Flowmeter

• US 4,185,498 A
• Filed: 07/20/1978
• Issued: 01/29/1980
• Est. Priority Date: 06/03/1977
• Status: Expired due to Term

• Current Assignee: ITT Industries (ITT, Inc.)
• Original Assignee: ITT Industries (ITT, Inc.)
• Inventors: Watson, Christopher A., Bearcroft, Kenneth E., Bronzite, Michael, Palmer, Alan G.
• Primary Examiner(s): Ruehl, Charles A.
• Application Number:
  US05/926,260
• Time in Patent Office: 558 Days
• Field of Search: 73/194 A, 73/597
• US Class Current: 73/861.27
• CPC Class Codes: G01F 1/66 by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level

Abstract

A flowmeter sometimes called ultrasonic, but sometimes not ultrasonic including two phase locked loops, a portion of each of which form a common path through amplifiers, an electronic attenuator with automatic gain control, a pulse detector, and a pulse or phase comparator. The pulse comparator, through switches, controls first and second voltage controlled oscillators on a time shared basis. First and second counters are connected from the first and second voltage controlled oscillators, respectively. The first and second counters supply transmission pulses to submerged first and second facing transducers, respectively, at different times. The voltage controlled oscillators are always driven until a later counter pulse coincides with a corresponding received pulse. Time sharing is, in part, accomplished by beginning energy propagation in opposite directions at successive times and before either pulse is received.

Claims

1. A flowmeter comprising:

a first transducer for mounting at a first point in a pipeline;

a second transducer for mounting in alignment with said first transducer, but at a second point in said pipeline spaced lengthwise from said first point;

first means including first and second voltage controlled oscillators to energize respectively said first and second transducers at first and second respective times to propagate pulses through fluid in said pipeline;

second means to receive pulses transmitted from said first and second transducers through said fluid and subsequently through said second and first transducers, respectively;

a first threshold detector of one polarity and of a first threshold level connected from said second means;

a first storage device;

a second storage device having an output lead, said first storage device being adapted to enable and to disable said second storage device, said first storage device being connected from said first threshold detector to enable said second storage device when said first threshold level is exceeded;

a second threshold detector of a polarity opposite said one polarity and of a second threshold level connected from said second means to said second storage device to transmit a received pulse from said second storage device on said output lead thereof when said second threshold level is reached, but only after said first storage device has enabled said second storage device;

third means operable synchronously with said first means to reset said first and second storage devices; and

fourth means connected from said second storage device output lead to said first and second voltage controlled oscillators to maintain the difference between the output frequencies of said first and second voltage controlled oscillators directly proportional to one condition of a fluid in the pipeline.

2. The invention as defined in claim 1, wherein said condition is the volume rate of flow of fluid in said pipeline.

3. A flowmeter comprising:

a first transducer for mounting at a first point in a pipeline;

a second transducer for mounting in alignment with said first transducer, but at a second point in said pipeline spaced lengthwise from said first point;

first means including first and second voltage controlled oscillators to energize respectively said first and second transducers at first and second respective times with first and second pulses to transmit vibrations through fluid in said pipeline in opposite directions, respectively;

second means to receive vibrations transmitted from said first and second transducers through said fluid and subsequently through said second and first transducers, respectively;

a first counter adapted to count a plurality of pulses before reset, and connected from said first voltage controlled oscillator (VCO);

a second counter adapted to count a plurality of pulses before reset, and connected from said second VCO;

third means connected from said second means and said first and second counters to control the frequency of said first VCO and to control the frequency of said second VCO in a manner such that a first pulse, transmitted at a first time by said first transducer, arrives at said second transducer a second time later than said first time by an integral number of counts of said first counter, and in a manner such that a third pulse, transmitted at a third time by said second transducer, arrives at said first transducer a fourth time later than said third time by an integral number of counts of said second counter;

fourth means responsive to one state of said second counter to gate the output of said first VCO to said first transducer; and

fifth means responsive to one state of said first counter to gate the output of said second VCO to said second transducer.

4. The invention as defined in claim 3, wherein sixth means are provided which are connected from said first and second voltage controlled oscillators to maintain the difference between the output frequencies of said first and second voltage controlled oscillators directly proportional to one condition of the fluid in said pipeline.

5. The invention as defined in claim 4, wherein said condition is the volume rate of flow of said fluid in said pipeline.

6. A flowmeter comprising:

a first transducer for mounting at a first point in a pipeline;

a second transducer for mounting in alignment with said first transducer, but at a second point in said pipeline spaced lengthwise from said first point;

first means including first and second voltage controlled oscillators to energize respectively said first and second transducers at first and second respective times to transmit vibrations through fluid in said pipeline in opposite directions;

second means to receive vibrations transmitted from said first and second transducers through said fluid and subsequently through said second and first transducers, respectively;

a time shared comparator having an output capacitor and third means to charge and to discharge said output capacitor when one received pulse arrives respectively after and before a corresponding pulse of the output of a voltage controlled oscillator (VCO) which caused the transmission of the pulse received;

first and second storage capacitors to provide input control voltages to said first and second VCO'"'"'s, respectively; and

first and second switches connected from said output capacitor to said first and second storage capacitors, respectively; and

fourth means connected from said first and second VCO'"'"'s to operate each of said first and second switches momentarily, respectively, to modify the charge on said first and second storage capacitors when necessary to change the VCO frequencies such that the said received pulses occur after an integral number of pulses of a corresponding VCO.

7. The invention as defined in claim 6, wherein first and second unity gain voltage amplifiers are respectively connected from said first and second storage capacitors, and third and fourth switches are respectively connected from the outputs of said first and second amplifiers to said output capacitor, and fifth means connected from said VCO'"'"'s to operate said third and fourth switches alternately and momentarily to charge said output capacitor before a received or corresponding pulse arrives to initial voltages equal to those of said first and second storage capacitors, said initial voltages minimizing the time required for correcting the charge on said output capacitor.

8. A compound phase locked loop for detecting a property of a fluid comprising:

a first voltage controlled oscillator (VCO) having an input and an output;

a second VCO having an input and an output;

a first transducer;

a second transducer, said first and second transducers each being adapted to transmit and to receive energy respectively to and from each other, the transit times of the propagation of energy from said first transducer to said second transducer and vice versa being a function of the acoustical velocity and volume rate of flow of a fluid located between said first and second transducers;

logic means connected from the outputs of both of said VCO'"'"'s to sequence operation, said logic means including first counter means connected from said first VCO to transmit first pulses only from said first transducer on a count of said first counter means, said logic means including second counter means connected from said second VCO to transmit second pulses from said second transducer on a count of said second counter means, but spaced in time from said first pulses and all received pulses;

a common receiver to act upon pulses received by both of said transducers, said common receiver producing received pulse edges;

a common pulse comparator connected from both of said VCO'"'"'s and from said common receiver to receive pulse edges therefrom, said logic means including third means to supply pulse edges for comparison from said first and second counter means to said common pulse comparator;

first and second electronic servo means connected from said common pulse comparator to said first and second VCO inputs, respectively, and actuable to cause a first alternate set of received pulse edges to lie in coincidence with edges corresponding to output pulses of said first counter means, and actuable to cause a second alternate set of said received pulse edges to lie in coincidence with edges corresponding to output pulses of said second counter means; and

first and second switch means to connect said comparator to said VCO inputs alternately on a time shared basis.

9. A phase locked loop comprising:

a voltage controlled oscillator (VCO) having an input and an output;

a pulse comparator having first and second inputs and an output;

means connected from said VCO output to transmit a pulse over a path which varies the propagation time, said transmitted pulse being received at the end of said path by said pulse comparator first input, said pulse comparator second input being connected from said VCO output, said comparator output being connected to said VCO input to act as an electronic servomechanism and to drive said VCO until the output thereof produces a predetermined number of integral cycles during the time period between the instant that said pulse is transmitted and the instant that it is received at said pulse comparator first input, said pulse comparator including a first capacitor to retain a voltage to drive said VCO, a second capacitor having a capacitance smaller than said first capacitor, first means actuable to charge said second capacitor periodically to the voltage of said first capacitor, second means actuable to charge or discharge said second capacitor depending upon the accuracy of the number and phase of said predetermined number of cycles, third means actuable to connect said first and second capacitors in parallel for equalizing the voltages thereon, and fourth means to actuate said first means, said second means, and said third means repeatedly in that order.