Precision flow control system

• US 7,465,382 B2
• Filed: 09/17/2002
• Issued: 12/16/2008
• Est. Priority Date: 06/13/2001
• Status: Expired due to Term

• Current Assignee: AB Sciex LLC (Danaher Corporation)
• Original Assignee: Eksigent Technologies LLC
• Inventors: Paul, Phillip H., Arnold, Don W., Rehm, Jason E.
• Primary Examiner(s): Phasge; Arun S
• Application Number:
  US10/246,284
• Publication Number:
  US 20030052007A1
• Time in Patent Office: 2,282 Days
• Field of Search: 204/600, 422/110, 422/105, 73/11.6, 738/610.7
• US Class Current: 204/600
• CPC Class Codes: G01N 2030/285 electrically driven carrier
• CPC Class Codes: G01N 2030/324 speed, flow rate
• CPC Class Codes: G01N 2030/326 pumps
• CPC Class Codes: G01N 30/32 of pressure or speed G01N30/36 takes precedence
• CPC Class Codes: G01N 30/34 of fluid composition, e.g. gradient G01N30/36 takes precedence
• CPC Class Codes: G05D 11/132 by controlling the flow of the individual components G05D11/133 takes precedence
• CPC Class Codes: G05D 7/0682 using a plurality of flow sources
• CPC Class Codes: G05D 7/0694 by action on throttling means or flow sources of very small size, e.g. microfluidics microvalves F16K99/0001; microstructural devices per se B81B

Abstract

A precision flow controller is capable of providing a flow rate less than 100 microliters/minute and varying the flow rate in a prescribed manner that is both predictable and reproducible where the accuracy and precision of the flowrate is less than 5% of the flow rate. A plurality of variable pressure fluid supplies pump fluid through a single outlet. Flowmeters measure the flow rates and a controller compares the flow rates to desired flowrates and, if necessary, adjusts the plurality of variable pressure fluid supplies so that the variable pressure fluid supplies pump fluid at the desired flow rate. The variable pressure fluid supplies can be pneumatically driven.

Claims

1. A low flow rate precision flow controller comprising:

(a) a pneumatic to hydraulic booster connected to a pressure supply for pressurizing a fluid so that it flows out of a fluid outlet;

(b) a flowmeter for measuring the flow rate of the fluid between the pneumatic to hydraulic booster and the outlet; and

(c) a servo-loop controller in communication with the flowmeter and the pneumatic to hydraulic booster, wherein the servo-loop compares the measured flow rate to a desired flow rate and adjusts the pressure from the pressure supply so that the fluid flows out of the fluid outlet at the desired flow rate, wherein the flow rate of the fluid is controlled solely by the controller adjusting the pressure;

wherein the desired flow rate is less than approximately 100 microliters/minute.

2. The flow controller of claim 1 wherein the desired flow rate is less than approximately 10 micro liters/minute.

3. The flow controller of claim 1 wherein the flow controller has a time response of less than one second so that when the measured flow rate does not substantially equal the desired flow rate, the measured flow rate will substantially equal the desired flow rate within one second.

4. The system of claim 1 wherein the flowmeter comprises:

(i) a metering capillary having a sufficiently long length and a sufficiently small inner diameter so that the pressure drop across the metering capillary is at least 5% of the input pressure to the metering capillary at the desired flow rate; and

(ii) a pressure sensor for measuring the pressure drop across the metering capillary.

5. The system of claim 1 wherein each flowmeter comprises:

(i) a metering capillary having a sufficiently long length and a sufficiently small inner diameter so that the pressure drop across the metering capillary is at least 50 psi at the desired flow rate and so that the flow rate of the fluid flowing from the booster to the fluid outlet is controlled to the desired flow rate; and

(ii) a pressure sensor, for measuring the pressure across the metering capillary.

6. A low flow rate precision flow controller comprising:

(a) a fluid inlet;

(b) a fluid outlet in fluid communication with the fluid inlet;

(c) a pneumatic pressure supply;

(d) a pneumatic to hydraulic booster located between the fluid inlet and the fluid outlet and in operative communication with the pneumatic pressure supply, wherein the pneumatic pressure supply causes the booster to force fluid out through the fluid outlet;

(e) a pressure modulator located between the pneumatic pressure supply and the booster, wherein the pressure modulator controls the amount of pneumatic pressure supplied to the booster;

(f) a flowmeter located between the booster and the fluid outlet wherein the flowmeter measures the flow rate of a fluid flowing from the booster to the fluid outlet; and

(g) a servo-loop controller in communication with the flowmeter and the pressure modulator, wherein the servo-loop compares the measured flow rate to a desired flow rate and instructs the pressure modulator to adjust the pneumatic pressure supply so that the fluid flows out of the fluid outlet at the desired flow rate, wherein the flow rate of the fluid is controlled solely by the controller adjusting the pneumatic pressure supply;

wherein the desired flow rate is less than approximately 100 micro liters/minute.

7. The flow controller of claim 6 further comprising a check valve between the fluid inlet and the booster so that the fluid flows unidirectionally from the fluid inlet to the booster.

8. The flow controller of claim 6 wherein the desired flow rate is less than approximately 10 microliters/minute.

9. The flow controller of claim 6 wherein the flow controller has a time response of less than one second so that when the measured flow rate does not substantially equal the desired flow rate, the measured flow rate will substantially equal the desired flow rate within one second.

10. A low flow rate precision flow controller comprising:

(a) a fluid inlet;

(b) a fluid outlet in fluid communication with the fluid inlet;

(c) a pneumatic pressure supply;

(d) a pneumatic to hydraulic booster located between the fluid inlet and the fluid outlet and in operative communication with the pneumatic pressure supply, wherein the pneumatic pressure supply causes the booster to force fluid through the fluid outlet;

(e) a pressure modulator located between the pneumatic pressure supply and the booster, wherein the pressure modulator controls the amount of pneumatic pressure supplied to the booster;

(f) a flowmeter located between the booster and the fluid outlet wherein the flowmeter measures the flow rate of a fluid flowing from the booster to the fluid outlet;

(g) a pressure sensor located between the pneumatic pressure supply and the booster;

(h) an inner servo-loop controller in communication with the pressure sensor and the pressure modulator, and

(i) an outer servo-loop controller in communication with the flowmeter and the inner servo-loop controller, wherein the outer servo-loop compares the measured flow rate to a desired flow rate and outputs a pressure setpoint to the inner servo-loop, and wherein the inner servo-loop instructs the pressure modulator to adjust the pneumatic pressure supply so that the fluid flows out of the fluid outlet at the desired flow rate, wherein the flow rate of the fluid is controlled solely by the controllers adjusting the pneumatic pressure supply,

wherein the desired flow rate is less than approximately 100 microliters/minute.

11. The flow controller of claim 10 wherein the flow controller has a time response of less than one second so that when the measured flow rate does not substantially equal the desired flow rate, the measured flow rate will substantially equal the desired flow rate within one second.

12. The system of claim 10 wherein the flowmeter comprises:

(i) a metering capillary having a sufficiently long length and a sufficiently small inner diameter so that the pressure drop across the metering capillary is at least 5% of the input pressure to the metering capillary at the desired flow rate; and

(ii) a pressure sensor for measuring the pressure drop across the metering capillary.

13. The system of claim 12 wherein the metering capillary has an inside diameter of less than approximately 50 microns.

14. A low flow rate precision flow controller comprising:

(a) fluid inlet;

(b) a fluid outlet in fluid communication with the fluid inlet;

(c) a pneumatic pressure supply;

(d) a pneumatic to hydraulic booster located between the fluid inlet and the fluid outlet and in operative communication with the pneumatic pressure supply, wherein the pneumatic pressure supply causes the booster to force fluid out through the fluid outlet;

(e) a pressure modulator located between the pneumatic pressure supply and the booster, wherein the pressure modulator controls the amount of pneumatic pressure supplied to the booster;

(f) a flowmeter located between the booster and the fluid outlet wherein the flowmeter measures the flow rate of a fluid flowing from the booster to the fluid outlet;

(g) a pressure sensor located between the booster and the flowmeter;

(h) an inner servo-loop controller in communication with the pressure sensor and the pressure modulator, and

(i) an outer servo-loop controller in communication with the flowmeter and the inner servo-loop controller, wherein the outer servo-loop compares the measured flow rate to a desired flow rate and outputs a pressure setpoint to the inner servo-loop, and wherein the inner servo-loop instructs the pressure modulator to adjust the pneumatic pressure supply so that the fluid flows out of the fluid outlet at the desired flow rate, and wherein the flow rate of the fluid is controlled solely by the controllers adjusting the pneumatic pressure supply,

wherein the desired flow rate is less than approximately 100 microliters/minute.

15. The flow controller of claim 14 wherein the flow controller has a time response of less than one second so that when the measured flow rate does not substantially equal the desired flow rate, the measured flow rate will substantially equal the desired flow rate within one second.

16. The system of claim 14 wherein the flowmeter comprises:

(i) a metering capillary having a sufficiently long length and a sufficiently small inner diameter so that the pressure drop across the metering capillary is at least 5% of the input pressure to the metering capillary at the desired flow rate; and

(ii) a pressure sensor for measuring the pressure drop across the metering capillary.

17. A low flow rate precision flow controller system comprising:

(a) a first and a second fluid inlet for first and second fluids respectively;

(b) a fluid outlet in fluid communication with the first and second fluid inlets;

(c) a first and a second pneumatic pressure supply;

(d) a first pneumatic to hydraulic booster located between the first fluid inlet and the fluid outlet and in operative communication with the first pneumatic pressure supply, wherein the first pneumatic pressure supply causes the first pneumatic to hydraulic booster to force the first fluid out through the fluid outlet;

(e) a second pneumatic to hydraulic booster located between the second fluid inlet and the fluid outlet and in operative communication with the second pneumatic pressure supply, wherein the second pneumatic to hydraulic booster causes the second pneumatic to hydraulic booster forces the second fluid out through the fluid outlet;

(f) a first pressure modulator located between the first pneumatic pressure supply and the first pneumatic to hydraulic booster, wherein the first pressure modulator controls the amount of pneumatic pressure supplied to the first pneumatic to hydraulic booster;

(g) a second pressure modulator located between the second pneumatic pressure supply and the second pneumatic to hydraulic booster, wherein the second pressure modulator controls the amount of pneumatic pressure supplied to the second pneumatic to hydraulic booster;

(h) a first flowmeter located between the first pneumatic to hydraulic booster and the fluid outlet wherein the first flowmeter measures the flow rate of the first fluid flowing from the first booster to the fluid outlet;

(i) a second flowmeter located between the second pneumatic to hydraulic booster and the fluid outlet wherein the second flowmeter measures the flow rate of the second fluid flowing from the second booster to the fluid outlet;

(j) a first pressure sensor located between the first pneumatic pressure supply and the first pneumatic to hydraulic booster;

(k) a second pressure sensor located between the second pneumatic pressure supply and the second pneumatic to hydraulic booster;

(l) a first inner servo-loop controller in communication with the first pressure sensor and the first pressure modulator;

(m) a second inner servo-loop controller in communication with the second pressure sensor and the second pressure modulator;

(n) a first outer servo-loop controller in communication with the first flowmeter and the first inner servo-loop controller, wherein the first outer servo-loop compares the measured flow rate of the first fluid to a first desired flow rate and outputs the comparison to the first inner servo-loop, and wherein the first inner servo-loop instructs the first pressure modulator to adjust the first pneumatic pressure supply so that the first fluid flows out of the fluid outlet at the first desired flow rate;

(o) a second outer servo-loop controller in communication with the second flowmeter and the second inner servo-loop controller, wherein the second outer servo-loop compares the measured flow rate of the second fluid to a second desired flow rate and outputs the comparison to the second inner servo-loop, and wherein the second inner servo-loop instructs the second pressure modulator to adjust the second pneumatic pressure supply so that the second fluid flows out of the fluid outlet at the first desired flow rate,

wherein the first and second fluids mix before flowing out of the fluid outlet and wherein the first and second fluids flow out of the fluid outlet at a flow rate of less than approximately 100 microliters/minute; and

wherein the flow rates of the first and second fluids are controlled only by their respective controllers.

18. The system of claim 17 wherein the first flowmeter is comprised of a first upstream pressure sensor, a downstream pressure sensor;

and a first metering capillary located between the first upstream pressure sensor and the downstream pressure sensor; and

wherein the second flowmeter is comprised of a second upstream pressure sensor;

the downstream pressure sensor; and

a second metering capillary located between the second upstream pressure sensor and the downstream pressure sensor;

wherein the metering capillaries each have a sufficiently long length and a sufficiently small inner diameter so that the pressure drop across each metering capillary is at least 5% of the input pressure to the metering capillary at the desired flow rate.

19. The system of claim 17 further comprising a separation column in fluid communication with the fluid outlet.

20. The system of claim 19 further comprising an injector between the fluid outlet and the separation column.

21. The system of claim 19 further comprising a detector in fluid communication with the separation column.

22. The system of claim 17 wherein the system has a time response of less than one second so that when a measured flow rate does not substantially equal a respective desired flow rate, the measured flow rate will substantially equal the respective desired flow rate within one second.

23. A low flow rate precision flow controller system comprising:

(a) a plurality of fluid supplies in fluid communication with a fluid outlet so that a plurality of fluids mix to yield mixed fluids before flowing through the outlet;

(b) a pressure source for each fluid, each pressure source applying pressure to the respective fluid for pressuring the respective fluid through the outlet;

(c) a flowmeter for each fluid located between the fluid supply and the outlet, each flowmeter measuring the flow rate of the respective fluid; and

(d) a controller for each pressure source in communication with the respective flowmeter and the respective pressure source wherein the controller compares the respective measured flow rate to a respective desired flow rate and adjusts the respective pressure source so that the respective fluid flows at the respective desired flow rate, wherein the flow rate of each fluid is controlled solely by its respective controller adjusting the respective pressure source, and wherein the fluids flow out of the fluid outlet at a flow rate of less than approximately 100 microliters/minute;

wherein at least one pressure source comprises;

(i) a pneumatic to hydraulic booster in operative fluid communication with the fluid supply; and

(ii) a check valve between the fluid supply and the booster so that fluid flows unidirectionally from the fluid supply to the booster.

24. The system of claim 23 wherein at least one of the controllers comprises:

(i) a pneumatic pressure supply in operative communication with the booster;

(ii) a pressure modulator located between the pneumatic pressure supply and the booster, wherein the pressure modulator controls the amount of pneumatic pressure supplied to the booster; and

(iii) a servo-loop controller in communication with a flowmeter and the pressure modulator, wherein the servo-loop controller compares the measured flow rate to the respective desired flow rate and instructs the pressure modulator to adjust the pneumatic pressure supply so that the fluid flows at the desired flow rate.