Fluid handling system for a fluid flow instrument

1. A method of controlling a fluid handling system to supply a working fluid to a fluid flow instrument, the method comprising:

receiving a compressible control fluid into a control fluid volume of a flow regulator;

supplying a first quantity of a substantially incompressible working fluid having a first pulse peak-to-peak value from a peristaltic pump to a working fluid volume of the flow regulator, the peristaltic pump having a first rotor and a second rotor attached to a common drive shaft, wherein shoes attached to the first rotor are rotationally staggered from shoes attached to the second rotor;

sending a sensor signal from a sensor to a controller, the sensor signal indicative of a position of a flexible barrier located between the control fluid volume containing the control fluid and the substantially incompressible working fluid volume containing the working fluid;

sending a control signal from the controller to the peristaltic pump;

controlling the peristaltic pump;

discharging a second quantity of the substantially incompressible working fluid having a second pulse peak-to-peak value from the working fluid volume of the flow regulator;

wherein the second pulse peak-to-peak value is less than the first pulse peak-to-peak value, and

wherein the control signal is determined, at least in part, as a function of the difference between the sensed position of the flexible barrier and a nominal position of the flexible barrier.

2. The method of claim 1 ,

wherein the substantially incompressible working fluid entering the working fluid volume has a nominal pressure of between approximately 40 psi to approximately 50 psi with a pressure pulse fluctuation of at least 2 psi (peak-to-peak), and

wherein the substantially incompressible working fluid exiting the working fluid volume has a nominal pressure of between approximately 40 psi to approximately 50 psi with a pressure pulse fluctuation of less than 0.010 psi (peak-to-peak).

3. The method of claim 1 , wherein the substantially incompressible working fluid entering the working fluid volume has a nominal pressure of between approximately 40 psi to approximately 50 psi with a pressure pulse fluctuation of at least 2 psi (peak-to-peak), and

wherein the substantially incompressible working fluid exiting the working fluid volume has a nominal pressure of between approximately 40 psi to approximately 50 psi with a pressure pulse fluctuation of less than 0.005 psi (peak-to-peak).

4. The method of claim 1 , wherein the control fluid is supplied to the control fluid volume at a substantially constant pressure of between approximately 40 psi to approximately 50 psi.

5. The method of claim 1 , wherein a pressure release valve is in fluid communication with the control fluid volume of the flow regulator.

6. The method of claim 1 , wherein the controller is a PID controller.

7. The method of claim 1 , wherein the controller is a PID controller, and wherein the derivative term of the PID controller has a zero coefficient.

8. The method of claim 1 , wherein the volume of the control fluid volume is greater than 200 mL.

9. The method of claim 1 , wherein the volume of the control fluid volume is greater than approximately 200 mL and wherein the volume of the working fluid volume is between approximately 15 mL and approximately 35 mL.

10. The method of claim 1 , wherein the ratio of the volume of the control fluid volume to the volume of the working fluid volume is between approximately 8 and approximately 12.

11. The method of claim 1 , wherein the flexible barrier is circular.

12. The method of claim 1 , wherein the flexible barrier is formed of EPDM.

13. The method of claim 1 , wherein the flexible barrier is positioned at a non-zero angle to the horizontal.

14. The method of claim 1 , wherein the control signal is a function of the difference in the sensor signal value from a predetermined nominal sensor signal value and of the accumulated difference in the sensor signal value from a predetermined nominal sensor signal value.

15. The method of claim 1 , wherein the sensor signal value reflects the difference from a predetermined nominal sensor signal and the control signal is a weighted sum of the sensor signal and an accumulation of previous sensor signal values.

16. The method of claim 1 , wherein the controller reads the sensor signal at least approximately three times per second.

17. The method of claim 1 , wherein the controller reads the sensor signal at a greater frequency than a frequency of the pulsed flow of the substantially incompressible working fluid supplied to the working fluid volume of the flow regulator.

18. A fluid handling system comprising:

a peristaltic pump having a first rotor and a second rotor attached to a common drive shaft with shoes attached to the first rotor rotationally staggered from shoes attached to the second rotor;

a flow regulator having a control fluid volume to receive a compressible control fluid, a working fluid volume to receive a substantially incompressible working fluid, and a flexible barrier positioned between the control fluid volume and the working fluid volume;

a sensor to provide a sensor signal indicative of a position of the flexible barrier; and

a controller to receive the sensor signal from the sensor, the controller providing control signals to the peristaltic pump that are determined, at least in part, as a function of the difference between the sensed position of the flexible barrier and a nominal position of the flexible barrier,

wherein the peristaltic pump supplies a first quantity of substantially incompressible working fluid having a first pulse peak-to-peak value to the working fluid volume of the flow regulator; and

wherein the controller controls the peristaltic pump to discharge a second quantity of the substantially incompressible working fluid having a second pulse peak-to-peak value that is less than the first pulse peak-to-peak value.

19. The fluid handling system of claim 18 , wherein, during operation, the working fluid volume is completely filled with the substantially incompressible working fluid.

20. The fluid handling system of claim 18 , wherein the substantially incompressible working fluid entering the working fluid volume has a nominal pressure of between approximately 40 psi to approximately 50 psi with a pressure pulse fluctuation of at least 2 psi (peak-to-peak), and

wherein the substantially incompressible working fluid exiting the working fluid volume has a nominal pressure of between approximately 40 psi to approximately 50 psi with a pressure pulse fluctuation of less than 0.010 psi (peak-to-peak).

21. The fluid handling system of claim 18 , wherein the substantially incompressible working fluid entering the working fluid volume has a nominal pressure of between approximately 40 psi to approximately 50 psi with a pressure pulse fluctuation of at least 2 psi (peak-to-peak), and

wherein the substantially incompressible working fluid exiting the working fluid volume has a nominal pressure of between approximately 40 psi to approximately 50 psi with a pressure pulse fluctuation of less than 0.005 psi (peak-to-peak).

22. The fluid handling system of claim 18 , wherein the control fluid is supplied to the control fluid volume at a substantially constant pressure of between approximately 40 psi to approximately 50 psi.

23. The fluid handling system of claim 18 , further comprising a pressure release valve in fluid communication with the control fluid volume of the flow regulator.

24. The fluid handling system of claim 18 , wherein the controller is a PID controller.

25. The fluid handling system of claim 18 , wherein the controller is a PID controller, and wherein the derivative term of the PID controller has a zero coefficient.