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EP0083633A1 - Controleur et detecteur d'ecoulement - Google Patents

Controleur et detecteur d'ecoulement

Info

Publication number
EP0083633A1
EP0083633A1 EP19820902407 EP82902407A EP0083633A1 EP 0083633 A1 EP0083633 A1 EP 0083633A1 EP 19820902407 EP19820902407 EP 19820902407 EP 82902407 A EP82902407 A EP 82902407A EP 0083633 A1 EP0083633 A1 EP 0083633A1
Authority
EP
European Patent Office
Prior art keywords
flow
fluid
signal
flowrate
tapered pin
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19820902407
Other languages
German (de)
English (en)
Inventor
Imad Mahawili
Timothy J. Boyle
Norvell A. Nelson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AMERICAN FLOW SYSTEMS Inc
Original Assignee
AMERICAN FLOW SYSTEMS Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by AMERICAN FLOW SYSTEMS Inc filed Critical AMERICAN FLOW SYSTEMS Inc
Publication of EP0083633A1 publication Critical patent/EP0083633A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
    • G01F1/20—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow
    • G01F1/22—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow by variable-area meters, e.g. rotameters
    • G01F1/24—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow by variable-area meters, e.g. rotameters with magnetic or electric coupling to the indicating device

Definitions

  • This invention relates to an electronic flow control system using a flow impact sensor in conjunction with electronic signal processing data and electronic control circuitry.
  • U.S. Patent 4,195,581 issued April 1, 1980 application entitled “Armored Rotameter” on an application of Fees discloses another type of structure described as “capable of accurately measuring low flow rates.”
  • This structure includes a metal body provided with a bore defining a vertical flow tube having a lower inlet into which a fluid to be measured is admitted and an upper outlet from which
  • OMPI S ⁇ . _ BO the fluid is discharged.
  • a pin rides up and down a slot as a float moves up and down the tube as a function of flow rate.
  • the pin is coupled to one end of a bar magnet link external to the meter body, the link being caused to swing to an extent and in a direction in accordance with float movement whereby an external bar magnet pointer follows the bar magnet link to indicate flow rate on the external scale.
  • a portion of the flow tube in which the pin moves is tapered.
  • a flow controller is provided incorporating a flow sensor which operates over both a “laminar” and what is called an “impact and discharge” flow regime-
  • a flow sensor which comprises a flow tube in one end of which is partially inserted a slidably moveable tapered pin.
  • the tapered pin is pressed into the flow tube by means of a spring loaded base plate with a curved cup-like re ⁇ ceptacle for that end of the tapered pin extending out of the flow tube.
  • the curved, cup-like receptacle is designed to completely reverse the direction of fluid flowing past the pin so as to prevent pressure variations sometimes existing in prior art impact sensors due to fluid impacting upon the plate and then moving perpendicularly to the direction of inlet fluid flow across the plate thereby creating a variable pressure ' region on the plate and iri erferring with the flow measurement.
  • the impact sensing structure comprises a cantilevered beam upon the free end of which is mounted a magnet.
  • the magnet travels in a curvilinear motion as a function of the impact of the fluid on the beam.
  • a Hall effect sensor is mounted on the outside of the flow chamber to detect motion of the magnet. The magnet moves in such a manner as to produce an output signal which partially corrects for the non-linearities inherent in the system.
  • the sensors provided in accordance with this invention are used in accordance with a signal condi ⁇ tioning circuit and either a digital or an analog proces ⁇ sing circuit to produce either a digital or an analog measure of the flowrate of the fluid whose flow is being measured at a selected temperature and pressure.
  • means are provided for compensating for pressure and temperature variations in the fluid whose flow is being measured, thereby to provide a measure of actual mass flow.
  • a micro ⁇ processor is employed to process the signals generated by the flow sensor.
  • This embodiment is particularly useful in the measurement of the mass flowrate of compressible fluids.
  • temperature and pressure sensors are also required.
  • the microprocessor therefore receives input signals representing flow data from the flow sensor, pressure from the pressure sensor and temperature from the temperature sensor. It processes these input signals to produce a measure of the actual mass flow. When this embodiment is used in a flow controller, this measure is
  • OMH SNATlb compared to the desired flow which is input to the system by the-operator.
  • the control valve is then adjusted so as to eliminate the difference between actual flow and desired flow. If desired, the actual flow rate is displayed to the operator.
  • a friction elimi ⁇ nation mechanism is provided and is selectively activated to ensure accurate readings from the flow sensor. This entire process is repeated continuously. If flow control is not required, this embodiment can be reduced to a pressure and temperature compensated mass flow meter by eliminating the control valve circuitry.
  • Figures la, lb and lc illustrate three different embodiments of the flow transducer mechanical portion of the flowmeter of this invention.
  • Figure 2 is a curve illustrating the output signal from a typical sensing device appropriate for use with this invention as a function of flowrate for one parti ⁇ cular fluid;
  • Figure 3 illustrates the output signal from a Hall effect sensor suitable for use with this invention versus flowrate for helium and nitrogen gases for a pin 2 having a taper of 0.062 "to 0.050";
  • Figure 4 illustrates the output signal from a Hall effect sensor suitable for use with this invention versus flowrate for watery-
  • Figure 5 illustrates the output signal from a Hall effect sensor as a function of pressure ' for a number of constant flowrates of nitrogen
  • Figure 6 illustrates the temperature correction factor associated with the output signals from the flow- meter of this invention as a function of different flow- rates
  • Figure 7 illustrates the electronic circuitry associ ⁇ ated with an embodiment of this invention used to convert the signals from the flow sensor, temperature sensor and pressure sensor to digital form and to generate a control signal in response thereto;
  • Figure 8 illustrates the signal conditioning circuit for use with the flow transducers disclosed in Figure 1 and the pressure sensor 101a disclosed in Figure 7;
  • Figure 9 illustrates the circuit used to produce a linear analog output signal from the output signal of the signal conditioning circuit disclosed in Figure 8;
  • Figure 10 illustrates the circuitry used to produce and display a digital output signal from the output signal of the signal conditioning circuit disclosed in Figure 8;
  • Figure 11 illustrates the relationship between absolute pressure and the pressure transducer output signal
  • Figure 12 is of use in illustrating the manner in which the flow sensor output signal and the pressure sensor output signal are used to generate a flow rate through three interpolations.
  • FIG. la illustrates the structure of the mechanical portion of one embodiment of this invention.
  • fluid whose flow is to be measured is passed into the structure through an input tube or nozzle 1 from a fluid source 16.
  • a tapered pin 2 carefully designed to provide a selected range of variable flow areas between the inner diameter of inlet nozzle 1 and the outer diameter of taper 2.
  • Taper 2 is freely mounted and is therefore capable of moving relative to inlet 1. As taper 2 moves out of inlet 1, the flow area between the outer diameter of taper 2 and the inner diameter of inlet nozzle 1 increases thereby allowing a larger flow rate.
  • the end 2a of taper 2 rests on the top surface 3A of deflector tube and impact plate 3.
  • the inner surface 3B of impact plate 3 (end face 3A of plate 3 is a portion of inner surface 3B) is preferrably carefully curved and contoured to reflect and turn 180° the fluid which impacts against " plate 3 after passing taper 2 so that this fluid then flows back up past taper 2 and the outside of tube to the exit connector 15.
  • Connector 15 allows the fluid to flow from the chamber formed in housing 8 and in which is mounted impact plate 3, and a portion of nozzle 1.
  • this inner surface 3B can also assume other shapes if desired provided the degradation in accuracy of flow measurement associated with a different shape is acceptable.
  • I pact plate 3 is mounted by means of spring 6 onto nozzle flange 17 which is mounted firmly in housing 8 by means of retainer nut 7.
  • "0" rings 9 seal cavity la to insure that there is no leakage into or out of this cavity.
  • Spring 6 insures that impact plate 3 is drawn closely adjacent to input nozzle 1 when no fluid is flowing thereby to bring tapered pin 2 firmly into nozzle 1.
  • taper 2 can penetrate sufficiently far into input nozzle 1 to block the flow of fluid. However this is not essential and taper 2 can, in some instances, be inserted only partly into nozzle 1 thereby allowing an annular area between the outside of pin 2 and the inside of nozzle 1 through which fluid can flow.
  • a magnet 4 Mounted on the bottom portion of impact plate 3 is a magnet 4. Magnet 4 is covered by either an elastomer such as Viton or a welded piece of steel to protect magnet 4 from corrosion by the fluid.
  • a printed circuit board 11 Placed on the bottom of housing 8 is a printed circuit board 11 on the inner face of which is mounted a Hall effect sensor which can, in one embodiment, be of the type known as a linear output Hall effect transducer or "LO ⁇ ET". Any other Hall effect - sensors can also be used as appropriate..
  • the deflection of the plate 3 may be detected by the use of optical methods, capacitance techniques, or reed switches for on/off flow sensing devices, or by direct coupling of plate 3 to a variable potentiometer for direct sensing of flowrate by measuring change in potentiometer resistance.
  • Printed circuit board 11 is mounted on the bottom of housing 8 by means of screws 12 and is spaced from housing 8 by spacers 13.
  • Impact plate 3 is held in cavity 1A by spring 6.
  • Spring 6 is sized so that in its nominal position of rest a sufficient space 14 is left between the bottom of impact plate 3 and the bottom surface 8A of housing 8 to allow impact plate 3 to move freely within its expected range of
  • the spring.rate and the taper geometry of pin 2 are selected to control the minimum and maximum flowrates through the system. In one embodiment suitable for measuring the flow of nitrogen, the spring rate was selected to be 0.9 lb/in and a taper was selected to yield a minimum measured flowrate of about 1 cc/min and a maximum measured flowrate of about 300 cc/min.
  • Figure IB illustrates another structure of this invention wherein the input nozzle 1 and the taper 2 are substantially as shown in the embodiment of Figure 1A.
  • taper 2 is allowed to rest freely on a canti ⁇ levered arm 3 at the free moving end of which is mounted a magnet 26.
  • the magnet again is preferably coated with a protective material, such as Viton, to protect the magnet from the fluid (possibly corrosive) whose flow is being measured.
  • Cantilever arm 23 is mounted on mounting block 25 by screw 24.
  • Magnet 26 is mounted upon the free moving end of arm 23 so as to be capable of motion relative to a sensing device 10 (preferably a Hall effect sensor) mounted on the inner surface of printed circuit board 11.
  • Printed circuit board 11 is mounted on the bottom of housing 8 in the same manner as the comparable board is mounted on the structure shown in Figure 1A.
  • Spacer 25 is sized to hold magnet 26 at a selected distance above the bottom surface of housing 8.
  • the structure shown in Figure 2B operates in a manner similar to that shown in 1A except that when fluid enters the input nozzle 1 and thereby displaces taper 2 to allow fluid to enter cavity 1A in housing 8, and to exit from output connecter 18, cantilevered arm 23 is depressed.
  • the movement of cantilevered arm 23 changes the relative locations of magnet 26 and Hall effect sensor 10 thereby changing the signal produced by sensor 10.
  • the output signal from sensor 10 can be calibrated to the flowrate for each type of fluid, the flow of which is being measured.
  • a substantial benefit is obtained from the structure shown in Figure IB from the fact that the motion of magnet 26 is nonlinear in relation to flow in such a manner as to tend to correct the output signal from Hall sensor 10 in the direction of being more linearly related to flowrate.
  • magnet 26 sweeps over an arc of approximately 0.100 inches in response to a flowrate which can vary from about 1 to 300 cc/min for example.
  • Cantilever arm 23 can be designed to have a number of different sizes to respond to a number of different flow- rates just as the spring 6 in the embodiment of Figure 1A can be similarly designed to accomodate a number of differen flowrates.
  • Figure 3C illustrates a third embodiment of the mechanical portion of this invention.
  • the structure is to some extent similar to that shown in Figure 1A and IB but differs where numbered differently.
  • fluid enters input nozzle 1 and displaces a tapered pin 2.
  • Taper 2 is mounted on a support 34 which is held by spring 37 to the bottom portion 38 of housing 8.
  • Spring-retaining bottom plate 38 is mounted above the bottom portion of housing 8.
  • printed circuit board 11 mounted as is the printed circuit board shown in Figure 1A.
  • Hall effect sensor 10 is mounted on the inner surface of printed circuit board 11 so as to detect the motion of impact plate 34.
  • Impact plate 34 contains as a portion thereof a magnet 36.
  • magnet 36 can be coated with a material such as Viton or a welded steel plate to protect corrosive liquids from attacking it.
  • Spring 37 is selected to have a desired spring rate and together with the taper selected for taper 2 to control the range of flowrates capable of being measured by the structure shown in Figure 3C. Fluid which enters cavity 1A exits through opening 18 as shown.
  • Typical curves of fluid flowrate versus output signal from the sensor 10 for use with the mechanical structure shown in Figures 1A, IB and 1C are shown in Figures 2, 3, 4, 5 and 6. It should be understood that these curves represent, however, different regimes of fluid flow through the device.
  • One feature of this invention is that it is capable of measuring flowrates for gases as low as one (1) cubic centimeter per minute, a flowrate which heretofore has been difficult to achieve. Yet the invention is capable not only of measuring flowrates at this level but also flowrates several orders of magnitude higher.
  • the structure of this invention operates in what is characterized as the laminar regime (corresponding to a flowrate of approximately 1 to 200 cubic centimeters per minute of nitrogen), and the impact and discharge regime corresponding to flowrates from about 200 cubic centimeters per minute up through the maximum flow capability of the device.
  • the surprising and nonobvious results of this invention are achieved in all regions but with particular emphasis upon the laminar region wherein reproducible and accurate flow measurements are obtained for flows as little as 1 cubic centimeter/min for gases.
  • a low frequency (two hundred to three hundred Hertz) vibration device is used intermitently to reduce internal friction in the structure and thereby obtain a more rapid and accurate response to changes in flows.
  • the force on taper 2 is predominantly the friction force of the fluid flowing past the taper.
  • the flowrate is necessarily extremely low within the laminar flow regime and thus the drag forces created on the taper are the only substantial forces tending to move the taper out of input nozzle 1 thereby to allow the passage of the fluid.
  • the spring (such as spring 6 shown in Figure 1A, cantilevered beam 23 shown in Figure IB, or spring 37 shown in Figure 1C) is sufficiently strong to restrain taper 2 from being forced out of nozzle 1.
  • the spring there can be a slight oscillatory motion set up between the fluid attempting to flow past taper 2 and the spring attempting to restore taper 2 to its normal position.
  • the equilibrium point is that which allows the flow of fluid in the steady state condition and this point is approached quite rapidly. No visible vibration appears in the flow using this system. Even when dither or vibration is used in an attempt to insure frictionless performance of the taper, the vibration is introduced at a frequency substantially different from the frequency of oscillation of the components of the flowmeter and thus does not appear in the fluid.
  • the fluid flowrate is large enough that the momentum of the fluid is sufficiently high to be of greater significance than the friction forces.
  • the two forces are substantially of the same magnitude and thus taper 2 responds to two different kinds of forces the friction drag forces along the skin of the taper and the impact forces of the fluid striking the taper and having its momentum changed as a result of the impact.
  • the impact flow regime predominates with the result that the taper behaves in a substantially quadratic manner according to theory.
  • the taper is carefully designed to insure proper response of the system over the range of flow in this regime.
  • the internal diameter of the nozzle was .062 inches.
  • a 0.5 inch taper 2 was used having a base outer diameter of 0.062 inches and a top outer diameter of 0.055 inches for a total taper of about 0.5°.
  • a flowrate greater than 300 cc/min results in less accuracy and reproducibility because of slight deformation of the spring as it approaches the deformation limits defined by Hooke's law.
  • Figure 4 shows two curves of the flowrate of water versus Hall sensor output signal for two different tapered pins 2 having the dimensions shown in Figure 4.
  • Taper 2 was fabricated of materials such as Teflon, Delrin, Kel-F or other plastics. Dissimilar materials are used for the taper 2 and nozzle 1 to prevent "lockup" of the taper in the nozzle, otherwise known as "galling." However, taper 2 and nozzle 1 can be made of the same material, if desired. In one embodiment using the same materials for taper 2 and nozzle 1, a 100° recess (made using a conical drill having a cone angle of 100°) in the nozzle tip eliminated the galling. The polishing of this recess after its formation removes sharp edges and results in taper 2 moving smoothly into and out of nozzle 1. Because both taper 2 and nozzle 1 are of the same material, adverse effects (such as taper 2 locking in nozzle 1) due to differential thermal expansion of the components when measuring the flow of fluid at other than the design temperature are eliminated.
  • adverse effects such as taper 2 locking in nozzle 1 due to differential thermal expansion of the components when measuring the flow of fluid at other than the design temperature are eliminated.
  • the sensors described above in conjunction with Figures la, lb and lc can be used in a digital flow meter, an analog flow meter, and a flow controller (either digital or analog preferably digital for ease of implementation).
  • the structure shown in Figures 8 and 10 depicts a digital flow meter at standard temperature and pressure.
  • the structure shown in Figures 8 and 9 depicts an analog flow meter as standard temperature and pressure.
  • the output signals from the structures of Figures 8 and 10 and Figures 8 and 9 repre ⁇ sents a mass flow rate at standard temperature and pressure or at some other single temperature and pressure for which the system is calibrated.
  • the structure shown in Figure 7 provides one means for carrying out this correction. While the structure in Figure 7 depicts in total a flow controller, by eliminating digital to analog converter 108, set point input 109, control valve amplifier 112 and control valve 114, the remaining circuitry function to correct the flowrate sensed by flow sensor 101c in accordance with the fluid temperature and pressure sensed by sensors 101b and 101a, respectively, and, in a manner to be described, to correct the flowrate for the actual temperatures and pressures of the fluid. The structure in Figure 7 does this through a digital processing technique. While this is the preferred embodiment of this invention, these corrections could also be made using analog circuitry.
  • Figure 8 illustrates the electronic circuit used in conjunction with the transducers disclosed in Figures 1A, IB or 1C to condition the signal from Hall sensor 10 prior to transmitting the signal to either an analog-to-digital converter or to an analog system.
  • the structure comprises a precision voltage reference 20, such as the H00701 manufactured by National Semiconductor Corporation, to provide the required supply voltage to Hall sensor 21 (product 91SS12-2 manufactured by Micro Switch Division of Honeywell).
  • Resistor Rl and potentio ⁇ meter R2 serve as a "zero adjust" circuit. By adjusting the setting of potentiometer R2 (typically 5K) the zero point on the output curve from Hall sensor 21 (see Figure 5) can be adjusted to a desired value.
  • the output signal from Hall sensor 21 is passed through resistor R4 (10K) to the inverting input lead of operational amplifier 22 (LM747).
  • the non-inverting input lead to operational amplifier 22 is connected to the adjustable potentiometer R2.
  • the output signal from ampli ⁇ bomb 22 is transmitted through resistor R6 (10K) to the inverting input lead of op amp 23.
  • the non-inverting input lead of op amp 23 is connected through resistor R9 (10K) to ground.
  • the output signal from op amp 23 is the output signal from the signal conditioning circuit and is designated as "A" in Figure 8. In the analog flow meter embodiments of this invention, output signal A is trans ⁇ mitted to the analog linearization circuit shown in Figure 9.
  • output signal A is transmitted to the digital conversion and display circuit shown in Figure 10.
  • output signal A is transmitted to analog multiplexer 103 shown in Figure 7.
  • the op amp 22 contains a feedback circuit comprising parallel-connected capacitor C4 (0.1 microfarad) and resistor R5 (10K ohms).
  • Op amp 23 includes a feedback circuit comprising series -connected resistors R7 (adjustable 50K ohms) and R8 (68K ohms) in parallel with capacitor C5 (0.47 microfarads).
  • Adjustable resistor R7 is used to adjust the gain of the signal conditioning circuit shown in Figure 8. Since the transducers shown in Figure 1 are, in general, nonlinear, the output signal A of the signal conditioning circuit is also, in general, nonlinear as shown in Figure 11 (which shows the output signal from the Hall sensor associated with pressure sensor 101A).
  • Figure 9 illustrates the analog linearization and output circuit used with this invention when the structure shown in Figures 1A, IB or 1C is used as an analog flow meter.
  • the analog circuit in Figure 9 produces a zero to 10 volt linear output signal from the generally non-linear output signal from the signal conditioning circuits 101 shown in Figures 7 and 8.
  • Analog multiplier 31 (AD 534 commercially available from Analog Devices Inc.) is con ⁇ nected as a squarer to square the output signal A from amplifier 23 shown in Figure 9 and produce an output signal C 2 A 2 on output pin 12.
  • the output signal C 2 A2 from multiplier AD534 is applied across resistors R12 (10K) and R13 (2k) to produce an output signal C 3 C_A 2.
  • C 3 C 2 A is transmitted to the inverting input lead of operational amplifier 32 (the well known M747) which is connected as a summing inverter.
  • Resistor potentiometer
  • R13 is adjustable to allow the magnitude of the constant
  • Op amp 33 merely inverts the output signal from op amp 32 to the proper polarity.
  • the output signal from op amp 33 is approximately linear in the range of 0 to 10 volts and provides a direct linear measure of the flowrate sensed by the flow transducer.
  • the output signal from op amp 23 (Fig. 8) is denoted as A which equals f(p) (i.e. which is a function of the sensed flow).
  • the output signal from amplifier 33 has its shape controlled by the constants C, , C 2 and C 3 - Constant C, is determined by the values of the two series connected resistors R10 and Rll.
  • R10 is approximately 83K ohms and Rll is approximately 17K ohms thereby making C- ⁇ equal approximately 0.17.
  • C 2 is determined by the internal structure of multiplier 31 and typically has a value of 0.1.
  • C 3 is determined by the setting of the wiper arm or adjustable terminal on potentiometer R13 having a total resistance of 2K ohms.
  • the wiper arm on potentiometer R13 is set to give a value for C- of from 0 to 0.16.
  • the linearity adjust the wiper arm on potentiometer R13
  • the gain adjust the wiper arm of the potentio ⁇ meter R7 connected as a variable resistor in the feedback circuit of amplifier 23
  • Figure 10 illustrates the digital circuit used with the digital flow meter embodiment of this invention.
  • the output signal A from the signal conditioning circuit of Figure 8 derived from the output lead of op amp 23 is applied to the input lead 13 of analog to digital converter 41 (comprising the well known AD574 circuit commercially available from Analog Devices Inc.).
  • Converter 41 is clocked by the output of the LM555 timer 42 (National Semiconductor Corporation) to provide a periodic conversion to digital form of the analog output signal from the signal conditioning circuit shown in Figure 8.
  • the output signal from converter 41 is a digital signal of twelve bits representing any one of 2 12 possible different signal levels.
  • the eleven most significant outputs of converter 41 are used to address the 2K byte electrically program ⁇ mable read only memories (EPROMs) 43 and 44 (for example, the 2516 commercially available from Texas Instruments Inc.) to provide an output signal corresponding to the information stored in the appropriate EPROM at the address identified by the digital eleven bit output signal from converter 41.
  • EPROMs 43 and 44 corresponds to the digitized version of the voltage versus curve shown in Figure 11 when the output signal from op amp 23 ( Figure 8) is derived from signal conditioning circuit 102A ( Figure 7) and represents pressure when derived from op amp 23 in signal conditioning circuit 102C ( Figure 7).
  • the output voltage from the signal conditioning circuit shown in Figure 8 is plotted versus the flowrate.
  • the output signal from the appropriate address in EPROM 43 or 44 ( Figure 10) cor ⁇ responds to the digital representation of the flowrate sensed by the structure of Figures 1A, IB or 1C and is transmitted in binary coded decimal to displays 45, 46 and 47 to provide a display of three digits corresponding to the flowrate.
  • displays 45, 46 and 47 comprise the well known 5082-7302s manu ⁇ factured by Hewlett-Packard Co.
  • Another embodiment of this invention is a flow con ⁇ troller with pressure and temperature compensation.
  • this embodiment can be reduced to a flow meter with pressure and temperature compensation by eliminating the control circuitry such as circuit elements 108, 109, 112 and 114, if it is so desired.
  • FIG. 7 illustrates in block diagram form, the electronic circuitry of one embodiment of this invention used as a flow controller.
  • micro ⁇ processor 105 receives as input signals certain processed data from pressure sensor 101A, temperature sensor 101B and flow sensor lOlC.
  • Pressure sensor 101A and temperature sensor 101B are each of a type commonly known in the art.
  • Flow sensor 101C is of the type previously described in this specification in conjunction with Figures 1A, IB and IC.
  • Pressure sensor 101a can be any pressure sensor of a type commonly employed in the measurement of fluid pressures and preferably will be a pressure sensor of the type shown in copending application serial no.Q6/?Ri .620 entitled “Pressure Transducer” on an application of Boyle, Nelson and Mahawili filed the same day as this application and assigned to American Flow Systems, Inc. the assignee of this application.
  • Signal conditioning circuits 102A and 102C comprise the structure as shown in Figure 8 (described infra).
  • the signal conditioning circuit shown in Figure 102B comprises a potentiometer connected so that the output current from the temperature sensor is passed through the potentiometer.
  • the magnitude of the input signal generated across the potentiometer is merely a function of the value of the resistance presented by the potentiometer to this current. This current is proportional to temperature.
  • Analog multiplexer 103 routes a desired output signal from one of signal conditioning circuits 102A, 102B and 102C to analog-to-digital converter 104.
  • A-to-D converter 104 converts this output signal to a digital signal.
  • Multiplexer 103 and A-to-D converter 104 are driven by output signals from microprocessor 105 generated in response to the internal program of microprocessor 105.
  • Microprocessor 105 is operated under control of in ⁇ structions in program memory 106.
  • Memory 106 also contains data to be used by the system in producing signals indi ⁇ cative of the mass flow rate of the fluid whose flow is being measured from the measurements of the pressure and temperature of the fluid and the flow rate passing the flow sensor 101C.
  • Program memory 106 comprises a read only memory ("ROM”) of well known design or an electri- cally programmable read only memory.
  • Address decoder 107 receives signals from program memory 106 and from microprocessor 105 for accessing or providing instructions to multiplexor 103, analog converter 104, memory 106 and certain components associated with the control portion of the circuitry and the user input and output portions of the circuitry comprising digital to analog converter 108, set point input 109 and output display 110.
  • Digital to analog converter 108 takes the output signal from microprocessor 105 representing in digital form the desired control voltage to be applied to the control valve amplifier 112.
  • Amplifier 112 controls control valve 114 to control the flow rate being sensed by flow sensor 101c.
  • This signal input to D-to-A converter 108 is produced by microprocessor 105 from the difference between the mass flow rate computed from the pressure, temperature, and flow sensor inputs and the set point input represented by the settings of input switches 109 of well known design (shown schematically only).
  • the analog signal from converter 108 applied to power amplifier 112 results in amplifier 112 producing an output signal adequate to drive control valve 114.
  • Output display 110 displays the measured flowrate.
  • Friction eliminato amplifier 111 provides power to a friction eliminator 113 which comprises a vibrating element.
  • friction eliminator 113 comprised a motor which vibrates owing to an unbalance in the rotating components of the motor.
  • the data bus 116 is the structure over which all data transactions between the microprocessor 105 and the other components of the circuit take place.
  • the control bus 117 is a group of signal lines, controlled by the microprocessor 105, which selects the circuit element to be activated for a particular data transaction with the microprocessor 105.
  • the control bus 117 also includes signal lines for starting an analog-to-digital conversion and selecting which of the three sensors 101A, 101B or 101C is to be routed through the analog multiplexer 103 to the analog to digital con ⁇ verter 108.
  • Another control line is responsible for turning on the friction eliminator amplifier 111 which drives friction eliminator 113.
  • Instructions and calibration data for the micro ⁇ processor 105 are contained in the program memory 106 and addressed through the address bus 115 which is also used by the address decoder 107 to derive some of the signals on control bus 117.
  • Each of the three sensors, flow 101C, pressure 101A and temperature 101B, is connected to a signal condi ⁇ tioning circuit 102C, 102A and 102C, respectively, which provides the offset and amplification to produce a $ to I ⁇ volt signal from each sensor.
  • These signals are connected to the analog multiplexer 103 which, in response to control signals, determines which output signal from circuits 102A, 102B and 102C will be connected to the analog to digital converter 104.
  • the analog to digital converter 104 periodically and repetitively converts the appropriate output signal to a digital form that can be processed by the microprocessor 105.
  • the output display 110 consists of a standard multi- digital LED display and data latches activated by signals on control bus 117.
  • the setpoint input 109 consists of a standard multi- digital thumbwheel switch with binary coded decimal outputs.
  • the control valve 114 requires a variable analog - voltage signal to be generated by the microprocessor 105. This is accomplished by connecting digital to analog converter 108 to the data bus and connecting a power amplifier 112 to the output of converter 108. Micro ⁇ processor 105 sends a digital signal to converter 108 which converts this signal to an analog voltage. Amplifier 112 applies the voltage to control value 114 at an increase power level.
  • the friction elimination circuit 111 is turned on and off by a signal on control bus 117 under microprocessor control. Circuit 111 is " simply a power transistor operated as a switch to turn the power to the friction eliminator mechanism 113 on or off.
  • Microprocessor 105 computes the mass flow rate from the magnitude of the input signals from the flow'sensor, pressure sensor, and temperature sensor. In the case when - the fluid being measured is a liquid, the effects of pressure and temperature are minor and the flow sensor output can be used directly to compute the mass flow. This is done by storing in the memory 106 the mass flow rate corresponding to selected output signals from flow sensor 101C. Subsequently, when the output signal from flow sensor 101C is measured, the mass flow rate is compute from the nearest data in memory corresponding to an output signal from flow sensor 101C greater than the measured one, and the nearest data in memory corresponding to an output signal from flow sensor 101C less than or equal to the measured one.
  • the mass flow rate for the measured output signal from flow sensor 101C is computed by a linear interpolation between these two points.
  • the flow sensor output signal and the pressure and temperature of the gas are all required to compute the mass flow rate. Ignoring, for the moment, the effects of temperature, the mass flow rate of a gas is a complex function of the flow sensor output signal and the actual pressure of the gas. That is, for a given flow sensor output signal, the mass flow rate is a function of the gas pressure, and for a given pressure the mass flow rate is a function of the flow sensor output signal.
  • a matrix of mass flow rates corresponding to selected values of flow sensor output signals and measured pressures is stored program memory 106 (Figure 7).
  • This matrix can be visualized as a standard two dimensional matrix in which the rows correspond to selected values of the output signal from flow sensor 101C, and the columns correspond to selected values of gas pressure.
  • the value of each point or location within the matrix equals the mass flowrate for a flow sensor output signal corresponding " * to the row of the matrix location and a pressure corres ⁇ ponding to the column of the matrix location.
  • the mass flow rate for any value of output signal from flow sensor 101C and pressure can be computed from the values stored in the matrix by interpolating among the four matrix values nearest to the measured point-
  • Figure 12 shows the relationship of certain data points such as A,B,C, and D, representing known mass flow rates corresponding to selected values of the output signal from flow sensor 101C and the pressure.
  • selected flow sensor 101C output signals such as SI and S2 correspond to rows of the matrix and selected pressures such as PI and P2 correspond to columns within the matrix. Therefore, memory 106 contains mass flow rate data for the points (PI, 52) (PI, 51) (P2, 52).
  • point A refers to memory location which contains the true mass flow rate (excluding the effects of temper ⁇ ature) for a output signal of Si from flow sensor 101C and a pressure of PI.
  • the memory does not have data for this point but has data for points such as A,B,C, and D.
  • a way of computing the mass flow rate corresponding - to point X from the available data is to perform three interpolations among the four points shown in Figure 12 as A,B,C, and D. These points represent the mass flow rates due to combined flow sensor 101C output signals and pressure SI and Pi, S2 and PI, SI and P2 and S2 and P2 respectively.
  • the first interpolation computes point E from the points A and B. E is computed by linear interpolation between A and B according to the position of S in the interval between SI and S2.
  • F is computed from the points C and D.
  • F ( (S-S1 )/( S2-S1 ) ) *D+( ( S2-S )/( S2-S1 ) ) *C
  • the accuracy of this calculation of X depends on the linearity of the mass flow as a function of the output signal of flow sensor 101C at constant temperature and pressure over the intervals A to B and C to D, and as a function of pressure at constant temperature and flow sensor output over the interval from E to F. Greater accuracy, if desired, can be achieved in. a well known manner by reducing the size of the intervals and/or using a nonlinear interpolation function.
  • the calibration temperature is the temperature at which the matrix of data relating to flow sensor 101C output signals and pressures to mass flow rates (such as used to calculate X) is measured.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)

Abstract

Une structure de mesure de l'écoulement d'un fluide comprend un passage d'écoulement (16) au travers duquel on fait passer un fluide dont on mesure l'écoulement et une goupille conique (2) montée coulissante dans le passage d'écoulement, se déplaçant en réponse à l'écoulement du fluide. Le degré de mouvement de la goupille conique est une fonction du débit du fluide. Une force de remise à l'état initial s'exerce sur la goupille à l'aide d'un ressort (6) de manière à ramener la goupille sur sa position nominale pour couper l'écoulement de fluide en l'absence de fluide. La goupille est montée de manière à déplacer un aimant (4) dont le mouvement est détecté par un élément de détection, d'une manière caractéristique un détecteur à effet de Hall (10). Le signal de sortie provenant du détecteur à effet de Hall est alors traité pour fournir une mesure du débit. Dans un mode de réalisation, le traitement de ce signal provenant du détecteur de Hall s'effectue premièrement en numérisant le signal, puis en comparant la valeur représentée par ce signal numérisé à des valeurs de débit/valeur du signal stockées sous forme de matrice dans une mémoire en fonction de la pression, puis en interpolant pour trouver le débit réel. Le détecteur d'écoulement (3) fonctionne sur un principe à impact et possède une forme concave en godet (3A) sur la surface ou a lieu l'impact du fluide pour obtenir un écoulement sans à-coup de ce fluide sur la surface.
EP19820902407 1981-07-09 1982-06-28 Controleur et detecteur d'ecoulement Withdrawn EP0083633A1 (fr)

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US28161981A 1981-07-09 1981-07-09
US28161881A 1981-07-09 1981-07-09
US281619 1981-07-09
US281618 1999-03-30

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DE3505706A1 (de) * 1985-02-19 1986-08-21 Rota Apparate- Und Maschinenbau Dr. Hennig Gmbh & Co Kg, 7867 Wehr Durchflussmesser
US4581944A (en) * 1985-03-18 1986-04-15 Controls Company Of America Electronic flow transducer assembly
US5222867A (en) * 1986-08-29 1993-06-29 Walker Sr Frank J Method and system for controlling a mechanical pump to monitor and optimize both reservoir and equipment performance
US5006044A (en) * 1987-08-19 1991-04-09 Walker Sr Frank J Method and system for controlling a mechanical pump to monitor and optimize both reservoir and equipment performance
WO1989002579A1 (fr) * 1987-09-09 1989-03-23 Walker Frank John Sr Procede et systeme pour commander une pompe mecanique afin de controler et optimiser les performances du reservoir et des equipements
DE4109694C2 (de) * 1991-03-23 1994-05-19 Hess Paul Durchflußmeßeinrichtung
EP0850401A4 (fr) * 1995-09-11 1998-08-19 Suregas Proprietary Limited Detecteur de flux gazeux
US9938805B2 (en) 2014-01-31 2018-04-10 Mts Systems Corporation Method for monitoring and optimizing the performance of a well pumping system
DE102016012498A1 (de) * 2016-10-19 2018-04-19 Meister Strömungstechnik GmbH Vorrichtung zur Bestimmung einer momentanen Durchflussrate eines fließfähigen Mediums und Verfahren zur Verwendung einer Vorrichtung zur Bestimmung einer momentanen Durchflussrate eines fließfähigen Mediums
CN117824767B (zh) * 2024-01-10 2024-12-27 斯特劳斯(山东)工业技术有限公司 一种多功能活塞流量计

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