Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.