Fischer & Porter Company

John S Yard

Peter J Herzl

Roy F Schmoock

Daniel J Evans

Elmer D Mannherz

Warren O Strohmeier

A mass flowmeter of the Coriolis-type in which fluid to be metered is conducted through a flow tube which is coiled to define a helix having a pair of identical measuring loops forming a double loop, on either side of which is an isolation loop. The fluid is admitted into the input of one isolation loop and is discharged from the output of the other isolation loop. The helix is concentric with a support structure having at one end a flow inlet to which the isolation loop input is affixed, and at the other end a flow outlet to which the isolation loop output is attached. A rigid bar parallel to the axis of the helix is joined to the junction of the measuring loops as well as to the respective junctions of each measuring loop and its associated isolation loop whereby the isolation loops then function as decoupling springs to effectively isolate the bar and the double measuring loop from external forces.

Coriolis-type flowmeter

An electromagnetic flowmeter in which fluid to be metered passes through a flow tube to intersect a magnetic field whereby the voltage induced in the fluid is transferred to a pair of electrodes mounted in the flow tube to yield a flow-induced signal having a random noise component. This field is established by an electromagnet supplied with an excitation current creating a magnetic field that is alternately turned 'on' and 'off' at a low frequency drive rate. The resultant flow-induced signal is sampled during each 'on' and 'off' field condition, successive differences therebetween serving to develop an analog output signal having a random noise content. To automatically adjust the output response time of the system as a function of the random noise content and thereby minimize the adverse effects of noise on the system, the analog output signal is fed to a statistical analyzer in which the signal is digitized before being supplied to a microcomputer programmed to determine the statistical significance of the difference between two arithmetic means. To this end, a first series of successive values of the digitized signal is used to establish the first mean and a first variance, and a second series of successive values to establish the second mean and a second variance. The computer, on the basis of the Student 't' statistic, calculates the difference between the two means to produce a digital output signal having the desired response time.

Electromagnetic flowmeter system having automatically adjusted response

An electromagnetic flowmeter in which fluid to be metered passes through a flow tube to intersect a magnetic field whereby the voltage induced in the field is transferred to a pair of electrodes mounted in the flow tube to yield a flow-induced signal. This field is established by an electromagnet supplied with excitation current through a periodically-operated switch to create a magnetic field which during each operating cycle is alternately turned on and off or reversed in flux direction at a predetermined drive frequency, as a consequence of which the signal includes undesirable noise components formed by even and odd harmonics of the drive frequency. To suppress such harmonic noise, the flow-induced signal is applied to a converter that includes a pair of synchronous demodulators operating in phase opposition and so synchronized with the periodically-operated switch that one demodulator passes its output to an integrator during the first half cycle of the drive frequency only in a gating interval in which the magnetic field is turned on and is at a constant flux level, and the other demodulator thereafter passes its output to the same integrator during the second half cycle only in a gating interval in which the magnetic field is turned off or is at a constant flux level in the reverse direction.

Harmonic noise suppression in electromagnetic flowmeter

An adapter for a vortex-shedding flowmeter serving to render the meter capable of measuring low flow rates below its normal operating range. The flowmeter includes a flow tube forming a passage for the fluid to be measured and an obstacle assembly mounted therein for generating fluidic oscillations which frequency is proportional to flow rate. The adapter includes means that act to restrict the effective area of the fluid traversing the obstacle assembly, whereby for the same velocity of flow past the assembly a smaller amount of fluid is metered. By providing a set of adapters introducing different areas of restriction, the meter is then able to function as a multi-range instrument.

Multi-range vortex-shedding flowmeter

An electromagnetic flowmeter having a flow tube which is interposable in a normally less-than-full fluid line. A pair of arcuate electrodes are mounted in the flow tube at opposed positions therein to span a substantial portion of the total tube circumference, whereby they are operative with respect to fluid in the tube in a range extending from a level close to empty to a level close to full. Associated with the flow tube is an electromagnet that is excited by a periodically-interrupted direct current to establish a magnetic field in the tube which is intercepted by the fluid passing therethrough to induce a signal in the electrodes. This signal is sampled during the steady state intervals of the magnetic flux to provide an output free of zero-shift error and of interference voltages. The flux distribution is such as to progressively decrease in intensity as one goes from the top to the bottom of the tube to provide an output signal which is indicative of flow rate and is independent of the liquid level so that an accurate reading of flow rate is obtained regardless of the level of fluid in the flow tube.

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Doylestown, PA, United States of America

John S Yard