Ultrasonic flow meter
AssigneeBadger Meter, Inc.
InventorsBock W. Lee, William H. Vander Heyden, Stephen S. Bell
Life of this patent
Estimating the term…
Abstract
An improved apparatus and method for measuring fluid flow in a conduit enables the transmission of ultrasonic signals through the fluid with low signal attenuation and unique phase determination. Ultrasonic burst signals are simultaneously transmitted to axially spaced receivers adjacent a conduit. The transmitted signal is made up of a signal burst having two different frequency signals. The signal frequencies are selected to prevent unwanted signal attenuation by entrapped gases in the fluid and to allow an unambiguous phase determination for the received signal burst.
Claims23
A flow detecting apparatus for measuring fluid flow in a conduit comprising:
- a. a pair of compressional energy transmitting and receiving transducer means adapted to be disposed adjacent said conduit for transmitting compressional energy signals along a path having a component axially of said conduit and a component transversely of said conduit, and for receiving said compressional energy signals transmitted along said path,
- b. means for generating a first signal having a frequency, f, less than a predetermined upper limit, for providing unambiguous phase detection between signals received by said transducer means,
- c. means for generating a second signal having a frequency f.sub.1,
- d. means for mixing said first and second signals to produce sideband frequencies f.sub.1 + f and f.sub.1 - f, said frequency f.sub.1 selected so that said sideband frequencies f.sub.1 + f and f.sub.1 - f are transmitted over a selected part of the spectrum,
- e. means for applying at least one of said sideband frequencies to said transducer means, for transmitting signal bursts in opposite directions along said path, and
- f. means for processing said received signals for providing a signal corresponding to (1) the transit time, t, of one of said signals along said path, (2) the square of the transit tiem t.sup.2, and (3) the difference in transit time .DELTA. t between said received signals, said processing means further providing a quotient signal proportional to .DELTA. t divided by t.sup.2, said quotient signal being substantially proportional to the velocity, v, of fluid flow such that .DELTA. t divided by t.sup.2 is proportional to v divided by l, where l is the length of said path.
In an ultrasonic flow measuring apparatus which provides a measure of fluid flow in a pipe by utilizing two spaced transducers for transmitting and receiving ultrasonic burst signals, said transducers providing an energy flow path therebetween having a non-zero component axially along said pipe, said apparatus providing transit time signals, t, for each of said received signals and difference time signals, .DELTA.t, representing the difference in time between corresponding transit time signals, and providing a flow determination utilizing a quotient signal .DELTA.t divided by t.sup.2, the improvement comprising:
- means for generating a first signal having a frequency f less than a predetermined amount,
- means for generating a second signal,
- means for mixing said first and second signals to produce upper and lower sideband signals,
- means for simultaneously applying said sideband signals to said transducers for transmitting same and
- means for mixing said received burst signals with a modulating signal for producing a single cycle sinusoidal waveform corresponding to each received signal.
A method of measuring fluid flow in a pipe from received pairs of signals comprising the steps of:
- a. generating a first signal having a frequency, f, selected to permit unambiguous phase comparision between said pairs of received signals,
- b. generating a second signal having a frequency f.sub.1,
- c. mixing said first and second signals to provide upper and lower side frequencies, said second frequency selected to permit substantially unattenuated signal transmission of said side frequencies through said fluid,
- d. simultaneously transmitting said side frequencies as a pair of oppositely directed burst signals along a path through said pipe,
- e. receiving said transmitted oppositely directed burst signals in axially spaced receiving means,
- f. utilizing said received signals for generating a transit time signal t corresponding to the time between simultaneous transmission and reception of said signals,
- g. generating a difference signal .DELTA.t corresponding to the time between said received burst signals, and
- h. providing a quotient signal .DELTA.t divided by t.sup.2 approximately proportional to v, where v is the fluid flow velocity.
Dependencies are inferred from the claim text.