Abstract: A magnetic flow meter has an electrically insulating member extending inward from an inner wall of a flow tube and extending along a selected axial portion of the tube. At least one pair of electrodes are placed adjacent opposite sides of the insulating member at a selected axial position so as to define a voltage sensing path. At least one of the electrodes is connected to an adjustment mechanism that allows the electrode to be set at a selected radial position, where the position can be selected so that the sensed voltage varies linearly with volumetric flow rate.

Abstract: A magnetic flow meter employs resonant circuit principles to increase the strength of the magnetic field to produce larger electrode difference potentials so that environmental influences have less effect on the operation of the flow meter. The flow meter may use an electromagnet that is resonant with a capacitor, generally at a frequency on the order of ten kHz. In addition, the meter comprises a magnetic field sensor and timing circuits that can sample the electrode difference potentials when the field is at a maximum and the time rate of change of field is instantaneously zero. Some versions of the meter operate in a one-shot mode and others operate with a burst of drive pulses.

Abstract: The flow responsive voltages detected at the electrodes of magnetic flow meters are typically reduced in magnitude by an electrical impedance shunting effect of the fluid on the electrodes. This problem is resolved by providing buffering electrodes located near, and preferably both upstream and downstream, of flow responsive sensing electrodes. The buffering electrodes are driven by amplifiers having signals detected by the flow responsive electrodes as an input. Thus, fluid in the vicinity of the flow responsive electrodes is forced to acquire an offset voltage which can reduce the shunting effect to a negligible level.

Abstract: A transit-time flow sensor determines a rate at which fluid flows by measuring a propagation time difference between upstream and downstream acoustic transmissions. This may involve providing an acoustic path consisting of sequentially traversed path segments and a repeating arrangement that uses the energy in a received pulse to repeat the pulse in the next sequential segment.

Abstract: Problems of instability and non-linearity in probe-type magnetic flow meters are ameliorated by either or both of a conductor coating connecting a tip portion of the probe with a supporting probe stem and either a shrouding arrangement or skewed end plates parallel to the flow direction that are arranged adjacent to the sensing electrodes and that act to straighten and confine fluid flowing past the electrodes.

Abstract: A transit-time flow sensor determines a rate at which fluid flows by measuring a propagation time difference between upstream and downstream acoustic transmissions. This may involve providing an acoustic path consisting of sequentially traversed path segments and a repeating arrangement that uses the energy in a received pulse to repeat the pulse in the next sequential segment.

Abstract: Combining a plurality of local flow measurements made at more than one location to generate a composite flow value can improve the accuracy of the overall measurement. The reliability and long term accuracy of a multi-sensor flow measurement are improved by a two-step process. During an initial learning period, when all of the local sensors are providing accurate local measurements, a calibration table is built up that associates each calculated composite flow value with the set of local flow signal values from which it was calculated. In a subsequent operational period each time the composite flow rate is to be determined the flow meter apparatus first checks to see if all the local sensors are working properly and, if one of them is not working properly, its output is replaced with the corresponding value from the calibration table.

Abstract: Problems of instability and non-linearity in probe-type magnetic flow meters are ameliorated by either or both of a conductor coating connecting a tip portion of the probe with a supporting probe stem and flat end plates parallel to the flow direction that are arranged adjacent to the sensing electrodes and that act to straighten and confine fluid flowing past the electrodes.

Abstract: A transducer assembly may comprise a thickness-mode piezoelectric ceramic body, a pair of foil conductors with mesh end portions, and a coupling medium used to fill in the interstices in the meshes. The foil conductors are held in contact with the electrode layers by a selected combination of adhesive mechanical clamping forces. One of the conductors is placed between one face of the ceramic body and a window that separates the transducer assembly from a fluid to be measured. The other conductor is held between the other face of the ceramic body and a backing body, which may be an acoustic isolator or a resonant isolating structure comprising a resonant body and an acoustic mass that is substantially heavier than the ceramic element.

Abstract: In thermal pulse flow measurements a relatively small bolus of flowing fluid is heated or cooled and the time required for the bolus to move downstream a known distance is measured. In many fluids, changing the temperature changes the acoustic transmission properties of the bolus from those of the rest of the fluid, so the bolus can be detected when it intersects an acoustic beam. The use of an acoustic beam or beams, which are usually defined between acoustic transmitting receiving transducers, typically provides a high frequency carrier which is modulated by the change in acoustic properties of the bolus when it passes between the two transducers. When compared to conventional thermal measurements, this acoustic approach provides faster response times and can thus be used for measuring higher flow rates.

Abstract: A fluid flow sensor uses pairs of acoustic transducers to generate quasi-helical acoustic beams reflected multiple times from an inside surface of a pipe. The transducers are arranged so that each two pairs generate counter-rotating beams. When fluid flowing in the pipe has both a rotary and an axial flow component the rotary component adds to the apparent flow rate measured in one rotational direction and subtracts from that measured in the other. Hence, a combination of transit time measurements along the two paths can be used to cancel out the effects of the rotary flow component and yield a measure of the rate of flow along the pipe axis. In some cases multiple probes are used to increase the amount of flowing fluid that is sampled.

Abstract: A probe type acoustic transit-time flow sensor has paired transducers arranged to generate quasi-helical acoustic beams making a plurality of reflective contacts with a pipe's interior wall. The transducers in each pair are spaced apart along the flow axis so that transit-time measurements can be used both to measure the internal diameter of the pipe and to determine a flow rate. These measurements are combined to yield a volumetric flow rate. Various numbers of pairs of transducers can be put on a single probe or on multiple probes and used to provide a more accurate representation of a flow profile and therefore a more accurate volumetric flow determination.

Abstract: An acoustic time-of-flight size measuring device is added to the sensing head of an insertion probe sensor which may be used for measuring the flow of fluid in a pipe. The size-measuring device defines an acoustic beam making a plurality of reflective contacts with the pipe's interior wall. A time-of-flight measurement of this path length provides an accurate measurement of the internal diameter of the pipe. The magnitude of the transit time signal can also be used as an indicator of both insertion depth and angular orientation of the probe with respect to the pipe axis. In addition, the arrangement allows one to sense acoustic path attenuation caused by factors such as the buildup of deposits.

Abstract: Ultrasonic transducers for use in time-of-flight flow measurement are made by clamping a conformal material between a face of a piezoelectric element and a housing so as to efficiently acoustically couple the piezoelectric element to a flowing fluid wetting the housing. Both in-line and probe sensing heads are described, where the in-line sensor heads make use of side-looking transducers. Acoustic isolation arrangements are used to ensure that the transducer transmits and receives acoustic energy in a single, well-defined direction. Various pre-loading arrangements, such as metal springs that can be set by driving a wedge between the spring and the housing, are used to controllably force the piezoelectric element toward the housing.

Abstract: A moving target flow sensor has at least one vane mounted on a shaft and rotated or oscillated in a flowing fluid. Changes in the drag forces are measured to determine the flow rate of the fluid, and, in some cases, to determine the direction of fluid flow. In some arrangements a compliant coupling is connected in a shaft between a drive transducer and a moving vane so that the instantaneous shaft speed can vary. In another arrangement, several vanes are driven by transducers that are controlled to provide a selected average rate of rotation or oscillation. In all cases, because only a change in either angular setting or angular speed of the shaft is detected, the flow sensor is able to operate over a relatively wide operating range and its long term drift is relatively low.

Abstract: Fluid flow rate can be measured by determining the torque on a shaft used to oscillate or rotate a vane in the fluid. An intermediate gear, which links a drive gear to a gear on the vane shaft, is mounted in a yoke so that the shaft torque tends to move the intermediate gear out of position. An actuator controlled by a feedback control system is used to maintain the intermediate gear in nominal alignment. The forces required for this null-balancing operation are representative of the torque, and thus of the fluid flow rate.

Abstract: An electro-magnetic transducer interacts with a fluid in a tube and serves as either a flow sensor or as a pump. One or more electro-magnet(s) provide a magnetic flux transverse to a selected portion of the tube. The transducer has an electrically insulating sheet scrolled about an axis parallel to or coincident with that of the portion of the tube and extending from an axial streamlined body to an inner wall of the tube. One or more pair of electrodes are attached to the scroll so as to define a spiral electrical path between the two electrodes of the pair. These electrodes are connected to a voltage measurement circuit if the transducer is configured as a flow sensor or to a source of electric power if the transducer is configured as a pump. In addition, a flow commencement sensor is combined with the electro-magnetic flow sensor to provide a power-saving flow metering arrangement.

Abstract: A target-type flow meter uses a target in a flowing fluid and selectively changes the orientation of the target with respect to the direction of flow of the fluid between two or mote orientations, where the target provides a different flow impedance in each of the orientations. This change in flow impedance gives rise to a corresponding difference in drag forces exerted on the target by the flowing fluid. Those forces, or displacements associated with them, are measured to determine the rate of fluid flow. In some cases the target may be a vane attached to a shaft rotated by a motor. In others, the target may be a vane structure attached to a post in a flexible fashion so that it can be oscillated transverse to the flow direction by fixed electromagnets acting on a permanent magnet portion of the vane structure.

Abstract: A significant problem in the flow probe art is that of accurately positioning a flow-sensing portion of the probe at a selected location within a pipe. Several arrangements are provided for determining the insertion depth of flow sensing probes, for measuring diameters of the pipes in which they are inserted, and for detecting the depth of those pipes. These generally involve adding to the flow probe a depth measurement device for generating an energetic beam that is reflected from the pipe or from an insertion fitting. One such sensor uses a phased array of piezoelectric element to serve both in a pulse-echo distance measurement device and in a time-of-flight flow measurement device.

Abstract: A time-of-flight flow sensor, of the type in which a measured phase difference between upstream and downstream acoustic propagations is representative of fluid flow rates, is operated at two distinct frequencies. Operation at a relatively low propagation frequency yields a first phase difference signal that is unambiguously representative of the rate of flow but that has a larger than desired measurement error. Operation at the higher frequency provides a lower measurement error, but may be ambiguous because of the modular nature of phase detectors. The low frequency phase difference signal can be used by a signal processor to determine a compensation term that can be combined with the higher frequency phase difference signal to remove the phase detector ambiguity, if one is present.