Fischer & Porter Company

Peter J Herzl

Warren O Strohmeier

Harold W Metzger

Victor P Head

Robert G Shaffer

Daniel J Evans

John S Yard

Robert J Augustine

Richard L Crumley

A mass flowmeter of the Coriolis-type having a primary wherein fluid being metered is conducted through a flow tube in the form of a double loop whose loops are excited by a driver to vibrate in phase opposition at the resonance frequency of the tuning fork. Because fluid passing through the flow tube is subjected to Coriolis forces, the vibrating loops are caused to torsionally oscillate in accordance with the mass flow of the fluid. A pair of sensors mounted on the respective loops sensor signals which are applied to a differential amplifier in a signal recovery system forming the secondary of the meter to produce an output voltage that is a function of mass flow. This output voltage is applied to the input of a microcontroller coupled to an indicator providing a reading of mass flow. The meter is calibrated so that at the resonance frequency under normal operating conditions it produces a reading proportional to mass flow. Because of changes in the density of the fluid and other variables encountered under actual operating conditions which bring about deviations in the resonance frequency and in the amplitude of the torsional oscillations, also applied to the microcontroller are frequency and amplitude signals which reflect these deviations. The microcontroller, in response to these signals, acts to correct the mass flow indication to provide an accurate mass flow reading.

Signal recovery system for mass flowmeter

A converter for converting a variable data frequency which lies in a low frequency range whose upper limit is about 200 Hz to a corresponding digital value. The converter includes an electronic counter having an enabling input and a count input. Derived from the data frequency is a data signal whose frequency is a given sub-multiple of the data frequency as selected by a digital computer. The data signal is applied to the enabling input to enable the counter for a period equal to the duration of a half cycle of the incoming data signal. Derived from an electronic clock operating at a constant frequency above 10,000 Hz is a clock signal whose pulse repetition rate is a given sub-multiple thereof as selected by the computer. These clock pulses are applied to the count input of the counter whereby the count accumulated therein is determined by the duration of the enabling period. This count is entered in the computer which, having selected the data signal and the clock signal, knows the scale factor, and can then, on the basis of the entered count, calculate the true period (P) of the data frequency (F) and provide a digital output corresponding to the frequency as determined by the equation F=1/P.

Frequency-to-digital value converter

A mass flowmeter of the Coriolis-type in which the fluid to be metered is conducted through a loop supported on a stationary frame, the loop having a natural resonance frequency. Mounted at the vertex of the loop is a ballistic vibrator which is electrically energized to cause the loop to vibrate at its natural frequency on either side of its static plane. The fluid passing through the loop is subjected to Coriolis forces, causing the vibrating loop to torsionally oscillate in accordance with the mass flow rate of the fluid. This torsional oscillation is sensed by a pair of strain gauge transducers mounted in balanced relation on opposite legs of the loop, whereby the signals yielded by the transducers have a difference in magnitude therebetween that depends on the amplitude of the torsional oscillation. These signals are applied to a differential amplifier whose output is proportional to the mass flow rate of the fluid.

Coriolis-type mass flowmeter

A mass flowmeter of the Coriolis type in which the fluid to be metered is conducted through a pipe which is coiled to form a double loop. The pipe is anchored at its inlet and outlet ends and also at its center which is the junction of the two loops to define a tuning fork in which the identical loops on either side of the anchored center function as tines that are free to vibrate as well as to twist. An electromagnetic driver mounted at the vertex of the double loop is electrically energized to cause the loops to vibrate in phase opposition at the natural frequency of the tuning fork. The fluid passing through the double loop is subjected to Coriolis forces, thereby causing the vibrating loops to torsionally oscillate in accordance with the mass flow of the fluid. Capacitance sensors are symmetrically mounted on the respective loops to yield signals having a difference in magnitude and phase that depends on the amplitude of the torsional oscillations, these signals being applied to a differential amplifier whose output is proportional to the mass flow of the fluid.

Double-loop Coriolis type mass flowmeter

An analog current-to-frequency converter which produces output pulses whose repetition rate depends on the current value. Included in the converter is an operational amplifier having an inverting input to which is applied a negative input voltage whose magnitude is proportional to the current value. The amplifier functions as an integrator which yields a positive output only when the voltage at its inverting input is negative. The integrator output is so coupled to the input of a one-shot as to cause the one-shot to generate an output pulse each time the integrator output crosses over from negative to positive. A NOR gate coupled to the one-shot acts to activate a switch only when the integrator output goes positive, the activated switch applying a positive reference voltage to the inverting input of the integrator through a balance resistor, thereby initiating a swing from negative to positive until a point is reached at which the integrator output goes from positive to negative. At this point the switch is deactivated to remove the positive reference voltage, the integrator output again going positive as a result of which the one-shot generates another pulse. Thus the integrator output in response to the applied negative input voltage oscillates from positive to negative to cause the one-shot controlled thereby to generate output pulses whose repetition rate is proportional to the value of the current being converted.

Current-to-frequency converter

A hybrid sensing system for a vortex-type flowmeter in which fluidic oscillations are generated at a frequency depending on the flow rate of the fluid being metered, the flowmeter being operative throughout a wide range of frequencies. The system includes both a thermal sensor whose signal, which is applied to a first pre-amplifier, has an amplitude that is relatively high in the low-frequency portion of the meter range, and a force sensor whose signal, which is applied to a second pre-amplifier, has an amplitude that is relatively high in the high-frequency portions of the range. The signal amplitudes of the pre-amplifiers are compared to effect control of a selector switch which acts to couple the pre-amplifier yielding a greater output at the prevailing frequency to a trigger generating pulses at a rate determined by this frequency and indicative of flow rate. The operation of the switch may also be made subject to the prevailing frequency so that a switch-over from the first to the second pre-amplifier will not take place even if justified by the amplitude difference therebetween, unless the then prevailing frequency exceeds a predetermined value.

Hybrid sensing system for vortex flowmeter

Each guide member of a fluidic oscillator has a diverter which acts to split the flow from the power nozzle into a control stream that is diverted toward the inlet of an associated feedback path and an output stream that is directed toward an output duct. The resultant fluidic forces exerted alternately on the diverters are sensed, and the sensor outputs are processed to generate a sinusoidal wave from which volumetric flow or mass flow output signals are derived.

Oscillatory flowmeter

An ultrasonic flowmeter for accurately measuring the flow rate of clean or dirty industrial process fluids passing through a pipe provided with upstream and downstream transducers. A transmission signal produced by a high-frequency generator acts to energize the transducers which are alternately excited at a relatively low switching rate whereby a beam emitted by the excited transducer is propagated through the fluid at an angle to the flow axis of the pipe and is intercepted by the other transducer to yield a received signal that is displaced in phase from the transmission signal to an extent depending on the transit time of the beam which reverses direction during each switching cycle. The received signals from the transducers are converted into a square wave that is compared to a wave derived from the transmission signal to produce a comparison output which is fed through a low-pass filter to exclude the high frequency content thereof. The filter yields a square wave in which the voltage drop between the upper level of the wave representing beam transit time in one direction and the lower level representing beam transit time in the reverse direction, reflects the time delay difference between these transit times. The flow rate of the fluid is then derived from the time delay difference.

Ultrasonic flowmeter for clean and dirty fluids

A vortex-shedding flowmeter for accurately measuring the flow rate of gases and liquid conducted through a flow tube provided with a dual-body shedder having a front section fixedly mounted across the tube, behind which is a pivotally mounted rear section separated from the front section by a gap configured to produce a fluidic feedback path so that a strong hydraulic interaction takes place between the sections and both actively contribute to the formation of periodic vortices which are alternately shed on either side of the shedder. The rear section is mounted on a pivot shaft extending along an axis normal to the flow axis of the tube, whereby the vortices which appear on either side of the rear section induce the rear section to oscillate. These oscillations are sensed to produce a signal representing the flow rate.

Dual-body vortex-shedding flowmeter

A Doppler-type ultrasonic flowmeter whose transmitting transducer is excited by an oscillator to project into the meter pipe a diverging beam of ultrasonic energy. The projected beam is reflected by contaminants carried by the fluid lying within the zone in which the projected beam intersects a reception beam converging toward a receiving transducer which picks up the reflected energy. The transmitted signal is mixed with the Doppler signal yielded by the receiving transducer to yield positive and negative beats which are applied to a low-pass filter from which is extracted a band of negative beat frequencies representing the disparate flow velocities of the contaminants within the zone dictated by the prevailing velocity profile of the fluid. This band is subjected to spectral analysis to determine the velocities of the contaminants and their relative percentages, from which the flow profile of the fluid being metered is calculated to ascertain the mean flow velocity thereof.

Doppler-type ultrasonic flowmeter

A camming device for centering a meter or other instrument having a cylindrical body with respect to the upstream and downstream pipes of a flow line in which the meter is interposed. Each pipe is provided with an end flange having a circle of bolt holes, the pipe flanges being bridged by clamping bolts which pass through the holes to encage and compress the meter, the holes having clearances allowing limited bolt play. Rotatably mounted on the meter body is a camming device provided with a symmetrical array of camming edges that tangentially engage the bolts. When the device is turned on the meter body, it acts to force the bolts to their extreme hole positions, as a result of which the meter body is caused to assume a position concentric with the bolt circle that is centered with respect to the pipes.

Centering device for flowmeters interposed in flow line

A vortex-shedding flowmeter capable of accurately measuring the flow rate of a liquid or gas even under extreme operating conditions. The fluid to be metered is conducted through a flow pipe having a shedder/sensor unit torsionally supported therein on a pivot axis normal to the flow axis of the pipe, said unit being caused to oscillate about said axis at a rate proportional to the flow rate of the fluid. The torsional support included a torque tube whose base is received within a bore in the pipe and is welded thereto and whose tip is welded to one end of the shedder/sensor unit to provide a closed structure preventing leakage of fluid from the pipe. These oscillations are converted into corresponding electrical signals by an external torque transducer operatively coupled to the unit by a sensor link assembly including a rod which extends into the torque tube and is welded to the tip thereof.

Vortex-shedding flowmeter with unitary shedder/sensor

A vortex-shedding flowmeter capable of accurately measuring the flow rate of a liquid or gas even under extreme operating conditions. The fluid to be metered is conducted though a flow pipe having a shedder fixedly mounted therein. A sensor which is caused to oscillate at a rate proportionate to the flow rate of the fluid is torsionally supported downstream behind the shedder on a pivot axis normal to the flow axis of the pipe, the torsional support including a torque tube whose base is received within a bore in the pipe and is welded thereto and whose tip is welded to one end of the sensor to provide a closed structure preventing leakage of fluid from the pipe. The sensor oscillations are converted into corresponding electrical signals by an external torque transducer operatively coupled to the sensor by a sensor link assembly including a rod which extends coaxially into the torque tube and is welded to the tip thereof.

Vortex-shedding flowmeter with torsional sensor mounted on torque tube

A dual output vortex-shedding flowmeter in which a liquid or gas to be metered is conducted through a flow tube having a shedding body transversely supported thereon, the flowmeter being usable in a custody transfer system requiring two independent output signals. Torsionally-supported behind the body and spaced therefrom by a gap is a drag-actuated sensor which includes a pair of parallel legs symmetrically disposed with respect to a spindle forming the fulcrum axis of the sensor, this axis being normal to the longitudinal axis of the tube. In operation, torques are developed alternately in the clockwise and counterclockwise directions, causing the torsionally-supported sensor to oscillate at a frequency proportional to the flow rate of the fluid. These oscillations are converted into corresponding electrical signals by a pair of transducers coupled to opposing ends of the spindle to provide two independent outputs.

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Morrisville, PA, United States of America

Peter J Herzl