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    • 专利摘要:
    METHOD FOR MEASURING THE GAS MASS FLOW THROUGH A HOLE, METER FOR MEASURING THE MASS FLOW OF A GAS, COMPUTER PROGRAM PRODUCT EXECUTABLE BY A PROGRAMMABLE PROCESSING APPLIANCE, AND A MEDIUM OF USABLE USED STORAGE. (200; 350) is used to measure the mass flow of a gas. The meter comprises a conduit (206), through which the gas flows in use. The conduit has a flow restrictor orifice (212), through which, strangled flow occurs in use. The flow restrictor orifice divides the conduit into an upstream part (214), upstream of said orifice, and a downstream part (216), downstream of said orifice. The meter also comprises a detector assembly (204), the detector assembly including a piezoelectric crystal oscillator (218) is in contact with said gas, when the meter is in use. The detector set is arranged: to activate the piezoelectric crystal oscillator, so that the piezoelectric crystal oscillator resonates at a resonant frequency; for measuring said resonant frequency of said piezoelectric crystal oscillator; and to determine, through the resonant frequency, the mass flow through the orifice.
    公开号:BR112013013329B1
    申请号:R112013013329-5
    申请日:2011-11-28
    公开日:2021-01-19
    发明作者:Neil Alexander Downie
    申请人:Air Products And Chemicals, Inc；
    IPC主号:
    专利说明:

    The present invention relates to a method and apparatus for measuring the mass flow of a gas. More particularly, the present invention relates to a method and apparatus for measuring the mass flow of a gas through a flow restrictor orifice, using a piezoelectric oscillator.
    The methods and apparatus described herein can be applied to systems, where fluids of relatively high pressure (for example, about 10 bar or more) are present, such as, for example, the supply of fluids in high pressure cylinders or factories using 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.
    The present invention is particularly applicable to permanent gases. Permanent gases are gases, which cannot be liquefied by pressure separately and, for example, can be supplied in cylinders at pressures up to 450 bar g (where bar g is a measure of pressure above atmospheric pressure). Examples are argon and nitrogen. However, this is not to be taken as limiting, and the term gas can be considered to cover a wider range of gases, for example, a permanent gas and a vapor of a liquefied gas.
    Vapors of liquefied gases are present above the liquid within a cylinder of compressed gas. Gases that liquefy under pressure, as they are compressed to fill 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 true gases, as they are liquidifiable by pressure or temperature around environmental conditions.
    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 electronic manufacturing, using corrosive, toxic or special gases high purity pyrophorics. Pressurized gas containers commonly comprise steel, aluminum or composites, 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 , such as hydrogen and helium.
    In order to distribute gases, effectively and in a controlled manner, from a gas cylinder or other pressure vessel, a valve or regulator is required. Often, the two are combined to form a valve with integrated pressure regulator (VIPR). The regulator is capable of regulating the gas flow, in such a way that the gas is distributed at a constant or variable pressure to the user.
    For many applications, it is desirable to know the gas flow from a gas cylinder. This can be critical for many applications; for example, medical applications. A variety of mass flow meter arrangements are known.
    A class of mass flow meters, which are commonly used in many industrial applications, are mechanical mass flow meters. These meters include mechanical components, which move or rotate to measure mass flow. One of these types is the inertia flow meter (or Coriolis flow meter), which measures the flow of the fluid through the effect of the fluid in molded tubes. Coriolis meters can measure a wide range of flow rates with high accuracy. However, in order to detect the flow, complex systems are necessary, such as actuation, detection, electronic and computational resources.
    Alternate mechanical mass flow meters are diaphragm meters, rotary meters and turbine meters. However, these types of gauges are generally less accurate and involve moving parts, which can be subject to wear and tear. In addition, gauges, such as rotary gauges, are only useful for measuring relatively low flow rates.
    An alternative class of mass flow meters are electronic flow meters. Two main types are thermal gauges and gauges
    ultrasonic. Thermal flow meters measure heat transfer through a heated tube to measure flow. Ultrasonic flow meters measure the speed of sound in the gaseous medium, sometimes averaging the speed of sound through various paths within the tube. However, both types of electronic flow meters generally require significant signal processing hardware and are generally expensive items.
    According to a first aspect of the present invention, a method is provided to measure the mass flow of a gas through an orifice, through which the strangled flow occurs, the method using a piezoelectric oscillator in contact with the gas upstream of the orifice, and comprising: a) activation of the piezoelectric crystal oscillator, so that the piezoelectric crystal oscillator resonates at a resonant frequency; b) measurement of the resonant frequency of the piezoelectric oscillator; and c) determining, from the resonant frequency, the mass flow of gas through said orifice.
    In providing such a method, the mass flow of a gas through a restrictor orifice can be easily determined using a robust and relatively inexpensive piezoelectric crystal oscillator, for example, a quartz crystal oscillator. The piezoelectric crystal oscillator will oscillate at a resonant frequency, which is dependent on the density of the gas, in which the oscillator is immersed. Since, under flow restriction conditions, the gas density upstream of the orifice is proportional to the mass flow through the orifice, a crystal oscillator can be used to measure the mass flow.
    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 (because it has a single resonant frequency, which is dependent on the environment in which the oscillator is located). In addition, a crystal oscillator is robust and, as a result, is not relatively affected by environmental disturbances. In addition, the components, which are necessary to operate such an oscillator, are compact and inexpensive.
    In one embodiment, the pressure upstream of said orifice is at least 0.5 bar higher than the pressure downstream of said orifice.
    In one embodiment, the method further comprises determining the temperature of the gas upstream of the orifice.
    In one arrangement, the gas is distributed from a valve or pressure regulator located upstream of the piezoelectric crystal oscillator.
    In one arrangement, the pressure regulator is electronically controlled in response to the mass flow of gas measured through said orifice.
    In one embodiment, said piezoelectric crystal oscillator comprises a quartz crystal oscillator.
    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.
    In one embodiment, the quartz crystal is cut in AT or SC.
    In a variation, the surface of the quartz crystal is directly exposed to the gas.
    In one embodiment, the detector assembly comprises a drive circuit. In a variant, the detector assembly comprises a drive circuit, which comprises a Darlington pair arranged in a feedback configuration from a common emitter amplifier.
    In one embodiment, the detector assembly comprises a source of energy. In one arrangement, the power supply consists of a lithium battery.
    In one embodiment, the detector assembly comprises a processor.
    In one arrangement, said piezoelectric crystal oscillator comprises at least two flat teeth.
    In one embodiment, said piezoelectric crystal oscillator has a resonant frequency of 32 kHz or more.
    According to a second embodiment of the present invention, a meter is provided to measure the mass flow of a gas, the meter comprising a conduit, through which the gas flows in use, the conduit having a flow restrictor orifice, through which, the flow restrictor orifice in use occurs, dividing the conduit into an upstream part, upstream of said orifice, and a downstream part, downstream of said orifice, the meter still comprising a detector assembly, the detector assembly including a piezoelectric crystal oscillator in said upstream portion, so that said piezoelectric crystal oscillator is in contact with said gas, when the meter is in use, said detector assembly being arranged: to drive the oscillator of piezoelectric crystal, so that the piezoelectric crystal oscillator resonates at a resonant frequency; for measuring said resonant frequency of said piezoelectric crystal oscillator; and to determine, from the resonant frequency, the mass flow through the orifice.
    In providing such an arrangement, the mass flow of a gas through a restrictor orifice can be easily determined using a robust and relatively inexpensive piezoelectric crystal oscillator, for example, a quartz crystal oscillator. The piezoelectric crystal oscillator will oscillate at a resonant frequency, which is dependent on the density of the gas, in which the oscillator is immersed. Since, under flow restriction conditions, the gas density upstream of the flow restrictor orifice is proportional to the mass flow through the orifice, a crystal oscillator can be used to measure the mass flow.
    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 (because it has a single resonant frequency, which is dependent on the environment in which the oscillator is located). In addition, a crystal oscillator is robust and, as a result, is not relatively affected by environmental disturbances. In addition, the components, which are necessary to operate such an oscillator, are compact and inexpensive.
    In one arrangement, the meter further comprises one or more of a drive circuit, a processor and a power source.
    In one embodiment, said piezoelectric oscillator comprises a quartz crystal oscillator.
    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.
    In one embodiment, the quartz crystal is cut in AT or SC.
    In a variation, the surface of the quartz crystal is directly exposed to the gas.
    In one embodiment, the detector assembly comprises a drive circuit. In a variant, the detector assembly comprises a drive circuit, which comprises a Darlington pair arranged in a feedback configuration from a common emitter amplifier.
    In one embodiment, the detector assembly comprises a source of energy. In one arrangement, the power supply consists of a lithium battery.
    In one embodiment, the detector assembly comprises a processor.
    In one arrangement, the drive circuit comprises a Darlington pair arranged in a feedback configuration from a common emitter amplifier.
    In one arrangement, the meter further comprises a temperature sensor arranged to determine the temperature of the gas adjacent to said piezoelectric oscillator.
    In one arrangement, the meter is disposed downstream of a valve or pressure regulator.
    In another arrangement, the meter is arranged to electronically control the valve or pressure regulator, in response to the mass flow measured through the flow restrictor orifice.
    In one arrangement, said piezoelectric crystal oscillator comprises at least two flat teeth.
    In an arrangement, said piezoelectric crystal oscillator has a resonant frequency of 32 kHz or higher.
    According to a third embodiment of the present invention, there is provided a computer program product executable by a programmable processing meter, which comprises one or more segments of software to perform the steps of the first aspect.
    In accordance with a fourth embodiment of the present invention, a computer-usable storage media is provided, having a computer program product, according to the fourth aspect stored therein.
    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 regulating assembly and a measuring assembly, according to a first embodiment of the invention; Figure 3 is a schematic diagram, showing a regulating assembly and a measuring assembly, according to a second embodiment of the invention; Figure 4 is a schematic diagram of a drive circuit for use with any of the first or second embodiments; Figure 5 is a schematic diagram, showing an alternative to the drive circuit for use with any of the first or second embodiments; Figure 6 shows a graph of the frequency of a quartz crystal (kHz) on the Y axis as a function of density (kg / m3) for a number of different gases; Figure 7 shows a graph of the frequency of a quartz crystal (kHz) on the Y axis as a function of the mass flow (in liters / minute) through an orifice; Figure 8 is a flow chart, illustrating a method, according to a described embodiment; Figure 9 shows a graph of the frequency behavior of different types of crystals; Figure 10 is a schematic diagram showing an alternative detector assembly, comprising two quartz crystals; and Figure 11 shows an alternative arrangement, which uses a remote electronic data unit.
    Figure 1 shows a schematic view of a gas cylinder assembly 10, according to an embodiment of the invention. Figure 1 shows a schematic view of a situation, in which the present invention can be used. A gas cylinder 100, regulator 150 and meter set 200 are provided.
    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 10 to remain standing on a flat surface.
    The body of the gas cylinder 102 is formed from steel, aluminum and / or composites, 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 gas cylinder body 102 opposite the base 102a, and comprises a helical thread (not shown) adapted to accommodate the valve 104.
    The gas cylinder 100 defines a pressure vessel, which has an internal volume V. Any suitable fluid can be contained within the gas cylinder 100. However, the present embodiment relates, 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.
    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. The outlet 110 it is adapted and arranged to allow the gas cylinder 100 to be connected to other components in a gas assembly; for example, hoses, tubes 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.
    Valve body 112 can be adjusted axially near or away from valve seat 114 by rotating a lever 116 to selectively open or close outlet 110. In other words, the movement of valve body 112 to near or away from valve seat 112 selectively controls the area of the communication medium between the inside of the gas cylinder body 102 and the outlet 110. This, in turn, controls the flow of gas from inside the gas cylinder gas cylinder set 100 for the outdoor environment.
    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 gas cylinder 100 and regulator 150. Inlet 152 of regulator 150 is arranged to receive 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, which leaves the outlet 110, will be greater than 20 bar and is more likely to be in the range of 100 - 900 bar.
    The outlet 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 conduits or devices (not shown), for which, gas is required.
    A measuring set 200 is located in communication with outlet tube 158, between outlet 154 and coupling 160. Measuring set 200 is located immediately downstream of regulator 150, and is arranged to determine the mass flow of the gas supplied at outlet 160.
    Regulator 150 and measuring set 200, according to a first embodiment of the present invention, are shown in greater detail in Figure 2.
    In this embodiment, regulator 150 comprises a single diaphragm regulator. However, the person skilled in the art should be readily aware of the variations, which can be used with the present invention; for example, a double diaphragm regulator or other device.
    Regulator 150 comprises a valve region 162 in communication with inlet 152 and outlet 154. Valve region 162 comprises a trigger valve 164 located adjacent a valve seat 166. The trigger valve 164 is connected to a diaphragm 168, which is configured to allow the translational movement of the trigger valve 164 towards and away from the valve seat 166, to open and close, respectively, an opening 170 between them. Diaphragm 168 is propelled resiliently by a spring 172 located on an axis 174.
    Regulator 150 can be operated to receive gas from outlet 110 at full cylinder pressure (eg 100 bar), but to deliver gas at a fixed, substantially constant low pressure (eg 5 bar) to the outlet 154. This is achieved by a feedback mechanism, whereby the gas pressure downstream of aperture 170 is operable to act on diaphragm 168 as opposed to the impelling force of spring 172.
    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, trigger 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, the opposing forces of the resistance of spring 172 and the pressure of the gas will result in an equilibrium position of the diaphragm and, therefore, in the supply of a constant pressure of gas in the outlet 154.
    A lever 176 is provided to allow a user to adjust the pushing force of spring 172, thereby moving the position of diaphragm 168 and, as a result, adjusting the balance spacing between trigger valve 164 and valve seat 166 This allows adjustment of the dimensions of the opening 170, through which the flow of high pressure gas can pass through the outlet 110.
    The measuring set 200 includes a body 202 and a detector set 204. The body 202 can comprise any suitable material; for example, steel, aluminum or composites. The body 202 comprises a conduit 206 and a housing 208. The conduit 206 is in communication with the interior of the outlet tube 158, and is arranged to connect thereto. Conduit 206 provides a communication path between output 154 and coupling 160 (and, concomitantly, user devices or applications connected to coupling 160).
    A diaphragm 210 is located inside conduit 206. Diaphragm 210 comprises a wall, which delimits a restrictor orifice 212. Diaphragm 210 forms a flow restriction inside conduit 206. Orifice 212 has a cross-sectional area A, which is small in relation to the cross-sectional area of conduit 406, such that the flow velocity through orifice 212 is in a strangled condition, as will be described later.
    Although diaphragm 210 is shown as a thin-walled diaphragm in Figure 2, this does not have to be so. The diaphragm 210 may have any suitable shape of wall, and may have a tapered profile, or may have a thickness greater than that shown. Alternatively, any suitable flow restriction can be used in place of diaphragm 210. For example, the flow restriction may comprise a portion of a tube of a smaller diameter than the rest of it. The skilled person should be readily aware of alternative flow restrictions, which can be used to provide a flow restrictor orifice 212, through which, the strangulated flow occurs, in use.
    In the present embodiment, conduit 206 has a length of the order of a few centimeters. Diaphragm 210 delimits an orifice 212 having a diameter in the range of 0.1 mm - 4 mm. This is sufficient to provide a restricted flow condition, and to provide a gas flow through orifice 212 between 11 and 40 liters / minute for gases, such as nitrogen or argon. For a gas, which has a lower molecular weight, the orifice diameter 212 can be reduced to achieve a similar flow. Alternatively, for larger flows, orifice 212 can be increased accordingly, as long as the upstream pressure is sufficiently greater than the downstream pressure, to create flow restriction conditions through orifice 212.
    Diaphragm 210 divides the interior of duct 206 into an upstream section 214, upstream from diaphragm 210, and into a downstream section 216, downstream from diaphragm 210. In use, when gas is flowing from outlet 154 of the regulator 150 into the upstream portion 214 of conduit 206, diaphragm 210 will act as a flow restriction, resulting in a pressure difference between upstream portion 214 and downstream 216 of conduit 206. Consequently, upstream portion 214 of conduit 206 is at a first pressure P1, and the downstream portion 216 of the conduit is at a second (and, in use, lower) pressure P2. This will be described in detail later.
    Housing 208 is located adjacent to riser portion 214 of conduit 206, and is arranged to contain at least a portion of detector assembly 204. The interior of housing 208 may be at atmospheric pressure, or may be in communication with the interior of the conduit 206 and, consequently, at the same pressure as the interior of the outlet tube 158. This eliminates the need for pressure communication between the housing 208 and the interior of the conduit 206.
    Alternatively, housing 208 may be provided as an integral part of conduit 206. For example, a portion of conduit 206 may be extended to accommodate detector assembly 204.
    These arrangements are feasible, because the inventors have found that only some 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 batteries have been found to behave particularly well under high pressures found within the upstream portion 214 of conduit 206. Consequently, battery 224 comprises lithium cells. However, suitable alternative energy sources will be readily contemplated by the qualified person.
    The potential location of detector set 204 fully within conduit 206 offers additional flexibility when configuring measurement set 200.
    In particular, the location of relatively fragile electronic components, entirely within the metal or composite material walls of the body 202 without the need for a protrusion, such as housing 208, provides considerable protection against accidental or environmental damage. This is particularly important, for example, in storage areas or depots, where gas cylinders may be located adjacent to other gas cylinders, heavy machinery or rough surfaces.
    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 an integral part of the detector assembly 204.
    The measuring set 200 is arranged to measure the mass flow of the gas, which passes through the orifice 212. This gas is measured by the detector set 204. The detector set 204 comprises a quartz crystal oscillator 218 connected to a drive circuit 220, a temperature sensor 222 and a battery 224.
    In this embodiment, the quartz crystal oscillator 218 and the temperature sensor 222 are located in communication with the interior of the upstream part 214 of the conduit 206, while the remaining components of the detector assembly 204 are located inside the housing 208 In other words, the quartz crystal oscillator 218 is immersed in the gas upstream of the diaphragm 210. A microprocessor 240 can also be supplied, either separately or as an integral part of the drive circuit 220.
    The drive circuit 220 and the quartz crystal oscillator 218 will be described in detail later with reference to Figures 4 and 5. Temperature sensor 222 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.
    In this arrangement, the 218 quartz crystal oscillator is constantly under isostatic pressure within conduit 206 and, consequently, does not experience a pressure gradient. In other words, any mechanical stress arising from the pressure difference between the outside atmosphere and the inside of the body 202 of the measurement set 200 is expressed throughout the body 202.
    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 the same reference numbers, not will be described here again.
    In the embodiment of Figure 3, regulator 300 differs from regulator 150 from the embodiment of Figure 2, in which regulator 300 is arranged to provide automatic control of gas from outlet 154, by means of a solenoid valve 302 The solenoid valve 302 comprises a armature 304, which is movable in response to an electric current through the coils (not shown) of the solenoid valve 302. Armature 304 is movable, to directly open or close the trigger valve 164 and, consequently , opening 170.
    The solenoid valve 302 shown in Figure 3 is in the normally open condition. In other words, in the absence of an electric current through the solenoid valve 302, armature 304 is in an extended position, so that the trigger valve 164 is open, that is, opening 170 is open. If a current is applied to solenoid valve 302, armature 304 will retract and trigger valve 164 will close.
    The skilled person should be readily aware of the alternative variations of the solenoid valve, which can be used with the present invention. For example, armature 304 can act directly on the diaphragm, or it can control the flow through a narrow duct, in communication with outlet 154, in order to regulate the movement of diaphragm 168. Alternatively, the trigger valve can be eliminated , and diaphragm 168 itself may be the valve element that directly controls the flow of gas from inlet 152 to outlet 154.
    The second embodiment comprises a meter set 350. The components of the meter set 350, in common with the meter set 200, are assigned the same reference numbers for clarity.
    The measuring set 350 is substantially similar to the measuring set 200 of the first embodiment. However, measurement set 350 also includes an electronic solenoid unit 352 connected to solenoid valve 302 and detector assembly 204. Solenoid unit 352 is arranged to receive a signal from detector assembly 204 and to control the solenoid valve 302 in response to that signal and therefore control the flow through regulator 300.
    The solenoid unit 352 can comprise any of the appropriate drive circuits for controlling the solenoid valve 302. 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 resistor, designed to provide a constant reference level and act as a comparator, can be attached to the positive terminal.
    An input from detector assembly 204 to solenoid unit 352 will cause solenoid valve 302 to function. For example, if the input signal from detector assembly 204 (or, alternatively, processor 240) exceeds a certain threshold level, the solenoid unit 352 can energize the solenoid valve 302. The solenoid valve 302 can be controlled digitally (ie, on or off), where a DC voltage is varied between a minimum and maximum value. Alternatively, the DC voltage of the solenoid unit 352 can be continuously variable to accurately adjust the position of the trigger valve 164 in an analogous manner.
    Additionally or alternatively, the solenoid unit 352 can control the solenoid valve 302 via a DC output, which comprises an AC component. Since the length of armature 304 of solenoid valve 302 is approximately proportional to the current applied, this causes armature 304 of solenoid valve 302 to oscillate. Such oscillations attenuate the "grip" of the armature 304, that is, they help to prevent armature 304 from becoming stuck or jammed.
    Alternatively, other control arrangements, such as FETs, microprocessors, or ASICs, can be used appropriately to control the operation of the solenoid valve 302. In addition, as discussed, the solenoid valve 302 can operate in digital modes (ie, connected / off) or analog (ie continuously variable), to allow exact movement of the trigger valve 164 or similar.
    The first or second embodiments may additionally comprise a monitor (not shown) to show a user the results of measurements made on the detected gas. Alternatively, the monitor can be located away from the meter sets 200, 350, and the relevant data can be remotely communicated.
    In order for the 218 quartz crystal oscillator to provide an accurate measurement, the 218 quartz crystal oscillator must be kept free of dirt, moisture, and other contamination. Although this is not a problem for packaged, commercially supplied gases (which are extremely clean), meter set 350 can be used in situations where environmental contamination can be a significant problem.
    Consequently, the measuring set 200, 350 is provided with a filter 354 located between the quartz crystal oscillator 218 and the main gas flow. The filter 354 can be of any suitable pore size. Pore sizes are in the range of 5 - 10 μm, being particularly suitable for this application. Filter 354 (or a similar filter) can be applied to the first embodiment described above.
    Alternatively, the filter 354 can be omitted if the quartz crystal oscillator 218 is located behind an opening, which is small enough to prevent the penetration of dirt or other contaminants. For example, an opening size of 0.25 millimeter would be suitable for use without a filter, as long as the pressure upstream of the gas can be measured in this way.
    For example, the first or second embodiments may 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 the body 202 and connected to the detector assembly 204 by means of a wire connector or equivalent.
    The antenna itself can be adapted and arranged to use any suitable communication protocol; for example, a non-complete list may be RFID, Bluetooth, Infra-red (IR) 802.11 wireless, frequency modulation (FM) transmission or a cellular network.
    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.
    For example, communication can be carried out by means of acoustic transmission from inside housing 208. A transmitter located within housing 208 can perform acoustic transmission. The transmitter can comprise, for example, a single fixed frequency piezoelectric resonator.
    A complementary receiver is also required and this component can be located away from the measuring set 200, 350, and can comprise hardware, such as, for example, a circuit tone detector with phase lock integrated into a microphone.
    Detector assembly 204 will now be described in more detail with reference to Figures 4 and 5. The quartz crystal oscillator 218 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.
    Two parallel surfaces of the 218 quartz crystal oscillator are metallized 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 may be forced to oscillate.
    The physical size and physical thickness of the quartz crystal determines the characteristic or resonant frequency of the quartz crystal. Indeed, the characteristic or resonant frequency of crystal 218 is inversely proportional to the physical thickness between the two metallized surfaces. Quartz crystal oscillators are well known in the art, and thus the structure of the 218 quartz crystal oscillator will not be described in detail here.
    In addition, the resonant frequency of 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 needed to oscillate the crystal in a given amplitude.
    In addition, the adsorption of gases or 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.
    However, in the present case, no coating is applied to the 218 quartz crystal oscillator. In fact, the deposition of material on the 218 quartz crystal oscillator is undesirable in the present case, as the measurement accuracy may be affected .
    As shown in Figure 4, the quartz crystal oscillator 218 of the present embodiment is in the form of a tuning fork and comprises a pair of teeth 218a of approximately 5mm, arranged to oscillate at a resonant frequency of 32.768 kHz. Teeth 218a are formed in the flat section of quartz. The tines 218a of the tuning fork normally oscillate in their fundamental mode, in which they move synchronously close to and away from each other at the resonant frequency.
    Fused (or non-crystalline) quartz has a very low temperature-dependent expansion coefficient 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.
    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 slope at the top of the peak is precisely zero.
    These quartz crystals are commonly available at a relatively low cost. In contrast to most quartz crystal oscillators, which are used under vacuum, in the present embodiment, the quartz crystal oscillator 218 is exposed to gas under pressure in conduit 206.
    The drive circuit 220 to drive the quartz crystal oscillator 218 is shown in Figure 4. The drive circuit 220 must meet a number of specific criteria. First, the quartz crystal oscillator 218 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 pressurized gas, such as hydrogen. Thus, the 218 quartz crystal oscillator is required to operate (and restart after a period of non-use) under a wide range of pressures.
    Therefore, the quality factor (Q) of the 218 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.
    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.
    The drive circuit 220 must be able to drive the quartz crystal oscillator 218, despite the variation of the Q factor. As the pressure in the gas cylinder 100 increases, the oscillator of the quartz crystal oscillator 218 will become increasingly more attenuated, and the Q factor will fall. The falling Q factor requires that a greater gain be provided by an amplifier in the drive circuit 220. However, if a very high amplification is provided in the drive circuit 220, the response from the quartz crystal oscillator 218 can make - if difficult to distinguish. In this case, the drive circuit 220 can simply oscillate at an unrelated frequency, or at the non-fundamental frequency of the quartz crystal oscillator 218.
    As an additional limitation, the drive circuit 220 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.
    The drive circuit 220 will now be described with reference to Figure 4. In order to drive the quartz crystal oscillator 218, the drive circuit 220 essentially receives a voltage signal from the quartz crystal oscillator 218, the amplifies, and feeds that signal back to the 218 quartz crystal oscillator. The fundamental resonant frequency of the 218 quartz crystal oscillator 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.
    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 220 is arranged to detect and maintain that oscillation frequency. The frequency can then be measured by microprocessor 240, used to calculate the appropriate gas property required by the user and, if necessary, emitted to an appropriate display medium (as will be described later).
    The drive circuit 220 is powered by a 6 V 224 battery. Battery 224, in this embodiment, comprises a lithium battery. However, alternative energy sources will be readily apparent to one skilled in the art; for example, other types of rechargeable and non-rechargeable batteries and an array of solar cells.
    The drive circuit 220 further comprises a common emitter amplifier with a Darlington pair 226. 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 by the second. This configuration allows a higher current gain to be obtained, when compared to each transistor separately. Alternatively, bipolar PNP transistors can be used.
    The Darlington pair 226 is arranged in a feedback configuration by a Common Emitter transistor (T1) 228 amplifier. A bipolar NPN junction transistor is shown in Figure 4. However, the person skilled in the art should be aware of alternative arrangements of transistors, which can be used; for example, a bipolar PNP junction transistor or transistors with a metal oxide semiconductor field effect (MOSFETs).
    The drive circuit 220 comprises another transistor T2 following an NPN emitter, which acts as a buffer amplifier 230. The buffer amplifier 230 is arranged to function as an attenuator between the circuit and the external environment. However, this feature is optional and may not be mandatory; for example, a FET can be connected directly, to drive circuit 220.
    A capacitor 232 is located in series with the quartz crystal oscillator 218. Capacitor 232, in this example, has a value of 100 pF and allows the drive circuit 220 to drive the quartz crystal oscillator 218 in situations where the crystal is contaminated, for example, by salts or other deposited materials.
    In addition, the drive circuit 220 can be optimized for quick start of the quartz crystal oscillator 218. In order to achieve this, an additional resistor and capacitor can be connected between the base of the transistor D1 and the ground. These components can include, for example, a 10 MQ resistor and a 10 nF capacitor.
    An alternate drive circuit 260 will now be described with reference to Figure 5. The drive circuit shown in Figure 5 is configured similarly to a Pierce oscillator. Pierce oscillators are known from digital clock IC oscillators. In essence, the drive circuit 260 comprises a single digital converter (in the form of a transistor) T, three resistors R1, R2 and RS, two capacitors C1, C2, and the quartz crystal oscillator 218.
    In this arrangement, the 218 quartz crystal oscillator functions as a highly selective filter element. The resistor R1 acts as a load resistor for the transistor T. The 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 inverter amplifier. Another RS resistor is used between the output of the T converter and the 218 quartz crystal oscillator, to limit the gain and to attenuate unwanted oscillations in the circuit.
    The 218 quartz crystal oscillator, in combination with C1 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 218 quartz crystal oscillator. The drive circuit 260 described above is reliable and inexpensive to manufacture, as since it comprises a relatively small number of components. This circuit is also specifically applicable for low pressure applications.
    As discussed above, the detector assembly 204 may include a microprocessor 240, which receives input from the quartz crystal oscillator 218 and drive circuit 220. The microprocessor 240 may comprise a suitable arrangement, such as an ASIC or FPGA. The microprocessor 240 is programmed to calculate and, if necessary, present and communicate a determination of the mass flow of the gas through the orifice 212.
    When used with the quartz crystal oscillator 218, the microprocessor 240 can be configured to measure the frequency or period of the signal from the drive circuit 220. This can be achieved, for example, by counting the oscillations over a period of time fixed, and conversion of that frequency into a density value, using an algorithm or a look-up table. This value is transferred to microprocessor 240.
    The microprocessor 240 also receives the temperature T measured from the temperature sensor 222. The microprocessor 240 is willing to perform, based on the inputs provided, a calculation to determine the mass flow of the gas through the orifice 212.
    Once the mass flow 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.
    Microprocessor 240 can optionally be designed so that mass production is identical across the entire 200 meter set, with different software and hardware features enabled for different gases.
    In addition, microprocessor 240 can also be configured to minimize energy consumption, by implementing standby or "sleep" modes, which can cover microprocessor 240 and additional components, such as drive circuit 220 and the power oscillator. 218 quartz crystal.
    Various schemes can be implemented; for example, microprocessor 240 can be at rest for 10 seconds every 11 seconds. In addition, the microprocessor 240 can control the quartz crystal oscillator 218 and the drive circuit 220 in such a way that these components are put on hold by it most of the time, with only the components most in need of energy being activated by ^ second every 30 seconds.
    The theory and operation of detector assembly 204 will now be described with reference to Figures 6 and 7.
    The 218 quartz crystal oscillator has a resonant frequency, which is dependent on the density of the fluid it is in. 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 an attenuation effect of the gas on the oscillations of the crystal, the gas adjacent to the vibrating teeth 218a of the tuning fork type 218 crystal 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. c1 c2 are geometrically dependent constants and δ is the thickness of the gas's surface layer, as defined by:
    Where n is the viscosity dependent on the temperature of the gas.
    The two parts of equation 1) concern: a) mass of gas additive on the teeth of the 218 quartz crystal oscillator and b) shear forces that arise in the outermost layer of the teeth during oscillation.
    The equation can thus be rewritten in terms of frequency and simplified to:
    Where
    displacement, and fo is the natural resonant frequency of the crystal in a vacuum.
    It was discovered by the inventors that a good approximation can be adequately obtained by the approximation:

    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 6 shows, for a series of different gases / gas mixtures, that the resonant frequency of the 218 quartz crystal oscillator varies linearly as a function of density.
    In general, the sensitivity of the 218 quartz crystal oscillator is that a 5% change in frequency is seen, for example, with oxygen gas (having a molecular weight of 32 AMU) at 250 bar when compared to pressure atmospheric. 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 or 900 bar g for helium and hydrogen.
    The 218 quartz crystal oscillator is particularly suitable for use as a density sensor as part of a mass flow 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 with commercially supplied gases, but not with air or in most pressure control situations.
    Since the density value is obtained from the quartz crystal oscillator 218, the mass flow of gas through orifice 212 can be determined. The mass flow rate, Q, through an orifice is defined as:
    3) Q = kvpA Where k is a constant, v is the velocity of the gas, p is the density of the gas upstream, and A is the cross-sectional area of orifice A. However, from the Bernoulli equation 6) :

    As the cross-sectional area of an orifice decreases, the gas velocity increases and the gas pressure will be reduced.
    The determination of the mass flow through orifice 212 depends on a condition known as "strangled" or "critical" flow. Such a situation arises when the gas velocity reaches sonic conditions, that is, when the flow restriction caused by diaphragm 210 is such that the velocity of the gas flowing through the orifice 212 reaches the velocity of sound. This occurs when the upstream pressure P1 is at least 0.5 bar above the downstream pressure P2.
    Once this condition is met, there is very little additional increase in air velocity through orifice 212. Therefore, in the condition of strangled flow, where v = c (the speed of sound in the gas in question), equation 5) become:

    Consequently, for an orifice having a fixed cross-sectional area A, the mass flow through orifice 212 is only dependent on the upstream density. This is the parameter that the 218 quartz crystal oscillator is willing to measure.
    In addition, the speed of sound c is proportional to the square root of the absolute temperature, VT. However, as previously described, temperature sensor 222 need not be particularly accurate. For example, if the temperature error is 0.5 K to 300 K, this only translates into a 1: 1200 error in the calculated speed of sound. Thus, for many applications, the 222 temperature sensor is not necessary and can be eliminated.
    Figure 7 illustrates experimental data from mass flow measurement. Figure 7 is a graph of the resonant frequency (in kHz) on the Y axis as a function of gas flow (in liters / minute) on the X axis for nitrogen gas. As shown, the graph is highly linear, and shows that the mass flow can be accurately measured using the 218 quartz crystal oscillator.
    In addition, the high precision of the 218 quartz crystal oscillator allows measurement at very high precision, with a resolution of parts per million. Together with the linear response of the 218 quartz density sensor to high densities and pressures, the high precision allows the mass flow of very light gases, such as H2 and He, to be accurately measured.
    A method, according to an embodiment of the present invention, will now be described with reference to Figure 8. The method described below is applicable to each of the first and second embodiments described above.
    Step 400: initialize measurement
    In step 400, the measurement of the mass flow of gas through orifice 212 is initialized. This can be activated, for example, by a user by pressing a button outside the housing 208. Alternatively, the measurement can be initiated by means of a remote connection, for example, a signal transmitted over a wireless network and received by the molecular weight meter 200, 350, through an antenna.
    As another alternative, or in addition, the molecular weight meter 200, 350 can be configured to start up remotely, or with a timer. The method proceeds to step 402.
    Step 402: activate the quartz crystal oscillator
    Once started, drive circuit 220 is used to drive the quartz crystal oscillator 218. During startup, drive circuit 220 applies a random noise AC voltage across crystal 210. At least a portion of said random voltage it will be at an appropriate frequency to cause the 210 crystal to oscillate. The 210 crystal will then begin to oscillate in sync with that signal.
    As will be noticed, the 218 quartz crystal oscillator is, in essence, an autonomous detector and trigger, since the resonant frequency of the crystal itself is being measured.
    Through the piezoelectric effect, the movement of the quartz crystal oscillator 218 will then generate a voltage in the resonant frequency range of the quartz crystal oscillator 218. The drive circuit 220 then amplifies the signal generated by the oscillator quartz crystal 218, 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 220. The narrow resonant band of the quartz crystal removes by filtration all the unwanted frequencies and the circuit drive 220 then drives the crystal quartz oscillator 218 at the fundamental resonant frequency f. Once the 218 quartz crystal oscillator has stabilized at a particular resonant frequency, the method proceeds to step 404.
    Step 404: measure the resonant frequency of the quartz crystal oscillator
    The resonant frequency f is dependent on the environmental conditions within the upstream portion 214 of conduit 206. In the present embodiment, the change in resonant frequency Δfé, for a good approximation, proportional in magnitude to the change in density of the upstream portion 214 of the conduit 206, and will decrease with increasing density.
    In order to make a measurement, the frequency of the 218 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 240. Processor 240 can also record the time, T1, when the measurement was started.
    Once the frequency has been measured, the method proceeds to step 406.
    Step 406: measure gas temperature
    In step 406, temperature sensor 222 measures the temperature of the gas within the upstream portion 214 of conduit 206. This measurement is carried out in order to accurately determine the speed of sound in the gas flow.
    As previously described, the temperature measurement need not be particularly accurate. For example, if the 222 temperature sensor is accurate to 0.5 ° C, then this corresponds to an error of only about one part in six hundred over the absolute temperature value necessary for calculating the speed of sound.
    Alternatively, this step may simply involve a fixed temperature value to be entered into microprocessor 240. This can occur, for example, in situations where a known temperature environment is used, or where a high degree of accuracy is not made required. In this case, temperature sensor 222 is not necessary.
    Step 408: determine the mass flow of gas
    This is done using equation 7) above, where the density p of the gas upstream of orifice 212 and, optionally, the temperature T of the gas are known. Thus, knowing the resonant frequency, measured in step 404, the known temperature T (optional) of the gas measured in step 406, an exact measurement of the mass flow through orifice 212 can be made. The method then proceeds to step 410.
    Step 410: Communicate and store results
    The mass flow of the gas can be presented in several ways. For example, a dial (not shown) connected to housing 208, body 202, or regulator 150, 300 can view the mass flow of the gas through orifice 212 (and as a consequence, the mass flow of the gas exiting coupling 160) . Alternatively, the mass flow measurement can be remotely communicated to a base station, or to a meter located in an adjacent accessory, as will be described later.
    As yet another alternative, the mass flow of gas at time T1 can be stored in a local memory, for said processor 240 to generate a time record.
    The method then proceeds to step 412.
    Step 412: turn off detector assembly
    It is not necessary to keep meter set 200, 350 operational at all times. On the contrary, it is beneficial to reduce energy consumption by turning off the 200, 350 meter set, when not in use.
    This extends the life of the 224 battery.
    The configuration of the drive circuit 220 allows the quartz crystal oscillator 218 to be restarted, regardless of the pressure in the upstream portion 214 of conduit 206. Therefore, meter set 200, 350 can be turned off, when necessary, in order to save battery power.
    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.
    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 9. As another example, a crystal oscillator, which operates at a frequency of 1.8 MHz, can be used.
    Higher frequency operation allows the pressure to be monitored more frequently, because a short period of time is required 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. As an 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.
    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.
    A suitable detector assembly 500 is shown in Figure 10. The detector assembly 500 comprises a first quartz crystal oscillator 502 and a second quartz crystal oscillator 504. The first quartz crystal oscillator 402 is a reference crystal, which is located inside a 506 vacuum sealed container. The first 502 quartz crystal oscillator is driven by a 508 drive circuit.
    The second quartz crystal oscillator 504 is a crystal similar to the crystal 218 described in the previous embodiments. The second quartz crystal oscillator 504 is exposed to the gas environment inside the housing 208. The second quartz crystal oscillator 504 is driven by a drive circuit 510.
    This comparison can be performed using an electronic mixer circuit 512, 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.
    In addition, the circuits used in the detector assembly 204 can be simplified, because only the frequency of difference must 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.
    In addition, all the electronics needed 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.
    An example of this arrangement is shown with reference to Figure 11. The arrangement comprises a gas cylinder assembly 60, comprising a gas cylinder 600, a regulator 602, and a mass flow meter 604. The gas cylinder 600, regulator 602, and mass flow meter 604 are substantially similar to gas cylinder 100, regulator 150 and meter set 200, 350, substantially as described above with reference to the previous embodiments.
    In this embodiment, the mass flow meter 604 comprises a quartz crystal oscillator and drive circuit (not shown) similar to the quartz crystal oscillator 218 and drive circuit 212 of the previous embodiments. An antenna 606 is provided for communication via any suitable remote communication protocol; for example, Bluetooth, Infrared (IR) or RFID. Alternatively, wired communication can be used.
    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.
    A connecting tube 608 is connected at the outlet of the gas cylinder 600. The connecting tube is terminated by a quick connection 610. The quick connection 610 allows the connecting tube, or the components, to be connected and disconnected easily and quickly of the gas cylinder 600.
    A quick connection unit 650 is provided for connection to gas cylinder 600. A complementary quick connection connector 612 is provided for connection to connector 608. In addition, the quick connection unit 650 is equipped with a data unit 652 The data unit 552 comprises a display 554 and an antenna 556 for communication with the antenna 604 of the gas cylinder assembly 60. The display 554 may comprise, for example, an LCD, LED or reading light display to minimize energy consumption and maximize the visibility of the screen.
    The data unit 652 can record various parameters measured by the detector assembly 602 of the gas cylinder assembly 60. For example, the data unit 652 can record mass flow 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 set of company data on the use of a particular customer.
    Alternatively, data from data unit 650 can be transmitted to a computer-activated welding machine (for welding applications) or other equipment using gas, to allow calculation of derived parameters, along with alert messages.
    In addition, the data unit 650 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 gas use; providing a multimodal operation, for example, a supplier / fill mode and a customer mode; allow data entry; provide data, such as a cylinder number, 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 summarized on the cylinder.
    Alternatively, all of the above examples can optionally be processed, stored or obtained from a system entirely located in (or within) gas cylinder 600 or housing 208, as discussed in terms of the set of 200, 350.
    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 ceramics, silicon oxide and zinc compounds, or dipotassium tartrate.
    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 herein, 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 described examples, within the scope of the present invention.
    权利要求:
    Claims (13)
    [0001]
    1. METHOD FOR MEASURING THE MASS FLOW OF A GAS THROUGH A DUCT, characterized by the fact that it comprises an orifice (210), through which a strangled flow is occurring, the orifice (210) dividing the duct into a part of the amount upstream of said orifice (210), and a downstream part, downstream of said orifice (210), the upstream part comprising a piezoelectric crystal oscillator (218) comprising at least two flat teeth and in contact with the gas at orifice amount (210), the method comprising: a) actuation (402) of the piezoelectric crystal oscillator, so that the piezoelectric crystal oscillator resonates at a resonant frequency; b) measurement (4040 of the resonant frequency of the piezoelectric crystal oscillator (218); and c) determination (408) of the mass flow of gas through said orifice (210), based on the relationship between the measured resonant frequency of the crystal oscillator piezoelectric and the density of the gas upstream of the orifice (210), and from the relationship between the density of the gas upstream of the orifice (210), the cross-sectional area of the orifice (210) and the speed of sound in the gas.
    [0002]
    2. METHOD, according to claim 1, characterized in that the pressure upstream of said orifice (210) is at least 0.5 bar higher than the pressure downstream of said orifice (210).
    [0003]
    3. METHOD, according to claim 1 or 2, characterized by the fact that the method still comprises the determination of the temperature of the gas upstream of the orifice (210).
    [0004]
    4. METHOD, according to claim 1, 2, or 3, characterized in that the gas is distributed from a valve or pressure regulator located upstream of the piezoelectric crystal oscillator (218).
    [0005]
    5. METHOD, according to claim 4, characterized by the fact that the valve or pressure regulator is electronically controlled, in response to the mass flow of gas measured through said orifice (210).
    [0006]
    6. METER FOR MEASURING THE MASS FLOW OF A GAS, characterized by the fact that it comprises a conduit (206) through which the gas flows in use, the conduit having a flow restrictor orifice (212), through which a strangled flow occurs, the flow restrictor orifice (212) dividing the conduit into an upstream part (214), upstream of said orifice, and a downstream part (216), downstream of said orifice, the meter (200; 350) further comprising a detector assembly (204), the detector assembly including a piezoelectric crystal oscillator (218) comprising at least two flat teeth in said upstream portion, so that said piezoelectric crystal oscillator is in contact with said gas, when the meter is in use, said detector set being arranged: to activate the piezoelectric crystal oscillator, so that the piezoelectric crystal oscillator resonates at a resonant frequency; for measuring said resonant frequency of said piezoelectric crystal oscillator; and to determine the mass flow through the orifice (210), from the relationship between the measured resonant frequency of the piezoelectric crystal oscillator and the gas density upstream of the orifice, and from the relationship between the mass flow, the density of the gas upstream of the orifice, the cross-sectional area of the orifice, and the speed of sound in the gas.
    [0007]
    7. METER, according to claim 6, characterized in that the meter still comprises a drive circuit, which comprises a pair of Darlington arranged in a feedback configuration from a common emitter amplifier.
    [0008]
    8. METER, according to claim 6 or 7, characterized in that it also comprises a temperature sensor arranged to determine the gas temperature adjacent to said piezoelectric crystal oscillator.
    [0009]
    9. METER, according to claim 6, 7 or 8, characterized by the fact that it is disposed downstream of a valve or pressure regulator.
    [0010]
    10. METER, according to claim 9, characterized in that the meter is arranged to electronically control the valve or pressure regulator, in response to mass flow measured through the flow restrictor orifice.
    [0011]
    11. METHOD OR METER, according to any one of claims 1 to 10, characterized in that said piezoelectric crystal oscillator comprises a quartz crystal oscillator.
    [0012]
    12. METHOD OR METER, according to any one of claims 1 to 11, characterized in that said piezoelectric crystal oscillator has a resonant frequency of 32 kHz or more.
    [0013]
    13. LEGIBLE MEDIA BY COMPUTER, characterized in that it comprises being adapted to execute the method presented in claims 1 to 5.
    类似技术:
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    BR112014029054B1|2021-01-12|method to automatically control the mass flow of a gas through an orifice through which, in use, the blocked flow is arranged to occur, controller to regulate the mass flow of a gas, and computer readable medium
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    US9690304B2|2017-06-27|Method of, and apparatus for, providing a gas mixture
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    BR112014029058B1|2021-06-22|ASSEMBLY OF SENSORS TO MEASURE PHYSICAL PROPERTIES OF A GAS UNDER PRESSURE WITHIN A GAS CYLINDER COMPRISING A GAS CYLINDER BODY AND A VALVE ARRANGEMENT THAT DEFINES A FIXED INTERNAL VOLUME OF A GAS CYLINDER, AND CYLINDER UNDER PRESSURE
    US20150168958A1|2015-06-18|Method of, and apparatus for, providing a gas mixture
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    同族专利:
    公开号 | 公开日
    ES2434260T3|2013-12-16|
    TW201226859A|2012-07-01|
    KR20130103583A|2013-09-23|
    MX2013005949A|2013-07-03|
    CA2817813C|2016-01-12|
    WO2012072597A1|2012-06-07|
    PL2458348T3|2014-01-31|
    CA2817813A1|2012-06-07|
    KR101480370B1|2015-01-09|
    BR112013013329A2|2016-09-13|
    US20130340859A1|2013-12-26|
    CN103328937A|2013-09-25|
    US9448094B2|2016-09-20|
    CL2013001504A1|2014-05-23|
    EP2458348B1|2013-08-14|
    CN103328937B|2015-12-02|
    EP2458348A1|2012-05-30|
    TWI448667B|2014-08-11|
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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]|
    2019-10-08| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2020-07-14| B06A| Notification to applicant to reply to the report for non-patentability or inadequacy of the application [chapter 6.1 patent gazette]|
    2020-12-22| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2021-01-19| 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:
    申请号 | 申请日 | 专利标题
    EP10192976.8|2010-11-29|
    EP20100192976|EP2458348B1|2010-11-29|2010-11-29|Method of, and apparatus for, measuring the mass flow rate of a gas|
    PCT/EP2011/071213|WO2012072597A1|2010-11-29|2011-11-28|Method of, and apparatus for, measuring the mass flow rate of a gas|
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