US 4,312,235 A · Sensor and meter for measuring the mass flow of a fluid stream

Abstract

A flowmeter for measuring the mass flow of a fluid stream, such as air, in a duct includes a sensor and electronic circuitry. The sensor includes a drag surface mounted to or forming part of an oscillatory element and mounted in the fluid stream for flow-damped oscillation. The oscillatory element is stimulated by a drive transducer and a pickup transducer senses the flow-damped oscillations. An intermediate circuit terminates the drive at a certain peak amplitude and measures the time interval required for the amplitude of the flow-damped oscillations to decay a predetermined amount. That interval is indicative of the fluid mass flow. The sensor may be a cantilevered beam. The beam may also be disposed behind a shroud and include a drag plate extending upstream of the shroud therefrom. The sensor may be a beam constrained to torsional oscillation about a longitudinal axis. The transducers are piezoelectric devices mounted on a beam in proximity with its neutral axis.

Claims22

Dependent claims

A mass flowmeter for measuring the mass flow of a fluid stream in a duct, comprising:

sensor means having a base and oscillatory means supported by and adapted for oscillatory motion relative to said base, said base being adapted to be fixedly positioned relative to said duct such that at least part of said oscillatory means extends into the duct for flow-damped oscillation in the fluid stream therewithin, said oscillatory means including drive transducer means responsive to an electrical input signal for stimulating oscillatory motion thereof and pickup transducer means for providing an electrical output signal indicative of the flow-damped oscillations thereof;
and
electronic circuit means being operatively connected to said drive transducer means for applying an electrical input signal thereto to stimulate said oscillatory means to a peak amplitude of oscillation and for removing said input signal and being operatively connected to said pickup means for subsequently determining the interval required for the amplitude of said oscillations to decay from a predetermined upper threshold value no greater than said peak oscillation amplitude to a predetermined lower threshold value, said determined interval being indicative of the mass flow of said fluid.

Dependencies are inferred from the claim text.

Sensor and meter for measuring the mass flow of a fluid stream

Life of this patent

Sensor and meter for measuring the mass flow of a fluid stream

Life of this patent

Abstract

Claims22