Flow measuring device based on predetermine class of liquid

• US 6,609,431 B1
• Filed: 09/29/2000
• Issued: 08/26/2003
• Est. Priority Date: 09/29/2000
• Status: Expired due to Fees

• Current Assignee: SYS Technologies (San Diego) (Kratos Defense & Security Solutions Incorporated)
• Original Assignee: Xellogy Incorporated
• Inventors: OʼNeil, Donald J., Tietsworth, Steven C., Goldstein, Lawrence H.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Dickens, Charlene
• Application Number:
  US09/676,101
• Time in Patent Office: 1,061 Days
• Field of Search: 738/614.2, 738/610.1, 738/615.3, 738/615.2, 738/610.2, 732/041.2, 222/56, 222/64, 222/129.1, 222/129.3, 222/145.5, 222/145.6, 222/189.06, 222/190, 222/413, 137/334, 137/486, 137/467.5, 137/101.21, 137/487.5, 137/468, 137/501, 137/504
• US Class Current: 73/861.52
• CPC Class Codes: B67D 1/0855 concerning the used flowmeter flowmeter per se G01F1/00, G01F3/00
• CPC Class Codes: B67D 1/1211 Flow rate sensor
• CPC Class Codes: G01F 1/36 the pressure or differential pressure being created by the use of flow constriction
• CPC Class Codes: G01F 1/6847 where sensing or heating elements are not disturbing the fluid flow, e.g. elements mounted outside the flow duct

Abstract

A flow meter and method for determining the corrected flow rate of a liquid falling into a predetermined class of liquids based on its viscosity and density is disclosed. The flow meter comprises a flow sensor for measuring an uncorrected flow rate of the liquid, a temperature sensor for measuring the temperature of the liquid, and a microprocessor for calculating the corrected flow rate based on the liquids predetermined class and the measured temperature. The flow sensor can include a restriction in the fluid flow path, first and second pressure sensors positioned one on each side of the restriction and a temperature sensor. The first and second pressure sensors measure the drop in fluid pressure created by the restriction and the temperature sensor measures the temperature of the liquid. By basing the corrected flow rate calculation on the predetermined class of the liquid, the calculation becomes a closed form solution that is deterministic providing for quick and accurate corrected flow rate calculation. A flow meter according to the present invention can be used in many applications such as, among others, liquid beverage dispensers and variable speed pumps.

Claims

1. A flow meter for determining a flow rate of liquid flowing in a fluid flow path in a confined space having a first diameter, the liquid falling into a predetermined class of liquids based on viscosity and density of the liquid, the flow meter comprising:

a flow sensor for measuring an uncorrected flow rate of the liquid flowing in the fluid flow path;

a temperature sensor for measuring the temperature of the liquid; and

a microprocessor means configured for determining a corrected flow rate of the liquid flowing in a fluid flow path in a confined space based on the predetermined class of the liquid and the measured temperature.

2. The flow meter of claim 1 further comprising:

a restriction in the flow path, the restriction creating a second diameter;

a differential pressure sensor for determining a differential pressure measured as a drop in pressure created by the restriction in the flow path

wherein the microprocessor is connected to the differential pressure sensor for receiving the differential pressure and the microprocessor is configured for determining the flow rate of the liquid flowing in a fluid flow path in a confined space based further on the measured differential pressure.

3. The flow meter of claim 2 wherein the differential pressure sensor comprises:

a first pressure sensor on a first side of the restriction, the first pressure sensor being configured for measuring pre-restriction pressure created in the confided space by the liquid flowing in the fluid flow path on the first side of the restriction

a second pressure sensor on a second side of the restriction opposite the first side, the second pressure sensor being configured for measuring post-restriction pressure created in the confided space by the liquid flowing in the fluid flow path on the second side of the restriction;

wherein the differential pressure is the difference between the pre-restriction pressure and the post-restriction pressure.

4. The flow meter of claim 2 wherein the confined space includes a first diameter, the restriction creates a second diameter and the flow rate is further determined based on the first and second diameters.

5. The flow meter of claim 3 wherein the first and second pressure sensors comprise silicon-based MEM sensors.

6. The flow meter of claim 2 further comprising a protective membrane positioned between the differential pressure sensor and the liquid.

7. The flow meter of claim 1 wherein the temperature sensor comprises a thermocouple positioned in the fluid flow path.

8. The flow meter of claim 1 wherein the temperature sensor comprises a resistive bridge.

9. The flow meter of claim 1 wherein the corrected flow rate is determined using the following equation:

$\frac{-a_1^{\mathrm{\prime <br><br>}}-\sqrt{{\left(a_1^{\mathrm{\prime <br><br>}}\right)}^2-4<br><br>a_0^{\mathrm{\prime <br><br>}}<br><br>a_2^{\mathrm{\prime <br><br>}}}}{2<br><br>a_2^{\mathrm{\prime <br><br>}}}$

where

a₀^′

=a₀Q_u;

a₁^′

=a₁Q_u−

1;

a₂^′

=a₂Q_u;

a₀, a₁ and a₂=predetermined coefficients based on the temperature and class of liquid; and

Q_u is the uncorrected flow rate measured by the flow sensor.

10. The flow meter of claim 1 further configured for use in a beverage dispensing machine for measuring the flow rate of liquid dispensed by the beverage dispensing machine.

11. The flow meter of claim 10 wherein the liquid is syrup which is mixed with water by the beverage dispensing machine to produce a beverage, the flow meter further including a valve for regulating the flow rate of the water based on the determined flow rate of the syrup.

12. The flow meter of claim 1 wherein the flow sensor is configured for use in a liquid dispenser, the flow meter further including a valve for controlling the amount of liquid dispensed by the liquid dispenser based on the determined flow rate.

13. The flow meter of claim 1 wherein the flow meter is configured for use in a variable speed pump for determining the flow rate of liquid pumped by the pump.

14. The flow meter of claim 1 further comprising a wireless communication system for transmitting the determined flow rate to a central control center.

15. The flow meter of claim 14 wherein the wireless communication system is further configured for receiving control signals from the central control center for controlling operation of the flow sensor.

16. A flow sensor for use in a liquid beverage dispenser configured to mix syrup and water to produce a liquid beverage, the flow sensor being configured for determining the flow rate of syrup flowing in a syrup flow path in a syrup dispensing conduit having a diameter and adjusting the flow rate of water based on the flow rate of syrup, the syrup falling into a predetermined class of syrups based on the viscosity of the syrup, the flow sensor comprising:

an orifice restriction in the conduit, the orifice restriction having an orifice diameter;

a differential pressure sensor for measuring the differential pressure created by the orifice restriction;

a temperature sensor for measuring the temperature of the syrup;

a microprocessor means connected to the temperature sensor and the differential pressure sensor for receiving the measured temperature and the differential pressure, for determining a flow rate of the syrup based on the measured temperature, differential pressure and predetermined class of the syrup; and

a valve connected to the microprocessor for regulating the flow rate of the water, wherein the microprocessor is configured to actuate the value to adjust the flow rate of water based on the determined flow rate of the syrup.

17. The flow meter of claim 16 wherein the differential pressure sensor comprises:

a first pressure sensor on a first side of the orifice restriction, the first pressure sensor being configured for measuring pre-restriction pressure created in the conduit by the syrup flowing in the syrup flow path on the first side of the orifice restriction; and

a second pressure sensor on a second side of the orifice restriction, the second pressure sensor being configured for measuring post-restriction pressure created in the conduit by syrup flowing in the syrup flow path on the second side of the orifice restriction;

wherein the differential pressure is the difference between the pre-restriction pressure and the post-restriction pressure.

18. The flow meter of claim 17 wherein the first and second pressure sensors comprise silicon-based MEM sensors.

19. The flow meter of claim 16 further comprising a protective membrane positioned between the differential pressure sensor and the liquid.

20. The flow meter of claim 16 wherein the corrected flow rate is determined using the following equation:

$\frac{-a_1^{\mathrm{\prime <br><br>}}-\sqrt{{\left(a_1^{\mathrm{\prime <br><br>}}\right)}^2-4<br><br>a_0^{\mathrm{\prime <br><br>}}<br><br>a_2^{\mathrm{\prime <br><br>}}}}{2<br><br>a_2^{\mathrm{\prime <br><br>}}}$

where

a₀^′

=a₀Q_u;

a₁^′

=a₁Q_u−

1;

a₂^′

=a₂Q_u;

a₀, a₁ and a₂=predetermined coefficients based on the temperature and class of liquid; and

Q_u is the uncorrected flow rate measured by the flow sensor.

21. The flow meter of claim 16 further comprising a wireless communication system for transmitting the determined flow rate to a central control center.

22. The flow meter of claim 21 wherein the wireless communication system is further configured for receiving control signals from the central control center for controlling operation of the flow sensor.

23. A method for determining a flow rate of a liquid flowing in a fluid flow path in a confined space having a first diameter with an orifice in the confined space having a second diameter, the liquid falling into a predetermined class of liquids based on viscosity and density of the liquid, the method comprising the steps of:

a) measuring a pressure differential created by the orifice;

b) measuring a temperature of the liquid; and

c) calculating the flow rate based on the measured pressure differential, measured temperature and predetermined class of liquid.

24. The method of claim 23 wherein the step of measuring a pressure differential further comprises;

measuring a pre-restriction pressure created by the liquid in the confined space on a first side of the orifice;

measuring a post-restriction pressure created by the liquid in the confined space on a second side of the orifice;

calculating the difference between the pre-restriction pressure and the post-restriction pressure.

25. The method of claim 23 further comprising the steps of:

periodically repeating steps a)-c) at predetermined time intervals.

26. The method of claim 25 further comprising the steps of:

multiplying the calculated flow rate by the predetermined time interval to determine a volume of liquid flowing during the predetermined time interval.