assembly 204 and the unit of solenoid 652.
[000206] Although the above embodiment has been described with reference to the molecular weight meter 650 and the fixed pressure regulator 622, other variations can be used. For example, the fixed pressure regulator 622 can be omitted or replaced with a variable pressure regulator, such as regulator 250 shown in Figure 3. In this alternative, the molecular weight meter 650 will require a pressure sensor, such as the pressure sensor 302 of the molecular weight meter 300 of the second embodiment.
[000207] Alternatively, the fixed pressure regulator 622 can be omitted and the molecular weight meter 650 can have a conduit for the atmosphere, as established in the molecular weight meter 300 of the third embodiment. In this situation, a pressure gauge is not necessary, since the pressure inside housing 202 of the molecular weight meter 650 will always be atmospheric pressure.
[000208] The operation of the gas mixer 600 will now be described. As discussed earlier, the 650 molecular weight meter is capable of determining the molecular weight of a gas, or the average molecular weight of a gas. When two gases are mixed in different proportions, the average molecular weight of the gas mixture varies, according to the relative proportion of each of the gases. Therefore, by measuring the average molecular weight of the mixture, and knowing the molecular weights of each of the individual gases, the proportion of each of the gases in the mixture can be determined.
[000209] The main flow rate of the gas from the first gas source 602 is defined by the main valve 614, which, as described above, is operable by a user. Once this has been defined, the molecular weight meter 650 is able to control the solenoid valve 616 to dispense the correct amount of gas from the second gas source 604 in order to achieve a desired proportional mixture of gases. This is done through the solenoid unit 652.
[000210] Therefore, if the gas proportion of the second gas source 604 is too high, the molecular weight meter 650, through solenoid unit 652, will close or partially close solenoid valve 616, to restrict the flow of gas from the second gas source 604. In parallel, if the gas proportion of the second gas source 604 is too low, the molecular weight meter 650, through solenoid unit 652, will open or partially open solenoid valve 616, to increasing the gas flow from the second gas source 604.
[000211] The above embodiment provides a low-cost, reliable and robust method for providing a mixture of gases, in which the proportion of each of the gases in the mixture can be determined and maintained accurately and reliably.
[000212] The variations of the above embodiments will be apparent to one skilled in the art. The exact configuration of the hardware and software components may be different and still fall within the scope of the present invention. An expert should be promptly aware of alternative configurations, which can be used.
[000213] For example, the embodiments described above used a quartz crystal oscillator, having a fundamental frequency of 32.768 kHz. However, crystals can be used, which operate at alternative frequencies. For example, quartz crystal oscillators, which operate at 60 kHz and 100 kHz, can be used with the embodiments described above. A graph, which shows the frequency change with density for different crystals, is shown in Figure 16. As another example, a crystal oscillator, which operates at a frequency of 1.8 MHz, can be used.
[000214] An operation with a higher frequency allows the pressure to be monitored more frequently, because a short period of time is necessary to sample a certain number of cycles. In addition, higher frequency crystals allow a shorter duty cycle to be used in a crystal "suspend" mode. By way of explanation, in most cases, the drive circuit and the crystal will spend most of the time switched off, only being switched on for a second or less, when a measurement is needed. This can happen, for example, once a minute. When a higher frequency crystal is used, the pressure can be measured more quickly. Therefore, the time, in which the crystal is operational, can be reduced. This can reduce power consumption and, at the same time, improve battery life.
[000215] In addition, the above embodiments have been described by measuring the absolute frequency of a quartz crystal oscillator. However, in independent electronics incorporated into a regulator associated with the gas cylinder, it may be advantageous to measure the change in the sensor frequency, by comparing that frequency with a reference crystal of the same type, but closed in a vacuum or a package of pressure. The pressure pack can contain gas at a selected density, gas under atmospheric conditions, or it can be opened to the outside atmosphere of the gas cylinder.
[000216] A suitable detector assembly 700 is shown in Figure 17. The detector assembly 700 comprises a first quartz crystal oscillator 702 and a second quartz crystal oscillator 704. The first quartz crystal oscillator 402 is a reference crystal , which is located inside a vacuum-sealed 706 container. The first 702 quartz crystal oscillator is driven by a 708 drive circuit.
[000217] The second quartz crystal oscillator 704 is a crystal similar to crystal 210 described in the previous embodiments. The second quartz crystal oscillator 704 is exposed to the gas environment within housing 202. The second quartz crystal oscillator 704 is driven by a drive circuit 710.
[000218] This comparison can be performed using an electronic mixer circuit 714, which combines the two frequency signals and produces an output with a frequency equal to the difference between the two crystals. This arrangement allows small changes to be neutralized, due, for example, to temperature.
[000219] In addition, the circuits used in the detector assembly 204 can be simplified, because only the frequency of difference should be measured. In addition, this approach is particularly suitable for use with a high frequency (MHz) crystal oscillator, where it can be difficult to directly measure the frequency of the crystal.
[000220] In addition, all the electronics necessary to measure and indicate density, mass, or mass flow, do not need to be mounted on, or inside, the gas cylinder. For example, electronic functions can be divided between units mounted on the cylinder permanently, and units mounted on any of a customer's stations, or temporarily mounted on the outlet of the cylinder, as the position normally used for a flow meter. conventional flow.
[000221] An example of this arrangement is shown with reference to Figure 18. The arrangement comprises a gas cylinder assembly 80, comprising a gas cylinder 800, a regulator 802 and a molecular weight meter 804. The gas cylinder 800, regulator 802 and molecular weight meter 804 are substantially similar to gas cylinder 100, regulator 150 and molecular weight regulator meter 200, 300, 400, 500, substantially as described above with reference to the previous embodiments.
[000222] In this embodiment, the molecular weight meter 804 comprises a quartz crystal oscillator and drive circuit (not shown) similar to the quartz crystal oscillator 210 and drive circuit 212 of the previous embodiments. An 806 antenna is provided for communication via any suitable remote communication protocol; for example, Bluetooth, Infrared (IR) or RFID. Alternatively, wired communication can be used.
[000223] As an additional alternative, acoustic communication methods can be used. The advantage of such methods is that remote communication can be carried out, without the need for an external antenna.
[000224] A connection pipe 808 is connected to the outlet of the gas cylinder 800. The connection pipe is closed by a quick connection 810. The quick connection 810 allows the connection pipe, or the components, to be connected and disconnected with ease and speed of the gas cylinder 800.
[000225] A quick connect unit 850 is provided for connection to gas cylinder 800. An additional quick connect connector 812 is provided for connection to connector 808. In addition, the quick connect unit 850 is equipped with a data unit 852. Data unit 552 comprises a display 554 and an antenna 556 for communication with antenna 804 of gas cylinder assembly 80. Display 554 may comprise, for example, an LCD, LED, or reading to minimize power consumption and maximize screen visibility.
[000226] The data unit 852 can record various parameters measured by the detector assembly 802 of the gas cylinder assembly 80. For example, the data unit 852 can record molecular weight as a function of time. Such a record can be useful, for example, for welding contractors who want to verify that the gas flow was present and correct during long gas welding procedures on critical components, or to provide a company data set on the use of a particular customer.
[000227] In addition, the 850 data unit can be arranged to provide the following functions: provide an audible or visual alarm if the type of gas changes; contain and display data on the type of gas; providing a multimodal operation, for example, a supplier / fill mode and a customer mode; allow data entry; provide data such as a cylinder number, the type of gas, a certificate of analysis, a history of the customer (who had the cylinder during which dates), safety and operational data can be contained in summary form on the cylinder.
[000228] Alternatively, all of the above examples can optionally be processed, stored or obtained, from a system entirely located in (or within) gas cylinder 800 or housing 202, as discussed in terms of meter operation molecular weight 200, 300, 400, 500.
[000229] Although the above embodiments have been described with reference to the use of a quartz crystal oscillator, a person skilled in the art should be readily aware of alternative piezoelectric materials, which can also be used. For example, a non-complete list may include crystal oscillators, comprising: lithium tantalate, lithium niobate, lithium borate, berlinite, gallium arsenide, lithium tetraborate, aluminum phosphate, germanium bismuth oxide, titanate ceramic polycrystalline zirconia, high alumina ceramic, composed of silicon oxide and zinc, or dipotassium tartrate.
[000230] Embodiments of the present invention have been described with particular reference to the illustrated examples. Although specific examples are represented in the drawings and described in detail here, it should be understood, however, that the drawings and detailed description are not intended to limit the invention to the particular form disclosed. It should be understood that variations and modifications can be made to the examples described within the scope of the present invention.

权利要求:
Claims (18)
[0001]
1. METHOD FOR MEASURING THE MOLECULAR WEIGHT OF A GAS, characterized by the fact that it uses a high frequency flat piezoelectric crystal oscillator in contact with the gas, the method comprising: a) use of said piezoelectric crystal oscillator to measure the density of the gas by using a drive circuit (212) configured to obtain a voltage signal from the piezoelectric crystal oscillator (210), to amplify the voltage signal and activate (552) the piezoelectric crystal oscillator with the voltage signal amplified so that the piezoelectric crystal oscillator resonates to a single resonant frequency despite changes in the piezoelectric crystal oscillator's Q-factor; and measuring (554) the said single resonant frequency of said piezoelectric crystal to determine the density (p) of the gas based on the approximation that a change in the resonant frequency (Z t) is linearly proportional to a change in density; and b) determining (556, 558, 560), from the density, determined or predetermined pressure of the gas, and determined or predetermined temperature of the gas, of the molecular weight of the gas.
[0002]
2. METHOD, according to claim 1, characterized by the fact that it still comprises the measurement of gas pressure.
[0003]
3. METHOD, according to claim 2, characterized by the fact that the gas pressure is measured using an electronic pressure sensor.
[0004]
4. METHOD, according to claim 1, characterized in that the predetermined pressure of the gas is the fixed outlet pressure of a gas regulator located upstream of said oscillator.
[0005]
5. METHOD, according to claim 1, characterized by the fact that the predetermined pressure of the gas is the atmospheric pressure.
[0006]
6. METHOD, according to any one of claims 1 to 5, characterized by the fact that it also comprises the measurement of the gas temperature with a temperature sensor.
[0007]
METHOD, according to any one of claims 1 to 6, characterized in that said piezoelectric crystal oscillator comprises at least two flat teeth.
[0008]
METHOD, according to any one of claims 1 to 7, characterized in that said piezoelectric crystal oscillator has a resonant frequency of 32 kHz or more.
[0009]
9. METER TO MEASURE THE MOLECULAR WEIGHT OF A GAS, characterized by the fact that the meter (200; 300; 400; 500; 600) comprises a housing (202; 502) having an entrance (208; 506) and an interior (206) to receive said gas to be measured, a detector assembly (204) comprising a high frequency flat piezoelectric crystal oscillator (210) located inside said housing, so that, in use, the piezoelectric crystal oscillator is in contact with said gas, said detector assembly comprising a driver circuit (210) and said detector assembly being arranged: to drive the piezoelectric crystal oscillator using the driver circuit, the driver circuit being configured to obtain a voltage signal from the piezoelectric crystal oscillator, to amplify the voltage signal and trigger the piezoelectric crystal oscillator with the amplified voltage signal so that the piezoelectric crystal oscillator resonates on a single reson frequency in spite of changes in the Q-factor of the piezoelectric crystal oscillator; to measure said single resonant frequency of said piezoelectric crystal oscillator, to determine the density (p) of the gas based on the approximation that a change in the resonant frequency (Δf) is linearly proportional to a change in density; and to determine, from the density, determined or predetermined pressure of the gas, and determined or predetermined temperature of the gas, the molecular weight of the gas.
[0010]
10. METER, according to claim 9, characterized in that the detector assembly comprises a drive circuit, comprising a Darlington pair arranged in a feedback configuration from a common emitter amplifier.
[0011]
11. METER, according to claim 9 or 10, characterized by the fact that it also comprises a pressure sensor to measure the gas pressure.
[0012]
12. METER, according to claim 11, characterized by the fact that said pressure sensor is an electronic pressure sensor.
[0013]
13. METER, according to claim 9 or 10, characterized by the fact that it is located downstream of the fixed pressure regulator, in which the gas pressure has a predetermined value, based on the output of said fixed pressure regulator.
[0014]
14. METER, according to claim 9 or 10, characterized by the fact that it also comprises a restrictive orifice upstream of said inlet and an outlet to the atmosphere downstream of said inlet, wherein said predetermined gas pressure is the pressure atmospheric.
[0015]
15. METER, according to any one of claims 9 to 14, characterized in that the detector assembly also comprises a temperature sensor.
[0016]
16. METER, according to any one of claims 9 to 15, characterized in that said piezoelectric crystal oscillator comprises at least two flat teeth.
[0017]
17. METER according to any one of claims 9 to 16, characterized in that said piezoelectric crystal oscillator has a resonant frequency of 32 kHz or more.
[0018]
18. COMPUTER-READABLE MEDIA, characterized by the fact that it executes a method according to claims 1 to 8.

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法律状态:
2018-12-18| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2019-08-27| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-01-28| B06A| Notification to applicant to reply to the report for non-patentability or inadequacy of the application [chapter 6.1 patent gazette]|

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2020-06-02| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2020-10-20| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 28/11/2011, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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EP10192972.7|2010-11-29|

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EP10192972.7A|EP2458377B1|2010-11-29|2010-11-29|Method of, and apparatus for, measuring the molecular weight of a gas|

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PCT/EP2011/071208|WO2012072596A1|2010-11-29|2011-11-28|Method of, and apparatus for, measuring the molecular weight of a gas|

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