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Abstract

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.

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First Claim