Abstract: An automated method and system for calculating the transit time of a pulsed signal transmitted from a first ultrasonic transducer to a second ultrasonic transducer is provided. The method includes measuring the amplitude of the pulsed signal received at the second transducer from the first transducer; measuring the amplitude of any noise proximate to the received pulsed signal; and calculating the signal to noise ratio of the received pulsed signal and the noise, respectively. If the signal to noise ratio is above a predetermined threshold, a first technique is automatically implemented for calculating the transit time of the received pulsed signal. If the signal to noise ratio is less than the predetermined threshold, a second different technique is automatically implemented for calculating the transit time of the received pulsed signal.

Abstract: A flow meter is powered by a loop power supply which supplies a supply voltage. A load is powered by a load voltage and includes at least a processor for calculating a flow rate, an ultrasonic transducer power circuit, and an ultrasonic transducer receiving circuit. A power regulating circuit is disposed between the loop power supply and the load and includes a power converter responsive to the supply voltage to vary the load voltage in response to a control signal, a safe storage device between the converter and the load for storing power and for delivering power when required by the load, and a control subsystem for providing the control signal to the converter based on the setting of the loop power supply by the load. A power management detects the load voltage and to reduces the power consumption of the load at one or more predetermined set points.

Abstract: An acoustic waveguide system including a waveguide, a housing with a port in one side of the housing for receiving the proximal end of the waveguide, the port opening into a channel in the housing. A first shear transducer is located in the channel of the housing and disposed on the waveguide, and a second shear transducer is located in the channel and disposed on the opposite side of the waveguide. The first and second transducers are configured to launch a torsional or an extensional wave in the waveguide depending on the orientation and polarity of the transducers.

Abstract: A tag flow measurement system wherein a first and a second measurement path are provided across a flowing fluid, and a receiver in each path receives signals modulated by scatters in the fluid. The direction of signal propagation in one path faces in an opposite sense to, e.g., is anti-parallel to, the direction of propagation in the other path, and the two receiver outputs are correlated to determine a time interval representative of flow velocity. In one embodiment each path is defined by a transmitter on one side of the conduit and a receiver on the other side of the conduit, and the positions or orientations of transmitter and receiver are reversed in the second pair. Thus, the first transmitter may lie on the same side of the conduit as the second receiver, and the second transmitter may lie on the same side of the conduit as the first receiver. Diametral or chordal paths may be used.

Abstract: A high sensitivity pressure sensor with long term stability including a housing with first and second chambers, a membrane separating the first and second chambers, a first electrode located in the first chamber and spaced from one side of the membrane forming a first capacitor therewith, and a second electrode located in the second chamber and spaced from an opposite side of the membrane forming a second capacitor therewith. A measuring circuit is connected across the first and second capacitors for measuring membrane displacement by detecting differences in capacitance between the first and second capacitors and a compensation circuit is configured to apply an electric field to the membrane as a compensating force by reducing the voltage difference between the first electrode and the membrane and simultaneously increasing the voltage difference between the second electrode and the membrane or vice versa to provide long term stability.

Abstract: A method of and system for analyzing the mass flow rate of a fluid flowing in a conduit wherein ultrasonic energy is transmitted along multiple v paths in multiple parallel quadrature planes through the fluid, the transit time of the ultrasonic energy through the fluid with and against the flow direction of the fluid is measured, and the flow velocity of the fluid in each quadrature plane is calculated based on the transit time in each quadrature plane. The density of the fluid in each quadrature plane is then determined and quadrature integration of the product of the fluid density and fluid velocity in each quadrature plane is performed to calculate the total mass flow rate of the fluid more accurately by eliminating errors associated with assuming that the density of the fluid in the conduit is uniform.

Abstract: A clamp-on ultrasonic measurement system for a gas or other fluid typically of low acoustic impedance such as low pressure steam or flare gas. The system includes a first ultrasonic signal transducer which clamps to the conduit, and a second ultrasonic signal transducer clamped on the conduit across from the first transducer. Each transducer is operated to transmit to, and receive from, the other along contrapropagation signal paths. The transducers generate a shear wave signal that skips within the conduit wall to coherently energize a region of the wall and launch ultrasonic signal energy at a defined angle across the direction of flow. The receiver is symmetrically arranged and positioned to respond to signal energy received along the path through the fluid.

Abstract: An oxygen sensor has a sensor body formed of a crystalline material, such as zirconia, with first and second electrodes disposed on a single surface thereof. The electrodes are arranged to induce superionic oxygen transport in the body along current paths extending at a shallow depth in the crystalline material at the electrode surface. The electrodes may be interdigitated or juxtaposed porous electrodes that define an exposed surface pattern of ionic conduction for sensing, and the electrodes are preferably poisoned to inhibit cross sensitivity to reactive components, such as hydrogen, that may be present in the environment. The electrodes may effect electrode-limited superionic conduction in a thin slice of single crystal material, or a polycrystalline yttria-stabilized zirconia film sensing body, and operate at a relatively low temperature in the range of 250-400° C., preferably about 300-350° C.

Abstract: A magnetic wind oxygen sensing device provides a local magnetic field defined by magnetic pole pieces, and employs a plurality of thermal elements in a bridge in the local magnetic field to measure oxygen concentration in a surrounding gas mixture, creating a magnetic wind and determining the thermal effects induced in sensing elements as a result of the wind. A pair of sensing elements are positioned such that one lies upstream and one downstream of each wind generator, and both are substantially in thermal equilibrium with adjacent gas so they are unaffected by changes in thermal capacity of background gas components. When oxygen is present, the two sensing elements are passively cooled below, and heated above the temperature set by a local heater, respectively. In the absence of oxygen, the sensors reside at the same temperature, so they are self zero-ing, and this zero point does not shift when background gases with differing thermal characteristics are present.

Abstract: An ultrasonic coupling assembly includes a barrier layer that contacts the wall, and a generally thicker layer formed of a compliant material such as zinc foil that extends over the first layer. A third layer may cover and enclose the compliant layer, e.g., by folding the first layer over and on top of the second layer to cover the edge faces thereof. An exemplary embodiment is implemented using gold foil approximately one mil thick for the first layer, and zinc sheeting approximately four mils thick for the second layer. Use of inert top and bottom, or outside, layers prevents the inadvertent installation of the coupling element with the compliant layer directly contacting the wall. Disk embodiments may employ a stack of separate disks formed of foils or sheets of the respective materials. For cryogenic applications, a material such as indium may be used for the second layer without risk of its alloying or migration through the first layer.

Abstract: An encapsulated or rigid bundle of rods forms a substantially non-dispersive buffer usable in extreme environments, operable over wide bandwidth, and repairable in the field. The rigid assembly extends through a nozzle or flanged pipe penetration to launch its signals directly in the fluid at a defined angle. The bundles are non-degrading wave guides to carry signals through degrading environments. This is useful for numerous stack, freestream and chordal path configurations, as well as clamp-on systems and special mode-converting configurations. Beam shaping and steering may be passively effected with patterned bundle constructions, and plural faces, which may be stepped or angled, may define multiple oblique, reflective or different length paths while mounted in spoolpieces at normal incidence.

Abstract: An ultrasonic system employs a path through a fluid to determine fluid density by a differential reflection coefficient measurement of fluid impedance Z and a fluid sound speed c. Preferred configurations use clamp-on (external) transducers and combine ultrasonic measurements of flow velocity V over one or more paths, to obtain the mass flow rate. Z is determined by comparing reflections from a reference target, which may be totally reflective, with reflections from a sensor target having an effectively lower Z, which may be close to that of the fluid. Both targets are preferably located to be cleaned by the natural flow of the fluid. The low-Z target is interrogated at least once. Vee blocks provide a compact combination of reference and sensor targets that can be integrated with a velocity-sensing flowcell. Folded-path flow cells compactly measure V alone or in combination with density.

Abstract: A clamp-on ultrasonic measurement system for a gas or fluid of low acoustic impedance, such as steam, two phase fluid or flare gas includes an ultrasonic signal transmitter which clamps to the steam or gas conduit, and first and second receiving transducers clamped in the shadow zone of the transmitter. The transmitter signal skips within the conduit wall with a characteristic skip distance Lp so ultrasonic signal energy is launched across the flow along plural paths over a region, and at an angle to the direction of flow. The receivers are positioned to receive the signal energy along different ones of said paths, modulated by tags or inhomogeneities in the flowing fluid. Cross correlation of the received signals then yields a peak correlation time interval or time delay from which the flow velocity is accurately determined.

Abstract: An ultrasonic measurement system performs a signal path measurement by directing ultrasonic signals through a gaseous material in a conduit, and processing the detected signals to determine sound speed and to derive the average molecular weight of an unknown hydrocarbon mixture present in the material. The processor includes a plurality of stored tables of critical constants of hydrocarbon mixtures as a function of the average molecular weight of the mixture, and is configured to iteratively set a hypothetical molecular weight, determine the corresponding critical properties, and compute a predicted sound speed. If the two speeds differ, a new weight is set and the procedure is repeated until the predicted sound speed matches the measured speed, indicating that the current estimate is the correct average molecular weight.

Abstract: A flow conditioning plate for interposition in a flow line has a pattern of apertures which introduces a flow irregularity characteristic of a commonly encountered irregular flow in a plant, such as the disturbance introduced by one or more junctions or fittings in the upstream flow path. The apertures may introduce a specific flow distribution, asymmetry of flow profile or swirl component, and these may be tuned to simulate a plant condition that occurs downstream of one or more bends, elbows or T junctions. The disturbance persists, or evolves in a known way for a well defined distance along the flow path to simulate field flow conditions, and a flow meter is tested or calibrated in the disturbed segment, preferably at a defined position, under known flow to produce a calibration table. The meter may then be later installed to measure the irregular flow in an unconditioned flow line at a plant.

Abstract: A zirconium oxide shell forms a chamber of fixed volume, and a controller monitors voltage across the shell indicative of difference between inside and outside oxygen levels, applying a signal to pump oxygen. Pumping is effected to empty the chamber, to develop an internal reference, for example by comparison to ambient air, for calibration, and thereafter to substantially continuously null the difference, i.e., to track the oxygen level of a sample environment. Integrated pump current yields a measure of the oxygen added to or removed from the chamber. A suitable material for forming the sensor is a mixture of about 91% zirconium oxide and 9% yttrium oxide, which is formed to shape as a paste or slurry and sintered at about 1400° C., and then platinum coated, for example by a CVD process, to form porous electrodes on each surface. The controller may apply a sequence of current pulses, and check the Nernst cell output indicative of &Dgr;P across the wall, until &Dgr;P=0.

Abstract: A sensor responds to a magnetic wind produced by the magnetic susceptibility of a target component gas, such as oxygen, which is present together with a background gas in a sample located in a measurement field produced in a measurement device. A background sampler also determines thermal and physical characteristics in a conditioned flow path, and a processor performs a computational correction on the detected magnetic wind signal to more accurately determine the concentration of the target gas. The background sampler includes a mass flow cell in series with a laminar flow device to measure heat capacity and viscous properties of the sample. It derives the gas viscosity from a differential pressure measurement; and preferably determines the heat capacity and thermal conductivity of background gases, the composition of which may be unknown, to compensate for their effects on the magnetic wind sensor elements.

Abstract: A method of moisture measurement wherein a moisture responsive element is subjected to the measuring environment and its thermal capacitance or resistance temperature coefficient is measured. A system operates by cycling a sensor element between a first temperature and a second temperature and determining the sensor capacitance at each temperature. The sensor capacitance difference, corresponding to its temperature coefficient, is then compared to a previously compiled table of gas humidity or dew point versus capacitance increment values. The differential measurement thus made automatically corrects for systemic error originating in equipment drift, cable capacitance change and various aging and slow hysteresis or sensor capacitance variations.

Abstract: A signal transducer mounts to a straight tube to measure the flow velocity of fluid flowing therein. The transducer operates at a frequency above cut-off allowing multiple modes to exist, and is mounted with a wedge of material having a sound speed less than the sound speed of the fluid, coupled to the conduit, and angled to launch a signal into the fluid at an acceptance angle that sends the lowest order mode acoustic signal axially through the fluid. Extraneous modes present at generally lesser magnitude convert to the desired mode, resulting in propagation of a coherent burst that is readily detected by a receiving transducer located further along the conduit. The wedge may be formed of hard plastic such as an acrylic, PVC or PEI having a shear wave velocity less than 1400 meters per second, and the launch geometry results in the attenuation, mode conversion or cancellation of higher mode signal energy components.

Abstract: A waveguide couples ultrasonic energy from a source on one side of a fluid-bounding wall, such as a conduit, into fluid on the other side of the wall. The waveguide has a buffer that couples to the source, and a seat with an exit face, while an intermediate portion contains a redirecting surface for internally redirecting energy propagated along the buffer toward the exit face to exit as a narrow directed beam. The waveguide core has a rectangular cross section which is narrow, i.e., has an aspect ratio above two and preferably above three or four, while the buffer has a length effective to thermally isolate or protect the source from the conduit. The waveguide attaches easily, either as a clamp-on or welded unit, to a pipe or spoolpiece, allowing local fabrication of massive or custom flow cells, such as large spoolpieces with Gauss-Chebyshev interrogation paths. Several guides may be positioned in an array to cover interrogation paths for an extended range of sound speeds or flow rates.