Signal recovery system for vortex type flowmeter

Claim 2

A signal recovery system for a vortex-type flowmeter in which the fluid to be measured is directed past a vortex producing element therein to induce fluidic variations whose fundamental frequency is a function of the flow rate, said fluidic variations as well as variations resulting from hydrodynamic noise being detected by a sensor in the form of a pressure or force transducer which yields an electrical signal that varies as a function of frequency; said system comprising: A. A voltage-controlled band-pass filter coupled to the output of the sensor to transmit only those frequencies which lie within a narrow range whose center frequency is determined by a control voltage applied to the filter, and to attenuate all other frequencies; B. Means to generate a control voltage having an amplitude related to the velocity of the fluid passing through the flow tube, said means including an amplifier responsive to the sensor signal to produce an output in which a linear relationship exists between frequency and amplitude and means to rectify said amplifier output to produce said control voltage; C. Means to apply said control voltage to said filter to adjust the band-pass setting thereof so that the center frequency approximately corresponds to said fundamental frequency; and D. Means coupled to the output of the filter and responsive to said fundamental frequency to indicate the flow rate.

Claim 3

A system as set forth in claim 1, wherein said last-named means includes a Schmitt trigger to convert the fundamental frequency to a square wave.

Claim 4

A system as set forth in claim 1, wherein said vortex-meter is of the type including a set of swirl blades.

Claim 5

A system as set forth in claim 1, wherein said vortex-meter is of the type including a vortex shedding body.

Claim 6

A system as set forth in claim 1, wherein said vortex-meter is coupled to the exhaust of an internal combustion engine, and said control voltage is derived from an operating characteristic of the engine.

Claim 7

A system as set forth in claim 5, wherein said control voltage is produced by means deriving pulses from the ignition system of the engine, and means converting the pulses into a d-c voltage whose amplitude varies as a function of the pulse repetition rate.

Claim 8

A system as set forth in claim 1, wherein the output of said amplifier is applied to said band-pass filter through an automatic-gain-control system wherein the signal applied to said filter has a substantially constant amplitude throughout the useful range of the vortex-type meter.

Claim 9

A signal recovery system for a vortex-type flowmeter in which the fluid being measured is conducted through a flow tube having a vortex-producing element therein to induce fluidic variations whose fundamental frequency is a function of fluidic flow rate, said fluidic variation and variations resulting from hydrodynamic noise being detected by a sensor which yields an electrical signal, said system comprising: A. An automatic-gain-control circuit constituted by an amplifier coupled to the output of the sensor and a rectifier coupled between the output and input of the amplifier to provide an automatic-gain-control bias therefor, said amplifier yielding an output in which the amplitude of the signal is substantially constant throughout the useful frequency range; B. An operational amplifier coupled to said automatic-gain-control circuit to produce an output in which the amplitude varies linearly in proportion to frequency; C. Means to rectify the output of said operational amplifier to produce a d-c control voltage whose amplitude increases in accordance with the frequency of the applied amplifier output; D. A voltage-controlled band-pass filter coupled to the output of said automatic-gain-control circuit to transmit only those frequencies which lie within a narrow range whose center frequency is determined by a control voltage applied to the filter; E. Means to apply the control voltage produced by said rectifier means to said filter to adjust the band-pass setting thereof so that the center frequency thereof approximately corresponds to said fundamental frequency; and F. Means coupled to the output of the filter and responsive to said fundamental frequency to indicate the flow rate.

Claim 10

A signal recovery system for a vortex-type flowmeter in which the fluid being measured is conducted through a flow tube having a vortex-producing element therein to induce fluidic variations whose fundamental frequency is a function of fluidic flow rate, said fluidic variation and variations resulting from hydrodynamic noise being detected by a sensor which yields an electrical signal, said system comprising: A. An automatic-gain-control circuit constituted by an amplifier coupled to the output of the sensor and a rectifier coupled between the output and input of the amplifier to provide an automatic-gain-control bias therefor, said amplifier yielding an output in which the amplitude of the signal is substantially constant throughout the useful frequency range; B. An operational amplifier coupled to said automatic-gain-control circuit to produce an output in which the amplitude varies linearly in proportion to frequency; C. Means to rectify the output of said operational amplifier to produce a d-c control voltage whose amplitude increases in accordance with the frequency of the applied amplifier output; D. A voltage-controlled band-pass filter coupled to the output of said automatic-gain-control circuit to transmit only those frequencies which lie within a narrow range whose center frequency is determined by a control voltage applied to the filter; E. Means to apply the control voltage produced by said rectifier means to said filter to adjust the band-pass setting thereof so that the center frequency thereof approximately corresponds to said fundamental frequency; and F. Means coupled to the output of the filter and responsive to said fundamental frequency to indicate the flow rate.