Analog signal processing method for vortex detector

Abstract

A vortex detector for low flow rates comprises a vane that is located downstream from a vortex generator and is connected at only one end in a canthever manner to a cylindrical housing, which defines a flow passage. The end of the vane connected to the housing includes an area of reduced thickness that acts as a resilient, plastic hinged joint to make it easier for weak vortices generated by the vortex generator to impart vibrations or deflections to of the vane. Strain gauge transducers in the area of reduced thickness detect deflections or vibrations of the vane and produce analog electric signals having amplitudes and frequencies that are related to the strengths, frequencies, and period of the vortices. The analog signals are converted to digital signals, which are indicative of strengths, frequencies, and periods of the vortices, but only such digital signals that result from corresponding analog signals with amplitudes above a threshold value are treated as originated from vortices action on the vane for purposes of determining vortex periods. Updated average vortex frequencies, calculated from vortex periods that are within an allowable deviation range, are used to determine instantaneous flow rates. The instantaneous flow rates are then processed through a smoothing function to stabilize flow rate outputs and displays.