External sensing system for vortex-type flowmeters

Claim 1

An external sensing system for a vortex-type flowmeter in which the fluid to be metered is conducted through a flow tube having an obstacle assembly therein producing periodic vortices which cause a deflectable element to vibrate at the same rate, these vibrations being transmitted to an external sensing point, said system comprising: A. a pneumatic cell whose body has a chamber therein covered by a diaphragm which is linked to said sensing point and is vibrated to generate a compressional wave corresponding to said periodic vortices; B. a pick-up cell whose body has a cavity therein which is covered by a pressure-sensitive transducer; and C. a pipe coupling said chamber to said cavity, whereby said compressional wave is conveyed to said transducer to generate an output signal, said pipe having a relatively small diameter to define a constricted passage offering significant resistance to said compressional wave to a degree causing said transducer to provide an output signal whose frequency is a function of the flow rate and whose amplitude is inversely proportional to said frequency and is therefore proportional to the mass of the fluid flowing through said tube.